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DESCRIPTIONEngineering Design Year Two Semester Two 3D Printer Product Design Group 14
Engineering Design and Structural Analysis Methods SESG2005
3D Printer Group Design Project
Berkeley, Jamie Flinton, Alan Huntingford, Joshua Knight, Robert Krueger, Hannes Olivier, Isabel Sunder, Shriram Tress, Dee Urbsas, Mikas Warmington, Joseph
24659975 24750522 24789518 24604216 24959308 24702269 24946222 24797367 24268518 24730157
Submission Deadline: 7th May 2013
Overall Perspective This project aims to investigate the potential for bringing the capability of 3D printing to a domestic scale. This technology has been revolutionary in the field since its introduction in 1987, providing flexible and efficient methods of prototyping and producing simple 3D parts, allowing complex modules to be produced quickly and easily. This is achieved by layering the chosen composite, resulting in a solid, accurate, low cost working parts, however although the cost of manufacture is dramatically reduced by use of this technology, the units themselves are extremely expensive and require a huge initial outlay which must be factored back in to the overall cost of the product. A need has therefore arisen for a low-cost, high-performance additive manufacture machine that could fill this void in the market and make 3D printing more widely accessible. This is essential for developing countries and a wide range of educational and industrial sectors if they wish to continue to be able to compete with the larger commercial companies and dominating worldwide producers. Due to the diverse applications of such a device, the target consumers for this product is overwhelming, with practical uses required in multiple industries, including architecture, healthcare, education and retail. Literature Review Our first point of research was to establish the main technologies used 3D printing, selective laser sintering, fused deposition modelling, and stereo lithography, for which we utilised the website 3ders1. This website follows the news, trends and resources of the 3D printing world and therefore provided us with a basis to begin our own project. Due to the low budget of this project, we established that fused depositional modelling was the most appropriate method as it is the cheapest, however each of the three methods are evaluated in more detail in the critical review. Another useful feature of this particular website was an in depth discussion on the applications of 3D printing, which was essential when establishing our target market. One of the most prominent uses of this technology is in the medical industry, however due to the high standards required in such a field, it is unlikely that our own design will be suitable. A more realistic application is the construction of aerofoil sections for use in wind tunnels, or prototypes for working parts, where quality constraints are not so strict. Such applications exploit the main advantage of a 3D printer; its ability to entirely form a part from a wide range of materials in a matter of hours. Our research then directed us to investigate RepRap technologies, found on RepRapWiki2. RepRap is a 3D printer made from plastic parts, which in turn is able to print plastic components, - in essence a self-replicating machine. Therefore if our final design is predominately plastic, it would be possible for us to utilise this feature for the production of spare parts, an advantage for the consumer. Furthermore, this strategy would be extremely low cost, an important feature of our product and design process. RepRap is also an open source community project, allowing anyone to manufacture their own 3D printer, resulting in a wealth of available information and previous research. Due to the wide range of styles and designs currently available for 3D printers, it was important to compare each concept in order to focus our design process towards the most appropriate outcome. The 3D printer comparison chart (see appendix 1) from makershed3 compares 5 different low cost 3D printers. These all fall within the category that our own printer should be designed around; low cost, small and for personal use, and therefore provided useful insights into our own research. All of the printers use fused deposition modelling, and use only a single extruder, but across the range provide a wide range of print volumes, from 100x100x100 (Printbot Jr) up to 250x152x152 for the Makerbot. This does however have cost implications, as prices range from $499 to $2199. It can therefore be seen that if the budget used in this
