Design for Additive Manufacturing 3662684624, 9783662684627

Table of contents :
Preface to the English edition
Contents
About the Authors
Preface to the English edition
1 Introduction
Bibliography
2 Basics
2.1 Process Chain
2.1.1 Product Design
2.1.2 Pre-Process (Computer Aided Planning)
2.1.3 In-Process (Computer Aided Manufacturing)
2.1.4 Post-Process
2.1.5 Finishing
2.2 Overview of Additive Manufacturing Processes
2.3 Product Creation Process of Additive Manufacturing
Bibliography
3 Component Selection
3.1 SWOT Analysis
3.1.1 Strengths
3.1.2 Weaknesses
3.1.3 Opportunities
3.1.4 Risks
3.2 Potential Assessment
3.2.1 Number of Pieces
3.2.2 Degree of Individualisation
3.2.3 The Complexity of Geometry
3.2.4 Material
3.2.5 Weight
3.2.6 Production Time
3.2.7 Post-Processing
3.2.8 Size
3.2.9 Nesting
3.2.10 Ecological Sustainability
3.3 Component Portfolio Analysis
3.4 Evaluation Catalogue for Component Selection
Bibliography
4 Creative Methods
4.1 Requirement Identification
4.2 Design Goals
4.3 Setting up Functional Structures
4.4 Effect Engineering
4.4.1 Potentials of Effect Engineering
4.4.2 Areas of Application of Effect Engineering
4.4.3 Additive Manufacturing Technologies for Multi-Material Production
4.5 Structure of a Product Architecture
4.5.1 Variation of Product Structure and Shape
4.5.2 Bionics
4.6 Embodiment Design Phase
4.6.1 Basic Design Rules
4.6.2 Design Principles
4.6.3 One-Piece Machine Method
4.6.4 From the Inside to the Outside
4.6.5 From the Outside to the Inside
4.6.6 Configuration from Modular Systems
4.6.7 Development of Model Series
4.6.8 Internal Structures
4.6.9 Structural Optimisation
4.6.10 Graded and Combined Materials
4.7 Development Environment
Bibliography
5 Restrictive Methods
5.1 Design Guidelines
5.2 Concrete Restrictions Using the Example of PBF-LB/M
5.3 Finishing Methods
5.3.1 Mechanical Finishing
5.3.2 Thermal Finishing
5.3.3 Chemical Finishing
5.4 Cost Calculation
Bibliography
6 Machine Setup
6.1 Material
6.1.1 Filaments
6.1.2 Powder
6.1.3 Fluid
6.1.4 Challenges
6.2 Machine Parameters
6.2.1 Fused Layer Modeling
6.2.2 Laser Based Processes
Bibliography
7 Validation and Quality Assurance
7.1 Process Simulation
7.1.1 Inherent Strain Method
7.1.2 Coupled Thermomechanical Simulation
7.1.3 Multi-Scale Approaches
7.1.4 Further Simplifications
7.1.5 Simulation Software
7.1.6 Procedural Model for the Evaluation of the Probability of Statement of Process Simulations
7.2 Process Monitoring and Control
7.2.1 Pyrometry
7.2.2 High-Speed Camera
7.3 Non-Destructive Testing
7.3.1 Computer Tomography (CT)
7.3.2 Optical Coherence Tomography (OCT)
7.3.3 3D Scan Image Correlation Systems
7.3.4 3D High-Speed Image Correlation Systems
7.3.5 Universal Testing Machine
7.3.6 Multiphysics Test Benches
7.4 Destructive Testing
Bibliography
8 Project Examples
8.1 Weight-Reduced Wheel Carrier for a Racing Car
8.2 Function Integration for a Raman Spectroscope
8.3 Weight-Optimised Bicycle Pedal Crank
8.4 Force Flow Adjustment for a Jack Lifter
8.5 Integrated Flow Channels for a Valve
8.6 Computational Design Synthesis of Individualized Implants
8.7 Design for the Sampling of Car Keys
8.8 Net-Shape Geometries for a Reflector
8.9 Multi-Material Design Using the Example of a Heat Exchanger
8.10 Design of a Particle-Damped Motorcycle Triple Clamp with Internal Effects
8.11 Time Savings Through the Use of Additive Repair
8.12 Conclusions and Lessons Learned
8.12.1 Human
8.12.2 Machine
8.12.3 Material
Bibliography
9 Business Models
9.1 Manufacturing Service Provider
9.2 Production Lot Size One and Small Number of Pieces
9.3 Production of Optimised Parts in Larger Quantities
9.4 Integration into a Line Production
9.5 Artistic Design
9.6 Decentralisation of Manufacturing Versus Warehousing
9.7 Additive Repair
9.8 Collaborative Customer
9.9 Handling Technology, Tool and Mould Making
9.10 Rapid Prototyping
Bibliography
10 Is Additive Manufacturing Worth It?
10.1 Environmental Sustainability—Life Cycle Assessment
10.2 Domain-Specific Applications and Economics
10.3 Digitisation and Teaching Concept
Bibliography
Design Catalogue of Additive Manufacturing Processes
Design Catalogue of the Design Guidelines
Glossary
Bibliography
Index

Citation preview

Roland Lachmayer Tobias Ehlers Rene Bastian Lippert

Design for Additive Manufacturing

Design for Additive Manufacturing

Roland Lachmayer · Tobias Ehlers · Rene Bastian Lippert

Design for Additive Manufacturing

13

Roland Lachmayer Institute for Product Development Leibniz University Hannover Garbsen, Niedersachsen, Germany

Tobias Ehlers Institute for Product Development Leibniz University Hannover Garbsen, Niedersachsen, Germany

Rene Bastian Lippert Hilti Entwicklungsgesellschaft mbH Kaufering, Germany

ISBN 978-3-662-68462-7 ISBN 978-3-662-68463-4  (eBook) https://doi.org/10.1007/978-3-662-68463-4 © Springer-Verlag GmbH Germany, part of Springer Nature 2024 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer-Verlag GmbH, DE, part of Springer Nature. The registered company address is: Heidelberger Platz 3, 14197 Berlin, Germany Paper in this product is recyclable.

Preface to the English edition

Due to the numerous positive responses to our German version “Entwicklungsmethodik für die Additive Fertigung”, we have decided to extend its reach by publishing an English edition. After an introduction to the fundamentals of additive manufacturing, this book describes specifications of components and processes, methods for assessing component suitability and applications of additive manufacturing as well as for developing concepts and designs. Furthermore, the design of components, their design to ensure functional requirements and manufacturability as well as methods and tools for component optimisation are presented. Derived from this, measures to ensure quality aspects are characterised. Furthermore, the integration of additive manufacturing methods into existing processes and the value chains or business models of additive manufacturing are discussed. The contents are linked holistically in the book in the sense of development processes of product creation. Finally, the question of how and when additive manufacturing is worthwhile from a sustainability perspective is explored. Complementing the first edition, the topics of component selection, process chain design and validation as well as quality control are presented in more detail. The book is supplemented by a glossary as well as design catalogues of additive manufacturing processes and design rules for additive manufacturing in the appendix. Hanover September 2023

Roland Lachmayer Tobias Ehlers Rene Bastian Lippert

v

Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 5

2 Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Process Chain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.1 Product Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.2 Pre-Process (Computer Aided Planning) . . . . . . . . . . . . . 2.1.3 In-Process (Computer Aided Manufacturing) . . . . . . . . . 2.1.4 Post-Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.5 Finishing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Overview of Additive Manufacturing Processes . . . . . . . . . . . . . . 2.3 Product Creation Process of Additive Manufacturing . . . . . . . . . . Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



7 9 9 10 10 11 11 11 15 19

Component Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 SWOT Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.1 Strengths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.2 Weaknesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.3 Opportunities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.4 Risks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Potential Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.1 Number of Pieces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2 Degree of Individualisation . . . . . . . . . . . . . . . . . . . . . . . 3.2.3 The Complexity of Geometry . . . . . . . . . . . . . . . . . . . . . 3.2.4 Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.5 Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.6 Production Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.7 Post-Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.8 Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.9 Nesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.10 Ecological Sustainability . . . . . . . . . . . . . . . . . . . . . . . . .

21 21 24 25 26 27 27 27 29 29 29 30 31 31 32 32 32

3

vii

viii

4

Contents

3.3 Component Portfolio Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Evaluation Catalogue for Component Selection . . . . . . . . . . . . . . Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

34 35 36

Creative Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Requirement Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Design Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Setting up Functional Structures . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Effect Engineering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.1 Potentials of Effect Engineering . . . . . . . . . . . . . . . . . . . 4.4.2 Areas of Application of Effect Engineering . . . . . . . . . . . 4.4.3 Additive Manufacturing Technologies for Multi-Material Production . . . . . . . . . . . . . . . . . . . . . 4.5 Structure of a Product Architecture . . . . . . . . . . . . . . . . . . . . . . . . 4.5.1 Variation of Product Structure and Shape . . . . . . . . . . . . 4.5.2 Bionics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Embodiment Design Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.1 Basic Design Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.2 Design Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.3 One-Piece Machine Method . . . . . . . . . . . . . . . . . . . . . . . 4.6.4 From the Inside to the Outside . . . . . . . . . . . . . . . . . . . . . 4.6.5 From the Outside to the Inside . . . . . . . . . . . . . . . . . . . . . 4.6.6 Configuration from Modular Systems . . . . . . . . . . . . . . . 4.6.7 Development of Model Series . . . . . . . . . . . . . . . . . . . . . 4.6.8 Internal Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.9 Structural Optimisation . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.10 Graded and Combined Materials . . . . . . . . . . . . . . . . . . . 4.7 Development Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

37 38 38 43 44 45 51 53 54 55 56 58 59 60 61 63 63 63 65 66 69 74 75 79

5

Restrictive Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 5.1 Design Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 5.2 Concrete Restrictions Using the Example of PBF-LB/M . . . . . . . 89 5.3 Finishing Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 5.3.1 Mechanical Finishing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 5.3.2 Thermal Finishing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 5.3.3 Chemical Finishing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 5.4 Cost Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

6

Machine Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.1 Filaments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.2 Powder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.3 Fluid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.4 Challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

105 105 105 106 108 108

Contents

6.2

Machine Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.1 Fused Layer Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.2 Laser Based Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

8

ix



109 109 112 121

Validation and Quality Assurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 Process Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.1 Inherent Strain Method . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.2 Coupled Thermomechanical Simulation . . . . . . . . . . . . . 7.1.3 Multi-Scale Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.4 Further Simplifications . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.5 Simulation Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.6 Procedural Model for the Evaluation of the Probability of Statement of Process Simulations . . . . . . . 7.2 Process Monitoring and Control . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.1 Pyrometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.2 High-Speed Camera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 Non-Destructive Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.1 Computer Tomography (CT) . . . . . . . . . . . . . . . . . . . . . . 7.3.2 Optical Coherence Tomography (OCT) . . . . . . . . . . . . . . 7.3.3 3D Scan Image Correlation Systems . . . . . . . . . . . . . . . . 7.3.4 3D High-Speed Image Correlation Systems . . . . . . . . . . 7.3.5 Universal Testing Machine . . . . . . . . . . . . . . . . . . . . . . . . 7.3.6 Multiphysics Test Benches . . . . . . . . . . . . . . . . . . . . . . . . 7.4 Destructive Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

123 123 124 125 125 126 126

Project Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1 Weight-Reduced Wheel Carrier for a Racing Car . . . . . . . . . . . . . 8.2 Function Integration for a Raman Spectroscope . . . . . . . . . . . . . . 8.3 Weight-Optimised Bicycle Pedal Crank . . . . . . . . . . . . . . . . . . . . 8.4 Force Flow Adjustment for a Jack Lifter . . . . . . . . . . . . . . . . . . . . 8.5 Integrated Flow Channels for a Valve . . . . . . . . . . . . . . . . . . . . . . 8.6 Computational Design Synthesis of Individualized Implants . . . . 8.7 Design for the Sampling of Car Keys . . . . . . . . . . . . . . . . . . . . . . 8.8 Net-Shape Geometries for a Reflector . . . . . . . . . . . . . . . . . . . . . . 8.9 Multi-Material Design Using the Example of a Heat Exchanger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.10 Design of a Particle-Damped Motorcycle Triple Clamp with Internal Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.11 Time Savings Through the Use of Additive Repair . . . . . . . . . . . . 8.12 Conclusions and Lessons Learned . . . . . . . . . . . . . . . . . . . . . . . . . 8.12.1 Human . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.12.2 Machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.12.3 Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

149 150 154 158 162 167 170 175 177

128 132 132 134 134 135 138 138 139 141 142 144 147

181 184 189 193 193 195 195 196

x

9

Contents

Business Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1 Manufacturing Service Provider . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2 Production Lot Size One and Small Number of Pieces . . . . . . . . . 9.3 Production of Optimised Parts in Larger Quantities . . . . . . . . . . . 9.4 Integration into a Line Production . . . . . . . . . . . . . . . . . . . . . . . . . 9.5 Artistic Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6 Decentralisation of Manufacturing Versus Warehousing . . . . . . . . 9.7 Additive Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8 Collaborative Customer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.9 Handling Technology, Tool and Mould Making . . . . . . . . . . . . . . 9.10 Rapid Prototyping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

203 204 205 205 206 207 207 208 210 210 212 213

10 Is Additive Manufacturing Worth It? . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1 Environmental Sustainability—Life Cycle Assessment . . . . . . . . 10.2 Domain-Specific Applications and Economics . . . . . . . . . . . . . . . 10.3 Digitisation and Teaching Concept . . . . . . . . . . . . . . . . . . . . . . . . Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

215 217 225 226 231

Design Catalogue of Additive Manufacturing Processes. . . . . . . . . . . . . .

233

Design Catalogue of the Design Guidelines . . . . . . . . . . . . . . . . . . . . . . . .

239

Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

249

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

253

Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

255

About the Authors

Univ.-Prof. Dr.-Ing. Roland Lachmayer  is Head of the Institute for Product Development at Leibniz Universität Hannover. He is a senator of Leibniz University, speaker for the “Tailored Light” graduate school, member of the scientific board of the Laser Zentrum Hannover e. V. (LZH), managing director of the Wissenschaftliche Gesellschaft für Produktentwicklung e. V. and, since 2018, speaker for the EFRE-funded GROTESK research network. Since 2019, Prof. Lachmayer has headed the Additive Manufacturing working group of the Cluster of Excellence PhoenixD. His previous publications include work on development methodology and numerous publications on additive manufacturing. Dr.-Ing. Tobias Ehlers  is Group Leader for “Printed Effects” at the Institute for Product Development at Leibniz Universität Hannover. Current research activities are the design of dynamically loaded structural parts produced by additive manufacturing. Research focuses on structural optimisation of particle-damped structural components and multi-material manufacturing. Dr.-Ing. Rene Bastian Lippert  is Group Leader for Mechatronic development at Hilti Entwicklungsgesellschaft mbH. Until 2021, he was responsible for the industrialization of additive manufacturing at Hilti AG. Before that, he led the group “Methods for Additive Manufacturing” at the Institute for Product Development at Leibniz Universität Hannover.

xi

Chapter 1

Introduction

Based on advances in digital geometry data processing and control technology, stereolithography was the first additive manufacturing process to be patented in 1984 by Chuck Hull [1]. Although additive manufacturing is thus a relatively young discipline, the effects that can be achieved with the various additive technologies in terms of efficient product and manufacturing process optimisation are of outstanding importance. These processes offer innovative and versatile possibilities for accelerated product design as well as extended optimisation of the design and manufacturing processes [2]. In addition, by using the technologies, following nature, it is also possible to produce parts with extreme complexity and internal structures, which was very difficult or impossible with conventional technologies. Lightweight design and energy savings, also in the product life cycle can thus be achieved with the same stability and load-bearing capacity [3]. The use of additive manufacturing processes, especially in small series production, has also made it possible and economically feasible to produce an increasing number of variants and individualised products, as disadvantages such as time-consuming work preparation and the large amount of time required for tool set-up can be overcome. This makes tool-free production and batch-size-adapted or customised production possible at low cost. Starting with the rapid prototyping of the 1990s via the applications in the “Do It Yourself Community”, additive manufacturing has now arrived everywhere in our industry. In the meantime, we understand additive manufacturing as a variety of processes for the layer-by-layer, tool-free production of components made of a wide range of materials using CAD models and numerically controlled systems. By coordinated positioning in three axes and local solidification of material, voxel for voxel parts are created. The result is a near-netshape geometry, which often still has to be reworked on the functional surfaces. The schematic layer-by-layer structure of a part using additive manufacturing is shown in Fig. 1.1 In the classic scheme of manufacturing processes according to DIN 8580, additive manufacturing can be classified as a special form of primary forming. In

© Springer-Verlag GmbH Germany, part of Springer Nature 2024 R. Lachmayer et al., Design for Additive Manufacturing, https://doi.org/10.1007/978-3-662-68463-4_1

1

1 Introduction

2 1

Virtual model

In-process 2

Material feed 3

z

y 5

Physical component

4

Layer generation x

Layer delivery Δz

Fig. 1.1  Schematic representation of the structure of additively manufactured parts [4]

accordance with VDI 3405, we refer to the technology level as additive manufacturing. The underlying level of the application areas in product creation is divided into: • • • •

Rapid prototyping Rapid tooling Direct Manufacturing Additive Repair.

