The group is very grateful for the guidance and help from the following people:
Dr Shaun Crofton, for his helpful and friendly support as supervisor. Shaun also supplied us with non-standard parts such as the M14 bolt and a large Aluminium rod for which we are very grateful.
Dr Paul Hooper, for his advice and guidance in programming and the overall conduct of the task.
Dr Daniel Plant, for his ideas regarding cylindrical printing and guidance as associate supervisor.
Mr Suresh Viswanathan Chettiar, for his assistance and supervision in the Polymer Technology Laboratory.
Paul Woodward and the workshop team, for their responsiveness and help, particularly during the manufacturing of the acrylic sheet.
Miss Sam Tolhurst, for her help processing expenses.
Alessandro Ranellucci and all the other open source contributors, for developing and sharing open source software such as Slic3r.
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APPENDICES
Appendix A1: Structural and Control Calculations
LASER CUTTING TESTS
To ensure that the laser cut acrylic sheets met their required dimensions, test parts were manufactured. Their nominal dimensions were compared to their actual measured dimension.
Measurements were performed with a micrometre and the results are presented in the following four tables. In red, the average laser width is computed.
Table 10: Results from the first laser cut test part
Reference Nominal dimension
Part 1 Part 2
Max error Average Laser width Meast 1 Meast 2 Meast 1 Meast 2
A 5.00 5.30 5.32 5.32 5.32 0.02 5.32 0.32
B 20.00 20.21 20.22 20.23 20.21 0.02 20.22 0.22 C 10.00 10.27 10.28 10.31 10.28 0.04 10.29 0.30 D 15.00 15.26 15.25 15.24 15.26 0.02 15.25 0.25
E 5.00 5.29 5.28 5.34 5.33 0.06 5.31 0.34
F 10.00 10.27 10.26 10.27 10.27 0.01 10.27 0.27 G 10.00 10.30 10.29 10.22 10.29 0.08 10.28 0.25 H 20.00 20.25 20.24 20.26 20.23 0.03 20.25 0.25
Average 0.04 0.27
Table 11: Results from the second laser cut: inner dimensions
Reference Inner
dimensions Meast 1 Meast 2 Max error Average Laser width
A 6.80 7.48 7.48 0.68
B 4.00 4.48 4.48 0.48
C 9.73 10.14 10.16 0.02 10.15 0.42
D 4.73 5.08 5.08 0.35
E 19.73 20.09 20.09 0.36
F 20.00 20.33 20.33 0.33
G 5.00 5.37 5.37 0.37
I 10.00 10.45 10.45 0.45
J 10.00 10.34 10.45 0.11 10.395 0.40
K 10.00 10.49 10.49 0.49
L 8.00 8.48 8.48 0.48
M 6.10 6.48 6.49 0.01 6.485 0.39
N 59.90 60.23 60.23 0.33
Average 0.42
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Table 12: Results from the second laser cut: outer dimensions
Outer dimensions
Meast 1 Meast 2 Average Laser width a 30.00 29.55 29.55 29.55 0.45 b 90.00 89.52 89.52 89.52 0.48
c 65.00 64.6 64.6 0.40
d 86.00 85.64 85.64 0.36
e 60.00 59.53 59.53 0.47
f 10.00 9.65 9.63 9.64 0.36
g 10.27 9.86 9.87 9.865 0.41
h 10.27 9.67 9.67 0.60
i 10.00 9.49 9.49 0.51
Average 0.44
Table 13: Results from the third laser cut test part
Ref Meast 1 Meast 2 Average Laser width
a 9.08 9.2 9.15 9.175 0.10
b 69.60 69.65 69.62 69.64 0.04 c 29.40 29.3 29.25 29.3 0.10 d 100.00 99.8 99.85 99.8 0.20
e 60.00 59.53 59.53 0.47
f 10.00 9.65 9.63 9.64 0.36 g 10.27 9.86 9.87 9.87 0.41
h 10.27 9.67 9.67 0.60
i 10.00 9.49 9.49 0.51
Average 0.28
MOTOR DYNAMIC TORQUE CALCULATIONS
To calculate the dynamic torque it is necessary to measure the mass moment of inertia Ig of the main components coupled to the print bed. It can be calculated using the following formula:
Where M is the total mass of the component, r its radius, ρ the density of the material and L its length. The mass moment inertia calculations are summarized in table 14.