production is accurate, our own design is likely to be limited to a small print volume. The chart also implies that print speed and resolution are both closely linked to the price of the printer, which is expected as investing in better parts will yield a higher quality print. For a low budget printer, print speed is likely to be about 70mm per sec. All main operating systems (Windows, Mac and Linux) are supported by all of the printers, an important design feature to consider, and most can use both ABS and PLA as a filament for printing. Additive3d4 provides another 3D printer comparison chart (appendix 2) comprising of many variants of printer. By examining the pros and cons of each printer it is again evident that cheaper printers (under 1000) will suffer from poor surface finishes and slow print speeds, such as in RepRap. PP3DP is a low cost printer which benefits from a low operating sound, another design parameter we decided to consider within our design. The Leapfrog printer can use a WIFI computer connection, however this could lead to slow data transmission and is seen as a gimmick simply raising the cost of the printer and was a feature we therefore discarded. Many printers use a heated platform to avoid the print warping, an essential property if FDM is used. A further advantage of certain printers is their ability to be modified allowing easy upgrades. This is essential to keep up with future developments, and accommodate changes for unique print projects. Although after careful analysis of the existing market there does not seem to be a distinct niche, due to the highly modifiable nature of 3D printers it will be simple to make a 3D printer optimised to suit our needs. As the budget for the printer is low it is likely that the quality of any prints will be limited, but none the less satisfactory for our needs. Our final point of primary research was into stepper motors, a common type of motor used in the robotics industry (see appendix 35). Their characteristics make them suitable for use in 3D printing as they move a known interval for each pulse of powder they receive. As each step is a known distance they are useful for repeatable positioning. Stepper motors can be either unipolar or bipolar, with unipolar motors being the more cost effective and therefore used for simpler applications6. They are powered by stepper drivers which allows them to be digitally controlled, another vital design feature. We were also able to utilise previous research7 to establish black box dimensions for the stepper driver (appendix 4). Critical Review of Design Alternatives The design of a 3D printer can vary in many ways due to the numerous solutions to the design challenge available through advancing technologies. These can be summarised into 3 main categories: laser sintering, stereo lithography, and fused deposition modelling. As can be expected each of these methods will have its advantages and disadvantages8. Laser sintering, also known as SLS, uses a laser to heat powder (usually white nylon9). As the powder is heated, neighbouring particles fuse together forming a cohesive a solid. A computer separates the desired model into slices, which are recreated by the layer by layer, eventually building a complete 3D model. When printing is finished, the model is encased in a block of powder, which is often removed manually. This allows for extra support for parts during the print process, allowing the design to be more complex. Powder that is not used can be collected and used in the next print to avoid waste and reduce production costs. The major limitation of this process is a restricted ability to produce hollow parts, as there would have to be a hole to allow the powder trapped inside to be removed. SLS is, however, capable of producing snap fits and hinges, which are of great benefit as to make them externally, would add to the complexity of the project. Additionally, parts made by laser sintering are usually heat and chemical resistant. Due to the manufacturing methods used within laser sintering, the model often has a rough surface finish, which can be expensive and time consuming to remedy. Further disadvantages include the limited colour choices associated with SLS, an issue almost uniquely associated with this method, due white nylon powder being the most common input. Additionally, SLS printing is generally messy and unsuited for personal use due to the need for the powder to be swept away and peeled from the finished. 10 Stereo lithography, also known as SLA, is somewhat similar to laser sintering due to its use of a laser11. In this case, however, it is a beam of ultra violet light and the principles of
photochemistry that are applied. Instead of powder, the laser beam of UV light is shone into a vat of photopolymer whose properties alter when exposed to UV light - in this case, hardening. Once again, the model is sliced by a computer and built up layer by layer until complete. Out of the three printing methods, SLA is the best technique to manufacture water resistant materials, and usually provides a good surface finish12. This does however have detrimental effects in other areas, as this capability requires the printer to be watertight in order to contain the liquid resin, increasing complexity, and the price of the resin (a minimum of $80 per litre), combined with the added expense of a laser, makes it far more costly than other methods.13 Fused deposition modelling (FDM) utilises different technologies, creating a 3D model by heating the model material (the filament) and then feeding it though an extruder14. By heating the