At the process level, there are now more than 15 different processes, which will be described later in the book in the design catalogue in Fig. 2.3. Among the most widespread processes are stereolithography [1], Powder bed fusion (PBF) [5] and fused layer modelling (FLM) [6]. The other processes are described in the appendix “Design catalogue of additive manufacturing processes” including a schematic representation. Thereby, especially under the aspects of efficiency and multi-materiality for the integration of effects or realisation of functionally graded materials, both the process development and the optimisation of these continue to be subject to a very dynamic development [7–9]. In many places, however, the potential of the technology only becomes apparent when the possibilities of additive manufacturing are specifically taken into account in its design. Current applications range from ultralight weight parts in series production in the aviation industry to personalising applications in the automotive industry, rapid repair, printed dental prostheses and visionary ideas and business models such as the printing of organs, textiles or consumer products based on purchased data sets [6]. Expectations go in many different directions, from design complexity and freedom, to tool-free and faster production, to high functional integration, to new business models, higher sustainability and a completely new way of dealing with materials in the professional sector [6, 10].

1 Introduction

3

Areas of application End customer area

Do It Yourself

Professional area

Art & Design

Visionary

Industrial

Architecture/Art

Military

Aerospace

Textiles/Clothing

Medical technology

Automotive

Toys/ Collectibles

Science

Medical technology

Film/Television

Food

Electronics

Fig. 1.2  Application areas of additive manufacturing at product level

However, the public discussion in recent years is also driven by Do It Yourself and Art and Design for the end-user sector. Figure 1.2 structures the applications in the consumer and professional sectors. Only on closer inspection does it become clear that the technology of additive manufacturing is an enabler for many new things, that it is developing rapidly, but that fundamental knowledge is still lacking in many places for its handling and sensible use. This applies in particular to product development, as this is where the key decisions are made for the technical but also commercial success of an innovation. Along the design process, however, work has also been done in recent years that can essentially be sorted as follows: • • • •

Product planning—Potential assessment, part selection Product design—effect engineering, shape optimisation and case studies Production—Process knowledge and design guidelines Product life cycle—logistics, additive repair

We have also worked intensively on the topic in research and have now organised workshops eight times together with other experts and published under the following titles: • • • • •

3D-Druck beleuchtet [11] Additive Manufacturing quantifiziert [12] Additive Serienfertigung [13] Konstruktion für die additive Fertigung 2018, 2019, 2020 [14–16] Innovative Product Development by Additive Manufacturing 2021, 2022 [17, 18]

1 Introduction

4

While these books are collections of essays, we will now formulate the insights gained in this work in the form of a development methodology for additive manufacturing. In detail, after an introduction to the topic, we will deal with the aspects of component selection, creativity methods and heuristics, concepts and procedures, manufacturing restrictions, validation and quality assurance, and business cases. We will classify these along the design process according to VDI 2221 and discuss the development-relevant aspects, strategies and implementation possibilities in an extended way. This book is thus intended to contribute to being able to raise the potentials of additive manufacturing and the “how” of its realisation in a structured form in the industrial context. It addresses the strategic level of decision-makers by answering the questions: “What are the potentials and how do we define them properly?” “Is additive manufacturing worth it?” “What do additive manufacturing process chains look like?”

… but also the developers with the aspects: “How do we proceed methodically?”, “How do we specifically proceed with the example?” “What do we need to develop?”

However, it is also the aim of the book to document the topic of development methodology for additive manufacturing for teaching purposes and to provide assistance for students, whom we are now supervising in the eighth run with the lecture “Development Methodology for Additive Manufacturing” at Leibniz Universität Hannover. Our book is divided into the following ten original chapters, which we have structured according to the chronology of a development process, but which can also be read in a different order depending on your interests. Chapter two deals with the basics of technology and methodology. It serves to understand the process chain, to structure the technology and arranges essential activities of the development for additive manufacturing along the process model according to VDI 2221. Chapter three deals with methods used to evaluate the potential of additive manufacturing. First, strengths, weaknesses, opportunities and threats of additive manufacturing are discussed qualitatively. This is followed by a potential assessment based on the 10 most important influencing factors. Based on this, a component portfolio analysis is carried out and finally an evaluation catalogue for component selection is presented. Chapter four deals with heuristics and methods that support creative conception and design. In detail, we deal with the topics: Requirements identification, design goals and constructive contradictions, functional structures, effect-engineering, building a product architecture and finally design strategies and the development environment.

Bibliography

5

In chapter five we present restrictive methods for component design. In particular, we address the design guidelines and concrete restrictions. Furthermore, post-processing methods and a cost calculation are presented. In chapter six, the focus is on the machine setup. Besides the material, machine parameters for production are introduced and the most important parameters are described. Building on this, measures for validation and quality assurance are presented in chapter seven. Here we discuss process simulation with the various simulation approaches and present a selection of software tools. Furthermore, process monitoring and control are dealt with. Finally, non-destructive and destructive testing are discussed. In chapter eight, the connections described above are explored in greater depth using eleven examples from our own work. Finally, the implementation aspect will be mapped both in the business model and in the order-to-delivery process. To this end, we will present ten business models related to additive manufacturing in chapter nine, following the methodology of the Business Model Canvas. In chapter ten, we explore the question of whether additive manufacturing is worthwhile at all. In particular, the sustainability aspects are discussed. Finally, the topics of digitalisation and the teaching concept are addressed. The attached glossary is essentially based on conventions of the DIN and VDI guidelines, but was also supplemented by us and is intended to support the readability of this book. The appendix also contains an overview of additive manufacturing processes. Furthermore, our catalogue of design guidelines can be found there as support for the concrete application.

Bibliography 1. Hull, C.W. Apparatus for production of three-dimensional objects by stereolithography, August 8, 1984. 2. Gebhardt, A. Additive Fertigungsverfahren: Additive Manufacturing und 3D-Drucken für Prototyping - Tooling - Produktion, 5., neu bearbeitete und erweiterte Auflage; Hanser: München, 2016, ISBN 978-3446444010. 3. Kranz, J. Methodik und Richtlinien für die Konstruktion von laseradditiv gefertigten Leichtbaustrukturen. Dissertation; Technische Universität Hamburg-Harburg; SpringerVerlag GmbH. 4. Lippert, R.B. Restriktionsgerechtes Gestalten gewichtsoptimierter Strukturbauteile für das Selektive Laserstrahlschmelzen. Dissertation; Gottfried Wilhelm Leibniz Universität Hannover, Hannover, 2018. 5. Deckard, C.R. Method and apparatus for producing parts by selective sintering, October 14, 1987. 6. Wohlers, T.; Campbell, R.I.; Diegel, O.; Kowen, J.; Mostow, N. Wohlers Report 2023: 3D printing and additive manufacturing: global state of the industry; Wohlers Associates: Fort Collins, Colorado, 2023, ISBN 978-1-6220-4966-0. 7. Lachmayer, R.; Bode, B.; Grabe, T.; Rettschlag, K. Integration spezifischer Effekte in Strukturbauteilen mittels additiver Fertigungsverfahren. In Konstruktion für die Additive

1 Introduction

6

8.

9.

10. 11. 12. 13. 14. 15. 16. 17. 18.

Fertigung 2019; Lachmayer, R., Rettschlag, K., Kaierle, S., Eds.; Springer Berlin Heidelberg: Berlin, Heidelberg, 2020; pp 1–10, https://doi.org/10.1007/978-3-662-61149-4_1. Ehlers, T.; Meyer, I.; Oel, M.; Bode, B.; Gembarski, P.C.; Lachmayer, R. Effect-Engineering by Additive Manufacturing. In Innovative Product Development by Additive Manufacturing; Lachmayer, R., Bode, B., Kaierle, S., Eds.; Springer Nature Switzerland AG: Cham, 2022; pp 1–19, https://doi.org/10.1007/978-3-031-05918-6_1. Oel, M.; Rossmann, J.; Bode, B.; Meyer, I.; Ehlers, T.; Hackl, C.M.; Lachmayer, R. Multi-material laser powder bed fusion additive manufacturing of concentrated wound stator teeth. Additive Manufacturing Letters 2023, 7, 100165, https://doi.org/10.1016/j. addlet.2023.100165. Kumke, M. Methodisches Konstruieren von additiv gefertigten Bauteilen; Springer Fachmedien Wiesbaden: Wiesbaden, 2018, ISBN 978-3-658-22208-6. 3D-Druck beleuchtet: Additive Manufacturing auf dem Weg in die Anwendung; Lachmayer, R.; Lippert, R.B.; Fahlbusch, T., Eds.; Springer Vieweg: Berlin, Heidelberg, 2016. Lachmayer, R.; Lippert, R.B. Additive Manufacturing Quantifiziert; Springer Berlin Heidelberg: Berlin, Heidelberg, 2017, ISBN 978-3-662-54112-8. Additive Serienfertigung: Erfolgsfaktoren und Handlungsfelder für die Anwendung; Lachmayer, R.; Lippert, R.B.; Kaierle, S., Eds.; Springer Vieweg: Berlin, Heidelberg, 2018, https://doi.org/10.1007/978-3-662-56463-9. Konstruktion für die Additive Fertigung 2018; Lachmayer, R.; Lippert, R.B.; Kaierle, S., Eds.; Springer Berlin Heidelberg: Berlin, Heidelberg, 2020, https://doi. org/10.1007/978-3-662-59058-4. Konstruktion für die Additive Fertigung 2019; Lachmayer, R.; Rettschlag, K.; Kaierle, S., Eds.; Springer Berlin Heidelberg: Berlin, Heidelberg, 2020, https://doi. org/10.1007/978-3-662-61149-4. Konstruktion für die Additive Fertigung 2020; Lachmayer, R.; Rettschlag, K.; Kaierle, S., Eds.; Springer Vieweg: Berlin, Heidelberg, 2021, https://doi.org/10.1007/978-3-662-63030-3. Innovative Product Development by Additive Manufacturing; Lachmayer, R.; Bode, B.; Kaierle, S., Eds.; Springer Nature Switzerland AG: Cham, 2022. Lachmayer, R.; Bode, B.; Kaierle, S. Innovative Product Development by Additive Manufacturing 2022; Springer International Publishing: Cham, 2023, ISBN 978-3-031-27260-8.

Chapter 2

Basics

Considering the complexity of the topic of additive manufacturing and its implications for product development, a methodology must structure and explain the technical as well as the operational process and recommend concrete methods for finding solutions. In this chapter, we will first discuss the structuring of the topic, the technology and the product creation process in general, as well as specific implications for the topic of additive manufacturing. The various aspects that support an engineer in the design process, such as the concrete procedure, heuristics and methods, tools, specifications and the connecting knowledge base, are then provided in the following chapters. The application areas of additive manufacturing are divided into the areas of rapid prototyping, rapid tooling, direct manufacturing and rapid repair: Rapid prototyping is defined as the “additive fabrication of parts with limited functionality, but with sufficiently well-defined specific characteristics” [VDI3405]. Specific features can be, for example, the geometry and haptics, whereas the materials and construction of the prototypes do not necessarily have to be identical to those of the series parts. Rapid tooling refers to “the use of additive technologies and processes to fabricate end products which are used as tools, moulds and mould inserts” [VDI3405]. A distinction is made between direct and indirect rapid tooling. In direct tooling, the tool inserts are produced by means of additive manufacturing. In the process chain of indirect tooling, the first process step involves additive manufacturing. The downstream process steps can be produced using conventional manufacturing processes. For example, the negative moulds of casting tools can be produced additively and the subsequent production of the tools can be carried out using conventional manufacturing processes.

© Springer-Verlag GmbH Germany, part of Springer Nature 2024 R. Lachmayer et al., Design for Additive Manufacturing, https://doi.org/10.1007/978-3-662-68463-4_2

7

2 Basics

8

Direct manufacturing is the additive fabrication of end products [VDI3405]. Additive repair is to be classified in the product life cycle in the use phase and is described as the use of an “additive manufacturing process for reconstructing and modifying prebuilt parts” [1, 2]. The main area of application is the repair of capital goods. Figure 2.1 shows the chronological order of the application areas of additive manufacturing in the context of the product creation process [3]. In the initial development phases, physical models produced by means of rapid prototyping can be used to generate development-relevant information for the early validation of product characteristics [4, 5] and, in particular, development times can be shortened through the rapid provision of samples. Rapid tooling is allocated to pre-series and small series and thus lies between rapid prototyping and direct manufacturing in the product creation process. Direct manufacturing can be used as a substitute for conventional manufacturing processes to produce end products. This makes it possible to dispense with tools and tool designs and is excellently suited for small quantities. The disadvantages of direct manufacturing are the long machine running times and often the quality assurance of the material properties, as well as the post-processing due to the “only” near-net-shape geometry [5]. A sub-area of tool and mould making can also be assigned to Direct Manufacturing, as tools or moulds can also be end products, depending on the perspective. Following product design, the additive repair can be used to reengineer and repair worn capital goods, also in combination with property improvements [1, 2, 6]. In the past, rapid prototyping dominated the applications of additive manufacturing technologies, whereas in recent years rapid tooling and direct manufacturing have dominated [7]. Additively manufactured end products increased in 2022,

Additive repair

Fig. 2.1  Additive manufacturing in the product creation process [3]

Service

Spare parts/ refurbishment

Series

Reengineering/ 3D scan

Small series

Direct Mounting

Preseries

Direct manufacturing

Direct tooling

Technical prototype

Prototype

Geometry / functional prototype

Concept model/ design prototype

Design

Rapid tooling

Indirect tooling

Rapid prototyping

2.1  Process Chain

9

taking the largest share with about 62% of the application areas [7]. The profit that could be achieved through additively manufactured end products increased by approx. 21% compared to the previous year [7]. The reason for this is the further development of the processes, with which part properties can now be achieved that in some cases exceed the quality of conventionally manufactured parts [4, 8]. But thinking in terms of new business models and the digitalisation discussion are also fuelling the development. The largest sectors in the manufacture of additively manufactured end products, measured in terms of global turnover, are the automotive industry, aviation and consumer products, each with around 15%. With the rise of additively manufactured end products, design for additive manufacturing is also coming into focus.

2.1 Process Chain If we look at additive manufacturing from the perspective of a new development or the product creation process, it is always, as shown in Fig. 2.2 it is always embedded in the context of a process chain consisting of design, pre-process, in-process, post-process and finishing.