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Table 14: Mass moment of inertia calculations
Part M (kg) r (m) ρ (kg.m-3) L (m) Ig (kg.m2)
Print bed 0,05 1240 0,25 3.04×10-3
Chuck 2 0,035 1.23×10-3
Shaft 0,006 7850 0,18 2.88×10-6
Gear on print bed 0,055 2720 0.012 4.69×10-4
Live centre 0.006 7850 0.02 3.20×10-7
Bearings 0,1 0.025 3.13×10-5
Gear on motor 0.012 2720 0.02 1.77×10-6
Motor 1.35×10-5
Total 4.79×10-3
TRANSMISSION BELT LENGTH
Evaluating the length of the pulley was essential as the pulley had to be of the exact length to limit backlash.
Figure 73: Schematic representation of the gear pulley system to measure the required pulley length
The length of the pulley depends on the angle alpha, which is defined in figure 72. By geometry, the angle can be determined:
Furthermore, from the right angled triangle:
( ) √ ( )
The length l of the belt can be obtained by summing its length on the small pulley, its length on the big pulley and twice the length h.
( )
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( ) (
) √ ( )
( ) (
) √ ( )
From the above calculations, a belt of length 276mm was used (92 teeth with a 3mm pitch).
MAXIMUM PRINT BED DEFLECTION
The rails are the major cause for the deflection of the print bed. Calculations are carried out to determine the maximum deflection if the rail slider is halfway along the rails.
( )
The maximum deflection, assuming a 2kg print bed (there are two rails) is of 0.249mm. This is a conservative estimate as most print beds are lighter than 1kg and the rail slider is not usually in the middle of the rails. Therefore, this is a maximum value and in practice the deflection will be much lower.
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Appendix A2: Detailed Bill of Materials
NO. DRAWING NO. PART NAME MATERIAL QTY
12 DMT-27-001 BEARING SUPPORT ALUMINIUM 1
13 - BEARING BRACKET PLA 1
36 DMT-27-004 MOBILE SUPPORT ALUMINIUM 1
37 - PRINT BED ALUMINIUM 1
Table 15: Detailed Bill of Materials
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Appendix A4: Detailed Drawings
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Appendix A5: Individual Critiques
ERWAN ROLLAND
The project proved to be a tremendous learning experience from both an engineering and a team building perspective. The project was organised effectively, and all key objectives were met within deadlines and budget. I suspect our performance was enhanced by our relative lack of prior knowledge concerning 3D printing, as the motivation of discovering a new technology carried us through the task
Being elected project manager, I was in charge of the organisational and planning of the project. I feel this aspect of the assignment was particularly successful, and I devoted much of my time to it.
Early on, I ensured that all team members had a common set of objectives and expectations for the project, in order to make certain that no misunderstandings would delay our conduct of the task. As such, I decided to discard some ideas which were not entirely in line with the initial brief.
While this led to some ambitious ideas being cast aside, I am confident these choices were necessary for the project to be completed on time.
I believe one of the key initiatives which led our team to success was the implementation of shared leadership. Each team member was given an area of the design in which they could contribute in a significant manner. While all decisions were shared, this prevented team members from feeling alienated or neglected. Regular meetings were implemented to ensure all members were aware of the other aspects of the design. As project manager, I had a good overview of the design process, and took care to ensure the design was being steered in the right direction.
Unfortunately, this led to some decisions being taken without the direct involvement of certain team members. However, I encouraged disagreements to be voiced in the open order to avoid frustrations from building up, and I believe everyone was satisfied with our final design.
One of the things I have learnt from this is the importance of self-evaluation and frequent feedback from other team members, particularly being in a leadership position. Indeed, this allowed me to realise I may have been too demanding from other group members at times. While I believe this attention to detail brought the overall quality of our prototype upwards, perhaps I should have been more diplomatic when suggesting large changes to be implemented. Thankfully, the team got on very well together and no one felt like their contributions were not being taken into account.
As project manager, I was also responsible for generating content for the report and putting it together. Perhaps I took a too involved approach, which caused the elaboration of the reports to last a long time. However, this time allocation was planned beforehand, and scrutiny of the report allowed us to highlight which aspects of the project could still be improved upon.