filament, it becomes less viscous and easier to extrude and manipulate, allowing the model is built layer by layer from the bottom up - similar to laser sintering. The path the extruder follows must be extremely precise due to filament cooling, and is often allocated by a computer to obtain the optimal route. It is possible to change the filament type to create support structures for the model, creating potential for greater design complexity. These support structures are soluble, usually in water, so when extrusion is finished it can be simply placed in a tank to remove the supports. Two main types of filaments are used when applying fused deposition modelling: polylactide (PLA) or acrylonitrile butadiene styrene (ABS). Each of these filament types will have implications on the characteristics of the model. Both PLA and ABS can be used as filament if an extruder is used as a construction method with each type having individual characteristics (appendix 5), however due to their differences, the printer is often optimised to accommodate only one type. PLA is plant based, and subsequently rich in starch. As a result, it is 100% biodegradable and wont produce any toxic material when decomposing, an important environmental factor. Conversely, ABS is petroleum based, limiting its commercial uses due to toxin levels. Economically there is no difference between the two15. The extrusion temperatures of the two types of filament are also different. PLA has a glass transition temperature of 58C, and ABS 100C, and as a result a higher temperature is required to extrude ABS effectively. When PLA is used a cooling system is therefore required16 to cool the model quickly before it droops. In contrast, ABS systems frequently use a heat bed to ensure that the first layer of the model adheres to the plate17, and also to prevent rapid cooling, which would also result in warping, Both filament types incur size limitations, as large parts will take longer to cool, often leading to drooping. All of the above methods were explored when generating concepts to meet the design challenge.
Engineering Design Methods
Customer Requirements After carefully analysing our research and the information above, and investigating the success of a number of printers with varying features, we decided on the 10 parameters we wanted to use as a design basis for our own project. These decisions were aided by our own personal experiences with numerous 3D printers and establishing which features would make our product most appealing to our target market, whilst still being feasible within our budget. Our requirements, set out below, are formalised in appendix 6. 1. 2. 3. 4. 5. 6. 7. 8. 9. Print resolution Print size Print speed Robust Ease of assembly Ease of maintenance Lightweight Low cost Ability on different terrains
Once selected, it was then essential that the features were prioritised appropriately to direct our concept generation, for which a Binary weighted matrix was used. From our matrix (as seen in appendix six), each requirement was compared directly to each other to determine the overall importance with respect to our final design. The results of this can be seen graphically in appendix 7. From analysis of this graph it was immediately evident that the primary function of the printer (to produce 3D models) was the most important capability, closely followed by robustness, and ease of assembly. Using this information, we were able to produce a simple design brief which we were able to utilise for our design concept generation.
Design Concept Generation
The information above was collaborated and in order to generate the most diverse and innovative selection of concepts possible, each member of the group designed and evaluated a design, which was then put forward along with a detailed explanation and evaluation. This allowed for multiple approaches and features to be considered and was thought to be the least limiting method of concept generation. As a result, the range of potential options available for further development was exceptionally broad and thought provoking. Our designs can be found in the appendix, labelled figures 8-17.
Design Concept Selection Our concepts designs from above were analysed carefully to assess their individual merits and positive features, and evaluate which we thought were worthy of further consideration. A large amount of this critical assessment can be seen on the drawings themselves, however below is a concise assessment of each concept. Concept One (appendix 8): Advantages: - Separable parts, cheap and easy to repair - Pre-existing control mechanism (cheaper, already tested/viable) - Lightweight, easy to move - Stable base - Easy to monitor/access plate Disadvantages: - Large amount of moving parts, high potential for degradation/wear - Large housing area required (bulky, storage issues) - Requires extra space below for teeth mechanism Concept Two (appendix 9): Advantages: - Less complex housing - Small compact design - Fewer moving parts (less potential for wear) - Simple control elements Disadvantages: - Effect of rotation on part must be considered, may be fragile - Commands must be converted into cylindrical coordinates (more complex commands) - Potential for material clogging in tube - Inefficient (lots of material melted even when quantity required is small) Concept Three (appendix 10): Advantages: - Simplistic design (easy to manufacture) - Closely linked to many other designs (easily sourced material)
