lathe-type 3D printer

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LATHE-TYPE 3D PRINTER ME3 DMT FINAL REPORTGROUP 27 ALEXANDROS KENICH MATTHIEU BURNAND-GALPIN ERWAN ROLLAND YOUSSEF IBRAHIM

LATHE-TYPE 3D PRINTER

ERWAN ROLLAND Project Manager

ME3 DMT FINAL REPORT MATTHIEU BURNAND MATTHIEU GALPIN BURNAND GALPIN

PEOPLE DMT Team Name

Head of Control Head of Control and Structure

Contact Number

Email

ERWAN ROLLAND

07 906 478 467

[email protected]

MATTHIEU BURNAND-GALPIN

07 824 967 269

[email protected]

ALEXANDROS KENICH

07 857 781 592

[email protected]

YOUSSEF IBRAHIM

07 896 669 666

ALEX KENICH Head of Programming

[email protected]

Supervising Team Name

Contact Number

Email

Room

DR SHAUN CROFTON

02 075 947 085

[email protected]

551

DR PAUL HOOPER

02 075 947 128

[email protected]

393

DR DANIEL PLANT

02 075 947 128

[email protected]

002

YOUSSEF IBRAHIM Head of Mechanical Design

GROUP 27 Supervis ing Team

VERSION 1.3 DMT Team Lathe Type 3D Printer

Checked: E.R, M.B, Y.I 04/06/2013

I

ABSTRACT This final report documents the design, making and testing of a novel lathe-type 3D printer. The prototype produced makes use of Fused Deposition Modelling and presents a viable alternative to Cartesian 3D printers currently in use. Methods were developed to generate G-Code machine commands which are used to produce these parts. The main objectives of the project were met; parts can be printed with good accuracy and with minimal effort. Through efficient management and organisation, the project was completed on time and under budget at £527. The additive lathe prototype is capable of printing parts exhibiting complex geometries exclusive to cylindrical 3D printers. Parts previously impossible to create using additive manufacturing such as springs and propellers can be made with ease. The infill and aspect of cylindrical components can be controlled more precisely than is possible on a conventional 3D printer, and filament can be interwoven to improve mechanical properties. The project could be extended by adding supplementary features to the software used to control the printer. In particular, writing code for a custom slicing procedure could streamline the generation of G-Code starting from a solid model. The printer provides an excellent foundation for these innovations to be implemented.

II

TABLE OF CONTENTS I. BACKGROUND ................................................................................................................................................1 I.1 INTRODUCTION ...............................................................................................................................................1 I.2 TECHNOLOGY REVIEW ....................................................................................................................................2 I.3 GROUP CONTRIBUTIONS .................................................................................................................................5 II. PROJECT PLANNING .....................................................................................................................................6 II.1 PRODUCT DESIGN SPECIFICATION .................................................................................................................6 II.2 GANTT CHART ...............................................................................................................................................8 II.3 QUALITY MANAGEMENT .................................................................................................................................9 III. DESIGN PROCESS ......................................................................................................................................10 III.1 DESIGN EVOLUTION ...................................................................................................................................10 III.3 STRUCTURAL DESIGN .................................................................................................................................13 III.4 CONTROL AND TRANSMISSION ....................................................................................................................16 III.5 MECHANICAL DESIGN .................................................................................................................................20 III.5 ELECTRONICS AND PROGRAMMING .............................................................................................................23 IV. MANUFACTURING AND ASSEMBLY ........................................................................................................30 IV.1 PERSPEX STRUCTURE ...............................................................................................................................30 IV.2 PRINTED PARTS.........................................................................................................................................31 IV.3 MACHINED PARTS ......................................................................................................................................32 IV.3 ASSEMBLY.................................................................................................................................................33 V.4 CALIBRATION ..............................................................................................................................................37 V. TESTING ........................................................................................................................................................38 V.1 TESTING THE PRINTER PROTOTYPE .............................................................................................................38 V.2 G-CODE GENERATION ................................................................................................................................41 V.3 TESTING THE PRINTED PARTS .....................................................................................................................45 VI. COSTING AND PURCHASING ....................................................................................................................47 VII DISCUSSION ................................................................................................................................................49 VII.1 SHORTCOMINGS AND POTENTIAL IMPROVEMENTS .......................................................................................49 VII.2 UTILITY OF THE CYLINDRICAL PRINTER AND POTENTIAL APPLICATIONS ..........................................................50 VII.3 PLANNING AND CONDUCT OF TASK ............................................................................................................51 VIII. CONCLUSION ............................................................................................................................................52 IX. REFERENCES ..............................................................................................................................................53 X. ACKNOWLEDGEMENTS ..............................................................................................................................53 APPENDICES ....................................................................................................................................................54 APPENDIX A1: STRUCTURAL AND CONTROL CALCULATIONS ................................................................................54 APPENDIX A2: DETAILED BILL OF MATERIALS .....................................................................................................59 APPENDIX A4: DETAILED DRAWINGS ..................................................................................................................60 APPENDIX A5: INDIVIDUAL CRITIQUES ................................................................................................................61