During the design process I took on the tasks related to Electronics and Programming, and was accountable for the key decisions shaping this aspect of the project. Given this side of the project was the least akin to mechanical engineering I found it difficult to communicate some of my ideas to the group. In hindsight, I should have encouraged other team members to take a more active role in this task, but this would have taken up time vital to the other parts of the design. Finally, I should have sought more help from the supervising team, who always provided valuable advice and experience when asked. Taking their suggestions on board more frequently could have resulted in an even more refined design.
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criteria. The human relationships, the transferrable and technical skills as well as the experience that I developed through this project are what really added value to the project.As Head of Control and Structure, my engineering knowledge was put to the test. Parts had to be designed in a coherent way, to ensure they were manufacturable and minimised backlash. I learnt much about precise transmission design and how to select motors. Automation and mechatronic systems are of ever increasing importance for engineering and this project opened my eyes to the importance of robotics. I learnt about G-Code, embedded systems such as the Arduino and Ramps which are essential functionalities used in many engineering domains. What I particularly enjoyed about this project is that it was multidisciplinary and developed my skills in many areas: design, manufacture, mechatronics, mechanics, materials science and project management. This made me aware of the importance of being well rounded which is a key quality for working in industry.
This project taught me much about team work. I applied knowledge I had gained from previous group projects and further improved them. There was great cohesion in the team and I think this was mainly due to the effort we put on communication. Our regular meetings, three times a week, ensured everyone was up to date on the most recent developments. This was a strong contributing factor to the success of the team as it created an emulating group spirit which increased overall motivation. In hindsight, the team building exercises at the beginning of the DMT were very useful as it enabled us to reach the “performing” stage much quicker.
The additive lathe project allowed me to put into practice the concepts that I learned during the Integrated Design and Manufacture course. I applied the concept of “kaizen” (continuous improvement) to the group and I feel this was particularly valuable to the group as it allowed us to learn from each other. By continually discussing ideas and proposing alternate solutions to problems we progressed as a team. This was particularly true as our skills were complimentary: I learnt much from Youssef’s manufacturing knowledge, Alex’s skills in the C language and Erwan’s different approach to management. The group was very open to criticism and I believe this increased our overall learning. Voicing concerns through constructive criticism allowed me to learn and teach much from the others in the group. By having an external view, I think we all developed our self-evaluation skills.
An important lesson that I learnt in this project is the importance of planning. At times we excelled in this domain, for example when we finished the printer early, in March. However we could have improved planning when it came to report writing. When writing the final report, I lacked structure before writing parts. This resulted in sometimes confused sections which I had to rewrite. Learning from this will allow me to write better structured reports in a more time efficient manner in the future.
A piece of advice that marked me during the project came from Dr Shaun Crofton who at one occasion told us to “keep it simple”. I understood the full significance of this when we were finding ideas for a changing diameter print bed. Although this could have been an interesting feature, this
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was not central to the project and added unnecessary complexity. Simple systems are often the most efficient and I do think in the end this contributed to the success of the project.
Working on this project also developed my general awareness of the additive manufacturing industry. 3D printing is a growing sector and is one that has the potential of revolutionising manufacturing processes. I learnt much in this project and developed a strong interest in this industry which allows me to have my own opinion on this matter. The project had such a profound impact on me that I am planning on making my own Cartesian printer. I am glad we decided to take on this project. Before this project I also believed that developing innovative ideas in Mechanical Engineering was limited to those with expert knowledge in a specific field. However this project proved me the opposite. I was in charge of designing the print bed assembly and this was one of the main innovations of the project. This taught me that being audacious and focusing on the problem is the key to innovation.
All in all, the collaboration with the team was mutually beneficial. I learnt that trust and compromise are key to the project success. Criticism has to be taken in a constructive way to allow for continuous improvement. By effectively working as a team, we managed to develop a novel and successful additive lathe.