2.1.1 Product Design The basic prerequisite for the production of physical objects by means of additive manufacturing processes is the availability of digital and completely closed Product design

CAP Pre-process

CAM In-process

CAM Post-process

Specify requirement

Data transfer

Material selection

Software print preparation

Build cycle

Separating from build platform

Design goals

Part placement

Cleaning

Sandblasting

Design methods

Process monitoring

Slicing

Photo shoots

Separating support structures

Vibratory grinding

Simulation / Optimisation Topology optimisation

Machine setup

High-speed camera

Verification

Functional surfaces

Manufacturing simulation Residual stresses

Pyrometry

Strength simulation Lifetime simulation

Warpage

Restrictionoriented design

Concepts for post-process

Finishing Thermal finishing

Part removal

Net-shape geometry

Fig. 2.2  Process chain of additive manufacturing

Visual inspection Evaluate process monitoring

Mechanical finishing

Coating Quality control Non-destructive testing

Destructive testing

10

2 Basics

three-dimensional volume models. There are basically three ways to generate such digital volume models: • Direct modelling in a 3D CAD system (Computer Aided Design) • Use of existing models • 3D digitisation (e.g. 3D scan) with subsequent data preparation. After the digital object data has been created (either by forward engineering or reverse engineering), it is usually made available as a standardised facet model in STL (Standard Triangulation Language; *.stl) or AMF (Additive Manufacturing Format; *.amf) for subsequent processes (see also Chapter 6). Forward engineering is the direct modelling in CAD and reverse engineering is the 3D digitisation of existing components. However, the design process for additive manufacturing includes many other activities such as planning, material selection, simulation and optimisation as well as the consideration of manufacturing restrictions, which will be discussed in detail below.

2.1.2 Pre-Process (Computer Aided Planning) In some systems, the pre-process is carried out directly in the machinery software, while other systems use separate software such as Cura, Netfabb or Magics to prepare the data. In this software, the first step is to place the part in the build space and support structures are created. The data is then prepared according to the process. This process includes the slice process, which is necessary for all additive technologies. This describes the cutting of the facet model into layers according to the process-defined layer thickness and the simultaneous determination of the layer information or contour lines per layer as well as the definition of further machine parameters. For example, laser power and scanning speed, material properties or filament feed can be set in the machine setup [9]. Sometimes process simulations are carried out at this point, based on the settings made, in order to detect and minimise residual stresses or thermal distortion. This is to ensure that no quality problems or process interruptions occur in the build cycle. Depending on the additive manufacturing process, the subsequent machine setup also includes the setting of the build space and build platform temperature or the definition of a inert gas atmosphere. Before the actual build cycle can begin, the machine must then be loaded with build platform, material and, if necessary, inert gas.

2.1.3 In-Process (Computer Aided Manufacturing) In the automated build cycle the desired objects are now built up layer by layer. In terms of materials, material supply and bonding mechanisms (e.g. fusing, fusing via binder, bonding, UV curing), a variety of processes are used, which differ

2.2  Overview of Additive Manufacturing Processes

11

greatly in terms of the energy required, the part size that can be realised, the part quality and the costs that arise [9]. So far, the engineering-relevant material groups of plastics (thermoplastics and thermosets), metals, ceramics and, to a certain extent, even glass can be processed. Camera or pyrometer-based process monitoring detects quality problems and enables intervention and readjustment or documents the successful in-process.

2.1.4 Post-Process Depending on the manufacturing process and part requirements, the in-process is followed by a more or less complex post-process [10]. In this process, the part is separated from the build platform, it is cleaned of excess material and support structures are removed. The excess material is recycled and reused. Quality assurance measures, such as measuring or x-raying the part, can be carried out on a random basis.

2.1.5 Finishing As a rule, the functional surfaces of the parts must be mechanically prepared in a further finishing step. Depending on the additive manufacturing process selected, the part can also be subjected to heat treatment to homogenise the material and reduce internal stresses. Furthermore, chemical or optical post-processing is possible and often recommended, especially for corrosion protection or for design-relevant parts [11, 12].

2.2 Overview of Additive Manufacturing Processes In order to describe, classify and differentiate between the numerous manufacturing processes, the method shown in Fig. 2.3 is used in the following to describe the numerous manufacturing processes. It classifies the processes according to the aggregate state of the processed material (solid or liquid), the form in which the material is provided (powder, strand, film or liquid) and the bonding mechanism used (direct thermal fusion, fusion via binder, bonding or curing using UV). In the main part of the design catalogue, essential additive manufacturing processes are listed. In addition to numerous publications, the processes of additive manufacturing are also described in VDI Guideline 3405 [12]. Therefore, in the following, only the structure and build cycle for fused layer modelling (FLM) for processing thermoplastic filaments, Powder bed fusion (PBF) for creating parts

Feedstock

Powder

State of matter

Material Jetting (MJT)

Vat Photopolymerization (VPP)

X

Multi-Jet Modeling (MJM)

Digital Light Processing (DLP)

Two-Photon Polymerization (2PP)

Stereolithography (SLA)

X

X

X

X

Laminated Object Manufacturing (LOM) X

Wire-Based Directed Energy Deposition (W-DED)

Directed Energy Deposition (DED)

Sheet Lamination (SHL)

Fused Filament Fabrication (FFF)

Material Extrusion (MEX)

Binder Jetting (BJT)

Binder Jetting (BJT)

X

X

X

X

Powder-Based Directed Energy Deposition (P-DED)

Directed Energy Deposition (DED)

X

X

Metals X

X

X

Polymers

Powder Bed Fusion of Metals Using an Electron Beam (PBF-EB/M)

Powder Bed Fusion (PBF)

Powder Bed Fusion of Polymers Using a Laser Beam (PBF-LB/P) Powder Bed Fusion of Metals Using a Laser Beam (PBF-LB/M)

Process description

Ceramics > 200

10 - 100 X

> 100

> 200

10 - 100 X

10 - 100 X

< 10

Layer thickness [µm] 45° 2

Pedals

1

Bottom bracket

design space

Active area

18 2 Basics

Bibliography

19

Bibliography 1. Zghair, Y. Rapid Repair hochwertiger Investitionsgüter. In 3D-Druck beleuchtet: Additive Manufacturing auf dem Weg in die Anwendung; Lachmayer, R., Lippert, R.B., Fahlbusch, T., Eds.; Springer Vieweg: Berlin, Heidelberg, 2016; pp 57–69, https://doi. org/10.1007/978-3-662-49056-3_6. 2. Zghair, Y.A. Additive repair design process for aluminium components. Dissertation; Gottfried Wilhelm Leibniz Universität Hannover, 2019. 3. 3D-Druck beleuchtet: Additive Manufacturing auf dem Weg in die Anwendung; Lachmayer, R.; Lippert, R.B.; Fahlbusch, T., Eds.; Springer Vieweg: Berlin, Heidelberg, 2016. 4. Gebhardt, A. Additive Fertigungsverfahren: Additive Manufacturing und 3D-Drucken für Prototyping—Tooling—Produktion, 5., neu bearbeitete und erweiterte Auflage; Hanser: München, 2016, ISBN 978-3446444010. 5. Lippert, R.B. Restriktionsgerechtes Gestalten gewichtsoptimierter Strukturbauteile für das Selektive Laserstrahlschmelzen. Dissertation; Gottfried Wilhelm Leibniz Universität Hannover, Hannover, 2018. 6. Ganter, N.V.; Ehlers, T.; Oel, M.; Behrens, B.-A.; Müller, P.; Hübner, S.; Althaus, P.; Bode, B.; Lachmayer, R. Do Additive Manufacturing Processes Enable More Sustainable Products? Circulation of Metallic Components Through Repair and Refurbishment by the Example of a Deep-Drawing Tool. In Innovative Product Development by Additive Manufacturing 2022; Lachmayer, R., Bode, B., Kaierle, S., Eds.; Springer International Publishing: Cham, 2023; pp 1–14, https://doi.org/10.1007/978-3-031-27261-5_1. 7. Wohlers, T.; Campbell, R.I.; Diegel, O.; Kowen, J.; Mostow, N. Wohlers Report 2023: 3D printing and additive manufacturing: global state of the industry; Wohlers Associates: Fort Collins, Colorado, 2023, ISBN 978-1-6220-4966-0. 8. Kranz, J. Methodik und Richtlinien für die Konstruktion von laseradditiv gefertigten Leichtbaustrukturen. Dissertation; Technische Universität Hamburg-Harburg; SpringerVerlag GmbH. 9. Kruth, J.-P.; Leu, M.C.; Nakagawa, T. Progress in Additive Manufacturing and Rapid Prototyping. CIRP Annals 1998, 47, 525–540, https://doi.org/10.1016/ S0007-8506(07)63240-5. 10. Frazier, W.E. Metal Additive Manufacturing: A Review. J. of Materi Eng and Perform 2014, 23, 1917–1928, https://doi.org/10.1007/s11665-014-0958-z. 11. Additive Serienfertigung: Erfolgsfaktoren und Handlungsfelder für die Anwendung; Lachmayer, R.; Lippert, R.B.; Kaierle, S., Eds.; Springer Vieweg: Berlin, Heidelberg, 2018, https://doi.org/10.1007/978-3-662-56463-9. 12. VDI Gesellschaft Produktion und Logistik. Additive Fertigungsverfahren: Grundlagen, Begriffe, Verfahrensbeschreibungen; Beuth Verlag: Berlin, 2014 (VDI 3405).

Chapter 3

Component Selection

The question of when and with what benefit additive manufacturing processes can be used in an industrial context is not easy to clarify and is often answered with rapid prototyping, small quantities or lightweight design. Occasionally, attempts are also made to convert components designed for classic manufacturing processes to additive manufacturing. To show that the strengths of the technology, especially in relation to additive “series production”, are much greater and more diverse, and how to recognise and implement them, is to be a major contribution of this book. The impressive compilation of successful applications of the technology shown in Fig. 3.1 and 3.2 should serve as motivation. In the following, an examination of the strengths, weaknesses, opportunities and risks of additive manufacturing is carried out to support the company's own idea generation and planning. Subsequently, methods of assessing the potential in the corporate context are presented and aspects and criteria of suitability in principle are discussed. This is followed by a component portfolio analysis. Finally, an evaluation catalogue for component suitability for additive manufacturing is discussed for this chapter.

3.1 SWOT Analysis The necessity of a development methodology for additive manufacturing is also based on the analysis of its strengths, weaknesses, opportunities and threats (SWOT analysis). On the one hand, this again shows the complexity of the topic and thus the challenges for its sensible use, but also the answers to be found by engineers with regard to the identification of potential and implementation in the development process.

© Springer-Verlag GmbH Germany, part of Springer Nature 2024 R. Lachmayer et al., Design for Additive Manufacturing, https://doi.org/10.1007/978-3-662-68463-4_3

21

22

3  Component Selection

Fig. 3.1  Additive manufacturing, Source: 1) Trumpf, 2) DMG Mori, 3) SLM Solutions, 4) IPeG Hannover

3.1  SWOT Analysis

23

Fig. 3.2  Additive manufacturing, Source: 1) DMG Mori, 2) SLM Solutions, 3) Prof. Kowalski, 4) EOS, 5) IPeG Hannover

24

3  Component Selection

Strengths, like weaknesses, describe the technology in the here and now, according to the method used here. Opportunities and risks, on the other hand, refer to the future and in this respect always only offer an assessment in relation to the progress that seems likely today.

3.1.1 Strengths The strengths of additive manufacturing technologies lie in very different areas: Through the simple production of prototypes and functional samples, errors in product design can be avoided. This results in a reduction of the development time and improvement of the development result. Due to the voxel-wise material application in additive manufacturing, complicated geometries can be created relatively easily and there is design freedom and design space that cannot be realised in other manufacturing processes or only with greater technical and economic effort. This allows designers and artists new forms of expression and, in industrial applications, the production of topology- and shape-optimised parts. Complex parts can be manufactured without tools within a few hours. The machine operator is only required for data and material loading and at the end of the build cycle for part removal and post-processing, while the actual manufacturing process runs automatically. In industrial manufacturing, a significant cost and time factor is the production of tools and assembly aids. For these, conventional manufacturing processes can often be replaced by additive manufacturing, so that an economic advantage also results here and solutions are generated more quickly. Additive manufacturing offers another economic advantage in spare parts management. If delivery times are long or spare parts are no longer available, they can be quickly reprinted or worn components can be repaired using additive repair. This enables a fast supply of spare parts and thus low downtimes of machines and systems. Additive manufacturing enables product individualisation with the aim of personalisation or differentiation to specific needs. Requirements of mass customisation, modular product structures and thus differentiation strategies can be supported in this way. Ultra-lightweight concepts can be realised through new design approaches, e.g. from bionics and internal structures in components as well as topology optimisation, using additive manufacturing. In this way, resources can be saved both in manufacturing and in moving masses over the product life cycle. Thanks to a high degree of design freedom, new functions can also be integrated into a part, such as internal cooling channels. A high level of functional integration also leads to less assembly work and, as a rule, a reduced number of parts as well as smaller insatallation space.

3.1  SWOT Analysis

25

Production processes can be decentralised through digital models and high manufacturing flexibility of individual additive manufacturing systems. This simplifies the use of contract manufacturing in the process chain and, if particularly pronounced, can itself lead to the customer taking on the role of producer by printing out purchased models themselves. Parts can be produced on site using additive manufacturing without major logistics costs, thus saving storage and logistics costs if necessary. Effects can be optimised and disturbance variables reduced through additive manufacturing. “In summary, in terms of product design, it can be said that additive manufacturing can be used primarily to address essential aspects of design complexity and overcome limitations. These include in detail: • the shape complexity (through, e.g. topology-optimised shape) • the hierarchical complexity through micro and macro structures • Material complexity in the sense of inhomogeneities or material mixtures (gradations) deliberately introduced into the material. • Logistical complexity • as well as the Functional Complexity through Functional Integration” [1].

3.1.2 Weaknesses The manufacturing process of additive manufacturing usually takes place within a relatively small build chamber on most machines, which in some processes must be completely filled with feedstock and limits the part size. This contrasts with processes such as fused layer modelling and directed energy deposition, whose build chambers can be quite large or which can be carried out freely in space using robots. Here, the physical limitations lie in the achievable accuracy. Due to the often long process times in the in-process, high machine costs are incurred for the production of additive components and the specially prepared raw materials are also often expensive. Due to the primary shaping character of additive manufacturing, quality assurance places high demands on the monitoring of machines and raw materials in order to document demonstrably flawless components. Contrary to common perception, additive manufacturing does not work without residual material. Depending on the process, this results from scrap, support material, but also from residual material from the process that can only be reused proportionally. The commercialisation of 3D printers for home use in particular is expected to increase the environmental impact of the increased production of plastic parts. Depending on the process and material, additive manufacturing can release emissions that are dangerous to humans. These are, for example, toxic fumes when melting certain plastics or fine metal powder in the inhaled air. To prevent damage

26

3  Component Selection

to health, protective measures are therefore prescribed for personnel in industry. There are currently no legal regulations for the home use of 3D printers. Long manufacturing times in the in-process make it impossible to integrate today's additive manufacturing into interlinked production. A significant increase in process speed or the rethinking of system concepts would be necessary to remedy this. Approaches are being pursued, for example, by parallelising systems and print heads for material application. But the handling of pre- and post-processes is also the focus of rationalisation.