- Cartesian operating system (able to use existing coding programmes) - Compact and stable design, simple stress analysis - Easy to locate, access and repair damaged parts Disadvantages: - High volume (storage issues) - Limited support structure, may be challenging to move - Wiring could interrupt print area Concept Four (appendix 11): Advantages: - Minimal amount of materials required - Compact - Potential to be self replicating Disadvantages: - Multiple moving parts, more complex programming - Potentially weak structure - May be unstable - No obvious location to store filament Concept Five (appendix 12): Advantages: - Stable base to prevent moving - More accurate/precise than other methods - Few mechanical parts reduces failure risk - Retractable for easy storage Disadvantages: - Bulky and may be heavy/hard to move - Expensive - Parts may be difficult to make/source - Complex controller system required - Often requires further setting of model Concept Six (appendix 13): Advantages: - Easily collapsible for simple storage - Lightweight and compact - Potential for self replication of many parts - Pre-existing controller system Disadvantages: - Would require feet to accommodate mechanism, potentially unstable - Multiple moving systems may be difficult to align (different rates) - Moving plate could disturb already deposited material Concept Seven (appendix 14): Advantages: - Innovative design, likely to generate interest - Very few moving marts, low likelihood of mechanical failure - Moving parts cheap and simple to replace Disadvantages: - No existing models, difficult to analyse/ develop operating system - Rollers and moving system will be heavy, difficult to manoeuvre - Very complex housing, fractional errors could be disastrous - Laser component very expensive Concept Eight (appendix 15): Advantages: - Very small, lightweight design - Extremely precise mechanism - Easy to access parts
- Few parts so reliable/ inexpensive - Uses pre-existing control systems Disadvantages: - Very basic functionality - Potentially unstable - Requires 2 mechanisms to work in unison Concept Nine (appendix 16): Advantages: - Complete freedom of movement, allows for more complex design - Heated plate for uniform cooling - Very stable base - Potentially collapsible for easy storage - Independently moving bearings, fast ad precise Disadvantages: - Requires production of complex bearings/sliders - Complex design, high potential for error Concept Ten (appendix 17): Advantages: - Very compact, easily moved and stored - Highly portable as no need for housing - Theoretically unlimited range of movement Disadvantages: - Complex movements, difficult to build/repair - Potentially requires new control system - Must be carefully aligned Careful consideration of all of these factors was essential, which was assisted by use of an effectiveness-versus-degree of difficulty graph (appendix 18), which allowed us to quickly eliminate the least appropriate concepts, and focus our attention on the benefits on the concepts with the most potential. An analysis of these most suitable designs was then required, achieved by considering how each design complied with our customer requirements (see appendix 19). A ranking system was adopted based on these results, which took a user decided ranking of how well each design matched our customer requirements, and multiplied that value by the requirement weightings established in our original matrix. This established concept 3 as our chosen design due to it being ranked highest, and having the most potential for further development. A number of factors contributed to this, such as its efficient use of design space, high levels of stability, relatively simple make-up, and a high availability of similar open source designs. It was however decided that a selection of the most prominent and beneficial features from certain other designs would be incorporated into our final concept to attain the most effective and superior design.
We did however identify a conflict in our design regarding a need to improve the stability, however this would have negative implications on the weight of the non-moving object. To find a solution to this, we utilised the TRIZ matrix18, which identified possible solutions of: 1: Segmentation 26: Copying 39: Inert Atmosphere 40: Composite Materials Further details of which can be found in appendix 20. After analysis of these, it was determined that the best solution for our own model would be to use a composite material. Following the section and implementation of our customer requirements, it was then required to identify the design parameters, which would need to be considered to enable us to meet our specification. These key parameters were as follows.