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DMT 27: Lathe-type 3D Printer

Department of Mechanical Engineering

I. BACKGROUND I.1 Introduction Fused Deposition Modelling 3D printers have recently garnered significant attention due to simplifications in design, leading to cheaper and more widely available printers. However, some limitations are associated to this technology, and several attempts have been made to overcome these [1]. The aim of the project described in this report is exploring one such possibility. A 3D printer was developed that, unlike a standard printer operating in Cartesian co-ordinates, operates in cylindrical co-ordinates. This is analogous to a lathe where material is deposited on a rotating cylinder rather than cut away. Efforts were also made to investigate the advantages of using a cylindrical printer over its Cartesian counterpart, exploring aspects such as the facilitation of creating certain geometries and the ability to control the disposition of the filament used to produce a printed part.

Figure 1: The Airwolf 3D printer operating in Cartesian coordinates

The report begins by introducing the topic of additive manufacturing and reviewing current 3D printing technology. Following this background information, the project plan used to conduct this project is briefly introduced. The design is explained in depth by exploring initial concepts and detailed features present in the final design. The design decisions concerning software and electronics are also presented. Manufacturing considerations and the assembly process are then outlined, followed by information relating to the assessment and testing of the finalised prototype and the parts it can produce. The project costing is then presented followed by a discussion of the project, including its main achievements and potential areas of improvement.

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DMT 27: Lathe-type 3D Printer

Department of Mechanical Engineering

I.2 Technology Review Increased interest in additive manufacturing methods has been accompanied by a popularisation of 3D printers. The applications of these devices range from rapid prototyping to specialist applications in medicine or aeronautics. While 3D printers are often grouped as single technology, they often operate using a variety of methods, and utilise a myriad of materials [1]. One of the most prominent 3D printing techniques is known as Fused Deposition Modelling (FDM). This method uses use thermoplastics such as ABS, polycarbonate and PLA, and has gathered considerable interest, as it is conceptually simple and relatively cheap. Material is fed into a heated nozzle, and laid upon a print bed while melted. As the layers solidify, a solid object is formed.

Heated Nozzle

Deposited material

Print bed Figure 2: Diagram of Fused Deposition Modelling (FDM)

[1]

The team decided to conduct a short literature review to understand the basics of 3D printing, and to identify some of the shortcomings which could be overcome with a cylindrical printer. Additionally, past attempts to design cylindrical 3D printers were reviewed in order for our project to build upon their limitations. Much of the on-going development surrounding FDM printers is concentrated around the RepRap Project (Replicating Rapid Prototyping Machine). The main advantage of these machines is that they can be built with standard components, and extensively customised. For these reasons, RepRap-type printers provide a good framework in which innovative features can be implemented with minimal cost and effort. These machines operate in Cartesian coordinates; the print head can move in the X and Z directions, while the printbed is free to move in the Y direction using stepper motors. A picture of a typical RepRap machine is shown in figure 3.

Z Axis motor

Print head

Print bed X Axis motor

Printed Fixtures

Control electronics

Figure 3: A typical RepRap 2.0 Mendel Printer

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DMT 27: Lathe-type 3D Printer

Department of Mechanical Engineering

The range of geometries obtainable by these printers is limited by the use of Cartesian coordinates. One of these limitations is the difficulty of producing parts with large overhangs. This can be remedied by using a second material as a support, which can be removed once the part is completed. However, this method is significantly more costly and more complex. Similarly, traditional FDM printers are often unable to create curved shapes with high accuracy. The smoothness of a circular part is limited by the step size on the motors. One of the shapes difficult to make on a Cartesian 3D printer is shown in figure 4 below. Z Z

Θ X

No overhangs

X Y

Large overhangs

Figure 4: Complex shape in on a Cartesian print bed (left) and cylindrical print bed (right)

Cylindrical-type 3D Printers One of the attempts made to further 3D printer technology is the additive lathe. Unlike a traditional lathe, the exact angular position of the cylindrical printbed can be controlled using a stepped motor. Material can be deposited on the rotating print bed using a print head which moves in the X direction.

Extruder Assembly

X Rails

Chuck Rotating Print Bed

Figure 5: Sketches of shapes difficult to make on a Cartesian printer

[2]

The additive lathe was created mainly as a proof of concept, and demonstrates the possibility of using a rotating print bed in a 3D printer with cylindrical coordinates [2]. Its main drawback stems from the omission of vertical mobility. As such, the range of parts that can be created is severely

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DMT 27: Lathe-type 3D Printer

Department of Mechanical Engineering

reduced. Components with overhangs which could be created in cylindrical coordinates cannot be made on this printer. Additionally, although a chuck is included, the design of the transmission does not enable the rotating print bed to be swapped for one with a different shape or material. Finally, this prototype cannot make use of existing software, and relies on custom electronics with reduced functionality. Only very simple parts can be produced by this printer, making it difficult to assess the increase in quality which can be offered by cylindrical printers. Furthermore, the design offers no upgradability, which would be desirable in order for a variety of print beds and materials to be tested. Some of the aspects related to cylindrical printing have recently been patented [3]. The patent gives a very general overview of the systems which could be involved in such a machine, but gives minor indications on how these features could be implemented. A diagram of this machine is presented in figure 6 below.