3.1.3 Opportunities The materials, processes and machines of additive manufacturing are continuously being developed and expanded [2]. Opportunities in the area of materials range from the manufacture of porous or graded materials to the processing of composite materials and bio-printing, i.e. the production of patient-specific organs from bioresorbable or biocompatible materials and cells [3]. Additive manufacturing also offers innovation potential for food printing and the production and 3D reconstruction of art [4, 5]. Additive manufacturing makes it possible to reduce the amount of material used in order to achieve improved material utilisation and consequently minimise waste. Components can be manufactured with optimised topology and shape and the best possible material distribution. In addition, the design freedom of additive manufacturing opens up a multitude of further potentials for part design, e.g. for vibration reduction [6–8]. The methodical support of product design is a field of research that has grown rapidly in recent years [2]. Future research is expected to increasingly address the design of parts with sensory and actuator properties through variable shape features, often referred to as 4D printing. The part costs currently imply a high innovation premium, since machines and starting materials are expensive for initially small quantities and volumes. Due to the generally low proportion of human labour, the opportunity lies in a significant price reduction with increasing efficiency of the systems and thus on the space-grabbing of the processes for even medium batch sizes. New research areas have developed that address the integration of additive manufacturing into industrial production, for example in the field of hybrid additive manufacturing as well as inspection and quality assurance [2, 3]. New business models arise from the megatrends of digitalisation, individualisation and especially in the context of product service systems. These are, for example, co-design, the shift of value chains, training concepts and the sale of highly specialised machines and CAD models. Success factors for the development towards data-driven business models include software-related engineering resources, cyber security and data security, as well as agile development environments and methods [9].

3.2  Potential Assessment

27

3.1.4 Risks Replications enable new dimensions of product piracy. In this context, 3D scanners as well as file-sharing networks pose a risk to the protection of intellectual property. Individual parts in particular can be easily replicated, so that existing business models (cheap acquisition, expensive maintenance) become redundant. Through the home use of 3D printers, geometries can be modelled and materialised at will, without taking legal regulations into account. This applies to intellectual property protection as well as to the production of prohibited items or safety–critical applications, such as the use of unsuitable materials and geometries for children's toys. The possibilities of decentralised manufacturing give rise to new questions regarding product liability. In the event of major damage or injury to a person, the question of the responsibility of the machine manufacturer, material supplier, CAD model provider and machine operator arises. The same questions apply to quality aspects and certifications. Cornell Bioengineer succeeded in producing an artificial ear that behaves and looks natural. The company “Organovo”, prints liver cells as well as eye tissue cells. Scientists have also mixed human stem cells with muscle cells from dogs to create an improved organ tissue. Ethical risks of bioengineering are not specific to additive manufacturing, however, but will need to be discussed at many other points of development as technical possibilities grow.

3.2 Potential Assessment For a potential assessment of whether a component or assembly is suitable for additive manufacturing, evaluation criteria must be identified and quantified. Table 3.1 shows the ten most important evaluation criteria. The quantification of these criteria depends to a large extent on the business model and the available machinery. The continuous development of machine technologies also influences the evaluation variables. Examples include the processing possibilities of new materials or the production of larger parts as a result of larger build spaces. For this reason, only the evaluation criteria are described in detail below.

3.2.1 Number of Pieces Additive manufacturing plays out its strengths particularly in small lot sizes (see Fig. 3.3). This is due to the fact that there is no need to build tools, assembly aids or elaborate work preparation and post-processing. The costs of additive manufacturing are often higher for larger quantities in small series or serial production.

3  Component Selection

28 Table 3.1  Assessment criteria for evaluating component suitability Evaluation criterion Number of pieces Degree of individualisation The complexity of geometry

Material Weight Production time Post-processing Size Nesting

Ecological sustainability

Rating size and scaling Small number of pieces; medium number of pieces; large number of pieces Evaluation based on the influence the customer has on value creation Evaluation based on the volume, the surface area, and the number of holes of the component—The more complicated, the more interesting for AM KO—criterion if no printable material can be used Evaluation based on the ratio of component volume to envelope volume Evaluation on the basis of the production height Evaluation based on the proportion of the surface that is reworked Evaluation based on the size of the envelope—Limitation due to build space dimensions of AM machines Evaluation based on the ratio of all part volumes of a build cycle to the build space cross-section multiplied by the build height Assessment on the basis of the CO2-emission of the part in relation to a reference value

Costs per part

Conventional manufacturing

Additive manufacturing

Lot size

Fig. 3.3  Exemplary progression of costs per component plotted against lot size

Nevertheless, there may also be potential for additive manufacturing here if additive manufacturing can realise significant added value in the use phase. An example of this is a piston of an internal combustion engine, where pollutant emissions can be reduced and the overall efficiency increased.

3.2  Potential Assessment

29

3.2.2 Degree of Individualisation Figure 3.4 shows how the acceptance curve for additive manufacturing depends on the degree of individualisation and the lot size and that there is considerable potential in the area of individualised production in particular. Possible examples in individualised mass production could be the production of customised implants or personalised clothing.

3.2.3 The Complexity of Geometry In Fig. 3.5 shows the relationship between the complexity of the part and the manufacturing costs in comparison with conventional manufacturing and additive manufacturing. In this context, additive manufacturing is often associated with the slogan “Complexity for Free”, which we do not entirely share, as complexity always means additional expenditure and should therefore always be designed to be as simple as possible. On the other hand, it is true that complexity is easier to master with additive manufacturing than, for example, with pure machining. Furthermore, in Fig. 3.5 there is an area in which solutions can only be realised by means of additive manufacturing.

3.2.4 Material All materials that can be processed into powder, strand, film, wax or resin are basically suitable for additive manufacturing of plastics, metals, ceramics or even glass or concrete. In practice, however, the variety of materials is limited due to the

Unsuitable for Additive manufacturing

Lot size

Generalised mass production

Generalised single-part production

Potential for Additive manufacturing Individualised mass production

Individualised single-part production

Degree of individualisation

Fig. 3.4  Portfolio of suitability for additive manufacturing depending on lot size and degree of customisation

3  Component Selection

Manufacturing costs

30

Additive manufacturing

Conventional manufacturing

Break-even point Conventionally not producible low

medium

Conventional Design

Part complexity

high

Design for additive manufacturing

Fig. 3.5  Complexity for free

business models of the material manufacturers. The following is a brief overview of the common materials in powder bed-based additive manufacturing. In the case of plastics, mainly PAEK, PA 11, PA 12, TPE, PS and PP are processed in PBFLB/P. In the case of metals, around 30 metal alloys for processing in PBF-LB/M are in the portfolio of the system manufacturers. These include mainly aluminium alloys, stainless steel, titanium, nickel-based alloys, tool steel, but also copper and cobalt-chromium alloys. Aluminium alloys were the most profitable materials in 2022, with a market share of around 25% [10]. Special alloys can sometimes be purchased from manufacturers at extra cost. Finally, it should be noted that the mechanical properties of additively manufactured parts can keep up with those of conventionally manufactured parts, especially for metals.

3.2.5 Weight The lower the weight of the part compared to the raw part needed for machining, the higher the potential for additive manufacturing. A high material saving indicates that conventional manufacturing can be more expensive or resources can be saved in the use phase. In Fig. 3.6 shows a reflector of a car for which an approx. 80% higher raw material utilisation could be achieved for additive manufacturing (PBF-LB/M) compared to conventional manufacturing (milling). In this case, this considerable increase in raw material utilisation means that the component is suitable for additive manufacturing.

3.2  Potential Assessment

31

Raw material utilisation approx. 3.5 %

Raw material for milling

End product Raw material utilisation approx. 85 % Raw material for PBF-LB/M

Fig. 3.6  Comparison of raw material utilisation using the example of a reflector

3.2.6 Production Time In order to keep the production time and thus the production costs low, the build height should be as low as possible. Flat parts that can be manufactured horizontally have a high potential for additive manufacturing.

3.2.7 Post-Processing When evaluating the post-processing effort, attention should be paid to net-shape geometries. In particular, it should be evaluated how much volume of support structures is used compared to the part volume, as the removal of support structures involves manual effort. Furthermore, accessibility to functional surfaces for post-processing should be given in order to produce fitting surfaces or tolerances. It should also be ensured that the reclamping operations for the machining finishing should be minimal. Sometimes even assembly aids should be printed directly on the part to simplify post-processing.

32

3  Component Selection

3.2.8 Size The size of the part plays a decisive role in assessing its suitability for additive manufacturing. In particular, the part must fit into the additive manufacturing machine. Chamberless manufacturing systems can produce parts with dimensions of several metres. This includes, for example, the printing of houses made of concrete, or large systems for the directed energy deposition of, for example, rocket structures. In contrast, chamber-based systems such as the PBF have comparatively small build spaces. Thanks to continuous system development, however, components with dimensions larger than 500 × 500 × 500 mm3 can now be produced here as well.

3.2.9 Nesting In addition to the maximum part dimensions, the shape of the part plays a decisive role in part suitability. The aim is to fill the build space with as much part volume as possible up to the desired build height. In order to achieve this, parts are arranged next to each other, the so-called nesting. Nesting is particularly relevant for chamber-based manufacturing processes. In additive manufacturing processes that do not require support structures, the components are often stacked on top of each other. In Fig. 3.7 shows a batch of 3D Benchys for selective laser sintering of plastic. When placing the parts, however, the heat conduction between the parts must also be taken into account in order to prevent part distortion. In addition to placing several identical parts, other parts can also be printed. Especially in the case of bulky parts, additional parts must also be printed in order to increase economic efficiency.

3.2.10 Ecological Sustainability In addition to the pure cost consideration, the ecological footprint is becoming increasingly relevant [11–13]. For this purpose, it is not only the production or the savings in the use phase that must be analysed. Instead, the entire process chain must be taken into account, from the extraction of raw materials, through production and use, to recycling. As a basis for decision-making, the CO2 emissions of additive manufacturing can be compared with those of conventional process chains [11, 14]. It has been shown that the ecological footprint of additive manufacturing in particular is low when materials that are difficult to extract, such as aluminium or titanium, are processed and a lot of material can be saved. Finally, it should be noted that one, two or more criteria can be included in the evaluation of part suitability, depending on the dominance of the design goals.

3.2  Potential Assessment

33

Fig. 3.7  Nesting on the example of a batch of 144 3D Benchys, for production in PBF-LB/PA12

Furthermore, the highest potential for additive manufacturing results when not one of the evaluation criteria addressed here is implemented well, but as many as possible. For some applications in aerospace, however, the aspect of weight, for example, is so dominant that simply the lightest functional part is the solution.

34

3  Component Selection

3.3 Component Portfolio Analysis Often, entire catalogues of components that were previously designed for conventional manufacturing are analysed in order to identify suitable parts for additive manufacturing. It should be noted that the potential can only be identified to a limited extent from the analysis of individual components, but only when several components or entire assemblies are considered. This procedure shows that CAD data is required and that the procedure is often only suitable for an adaptive design. In the case of a new design, on the other hand, an existing component cannot simply be evaluated, but the potential must already be identified in the conceptual design phase. For this purpose, it must be possible to estimate the effort and the required know-how already during the idea generation phase, so that a rough pre-selection can be made with regard to additive or conventional manufacturing. Methodologically, all kinds of intuitive creativity techniques, such as brainstorming, brain writing, method 653, gallery method or five hats method, are available to support this. In the next step, the capabilities and restrictions of the envisaged manufacturing processes must be analysed in order to compare them with the component requirements and to filter out suitable manufacturing processes that can be used in a technically and economically sensible way. If there is insufficient experience of one's own, there is some scientific work that deals with the question of how estimates can be made about the sensible use of additive manufacturing on the basis of general similarities. In order to make predictions on the basis of these similarities, the component geometry does not have to be known in detail. However, quantifiable properties must be recorded that reflect the geometric properties of the part. In addition to the volume, a key figure describing the complexity is usually used to distinguish between simple cubes and more or less complicated parts. Depending on the objective function, however, the potentials that can be found are often very small. Thus, when looking through thousands of parts, often only ten or fewer parts with potential can be defined, of which then, on closer analysis, perhaps only one or two really worthwhile process changes can be identified. In the case of multi-criteria objective functions, the individual degrees of objective fulfilment can also be represented as objective spiders. Figure 3.8 shows the target spider of an additively manufactured special reflector. The maximum target fulfilment is evaluated with 10 points. As an evaluation procedure for assessing the ideas and potentials of additive manufacturing, we also recommend the methods of technical–economic evaluation described in more detail in VDI 2225.

3.4  Evaluation Catalogue for Component Selection

35 Number of pieces

Sustainability

Individualisation

Nesting

Size

Complexity

4 4

6

6

10

8

2 2 Material

Post-processing

Weight

Production time

Fig. 3.8  Target spider for an additively manufactured special reflector

3.4 Evaluation Catalogue for Component Selection In this section, the basic framework of a techno-economic assessment for the ten most important assessment criteria is presented as an example. As already described in Sect. 3.2, it is necessary to determine the weighting of the evaluation criteria separately for each application. In Table 3.2 shows a techno-economic framework for additive manufacturing that can be applied and extended to the corresponding use case.

Table 3.2  Techno-economic framework for additive manufacturing Evaluation criterion Points Small quantities High degree of individualisation Complicated geometry Material available Low weight Low expected production time Low post-processing effort Component size smaller build space size Component can be manufactured well together with other components in one build cycle Ecologically sustainable product design 10

1 2 3 4 5 6 7 8 9

n

…

Overall assessment

Weighting

Score P1 × G1 P2 × G2 P3 × G3 P4 × G4 P5 × G5 P6 × G6 P7 × G7 P8 × G8 P9 × G9 P10 × G10 Pn × Gn

n i=0 Pi ×Gi  n i=0 Gi

36

3  Component Selection

Bibliography 1. Kumke, M. Methodisches Konstruieren von additiv gefertigten Bauteilen; Springer Fachmedien Wiesbaden: Wiesbaden, 2018, ISBN 978-3-658-22208-6. 2. Schmitt, P.; Zorn, S.; Gericke, K. Additive manufacturing research landscape: A literature review. Proc. Des. Soc. 2021, 1, 333–344, https://doi.org/10.1017/pds.2021.34. 3. Tofail, S.A.; Koumoulos, E.P.; Bandyopadhyay, A.; Bose, S.; O’Donoghue, L.; Charitidis, C. Additive manufacturing: scientific and technological challenges, market uptake and opportunities. Materials Today 2018, 21, 22–37, https://doi.org/10.1016/j. mattod.2017.07.001. 4. Ernst & Young Global Limited. 3D printing: hype or game changer?—A Global EY Report 2019, 2019. 5. Rautray, P.; Eisenbart, B. Additive manufacturing—Enabling digital artisans. Proc. Des. Soc. 2021, 1, 323–332, https://doi.org/10.1017/pds.2021.33. 6. Ehlers, T.; Tatzko, S.; Wallaschek, J.; Lachmayer, R. Design of particle dampers for additive manufacturing. Additive Manufacturing 2021, 38, 101752, https://doi.org/10.1016/j. addma.2020.101752. 7. Ehlers, T.; Lachmayer, R. Design of Particle Dampers for Laser Powder Bed Fusion. Applied Sciences 2022, 12, 2237, https://doi.org/10.3390/app12042237. 8. Ehlers, T. Auslegung partikelgedämpfter Strukturbauteile für die Additive Fertigung. Dissertation; Gottfried Wilhelm Leibniz Universität Hannover, Hannover, 2023, https://doi. org/10.15488/13789. 9. Welte, T.; Klipphahn, F.; Schäfer, K. Wie die Luft- und Raumfahrtindustrie von digitalen Geschäftsmodellen und Megatrends profitiert. In Geschäftsmodelle in die Zukunft denken; Tewes, S., Niestroj, B., Tewes, C., Eds.; Springer Fachmedien Wiesbaden: Wiesbaden, 2020; pp 119–130, https://doi.org/10.1007/978-3-658-27214-2_9. 10. Wohlers, T.; Campbell, R.I.; Diegel, O.; Kowen, J.; Mostow, N. Wohlers Report 2023: 3D printing and additive manufacturing: global state of the industry; Wohlers Associates: Fort Collins, Colorado, 2023, ISBN 978-1-6220-4966-0. 11. Ehlers, T.; Wurst, J.; Lachmayer, R. Bewertung der ökologischen und ökonomischen Nachhaltigkeit in der Additiven Fertigung. In Konstruktion für die Additive Fertigung 2019; Lachmayer, R., Rettschlag, K., Kaierle, S., Eds.; Springer Berlin Heidelberg: Berlin, Heidelberg, 2020; pp 177–199, https://doi.org/10.1007/978-3-662-61149-4_12. 12. Wurst, J.; Schneider, J.A.; Ehlers, T.; Mozgova, I.; Lachmayer, R. Corporate Strategy Based Quantitative Assessment of Sustainability Indicators at the Example of a Laser Powder Bed Fusion Process. In Sustainable Design and Manufacturing; Scholz, S.G., Howlett, R.J., Setchi, R., Eds.; Springer Singapore: Singapore, 2022; pp 34–44, https://doi. org/10.1007/978-981-16-6128-0_4. 13. Ganter, N.V.; Ehlers, T.; Oel, M.; Behrens, B.-A.; Müller, P.; Hübner, S.; Althaus, P.; Bode, B.; Lachmayer, R. Do Additive Manufacturing Processes Enable More Sustainable Products? Circulation of Metallic Components Through Repair and Refurbishment by the Example of a Deep-Drawing Tool. In Innovative Product Development by Additive Manufacturing 2022; Lachmayer, R., Bode, B., Kaierle, S., Eds.; Springer International Publishing: Cham, 2023; pp 1–14, https://doi.org/10.1007/978-3-031-27261-5_1. 14. Wurst, J.; Ganter, N.V.; Ehlers, T.; Schneider, J.A.; Lachmayer, R. Assessment of the ecological impact of metal additive repair and refurbishment using powder bed fusion by laser beam based on a multiple case study. Journal of Cleaner Production 2023, 423, 138630, https://doi.org/10.1016/j.jclepro.2023.138630.