Weight of moving object Weight of stationary object Length of moving object Length of stationary object Area of moving object Area of stationary object Volume of moving object Volume of stationary object Speed Force Tension/Pressure Shape Stability Durability of moving object Durability of stationary object Temperature Energy spent by moving object Power Energy lost Substance wasted Information lost Time lost Substance mass Reliability Measurement accuracy Manufacturing accuracy Manufacturability Convenience of use Reparability Adaptability Device complexity Control complexity Automation level Productivity
These particular parameters were selected as we believed that they were thorough and covered all the essential components and considerations of our design, including performance, aesthetics, practicality and environmental impact. These parameters were tabulated along with our chosen customer requirements and a matrix of mappings was used generate a normalised set of weightings. The information provided by the table (located in full on the enclosed CD-R) was displayed graphically, as seen in appendix 21, and evaluated to form a comprehensive parameter ranking which could be used to evaluate our chosen design. From the results of this, it can be seen that although the majority of outcomes largely accord with logical judgement, such as complexity, accuracy, manufacturability and substance volume being the most essential points to consider, there are a number of variables that were unexpectedly located in the ranked outcomes. Shape was considered to be in the top 25% of important parameters, a factor which would previously not have been regarded with a great deal of importance, whereas factors such as energy consumption and efficient usage were considered largely irrelevant when compared to other factors. This allowed us to consider minor alterations within our own design, and take the necessary actions to ensure all of our customer requirements and design specifications were being met as closely as possible. As a result, we integrated threaded rods into the frame making it easier to build due to the reduction in required parts, and far more aesthetically pleasing, which was a factor brought to our attention by the matrix. Although this will be more complex to execute, it was identified as a unique solution, providing us with an original selling point, and is a far more advanced design that requires less operating space. It is clear from this that analysis of key parameters is a vitally important part of the design process, allowing the focus of customer requirements to be quantified and re-evaluated continually throughout the project to ensure that the best possible product was created.
Once the final alterations to our design had been made in accordance with the design parameters above, the overall weighted design merit of each customer requirement had to be evaluated to assist in determining the success of our design. This was achieved by creating a CODA spreadsheet, as seen in appendix 22, and on the enclosed CD-R, and the parameters were solved via excel to establish our overall design merit. From this it was possible to perform a design optimisation to determine the optimum values for our engineering design variables. These are displayed in appendix 23, with separated graphs found on the CD-R. This provided the optimum numerical values for each individual point of consideration, and gave us a set of ideal conditions to work towards. Although these may not be practically achievable, it allows our calculations and finite analysis to be far more accurate, and therefore increase the likelihood of developing a successful product that is suitable for our target market.
Cost Estimation A cost analysis was carried out using the information generated above which would eventually result in a comparison between the merit and cost of each parameter. This was achieved using
Vanguard, from which we were able to develop a chart of total costs, with the components of the printer as a whole further separated into their independent constituents, allowing a breakdown of costs if something were to be overpriced. This can be seen in appendix 24. All the elements to the left hand side have been calculated by multiplying the elements to the right with each other, and the cost of each of the aspects of the merit have been calculated individually as a combination of either of the 4 elements that make up the entire cost of the 3D printer. A number of calculations based on merit and cost were carried out as a result of this (appendix 25), which resulted in the production of the Merit vs. Cost Plot seen in appendix 26. This enabled us to evaluate each components cost/value trade off, from which it was ascertained that it was not in our interest to improve on certain aspects, as the benefit we would achieve from it would be outweighed by the cost of its implementation. An obvious example of this is the printer speed, which is one of the most expensive features, but has an extremely low merit value of only 0.74. This had a large impact on many of our later decisions such as the inclusion of threaded rods (see Finite Element Analysis).