Deposited material Printhead

Rotating bit

Electronics

Figure 6: Diagram of a cylindrical printer

[3]

Conclusion While there have been some attempts to create a cylindrical 3D printer, most have been experimental, and no complex parts have been printed. As a result, many of the features which seem to be made possible with cylindrical printing are still hypothetical. The priority of the project is to construct a prototype which demonstrates some of these novel features. Another significant challenge is to integrate electronics and software with the printer. The main shortcomings of past projects which must be resolved with the project are presented in figure 7 below.

Implementation of a vertical axis

Integration of electronics

Feature interchangeable printbeds

Create more complex parts

Identify main limitations of concept

Show overhangs can be avoided

Show viability of overhangs

Figure 7: Main objectives of the DMT prototype

Show off interweaving

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DMT 27: Lathe-type 3D Printer

Department of Mechanical Engineering

I.3 Group contributions The group benefitted from excellent team cohesion and maintained well-distributed responsibilities and work amongst team members. While all team members contributed to the overall design, problem solving and report writing, each team member focused on particular aspects of the project. ERWAN: PROJECT MANAGER As project manager, Erwan coordinated the team’s efforts and scheduled meetings. He was a driving force in maintaining the team’s motivation high and ensured deadlines were met. Erwan played a pivotal role in the Electronics and Programming aspects of the project, as he was responsible for selecting and implementing hardware and software solutions for the printer. He was also in charge of modifying and tweaking the printer’s firmware to adapt it to cylindrical coordinates. As project manager, Erwan also held the responsibility for ensuring the quality of the reports. He was in charge of assembling the reports, unifying the formatting and final editing. MATTHIEU: HEAD OF CONTROL AND STRUCTURE As Head of Control, Matthieu worked on obtaining the best possible printing accuracy. To this effect, he was responsible for selecting the motors and designing the transmission while minimising backlash. He was also in charge of designing the print bed assembly and all the components that relate to it. He was also the main architect of the CAD model and ensured the overall design was coherent. As such, he played a vital role in the manufacturing process and ensured quality control. Matthieu was also in charge of the acrylic sheets, from purchase to the design. He conducted and evaluated the impact of the laser cutter on the Perspex sheet and updated the CAD file accordingly. Matthieu also played a significant role in programming; he developed and tested the MATLAB program. Finally, along with Erwan, he was responsible for editing and proofreading the reports. YOUSSEF: HEAD OF MECHANICAL DESIGN In the design process, Youssef held responsibility for the design of the X and Z axis components. He adapted standard RepRap x and z axis components for cylindrical printing. He distinguished himself in the manufacturing and assembly process. He played a key role in manufacturing and used his technical abilities to fix problems during the assembly process. Once the printer was assembled, he contributed heavily to increasing the practicality and aesthetic appeal of the printer. Along with Matthieu, he was an important contributor to the CAD. Finally, he generated innovative ideas for the poster. ALEX: HEAD OF ELECTRONICS AND PROGRAMMING Alex played varied roles as part of the team. As head of electronics and programming, Alex contributed to the programming through his expert knowledge of C. Possessing clear artistic skills; he was in charge of visual representation and photography of the printer. His skills in scene setting and lighting ensured aesthetic and precise representations of the printer and test parts. Alex also brought forward his image processing skills to design the poster. He also made subtle modifications to the CAD file, and was the driving force behind the assembly drawing. Finally he kept track of the teams spending and budgeting.

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DMT 27: Lathe-type 3D Printer

Department of Mechanical Engineering

II. PROJECT PLANNING One of the main aims of the project was to demonstrate the viability of the cylindrical 3D printer concept. As such, the team’s approach to the project was relatively unrestrained and free of commercial considerations. One limitation however was the project budget, which could not exceed £600. As a result of these criteria, the group prioritised innovation over cost-effectiveness, exploring different methods and perspectives towards the realisation of the end product.

II.1 Product Design Specification Starting from the project brief, a Product Design Specification (PDS) was produced in order to identify the key requirements which our project would need to satisfy. Additionally, these objectives were quantified in order to provide a framework for the design process. The criteria outlined below are of varying importance to the success of the project and a weighting from 1 (low importance) to 6 (high importance) was assigned to each criterion. Table 1: Product Design Specification: Performance and Safety

Aspect

Criteria High precision printing Homogeneous deposition

Performance

Quality

Robustness

Safety

Efficiency

Low risk to user

Objective

Testing

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