Chapter 4

Creative Methods

In the following chapter, the creative methods of “Design with Additive Manufacturing” are presented before the restrictive methods of “Design for Additive Manufacturing” are considered in the following chapter. The creative methods also include the approaches for selecting and evaluating application areas, parts and manufacturing processes, which were already described in the previous chapter. However, the focus is on the use of the design freedoms and potentials for expanding the design space. To this end, in Sect. 4.1 requirements are specified in the form of a checklist, which must be taken into account in additive manufacturing. Subsequently, the design goals and constructive contradictions are presented in Sect. 4.2. It should be emphasised that by pursuing several design goals in the conceptual design phase, a clear added value can be realised compared to conventionally manufactured products. Based on design goals and contradictions, we address the general functional structure in Sect. 4.3, from which the necessity of effect engineering (Sect. 4.4) emerges. Subsequently, in Sect. 4.5, the product architecture is elaborated and approaches from bionics are presented. Based on this, methods for the embodiment design, such as design principles, the one-piece machine method and methods of structural optimisation, are considered in detail in Sect. 4.6. Finally, in Sect. 4.7 discusses the development environment. Figure 4.1 shows the expansion of the solution space in the conceptual design phase through the potentials of additive manufacturing (Design with X) and in the embodiment design/detail design phase the need to limit this space until a concrete solution is found (Design for X). Furthermore, the question arises as to which product design activities the methods from Fig. 4.1 and what their specific characteristics are. For this purpose Table 4.1 assigns the methods, which we will discuss in more detail below, to the various product design activities. Thereby Table 4.1 is not intended to define a rigid sequence of methods and process steps, but rather to represent a flexible selection of suitable methods that can be used according to the type of company and the specific case. Furthermore, in addition to the methods specifically discussed here, all other methods used in the context of design can also be used. © Springer-Verlag GmbH Germany, part of Springer Nature 2024 R. Lachmayer et al., Design for Additive Manufacturing, https://doi.org/10.1007/978-3-662-68463-4_4

37

4  Creative Methods

Design with X

Methods for component selection Chapter 3 • • •

Identifying business models Potential assessment Valuation methods • VDI 2225 • Technical-economic evaluation

Visual objects Application examples Moodboards Checklists

Design for X

Solution

Creative methods for AM Chapter 4 • • • • • • • •

Overarching methods • • • •

Size of the

Task

design space

38

•

Prioritise design goals Function integration Effect-engineering One-piece machine method TRIZ based invention methodology Bionics Use of internal structures FEM simulation and optimisation • Topology optimisation • CFD simulation Intuitive and discursive creativity techniques

Restrictive methods for AM Chapter 5 • • • • • •

• • •

Basic design rules Design principles Design guidelines Process chain design Simulation • Strength simulations • Process simulations Machine preparation • Manufacturing parameters • Laser power • Scanning speed • Exposure strategy • Nesting Post-processing and finishing Post-heat treatment Quality assurance

Fig. 4.1  Component selection, creativity methods, and rules in the context of AM

4.1 Requirement Identification During the transition from pre-development to design, the requirements on the latter must be clarified precisely. In addition to the design goals and the function, the requirements for the design in terms of production-oriented design result from the resources available in the production process as well as a multitude of secondary functions and disturbance variables relevant in the product life cycle. In addition, with regard to the actual design, it must be clarified where the models come from and how their quality can be ensured, as well as which tools are to be used to prepare the data for the machine. With regard to the in-process, the material and machine questions must be answered. For the post-process, the questions of thermal, mechanical and other post-processing of the surfaces must be clarified. In addition, quality assurance and validation play a decisive role. Table 4.2 shows a list for determining the requirements related to additive manufacturing, divided into the process steps design, pre-process, in-process, post-process and finishing.

4.2 Design Goals Hague et al. are the first to describe the effects of additive manufacturing on product design. The design potentials are described in terms of better product performance, cost reduction through substituted assembly steps or the implementation

4.2  Design Goals

39

Table 4.1  Collection of methods for additive manufacturing structured by activities Activities in product design Finding an idea

Clarifying and itemising the problem or task

Determining functions and their structures

Assessing and selecting the solution concept

Subdivision into modules and interface definitions Designing the modules

Elaborating the details of execution and use

Methods and tools with reference for additive manufacturing • Visual objects • Application examples • Moodboards • SWOT analysis • Prioritise design goals • Potential assessment • Identifying business models • Checklists • TRIZ based invention methodology • Bionics • Effect engineering • Use of internal structures • Intuitive and discursive creativity techniques • Visual objects • Application examples • Moodboards • Potential assessment • VDI 2225 • Technical–economic evaluation • Basic design rules • Design principles • Design guidelines • Function integration • One-piece machine method • FEM simulation and optimisation • Topology optimisation • CFD simulation • Strength simulation • Process simulation • Process chain design • Post-process and finishing concepts • Post-heat treatment • Quality assurance • 3D models/STL data sets • Machine preparation

of innovative design elements [1, 2]. Becker et al. describe a list of general design proposals and refer to the potential of function integration and component merging [3]. Burton also targets part merging through additive manufacturing and describes a knowledge transfer tool for designers. [4]. Other works show the design potential of additive manufacturing through specific case studies. Eyers and Dotchev describe the example of product individualisation of medical devices through mass customisation [5]. Petrovic et al. also describe a case study on exploiting the design freedom of additive manufacturing. Here, the design goal of integrated cooling channels is investigated [6]. Bin Maidin et al. describe a comprehensive database of design elements to show designers suggestions during part design [7].

4  Creative Methods

40 Table 4.2  Checklist for determining requirements for AM parts # 1 1.1 1.2 1.3 1.4 1.4.1 1.4.2 1.4.3 1.5 1.6 1.7 1.7.1 1.7.2 1.7.3 1.8 1.9 1.10 1.11 2 2.1 2.2 2.3 2.4 2.5 2.5.1 2.5.2 2.5.3 2.5.4 2.6 2.7 3 3.1 3.2 3.3 3.4 4 4.1 4.2 4.3 4.3 4.4

Criteria Product design Design goal(s) defined Main function(s) defined Secondary function(s) defined Material Material selected Material parameters are available Costs calculated Prioritised design goals Design methods selected Simulation Topology optimisation carried out Strength proven Life span simulated Manufacturing process selected Manufacturing restrictions observed Netshape geometry is available Data formatted in neutral data format Pre-process Effects of part orientation on part properties considered Part built on support structures Part data sliced Machine setup selected Manufacturing process simulation Residual stresses simulated Part warpage simulated and compensated Critical areas identified Support structures optimised Concepts selected for post-process Iterations Shape/Process Post-process Process monitoring selected Part removed from build platform Clean part Verify part Finishing Mechanical finishing Thermal finishing Chemical finishing Quality assurance Component validation

4.2  Design Goals

41

Doubrovski et al. take up this idea and show a concept for a collaboratively editable knowledge database, analogous to a wiki system [8]. With reference to product supply change and process change according to the classification by Boyton, Victor and Pine, the potentials of additive manufacturing lie particularly in the areas of innovation, fast time to market and mass customisation. The scientific papers show that the same or similar design potentials are repeatedly discussed, especially in relation to the PBF-LB/M. As shown in Table 4.3 these can be summarised into eleven design goals [9, 10]. The aspect of time saving is not a design goal in the narrower sense, but it plays a major role in relation to the potential of additive manufacturing, since in many cases shorter throughput times can be realised. In order to ensure a technically sensible and economical use, the parallel fulfilment of several design objectives is often also to be aimed for, whereby it can then make sense to classify main objective and secondary objectives or to carry out a weighting within the multi-criteria objective function. Figure 4.2 shows the link between design goals, design options and concrete added value for the design. The concrete added value that can be achieved through the stringent pursuit of design goals is shown inside the figure. These include, for

Table 4.3  Design goals of additive manufacturing 1.

#

Design goal Material savings

2.

Functional integration

3.

Thin-walled

4.

Force flow adjustment

5.

Integrated channels

6.

Mass customisation

7.

Shaping and design

8.

Net-Shape geometries

9.

Local property adjustment

10.

Internal effects

11.

Time saving

Description Reduction of material use as well as resource savings by increasing material utilisation Implementation of the greatest possible number of technical functions through a minimum use of parts Use of thin-walled and filigree geometries to reduce weight while maintaining constant general conditions Material arrangement according to the stresses for weight reduction or improvement of the mechanical component properties Use of internal ducts to meet specific applications, such as the flow of liquids or the integration of cable routing Adaptation of a part to specific customer requirements through individual solutions or the involvement of the customer in the product design process Implementation of free-form surfaces as well as increasing the ergonomics and usability of a part Implementation of predefined, complicated precast surfaces based on simulation results, such as flow-optimised surfaces or light distributions Local adjustment of the properties of a voxel by material grading or parameter variation Implementation of actuator or sensory properties by means of powder displacements, variation of the melting behaviour or geometric measures Rapid Prototyping, Rapid Repair, Rapid-X

Fig. 4.2  Linking design goals, design options and concrete added value

Integrated channels

Flow improvement

Function extension

Cooling close to contours Surface textures Large cross-section changes Free radius design Undercuts Free-form surfaces Internal structures Porous structures

Heat transfer improvement

Isolation improvement

Energy absorption enhancement

Höhere Effizienz bei der Energiewandlung und Transport

Improvement in design, optics and aesthetics

Reduced Postprocessing effort

Reliability increase

Assembly facilitation

Internal effects Sustainability improvement Smart components Stress reduction Weight reduction Damping improvement

Material savings

Continuous material transitions Embedding of additional parts Powder embedding Multi-material design

Function adjustment Outer lattice structures Surface textures Undercuts Mass customisation Free-form surfaces Small distances between features Embedding of additional parts Function extension Surface textures Small distances between features Elements that move in themselves Undercuts Free-form surfaces Integral design

Shaping and design

Cooling close to contour Elements that move in themselves Functional integration Self-supporting overhangs Free-form surfaces Internal structures

Net-Shape geometries

Local property adjustment

Assign different properties to each voxel Continuous material transitions Variation of part density Powder embedding Multi-material design Internal structures Wall thickness combination

Wall thickness combination Joint reduction Sandwich design Small distances between features Multi-material design Thin-walled Internal structures Integral design

Bionic Design Topology Optimisation Undercuts Joint reduction Free-form surfaces Internal structures Wall thickness combination Continuous material transitions

Force flow adjustment

Bionic design Internal structures Small distances between features Free-form surfaces

Thin-walled

Functional integration

Cooling close to contour Elements that move in themselves Small distances between features Multi-material design Free-form surfaces Internal structures Embedding of additional parts Integral construction

42 4  Creative Methods

4.3  Setting up Functional Structures

43

example, stress reduction, damping improvement or flow improvement. In order to achieve this added value, the corresponding design options are arranged on the outside. The individual design goals link the concrete added value and the design options.

4.3 Setting up Functional Structures Additive manufacturing offers special possibilities here, as the designer is given a lot of freedom in terms of design compared to other manufacturing processes. On the one hand, this refers to the design of the geometry: • • • •

Shape—free-form surfaces and function integration Topology—also for example internal structures Dimensions—up to multiscale number of surfaces—relatively low complexity.

But there is also scope for design with regard to the material parameter by leaving the paradigm of the homogeneous material: • Material parameters in the part can be graded by machine settings and thus material grading can be used in a targeted manner. • Also, depending on the process, materials can be combined in the process and thus multi-material parts can be realised. After the problem formulation has been completed and the design goals have been defined and prioritised, the main function can be derived. The main function is to be formulated in a solution-neutral way and is composed of the following aspects: energy, material and/or signal conversion [11]. In order to describe the main function as precisely as possible, it must be divided into sub-functions in the next step. By breaking down the main function into sub-functions, the degree of complexity is also reduced and the overall task is thus manageable. The result is a functional structure. It must be taken into account that the solution neutrality decreases with increasing concretisation. An important point in the conceptual design phase is the identification of conflicting goals from the functional structure. At this point, the potential of additive manufacturing can be specifically addressed, for example, by solving the conflict of objectives of high stiffness and high damping at the same time through the effect of particle damping. Furthermore, multi-material manufacturing can be used specifically to realise local property adjustments. The added value that comes with this is a higher degree of functional integration and better part performance. So far, there is only a small selection of additive-specific solution principles and methods for the realisation of sub-functions, so the method of effect engineering is examined in more detail in the following section.

44

4  Creative Methods

4.4 Effect Engineering The challenges facing our society are manifold and range from the generation of sustainable energy to nationwide mobility and healthcare. Examples include efficient power plants and energy storage systems as well as vehicle drive concepts, but also durable and affordable prostheses and implants. Limited resources are available to meet these challenges. This requires products that fulfil their function in an energy- and material-efficient way throughout their entire life cycle [12–14]. Engineers realise the functions of products at component and system level with the help of effects that are based on natural laws [15]. The part shape is described by geometry and material. Additive manufacturing technology enables design and material freedom, such as internal structures and graded materials [16, 17]. This makes it possible to manufacture ultra-light components with high load-bearing capacity and functional integration in a resource-saving way. Effects as effective principles can be implemented in this way in a novel, improved, individual or combined way. However, only initial approaches are known for this, which only show the basic functionality and are mostly of an exploratory nature. For the next generation of product design of structural components, the technology of additive manufacturing therefore promises great potential for optimisation [16]. There is now a whole series of scientific papers on design for additive manufacturing (DfAM), its potential and the associated process [18–21]. Although the further development of manufacturing and process technology is being intensively accompanied scientifically, there is still a need for research with regard to the interaction between the manufacturing process and the effects to be realised. The question of how to design for additive manufacturing processes has also received little attention so far in the DfAM research field [9, 21]. Only a few papers deal with the realisation and optimisation of effects through additive manufacturing. [22–25] or the question of adapting the design process and suitable procedures, methods and tools for the product design of additively manufactured parts [21]. The decisive phases of conceptual design and embodiment design have so far been analysed methodically only to a limited extent [21, 26, 27]. Yet it is precisely here that the potential lies for influencing their efficiency and the controllability of disturbance variables by integrating and combining effects [15]. In particular, the focus should be on the core components of machines. Thus, effects such as damping and structural properties [28], heat and mass transport [29] as well as the guidance of electric or magnetic fields [30] can be combined. Any contradictions in the design of the effects can be significantly reduced by means of additive manufacturing [16, 18]. The aim should therefore be to realise effects through additive manufacturing in such a way that they guarantee optimum functionality with minimum use of resources. If several functions, for example the conduction of magnetic flux, the reduction of eddy currents and heat transport, are to be realised simultaneously, the interactions are decisive and must be researched and implemented with regard

4.4  Effect Engineering

45

to multi-criteria optimisation [31]. To achieve these goals, theory-based concepts and models for the implementation of functions through “printed effects” must be developed, which exploit the material-technical and constructive design possibilities of additive manufacturing. This requires precise knowledge of the interactions between material, manufacturing process and part design. For this purpose, the method of effect engineering [32] will be discussed below, with the help of which efficient products with a high degree of functional integration can be manufactured in the future. The potential of effect engineering will then be demonstrated using an application example. Finally, new manufacturing technologies in additive manufacturing are presented, which are essential for the implementation of effect engineering.