Engineering Calculations Basic Calculations
Due to the large volume of components required for the building of a 3D printer, and the large amount of sources already available, it was decided that, although we were capable of making a high quantity of the necessary parts, a select few would be both cheaper and easier to purchase directly. The extruder we are using is largely based on the Wade geared extruder19 selected for both its design simplicity and ease of implementation and integration. This type of extruder is also capable of relatively high-speed printing, which is easily controllable through internal gear manipulation (appendix 27). Some alterations to this design were necessary however to ensure the extruder fitted on our own carriage. As our printer was designed to be largely self replicating, many of the key components such as the body and the gears, can be formed via 3D printing, resulting in cheaper and lighter parts than if they were cast from metal. This has the added benefit of requiring a lower amount of torque to drive the machine and a dramatic decrease on the working loads. Our design also utilises many standard issue components such as screws and bolts, these can be easily and economically sourced without issue, again reducing workload and product cost. We are also using the J-head Mk V nozzle20 sources from the site. There is very little difference between each version with respect to our limited usage; therefore we selected this one based on its lightweight properties and durable aluminium nozzle. It is also one of the most recent versions, offering a more compact body and increased melt zone length. We opted to design and produce our own heating bed based on the design in appendix 2821, which offered all of the required features, such as preventing warp on cooling and allowing for adhesion to the surface, but was an inadequate size to be incorporated in our own product. Our required print area is 290mmx275mmwhereas the area for this product is 200mm x 200mm, meaning this design can simply be up scaled to suit our specification. The software required to run the 3D printer is all open-sourced, making it easily available and free of cost, providing both a practical and economical solution to the operating conditions. It is simple to design a 3D model in any CAD software (such as SolidWorks), which the printer software converts into a printable file format. Our chosen software was Blender22, due to its wide range of features and strong user recommendations23. To drive the printer motion in all three directions, a stepper motor was determined to be the best solution, as these convert the motors rotational motion into fixed translational. The most appropriate product we located was the STP-DRV-8010024 as the company was reputable and this was the most suitable motor they provide.
The printer also requires a set of belts/pulleys in order to operate which were the most difficult of all our components to source due to our design requiring them to have an M10 thread. As a result of this, we opted to design our own based on the most suitable existing product available25. By doing this, it is possible to match our specification precisely, but still use the belt compatible with the pulleys ours are modelled on.
Finite Element Analysis To allow the construction of the printer to be manageable, it was broken down into 2 main parts that could be created separately and then recombined to produce the finished article. Although each required a combination of numerous sub-parts, this was seen to be the most practical approach. The primary structure and framework formed one component, and although initially designed to the final concept design, the following alterations were made to ensure its functionality. The position of plate and extruder is controlled using threaded rods instead of belts for better precision. Although this results in a reduction of printing speed, the improvement in quality supersedes this. The replacement M12 rods will be connected to motors using belt-pulley systems with varying pulley sizes to increase production speed without losing precision. For better aesthetics, easier assembly and to minimise the number of parts required, some of the threaded rod incorporated into the frame. This particular feature was considered to be revolutionary as none of our researched features employed this as a solution. The frame itself is made out of M12 threaded rods, connected with plastic parts printed by another 3d printer (self-replicating) This produced the frame model seen in appendix 29, for which a full parts list of the plastic elements can be found in appendix 30, and the metal elements in appendix 31. The second main component is formed of the extruder (appendix 32), which controls the movement in the x plane. Although this is made up of significantly less components, their construction and operation is significantly more complex. The main improvement related to this was positioning the extruder fixing plate sideways, further increasing the maximum printing area. As with the frame, one of the rods is an M8 threaded rod that moves the extruder, with the other remaining a 8mm smooth rod to provide stability. Again, the threaded rod slows down printing, but increases precision. The two plastic components and the slider are 3d printed to further the printers ability to self-replicate, whereas the extruder is an open source model of the one we would purchase if the printer were ever built (appendix 33). The only variation incorporated into this part would be to increase the separation distance of the mounting holes from 50mm to 75mm in order to be compatible with our framework. These were then combined to form the complete SolidWorks model of our finalised printer (appendix 34). Its operation is explained further in appendix 35. It is this model which was to undertake Finite Element Analysis. The aim of this testing was to ensure that the frame of our printer can withstand the forces applied. Since an FE analysis of our whole design would be too complex and time consuming we created another model with certain assumptions: 1) Frame parts do not move 2) Threaded rods used in the real design replaced by solid bars (with inner diameter of the threads) 3) The extruder can be replaced by a point mass pointing vertically downwards 4) The printer is fixed to a perfectly rigid ground 5) For the simulation the frame is transformed into a single solid object out of only one material (plain carbon steel) Due to the high impact of these simplifications on the accuracy of our results (especially No. 5), the absolute values obtained from the simulations (e.g. for stresses, displacements) were very