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ALEXANDROS KENICH
Before starting this project, 3D printing was a technique which I had only heard about a few times and in each instance, it was presented as a complex process far beyond the capability and means of students. It was therefore enlightening to witness the gradual realisation of our own printer. Of all the knowledge and skills I have gained while working on this project, I would say that the most significant was how it expanded my notion of what is possible with limited resources and concerted efforts. these tested our resourcefulness and helped me develop my lateral thinking as well as providing valuable experience of working with these materials and systems. Furthermore, as this project was more demanding than the one from last year, it required that I improve my time management and organisational skills in order to keep up to date with the project as well as my other courses or risk being overwhelmed with work towards the deadlines. Additionally, the importance of effective communication became very clear as a result of working on this project. Our regular meetings during the week were vital for progressing with tasks and resolving issues in the project while also keeping each other aware of any subtle changes or events which would otherwise have not been known, such as a small dimensional change in a model to incorporate a new component or availability of a member to attend on certain days.
As head of programming, my efforts were focused on the development of the Arduino code mainly in order to accommodate a rotational axis for cylindrical printing. The code used for Cartesian printers is open source so that was used as a foundation to build upon. I used skills that I had gained from the Embedded C course which I completed this year. This greatly aided my understanding of the existing code because the Arduino board uses a language which is very similar to C. One problem which came up once we started printing was the low quality of the infill of printed parts. These initial parts had thin and erratic infills which severely reduced their structural integrity. To rectify this, I altered the code to increase the nozzle diameter. This meant that the extruder would draw more filament in order to satisfy the increased calculated mass flow implied by a larger diameter nozzle. Once the optimal nozzle diameter was found, the infill became consistent and completely free of voids. This made the parts we printed thereafter much stronger as shown by their performance in the loading tests we carried out.
In hindsight, I would have given myself more time in the earlier stages of the project to understand and prepare for my assigned tasks fully so that I could complete them in a shorter period of time and also be able to assist the other group members with their tasks in order to spread the workload. I would also take up more of the CAD tasks rather than split them evenly between members because I believe this area is one of my strengths and this would also eliminate issues with cross-referencing when producing drawings due to different component versions and inconsistencies due to different authors. In all other regards, the project went smoothly and it was a fun and fulfilling journey together with an excellent group.
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YOUSSEF IBRAHIM
The project was a success. Progress was smooth and steady, leading to very satisfying results. All the goals were met, and all deliverables were achieved in accordance with the original plan set at the beginning of the project. In my opinion, this was due to realistic and accurate organisation, as well as excellent delegation of tasks which conformed with the strengths of each group member.
Another, perhaps more important, influential aspect on the group’s performance was the excitement associated with 3D printers. Demystifying the concept and seeing it at work was one of my main motivational drivers, and I am sure my group members shared the same sentiment.
I was particularly impressed by the group dynamics during the project. The project was broken down into separate sections; each member being allocated responsibility for the section in which they exhibited the strongest understanding. Communication was effective and plentiful leading to great ideas being generated readily. The diverse range of skills and interests held by each member contributed to a well-balanced performance without excessive emphasis being placed on any one aspect.
I was able to witness first-hand the benefits of mutual respect and admiration, as well as punctuality as compared to my previous experience with group work. An efficient group formation phase lead to more time being spent focusing on the project at hand and less time spent on group relations. This emphasised the importance of establishing firm foundations with group members before any real progress can be made.
My role in the project was rooted in design and manufacturing, being the head of mechanical design. I took an active position in producing conceptual overall design solutions to the main problems the project had to face. I found that most of my initial ideas were very ambitious, and so eventually had to be abandoned as the extent of our capabilities became clearer. The influence of costing and availability of components also began to place unexpected restrictions on design, as I had previously not realised their effect.
Once the final design was agreed upon and all the relevant purchase orders were placed, manufacturing considerations became my main focus. Owing to my great interest in manufacturing, I played the lead role in producing most of the machined parts, as well as keeping track of and organising all the components as they arrived. Many alterations had to be made to the final design in order to ease manufacturing and assembly. Making the most of the available material also imposed some design changes as to minimise wastage. I also played a key role in assembly and fitting once all the components were available. It was during this phase that quick adaptive thinking became important in order to deal with unforeseen setbacks. Finally, I found myself concerned with aesthetics and convenience, for example spawning the addition of the filament spool to the design post assembly.
In conclusion, I realised that my view has perhaps been too narrow. My contributions to the programming and software side of the project were very limited, and I found myself unable to reproduce the printer alone had I had the desire to make one for personal use. This brought to light the importance of keeping a general idea of the task as a whole, preventing the loss of touch with the main objectives of the project. Otherwise, it was an extremely rewarding experience with a brilliant group and a pleasure to have undergone.