4.4.1 Potentials of Effect Engineering Requirements are the basis of every product design. The requirements result from the overriding objectives, such as a reduction in the use of resources or an increase in efficiency or service life. The starting point for product design can also be social aspects such as the customer's desire for increasingly individualised products [33] or the improvement of existing product properties [34] e.g. the increase of performance or an improved biocompatibility of materials [35]. The derived requirements for the product are broken down into required product properties and functions [15]. Properties are measurable values that the part must fulfil, such as an efficiency or a maximum weight. Functions are, among other things, the conversion of energy, signal or information. For this purpose, the function can be divided into sub-functions. To achieve the defined (partial) functions, suitable effects are combined and implemented in the shape of a component. To implement novel design methodologies, it is necessary to extend the existing limits of manufacturing. The combination of different materials through multi-material manufacturing requires a comprehensive understanding of the material system thus created and thus a complete reconsideration of the manufacturing parameters. New concepts must also be developed for both manufacturing and recycling. Figure 4.3 shows the printed effects in the context of the development methodology to explain the connection. The design freedom of additive processes results in outstanding opportunities to mitigate conflicting goals that typically occur in the development process and thus to realise functions more efficiently in parts. Up to now, parts to be manufactured additively have already been designed with regard to thermal and mechanical properties [36–38]. However, the conceptual design is only based on experience. A holistic and systematic approach is lacking [39]. Typically, in order to solve conflicting goals in development, contradictory “disturbing” effects are outsourced to sub-modules and each module is optimised on its own. This means that potentials with regard to the higher-level objectives of product design are not exploited. However, the higher the realisable degree

4  Creative Methods

46 Create prototypes

"Printed effects"

Validation of the function

Matching the properties

Shape

Realisation

Properties

Task clari-

fication conceptual design embodiment design

Development methodology

detail design

Process management

Functions Requirements

Ecological

Economic

Social

Goals

Fig. 4.3  Development methodology for integrated, high-efficiency, “printed effects” [32]

of effect integration, the better these higher-level objectives are implemented. Therefore, a new approach is needed in product design that takes a holistic view of the effects and attempts to optimise them not individually but in combination. Thus, there is an essential need for research to combine effects and to identify a compromise between contradictory effects, to methodically process them and to optimise the design on this basis. A successful approach to resolving constructive contradictions is TRIZ or the further development TRIZ REVERSE [40–43]. TRIZ is a collection of methods for the systematic design of innovative products. As a result, a methodical tool is available with which contradictions in technical systems can be specifically identified and solved [41]. One of these methodological tools is the contradiction matrix in combination with the innovative principles [40, 41]. The innovative principles provide a solution approach for each contradiction, but not a complete solution [41]. The engineer's empirical knowledge is still required to design the solution approach. In Fig. 4.4 shows an excerpt of the contradiction matrix. In total, the contradiction matrix contains 39 (technical) parameters, with the improving parameters listed on the left margin and the worsening parameters on the top margin. In the access part of the matrix, the innovative principles for solving the contradictions are listed. The intersection of the improving and the worsening parameters in the matrix indicates the innovative principles for solving the contradiction.

4.4  Effect Engineering

2

…

3

…

8,15, 29, 34

Weight of moving object

1

Weight of stationary object

…

2

Length of moving object

3

…

…

…

…

…

Strength

14

1, 8, 15, 40

1, 26, 27, 40

1, 8, 15, 35

…

…

…

…

…

…

…

… 8,15, 29, 34

…

Strength

1

Length of moving object

Improving parameter

Weight of stationary object

Worsening parameter

Weight of moving object

47

…

14

…

18, 27, 28, 40 2, 10, 27, 28 8, 29, 34, 35 …

… … … … …

…

Fig. 4.4  Excerpt of the classical contradiction matrix according to Altschuller [40, 41, 43]

In order to concretise these general innovative principles, the TRIZ REVERSE is suitable [41, 42]. Here, experts take a closer look at an effect and try to assign this effect to different innovative principles in order to provide proposed solutions for various contradictions. In this way, expert knowledge is made generally accessible. TRIZ REVERSE is particularly relevant in the field of additive manufacturing in order to make new realisations of effects available to the general public. The procedure for TRIZ REVERSE will be shown below as an example for the effect of particle damping. By means of powder bed-based additive manufacturing systems, unfused particles can be integrated into the interior of the part during production. The powder-filled cavities lead to a significant increase in damping, so that external damping elements can be dispensed with, which offers added value especially for dynamically loaded structural components [44]. The effect of particle damping can be assigned to the following innovative principles: • • • • •

Local quality (3) Universality (6) Doll in the Doll (Matryoshka) (7) Cushion in Advance (11) Composite materials (40)

Subsequently, the contradiction matrix is reduced to the (technical) parameters in which the previously identified innovative principles occur. In this way, it can be deduced from the contradiction matrix for which contradictions the particle damping effect could be a possible solution. In Fig. 4.5 shows an excerpt of the contradiction matrix for the particle damping effect.

4  Creative Methods

Length of stationary object

…

1

2

3

4

…

Loss of energy

Length of moving object

Improving parameter

Weight of stationary object

Worsening parameter

Weight of moving object

48

…

22

…

6

…

Weight of moving object

1

…

Weight of stationary object

2

…

Length of moving object

3

…

7

…

Length of stationary object

4

…

6

…

…

…

…

…

Loss of energy

22

…

…

…

…

…

…

6

6

6,7

6,7

…

…

…

…

…

…

…

… …

Fig. 4.5  Excerpt of the contradiction matrix for the effect of particle damping

In [41, 42] the TRIZ REVERSE approach was integrated into a development environment so that constructive contradictions can be solved semi-automatically. However, the multicriteria interpretation of effects and their mappings in development environments remain challenging. Furthermore, the interactions between the materials used, the manufacturing process and the effects must be systematically analysed and the efficiency of the effects optimised on the basis of this knowledge. Table 4.4 shows—without claiming to be exhaustive—a collection of effects for which additive manufacturing could deliver significant added value or could do so in the future. The following is an example of the effect engineering approach. Effect engineering is an approach to break down global requirements to local properties. As with topology optimisation, each element within the structure is evaluated and an iterative decision is made as to which properties would be most beneficial to the part. Additive manufacturing makes it possible to change the properties locally in the first place, so that local areas with particle dampers [51–54], thermal conductors (by filling media into cooling channels, creating insulating air pockets, or making multi-material parts) [89], cavities, etc. can be realised [16]. To evaluate the efficiency, the load on the individual elements of a discretised model is analysed. Figure 4.6 shows an example of this optimisation process using a discretised beam on which a load spectrum of thermal (T) and mechanical (F, I) loads acts. In the initial situation, the multitude of elements are not loaded, or the material of the element is not suitable for the occurring load. In order to increase the performance, the part must be optimised. If the part is optimised in terms of stiffness, efficiency can be increased because the component mass can be saved.

4.4  Effect Engineering

49

Table 4.4  Effect collection of printed effects [32] No. 1.

Effects Biomedical effects

2.

Damping effects

3.

Electrical effects

4.

Magnetic effects

5.

Shape memory effects

6.

Thermal effects

Applications Drug delivery Tissue engineering Regenerative medicine Endovascular surgery Orthodontics Orthopaedics Bioprinting Biomedical devices Particle damping • Blades and blisks • Brake discs • Brake shoe holders • Cutting tool holders • Gears • Motorcycle tripple clamps • Wheel carrier Internal structures • Particle accelerator • Components for the aerospace industry Heating elements Electric motors Sensors Flexible circuits Resistive actuators Electric motors optical lenses Sensors 4D printing • Self-assembly, • Multifunctionality or self-adaptability • Self-repair • Soft Robotics • Civil engineering  Heavy duty actuators Heat exchangers Injection nozzles Injection moulds Die casting Piston Heat sink for Nd:YAG laser crystals Spark plug Gas turbine Actuator Sensors

Source [45] [45] [45] [46] [46] [46] [47] [47] [48–50] [28, 51] [52] [53, 54] [55] [56, 57] [58] [59] [60, 61] [62] [63] [64] [18, 23, 30, 65] [30, 66] [67] [68] [69] [69–71] [72] [73] [74] [75] [29, 76–79] [80] [81] [82] [31, 83] [84] [85] [86, 87] [64, 88] [64]

Nevertheless, with this design method the part is still not optimally adapted to the further loads (thermal and impulse). In order to improve the part further, other physical effects must be included. For example, high heat dissipation can be realised through multi-material production or the integration of cooling channels. In

4  Creative Methods

50

order to ultimately obtain an optimal part, additional particle dampers should be integrated into the part. It should be emphasised that effect engineering should be formulated as a single optimisation problem in order to be able to calculate the best material distribution. In the lower part of Fig. 4.6 shows an exemplary histogram for the element load of the individual variants. The element performance is plotted on the abscissa. This describes the stress level of the element for the dominant stress type. With such an approach, the optimal material distribution can be realised with minimum weight and thus maximum efficiency, which also increases the power density.

Initial situation

Stiffness-optimised

Optimisation of stiffness and thermals High conductivity

T F

I

T F

I

T F

I

T F Optimisation of stiffness, thermics, damping

I

high damping

High stiffness

Air F: Force

T: Temperature

I: Impulse

0,4 0,35

Rel. frequency [-]

0,3

0,25 0,2 0,15 0,1 0,05 0 0

10

20

30

40 50 60 70 Element Performance in %

80

Initial situation

Stiffness-optimised

Opt. of stiffness and thermal

Opt. of stiffness, thermal, damping

Fig. 4.6  Performance enhancement through effect engineering [32]

90

100

4.4  Effect Engineering

51

The design and evaluation of these effects in a part is a challenge, because on the one hand effects must be understood and characterised and on the other hand algorithms for the local integration of effects must be developed. For this purpose, targeted multi-objective optimisers have to be developed, with which the rough shape and material distribution can be determined. In addition to the simulative design, development environments should be built that have the process chain in mind [24]. However, the methodical procedure for effect engineering is very application-specific and shall be shown exemplarily for the dynamic and thermomechanical stresses.

4.4.2 Areas of Application of Effect Engineering A useful application example for the effect engineering method is a diesel piston for trucks. In general, thermomechanically loaded structures must withstand several types of loads. The mechanical loads must be transferred from the source (e.g. pressure or contact forces) to a sink (e.g. bearing). The path that requires the least amount of material or mass can be found through topology optimisation [90, 91]. Normally, the approach taken here is to remove material where stresses are low. Thermal stresses, on the other hand, are caused by a heat flow that passes through the part. This creates a temperature gradient from the source to the sink. Taking into account thermal expansion, elements with a high temperature expand more than their neighbours with lower temperatures. The elastic modulus of the material transforms these expansions into very high stresses [92, 93]. The problem is exacerbated when considering that structural parts usually operate under high stresses. Building a topology optimisation in terms of thermal, stiffness and mass turns out to be challenging as the right elements have to be removed to reduce the resulting stresses. This topic is not new and has been addressed in various optimisation approaches [93–95]. In particular, the design freedom created by additive manufacturing pushes established algorithms to their limits. The presented approaches are mostly a proof-of-concept for thermomechanical topology optimisation and only show 2D designs with filigree fractal structures, similar to those of Bendsøe and Sigmund [91] shown heat flow optimisations. Real parts in high-temperature applications such as pistons, turbochargers or turbine parts are exposed to various types of loads. Vibrations in combination with high fatigue life requirements prohibit fractal structures as described in [96, 97]. In addition, the high temperatures weaken the material by increasing elastic and plastic deformation. Optimisation for these applications must therefore include heat sinks such as cooling channels and take dynamic loads into account, or at least favour coherent structures where the mechanical loads are taken into account. The effect engineering approach here is to discretise the structure and analyse each element for the cause of the stress (see Fig. 4.7). In iterative steps, the elements are then transformed so that the stress is distributed in the structure. This

52

4  Creative Methods Element load

Temperature None Mechanical Thermal expansion

Fig. 4.7  Load distribution by heat and pressure on a piston designed for additive manufacturing [32]

can be, for example, a cooling channel, a structural material or simply a cavity. The cooling channels can either be filled with a fluid or a multi-material fabrication of copper for high thermal conductivity and a nickel-based alloy for high mechanical strength is preferred [61, 98]. In this way, not only mechanical but also thermal stresses can be compensated. To ensure the integrity of the material, the mechanical and thermal loads must be distributed as evenly as possible across the structure. This is to avoid excessive stresses, damage and failure in a component exposed to high temperatures and pressures. The additional degree of freedom provided by the combination of two materials allows a wide range of effects to be integrated into the product design process. In particular, the use of copper with very high electrical and thermal conductivity in combination with a steel alloy as a construction material offers a wide range of possible applications [61]. Another example of the use of thermal conductivity is the use of additive multi-material manufacturing in heat exchangers. Due to the high thermal conductivity of copper and a large surface area due to the degrees of freedom of the manufacturing process, the heat transfer between two media is more efficient, so that the power density of the heat exchanger can be increased. At the same time, the use of steel can ensure sufficient rigidity at necessary points and on the housing. Other possible applications are also conceivable. For example, tools such as dies in extrusion can be cooled in a process-integrated manner by using copper in areas close to the surface. In combination with a tool steel as secondary material, the necessary strengths for the forming process are nevertheless achieved. In contrast to cooling, induction heating can be used to heat parts in forming tools by exploiting the high electrical conductivity of copper. The required copper coil can be integrated directly into the tool using multimaterial additive manufacturing [99].

4.4  Effect Engineering

53

Integrated coils can also be used to realise component-integrated sensors that detect effects based on electric or magnetic fields. For example, an eddy current test can be performed with two coils to detect cracks or similar parts failures that occur during the product life cycle. Another possible application is the integration of an electromagnetic flow meter in areas that are inside a part and therefore cannot be reached with conventional sensors.

4.4.3 Additive Manufacturing Technologies for MultiMaterial Production The further development of additive manufacturing processes is crucial for the implementation of effect engineering. For example, there are commercial systems for the multi-material production of plastics and metals. With fused layer modelling (FLM)-printers, the material can already be varied locally through several nozzles or print heads and, for example, hard and ductile materials can be processed in one part. In addition, the system technology is already so advanced that sensors can be integrated into components. Either by stopping the build process and inserting the electrical component or by locally integrating nanoparticles directly into the part. However, the latter process is still at the research level. In the field of metallic multi-material production, DED systems already exist [100–102]. This makes it easy to produce multi-materials and functionally graded materials (FGM). For example, copper cooling channels can be integrated into parts or the part hardness can be graded. In addition to DED, there are also modified PBF-LB/M systems that can be used to produce multi-material components [103]. The multi-material design makes it possible to realise physically contradictory effects in one part. With conventional manufacturing processes, these multi-material parts with arbitrarily complex geometries can only be realised with a high technical and economic effort [9]. Figure 4.8a shows an example of a system for the additive manufacturing of multi-material parts using the PBF-LB/M system. The build cycle can be viewed as an explanatory film at [99]. The starting material in powder form is applied via drums as a coating mechanism. The special feature is that the respective powder adheres to the surface of the drum by means of a vacuum and can be selectively detached within a build-up layer by means of local overpressure. This makes it possible to create complex 3D multi-material parts that have any material distribution in all three spatial directions (see Fig. 4.8b). Compared to DED, the PBFLB/M method is characterised by a higher precision of the process, which leads to a high accuracy of the part geometry and a better surface roughness [104]. In addition, materials that are difficult to weld, such as titanium and aluminium, can be processed. However, the long production times and the small build space are disadvantages.

4  Creative Methods

54

a

b

Voxel-wise Voxelweiser material application Materialauftrag

z Material Material A A

Material Material B B

Fig. 4.8  Schematic representation of the PBF-LB/M process with integrated multi-material coater (a), exemplary 3D multi-material part (b), [32]

Finally, the effect engineering method will be implemented in the additive manufacturing process chain from Fig. 2.2 (see Fig. 4.9). It can be seen that so far especially the phases of task clarification, pre-, in- and post-processing have been methodically examined and now a methodical approach in the phases of conceptual and embodiment design has also been elaborated, whereby further methods of embodiment design will be dealt with in the next sections. For explanation and concretisation, in chapter 8 further application examples are presented and discussed in detail, in which effect engineering provides a clear added value. The examples make it clear that effect engineering is an emerging field and that the potential of additive manufacturing is far from exhausted.

4.5 Structure of a Product Architecture After effects have been identified in the previous section to solve conflicting goals, the next step is to build a product architecture and to underpin the effect engineering method with further methods and tools. For this purpose, the product architecture consisting of functional structure (functional description of the product) and product structure (physical structure of the product) is presented in the following section. The structure of the functional structure has already been discussed in Sect. 4.3. The product architecture pursues the goal of assigning corresponding components/modules of a product to the sub-functions. For example, the method of the one-piece machine (Sect. 4.6.3) can support the assignment of sub-functions and parts. The system boundaries of a module are determined by the extent to which the individual functions interact with each other [105]. In the case of strong bindings, the functions are integrated into a part/module; in the case of a weak binding, these can be outsourced to separate parts/modules. In Fig. 4.10 shows the product architecture of a truck diesel piston.

4.5  Structure of a Product Architecture Product design

55 CAM In-process

CAP Pre-process

CAM Post-process

Thermal finishing

Data transfer Task clarification Specify requirement

Software print preparation

Build cycle

Separating from build platform

Part placement

Mechanical finishing

Process monitoring

Cleaning

Sandblasting Vibratory grinding Functional surfaces

Material selection

Slicing

Photo shoots

Separating support structures

Design goals

Machine setup

High-speed camera

Verification

Manufacturing simulation Residual stresses

Pyrometry

EffectEngineering Detail design

Part removal

Visual inspection Evaluate process monitoring

Warpage

Net-shape geometry

Finishing

Coating Quality control Non-destructive testing

Concepts for post-process

Destructive testing

Effect-Engineering TRIZ REVERSE

• • • • • •

Conceptual design

Embodiment design

Effect characterisation

Identify conflicting goals

Mathematical problem formulation

Building an effect database

TRIZ

Multicriteria optimisation

Conflict of objectives resolved

Consideration of manufacturing restrictions

Create and evaluate solution variants

Structure of parameterised CAD model

Principle solution identified

Final solution

Contradictions Drug supply vs. accessibility Stiffness vs. damping Strength vs. electrical conductivity Strength vs. thermal conductivity Conductive vs. non-conductive Active vs. passive system Contradiction matrix for AM

• • • • • •

Effects Biomedical effects Damping effects Electrical effects Magnetic effects Shape memory effects Thermal effects

Fig. 4.9  Classification of effect engineering in the development process of additive manufacturing [32]

4.5.1 Variation of Product Structure and Shape With regard to the optimisation of components and assemblies, the systematic combination and variation of product structure and shape as well as bionics, especially with its suggestions for the use of internal structures, are also of particular importance in the context of additive manufacturing. In principle, when designing active spaces, active surfaces and pairs of active surfaces are defined and the design parameters topology, area, dimensions, numbers, surface and material as well as tolerances are successively concretised. Here it is possible to rethink part designs under the aspect of additive manufacturing with regard to their design parameters and to vary these in a targeted manner in order to arrive at new concepts:

4  Creative Methods

56

Module A Driving force

Combustion

Temperature control

Seal Remove oil film Movement

Guide Transfer power

Bowl Oil gallery

Module B Ring grooves

Module C Skirt Module D Pin boss

Functional structure

Product structure

Fig. 4.10  Product architecture of a piston [106]

• The topology of parts can be used to reduce or simplify assembly by swapping the inside and outside. Frequently shown examples in this context are also parts that are completely printed around so that they are enclosed by other parts, e.g. balls in bearings or gears or complete gear modules. • Surface shapes can be varied to realise effects more efficiently or to increase the achievable precision through modified process chains and, if necessary, post-processing steps. • Dimensions can be varied and, in particular, multi-scale (combining large and small structures) can be addressed. • Highly integrated solutions can be realised in principle, especially in the printing of plastic parts, by integrating film joints, hinges, hooks and hook-and-loop fasteners and help to reduce the number of parts and fasteners. • Surfaces can be defined in terms of their roughness under tribological aspects. • Not all materials are qualified for additive manufacturing, but solutions can often be found through material alternatives. However, the number of new materials for additive manufacturing is constantly increasing. • Tolerances and tolerance chains have to be rethought depending on the process.

4.5.2 Bionics Bionics deals with the transfer of phenomena from nature to technology. The oldest known example of this is Leonardo da Vinci's idea to transfer bird flight

4.5  Structure of a Product Architecture

57

to flying machines. Bionics is based on the assumption that living nature develops optimised structures and processes through evolutionary processes from which humans can learn. With a view to nature, additive manufacturing in combination with CAE tools offers good opportunities to adopt the form language of biological models compared to classical processes. The key here is the technology of freeform surfaces, the alternation between micro- and macro-structuring as well as internal structures and the use of extensive simulations. In addition, the targeted adjustment of surface properties, in particular roughness, can be used to reproduce effects from nature such as the bonding effect and targeted wettability. Material parameters can also be varied in a targeted manner to create functionally graded materials and material combinations in the build cycle and thus overcome the technical paradigm of the homogeneous material. A process model for product design according to the principle of bionics is shown in Fig. 4.11. The following steps can be derived from this: 1. 2. 3. 4.

Situation analysis: The situation is analysed Formulation of goals: The goal to be achieved is defined. Analysis–Synthesis Cycle Determination of the biological analogue system that is considered for finding the solution 5. Information gathering: All information about the technical system is gathered together

Selection of solution

Search for solution

Search of objective

Problem Determination of the biologic analogue system

Analysis of situation

Information procurement Formulation of objective Analysis of the biological system Analysis / Synthesis

Tech. / econom. Boundary conditions

Assessment

Decision

Assessment of transferability Derive solution principles Application of the solution principles to the technical system

Solution

Fig. 4.11  Process model for product development according to the principle of bionics, based on VDI 6220

58

4  Creative Methods

6. Analysis of the biological system for its functioning 7. Assessment of transferability, whether the biological system is transferable to the technical system 8. Derivation of solution principles 9. Application of the solution principles to the technical system 10. Evaluation of the solution principles which should be pursued further 11. Deciding which solution principle to develop further Case bases, consisting of digital or physical visualisation objects of bionics, are particularly suitable here for finding ideas. Through the visualisation and haptics, the designer can get a good overview in a short time in order to find suggestions and ideas for their own task. With the help of this approach, bionic principles can be applied to technical products, as shown in Fig. 4.12 illustrated. For example, engine pistons can be developed with bionic structures inspired by the structure of human bones. The bony structure is added in stressed areas, with the structure being optimised by the stresses that occur. This approach allows the pistons to be manufactured with a material saving of up to 20% while increasing stiffness. A large database of solution principles from nature can be found, for example, at Ask Nature [107].

4.6 Embodiment Design Phase The result of the design process is a description of the object to be developed and certain requirements. Experience has shown that different design procedures are used depending on the product and industry. These are relevant levers for arriving at a suitable design in a targeted manner. Some of them are reflected in the

Fig. 4.12  Engine piston with bionically optimised structures in areas of increased load, courtesy of MAHLE GmbH

4.6  Embodiment Design Phase

59

following with reference to additive manufacturing. The starting point for this section is the basic design rules. In order to specify these, design principles with reference to additive manufacturing are then presented. Since function integration plays a decisive role in additive manufacturing, the method of the one-piece machine is presented. Subsequently, strategies such as from “inside to outside” and from “outside to inside” are presented. Building on this, the configuration of modular systems and the development of series are described. Since additive manufacturing addresses lightweight design to a large extent, load-adapted internal structures are addressed for the design. This is followed by optimisation strategies for structural optimisation. Finally, functionally graded and combined materials are presented.

4.6.1 Basic Design Rules The design of parts for additive manufacturing is also determined by the following basic design rules: • • • •

Simplicity Clarity Safety Sustainable

Although complexity is often easier to realise in additive manufacturing than in classic processes, it should be minimised for reasons of quality assurance and clarity. In the field of additive manufacturing, a high degree of complexity often goes hand in hand with a high degree of functional integration. In the case of wear parts, however, it must be taken into account that the entire part and not individual wear parts have to be replaced and thus the repair costs are higher. For these reasons, simple designs should be preferred. With regard to the safety of the manufactured parts, special challenges arise for process monitoring and part inspection due to the individual original shaping of the material. In particular, the part properties depend to a large extent on the properties of the starting material and the process parameters. Additive manufacturing certainly has great potential in terms of sustainability. However, this has so far only been partially tapped -as we will discuss in Sect. 10.1 of this book. Especially due to the public pressure to develop sustainable products, this point should be addressed in the design principles of additive manufacturing. This point implies developing efficient products, saving resources and acting economically. Thus, solutions are realised that are clearly superior to conventional products and compensate for the partly higher production costs in the use phase.

60

4  Creative Methods

4.6.2 Design Principles After the design objectives in Sect. 4.2 the question now is how to implement them. A good way to deal with the internal contradictions in design is to use empirical knowledge, which is formulated in design principles. Six relevant design principles for the design of additive parts are presented below [11]. Subsequently, in the following section, further methods for part design are discussed and the methods mentioned here are dealt with in detail. Principle of Equal Design Strength The aim is that the component strength should be the same throughout the entire component over the intended operating time. For this purpose, a homogeneous stress distribution is to be aimed for. To achieve this, the topology, shape and material can be adapted as design parameters that can be influenced. Methods for structural optimisation can be used to adapt the topology. For the shape of the part, free-form geometries should be used where possible in order to avoid sharp deflections or abrupt cross-sectional transitions. With the material, both the material can be changed and a multi-material design can be introduced. As an added value, local overdimensioning can be minimised and lightweight design can be addressed. Principle of Direct and Short Force Transmission The aim is not to carry forces around, but to direct them as directly as possible to the force transmission point with minimal deformation. This approach can minimise the use of materials and create a lightweight design. For this purpose, the topology and shape can be adapted as design parameters that can be influenced. Measures for structural optimisation and the active surface-based design are particularly suitable for this. This procedure can prevent premature component failure and increase the component service life. Principle of Coordinated Deformations The aim is to match deformations between adjacent components. The design should be chosen in such a way that the relative deformation is rectified and small. For this purpose, the topology, shape and material can be adapted as design parameters that can be influenced. Where possible, free-form geometries should be used for the component transitions in order to be able to better conduct the force from one component to another. Furthermore, functionally graded materials can be used to match the component deformations to each other. For example, functionally graded thermal barrier coatings are used in aerospace to prevent cracking. Overall, a uniform stress transition is realised and stress peaks are prevented. Principle of Force Compensation The aim is to compensate for forces that do not serve the main function (disturbance variables). In addition to known design approaches such as compensating elements or a symmetrical arrangement, material properties can be changed locally in additive manufacturing in order to dissipate energy. For example, integrated particle dampers can be produced for vibration-prone components in order to significantly reduce vibrations (principle of stability).

4.6  Embodiment Design Phase

61

Principle of Separation of Tasks The aim is for each function to be implemented by a separate function carrier. For this purpose, the topology, shape, number and material can be adapted as design parameters that can be influenced. Using the method of the one-piece machine, several components can be combined into one component that fulfils the same function. Furthermore, additive manufacturing allows several functional carriers to be integrated into one component by means of the multi-material design method. This has the advantage that individual functional carriers can be designed separately, but connection points are saved. Effect engineering is particularly suitable for this. An example would be the parallel implementation of high stiffness with high damping through a stiff design with integrated particle dampers. Principle of Self-Help The aim is for the system to adapt to the environmental conditions. Sensors can be integrated into additively manufactured parts that transmit information about the part load These can be integrated directly into the part in one manufacturing step, both by interrupting the build cycle and by multi-material manufacturing. This has the advantage that parts can be stressed to the limit of their service life and inspections or maintenance intervals can be extended as a result. Other principles that are not considered in detail here are • • • •

Principle of effective use of materials Principle of bistability Principle of low-fault design Principle of matched semi-finished products.

However, there are also additive-specific principles, as described in detail in the following works, for example, although the term principle is not always used quite correctly here. • • • • •

Conception of design principles for AM [108, 109] AM Design Catalogue [110] AM Design Heuristics [111] AM design Database [7] Principle of the one-piece machine [21]

4.6.3 One-Piece Machine Method With the one-piece machine concept, we proceed as if everything could be printed in one process and only place separations and connecting elements where it is absolutely necessary. In many cases, this thought model leads to a significant reduction in interfaces and connecting elements. As a result, maximum functional integration can be realised. This method is illustrated in Fig. 4.13 using the example of a motorcycle triple clamp, in which a total of 18 parts could be saved.

4  Creative Methods

62

Initial situation

• Motorcycle triple clamp with handlebars • Consisting of 25 parts • Optimise for PBF-LB/M

One-piece machine

Mental fusion of all components to a single part

Unravel step by step Consideration of: • build space restrictions (handlebars) • Mounting (handlebar) • Relative movements (particle dampers) • Wear parts (not relevant) • Material issue (not relevant) → Savings of 18 parts

Fig. 4.13  One-piece machine method using the example of a motorcycle triple clamp

4.6  Embodiment Design Phase

63

4.6.4 From the Inside to the Outside Particularly in the design of machines (internal combustion engines or electric motors, turbines or gearboxes …), design is often carried out from the inside out. This means that variables relating to the power conversion are calculated and the machine is designed around them. Even parts that are complex to manufacture additively can lead to optimisations here, in the centre of the machine, for example the piston of an internal combustion engine. These then have a positive effect on the entire system. For example, the system as a whole can become smaller and lighter or have optimised sustainability properties.

4.6.5 From the Outside to the Inside Figure 4.14 shows a lightweight structure made of the polymer PLA that makes full use of a possible build space. This has considerable advantages in terms of stiffness and weight compared to smaller solid structures. Here, the approach was from the outside—build space restrictions—to the inside and the necessary active surfaces were favourably placed in the structure. Such design strategies can also be found when package specifications are made—such as for supplier components in automotive construction or when installing equipment in cabinets or container units.

4.6.6 Configuration from Modular Systems In the context of modular systems, such as those used for electrical or air-conditioning installations and in plant construction, the design is created by

Fig. 4.14  Self-supporting body of a printed model car, for production from PLA in Fused Layer Modeling

4  Creative Methods

64

configuring standardised components. These are not usually produced by additive manufacturing. However, additive manufacturing gains importance in this context through customised individual parts, adapters, spare parts or even on-site repair solutions. The configuration of modular systems is to be exemplified by the example of a tea machine in the high-end sector. A special characteristic is the adaptability to the kitchen or room furnishings, which is achieved through exchangeable housing panels. To individualise the tea machine, interfaces are defined for setting up a configurator, which enables the design of a housing panel. The customer should be given as much freedom of design as possible, but the solution space is defined taking into account design guidelines and predefined design variables. The tea machine as well as a selection of different housing panels are shown in Fig. 4.15. A laser-sintering system is chosen as the manufacturing system for the housing elements. PA is determined as the material, which means that no additional support structures need to be considered for production, as the surrounding powder bed provides sufficient support for the parts. Relevant restrictions are formulated for product design, on the one hand the minimum wall thickness that a housing part may have, and on the other hand the size of the build chamber of the laser-sintering system so that the parts can be manufactured in one piece. In order to be able to realise different colours, the sintered parts are subsequently dip-coated. A design configurator is developed to describe the design solution space, which ensures that neither other assemblies are affected when the housing panels are adapted, nor that design interfaces can be moved or eliminated. Since the configurator is also available for end customers, a simple configuration dialogue is implemented in which the customer can shift the boundary of his individual housing panel according to his wishes by adjusting points on the outer edge, see Fig. 4.16. Furthermore, a text can be imprinted on the housing panel and the colour of the

Built-in housing panels

Individualised housing panels

Fig. 4.15  Tea machine with customisable housing panels

65

Height [mm]

4.6  Embodiment Design Phase

Width [mm] Fig. 4.16  Design configurator of the customisable tea machine

panel can be selected. Further features are conceivable and can be constantly added. In relation to the size of the build chamber, a maximum of 60 housing panels can be produced within one build cycle. The build time is about 30 h including the cooling time, cleaning of the parts and dip coating. With larger machines and larger build chambers available on the market today, it is even possible to produce up to several hundred panels in 50 h within one build cycle. In both cases, the individual panels would be ready for shipment after a few days. In terms of the business model, it is noticeable that the panels are not the biggest cost factor, but that the customised logistics and administration cause the most costs.

4.6.7 Development of Model Series An essential aspect of the development of model series is scaling while maintaining function and architecture. The digital models as a prerequisite for additive manufacturing offer the possibility of rapid and, thanks to additive manufacturing, highly individual scaling, even of original moulded parts.

4  Creative Methods

66

4.6.8 Internal Structures Special attention is first paid to internal structures, as they are actually found everywhere in nature adapted to loads. Figure 4.17 shows exemplary structures from biological models and their technical analogies. When using regular structures, the question arises under which stresses which structures can be used appropriately. In Table 4.5 provides a suitable overview. These are often used to increase the build progress inside parts subject to low loads and to save material. However, if structures are also selected with loads in mind, a distinction is made between three types: • Periodic—filling the build space with regular structures • Quasi-periodic—the use of regular structures with variation of individual parameters, for example the bar thickness • Random—the stochastic adaptation of structures under e.g. the paradigm of constant stresses in the material by means of topology optimisation calculations. Periodic Internal Structures There are different approaches for modelling inner structures. The periodic inner structures are often created in slicer software. Here, the, usually periodic, two- or three-dimensional pattern of the inner structure is created in the part. During the slicing of the desired part geometry, the pattern is generated exclusively within the part boundary of each slice. Disadvantages of this form of modelling are mainly the lack of modification and alignment possibilities of the inner structure. Controllable parameters are usually only the pattern and the fill density of the inner structure. In Fig. 4.18 shows the generation of the inner structures using the commercial slicer software Cura as an example. The lack of alignment of the inner structure to the part surface can lead to unpredictable part behaviour in highly loaded structural parts.

Trusses Honeycomb Horsetail

Bones

Spider web Fig. 4.17  Structures from biology and technology

Bamboo Diatom

4.6  Embodiment Design Phase

67

Table 4.5  Suitable structures according to load type Inner structure Solid material

Rank bend –

Rank train/ pressure –

Rank weight –

Main application –

Struts

10

11

2

Bending

Cuboid

7

5

3

Bending, pressure

Honeycomb

4

3

8

Bending, pressure

Honeycomb stiffened Truss FCC

1

1

11

Bending, pressure

11

4

1

Bending

Truss BCC

8

2

3

Bending, pressure

Bamboo

2

6

9

Bending, torsion

Spider web

9

7

3

Torsion

Horsetail

5

10

6

Torsion, bending

Polygons

6

9

7

Bending

Diatom

3

8

10

Bending, torsion

Fig. 4.18  Creation of two-dimensional periodic inner structures in the software Cura by the company Ultimaker

4  Creative Methods

68

A more complicated but far more effective procedure is to create the inner structures by using unit cells. The three types of inner structures, periodic, quasi-periodic and randomised, can be demonstrated using the example of a clamped beam as shown in Fig. 4.19a. For this purpose, the volume of the beam is divided into three-dimensional voxels (cf. Figure 4.19b). Geometries can then be inserted into each of these voxels, in the form of unit cells, which can be customised to represent the internal structure. During periodic filling of the design space, the voxels are filled with identical unit cells, creating a repeating structure. In Fig. 4.20 a periodic inner structure with a body centered cubic unit cell is shown in different views. Critical when using periodic structures are the very different stresses in the material depending on the load case, especially in the transition areas, e.g. to the solid material. However, it should also be noted that minimum bar thicknesses must always be realised and notch effects should also be kept small and taken into account in the interior of the structures. In some processes, it must also be ensured that powder, for example, can be removed from the cavities of the structures. a

b

Fig. 4.19  a) Clamped beam as well as b) the corresponding voxelisation of the volume

a

b

c

Fig. 4.20  Periodic internal structure with body centered cubic unit cells in a) the isometric view, b) front and c) side view

4.6  Embodiment Design Phase

69

Quasi-Periodic Internal Structures One advantage of this approach is the adaptivity in the creation of the inner structures. Thus, even as in Fig. 4.21 the bar thicknesses in the unit cells can be adapted. The bar thicknesses can also be graded. Randomised Internal Structures Randomised inner structures can be realised, for example, by using Voronoi structures. This type of inner structure is created by randomly scattering points in a volume. The volume is then divided into mosaic-like polyhedra called cells. One polyhedron around each point, consisting of the area of the volume closer to that point than any other. The general procedure of creating three-dimensional Voronoi structures is shown in Fig. 4.22.

4.6.9 Structural Optimisation Mathematical optimisation is also used when designing parts and solutions in the context of additive manufacturing. In principle, both the methods of parameter-based shape optimisation and the methods of mesh-based shape optimisation and mesh-based topology optimisation are suitable (see Fig. 4.23). The main difference between the methods lies in the design variables and thus in the type of change. • When dimensioning the size of the existing structural elements is optimised without changing the shape. The design variables are the geometric parameters, here for example the bar thicknesses of regular structures. a

b

c

Fig. 4.21  Quasi-periodic internal structure with graded body centered cubic unit cells in a) the isometric view, b) front view and c) side view

70

4  Creative Methods

Fig. 4.22  Procedure for generating randomised inner structures in the form of Voronoi structures

• With shape optimisation the optimal shape is determined for already existing structural elements. In this so-called mesh-based optimisation, the design variables are the coordinates of the mesh points and often free-form geometries result as the optimised solution. • In topology optimisation the optimal material distribution is determined for a given design space. The design variable is a pseudo-density of the material, whereby in a complementary step the areas of the material with very low density are removed and thus the component is defined in its topology and shape. These optimisation strategies are also relevant for the load-appropriate design of the internal structures presented in Sect. 4.5.3. A decisive advantage of internal structures, e.g., lattice structures, lies in their ability to optimize the topology of a part by locally adjusting its mechanical properties. In particular, compliance can be specifically modified to ensure efficient performance. Thus, various effects can be realized by choosing a particular structure, the type of structure, and its modelling [113, 114]. Thus, direct parameter optimisations of the bar thicknesses, as well as the indirect transfer of results from topology optimisations, can be applied to the unit cells. In the case of parameter optimisation, the inner structure is calculated directly numerically and the bar thicknesses are optimised automatically by grading strategies of the unit cells. In indirect optimisation, the component is homogenised and calculated using topology optimisation methods. The results of this topology optimisation can then be transferred to the component by using quasi-periodic structures. A topology optimisation with optimised load paths for the represented load can thus be achieved by grading the web thicknesses in the periodic unit cells. In Fig. 4.24 the quasi-periodic inner structures of the cubic space-centred unit cells are shown after density optimisation.

4.6  Embodiment Design Phase

71

Topology optimisation:

Shape optimisation:

Dimensioning:

Fig. 4.23  Types of structural optimisation, according to [112]

a

F

b

c

Fig. 4.24  Quasi-periodic internal structure with graded body centered cubic unit cells in a) the isometric view showing the load, b) front view with optimised load paths indicated (red dashed) and c) side view

This parametric procedure also allows randomised structures to be optimised according to the type of load. Thus, the randomly scattered point cloud can be adjusted directly by parameter optimisations or, for example, indirectly optimised by the previously generated results of the structural optimisation. In the indirect approach, the space centres of the respective cell used in the decomposition are filtered and aligned according to the optimised load paths of the topology optimisation. Thus, the density of space centres near the optimised load paths is higher than in the outer areas, as shown in Fig. 4.25 shown.

4  Creative Methods

72

a

F b

c

Fig. 4.25  Stochastic internal structure with Voronoi cells in a) the isometric view showing the load, b) front view with optimised load paths indicated (red dashed) and c) side view

With this form of stochastic lattice structures, an additional combination with structural gradients can be realised, as shown in Fig. 4.26 illustrated. Additive manufacturing offers special opportunities due to the degree of manufacturing freedom with regard to topology-optimised geometries. The commonly used approach is the “Solid Isotropic Microstructure with Penalization Approach” (SIMP), which is based on the homogenisation method [91]. In the SIMP method, each element i is assigned a pseudo-density ηi between 0 and 1. Thus, the optimisation problem is described by the following objective function and restriction:

Objective function : max K E

Restriction :

N ∑

ηi = V

i=1

where K is the stiffness, E is the modulus of elasticity, N is the number of elements and V is the given volume. Through an iterative process, the pseudo-density is distributed according to a sensitivity analysis that describes the influence of a change in the pseudo-density on the total stiffness. Therefore, a descriptive equation of the relationship between pseudo-density and modulus of elasticity is necessary.

4.6  Embodiment Design Phase

73

a

F b

c

Fig. 4.26  Stochastic and graded internal structure with internal structure with Voronoi cells in a) the isometric view with representation of the load, b) front view with indicated optimised load paths (red-dashed) and c) side view

This description according to SIMP is: p

Ei = ηi E0 Thereby p is a “penalty factor”. Through this equation, one can calculate an elastic modulus value for intermediate pseudo-densities. The function of the penalty factor is to avoid the intermediate pseudo-density and bring the values close to 0 or 1, as other values have no physical meaning. Usually p is equal to or greater than 3. As a rule, however, the geometries resulting from the calculation are not produced directly. Rather, it is necessary to process the calculation results, such as smoothing surfaces and realising minimum wall thicknesses. In particular, attention must also be paid to the fact that a closed solid model must be available for additive manufacturing. Figure 4.27 illustrates this process for the optimisation of the mounting structure of vehicle pedals. [115]. The optimised shape is usually complicated and often cannot be produced by conventional manufacturing processes without serious simplifications. Additive manufacturing can realise significantly more complicated design. Figure 4.28 shows the mounting structure of the pedals printed in aluminium using PBF-LB/M according to the procedure explained above.

4  Creative Methods

74

a

b

c

Fig. 4.27  a) Design space with boundary conditions, b) Result of topology optimisation, c) Graphically post-processed CAD model of the final shape

Fig. 4.28  Printed optimised mounting structure for vehicle pedals

4.6.10 Graded and Combined Materials Voxel-wise material application makes it possible to vary the material properties in additive manufacturing within a part by varying the machine parameters. This results in the following interesting design possibilities: • The surface quality of the components can be kept high by slow material application and at the same time a fast build progress can be realised inside the part by high power input. In the case of parts that are subject to low mechanical loads, complete melting of the material is sometimes dispensed with and layers of material are only partially “bonded”. • Heat transitions and energy absorption can be varied in a targeted manner by insufficient fusion of powder and quasi-porous structures—transitions can thus be continuously adjusted. • Different consolidations can be used as predetermined breaking points.

4.7  Development Environment

75

• Damping and vibration properties can be optimised by combining fused material with non-fused powder. • The optimisation of material and heat transport through flow-optimised channels and microstructured surfaces is possible. Furthermore, the targeted local combination of materials in parts is possible, whereby many technically relevant effects can be optimised. Even though many considerations in this regard are still at the research stage and the required machine concepts, at least for metals, are essentially still experimental set-ups, some further examples are given below: • The highly integrated manipulation of electromagnetic fields by combining conductive and non-conductive material in the part. • The optimisation of heat transfer and thermal stresses through graded materials. Metals, for example, can be adapted to ceramics, glasses or crystals by grading. • Mixed materials can also be used to increase component-specific and local chemical resistance. • Mixed materials can also be used to create highly integrated tribological systems for specific applications. In Fig. 4.29 shows examples of multi-material parts that were produced in the PBF-LB/M. Figure 4.29a represents a stator tooth of an electric motor and Fig. 4.29b shows a section of a heat exchanger.

4.7 Development Environment Modern product creation processes, as the sum of product design and production preparation, are supported by computer-aided development, planning and quality assurance environments. These are also referred to as computer-aided engineering (CAE) and computer-aided manufacturing (CAM) and collectively as the CAX environment. However, materials, physical models, machinery, jigs and tests still a

b

Fig. 4.29  Multi-material parts produced in PBF-LB/M: a) Stator tooth, b) Part of a heat exchanger

76

4  Creative Methods

play an important role. In Fig. 4.30 shows a selection of additive-specific software solutions for the product creation process, which will be discussed in detail below. The task of a CAE environment in this context is the handling of the digital product in the dimensions geometric model, physical model and product data. In most cases, the CAE environment is based on CAD systems and data exchange formats with which the information can be transferred between development and other areas. It also includes simulation tools, often based on FE methods, optimisers and product data management software. Widely used software in the field of design for additive manufacturing are, without claiming to be exhaustive, Autodesk Fusion, Creo or Rhino. A challenge for additive-specific design is the modelling of free-form surfaces. Classic software functions such as “extrusion”, “rotation” or “sweep” are no longer sufficient here, so that the range of functions offered by conventional software manufacturers is being continuously expanded. In particular, software programmes from the field of industrial design, such as Rhino, are becoming increasingly important, as these programmes have already been used for modelling freeform geometries for some time. In addition to the use of CAD programs, FEA programs are also used in the design phase for simulation and optimisation. These include Abaqus, Ansys or Comsol, among others. The task of the development environment is to enable interaction between CAD and FEA, such as parameter studies. However, the parameterised component reconstruction on the basis of FEA calculations is currently challenging, as these often still have to be reconstructed manually. Computer Aided Planning (CAP) follows the design phase and prepares the parts for the additive manufacturing process. This includes placing the parts in the build space, generating support structures, slicing the parts and process simulation. The last point in particular, process simulation, is becoming increasingly important. For example, the Free Float software offers the possibility to adapt process parameters and support structures individually to the part. By locally adapting the process parameters, it is possible to maximise the length of support structure-free overhangs at small down-skin angles δ