inaccurate and of limited use. We can however use those values to compare the performance of different design geometries. As well as the above, a draft quality mesh was used to enable us to simulate the required situations with the limited amount of computational power available. 3 different test scenarios were evaluated with varying amounts of reinforcement. Each frame is meshed with the default SolidWorks mesh size (medium), leading to a meshing time of around 3 to 5 minutes per frame on the University PCs. The follow up simulations take around 5 to 8 minutes each. Therefore the mesh size chosen seems to be a good compromise between accuracy and calculation time. The results of these tests can be found in appendix 36. This allowed us to evaluate the component in a number of different ways: - Bending: From the simulations we can see that the maximum stress in the frame without any supports is by far the largest; more than 3 times as large as in the frame with double reinforcements. The max stress in the frame with single reinforcements is around 2/3 of that in the unsupported frame. The displacement values for all 3 versions are negligibly low. Under normal operation the printer would probably not experience any force of higher magnitude, therefore reinforcing the frame because of possible bending is not necessary. - Twisting: Similar results were seen here to those in the bending test. The deformation, although still very small, becomes far more significant due to its directions. As a result, any moving parts (such as the printing plate) could jam and cause serious damage during operation. While it is relatively unlikely that twisting will occur during normal operation, reinforcements would be required if signs of twisting appeared. - Buckling The buckling test shows that the buckling factor for the reinforced frame versions is about twice the factor of the unsupported version. Even though we applied a relatively large force of 100 N, we can see that the load factors are very high (above 200). Of course the load factors for the real printer will be lower than this, but it indicates that buckling is not really an issue for the printer during a normal operation. Even the unsupported frame will be strong enough to withstand all forces occurring in normal use. Buckling is therefore not a reason for us to add supports. From the simulations we ran on the different frame versions, we can conclude that supporting the frame is not required provided the printer will be used under normal conditions. To prevent potential twisting induced damages, a solution would be the addition of supports. For our design this means that we should only add supports where their inclusion does not have negative implications elsewhere, such as if they were to block access to the printer area. As a result it was decided that the impact of adding support on both cost and complexity would be too large to be beneficial to us, and the supports were not incorporated.
Summary, Conclusions and Future Work Summary
There were a large number of considerations that had to be accounted for in undertaking this project, which required a diverse and in depth range of research and development methods. This, combined with the deign choices in an already large market, has led to an extensive project which exploits numerous techniques in research, management, design development and product analysis. Our initial task was to research the product market and evaluate existing designs and their suitability to our own project restraints. Although the technologies at hand and the project budget were both quickly established as limiting factors, through restricting our target market and lowering our expectations of quality we were able to identify a likely line of development and ascertain an appropriate and relevant target market. This was a vital stage within our project
as it allowed us to focus the following stages of development and direct our decision-making processes. It was clear from our market research that different consumers have varying expectations and criteria regarding their choice of printer, and therefore that our customer requirements would have to be carefully tailored for the product to be a success. In light of this, and our own personal thoughts on the matter (as our product is designed for personal use), we developed a collection of variables that we found to be of most value to an independent user of the printer. These were ranked using a collection of industry-accredited techniques to further direct our focus and allowed for the generation of several potential concepts. Despite our designs being centred around these pre-decided characteristics, there were still a number of issues surrounding many, highlighting them as unsuitable for further consideration. This led us to employ a selection of analysis techniques, including TRIZ, CODA and QFD analysis, to narrow down and improve our concepts until only one remained. This was to form the basis of our final design. Although supposedly the most appropriate solution to our design problem regarding customer satisfaction, it was by no means complete or optimised. Far more extensive consideration of its features and practicalities, as well as individual components, was therefore required. This was broken down into 3 main areas functionality, cost and build practicality. These were evaluated using extensive parameter optimisations and cost estimations to establish the exact functionality level attainable and how economically viable it would be to reach these targets. Following this, if found to be feasible, the design was altered to incorporate it, if however the optimisation would be too costly, or designing the component was impractical and overly complex, a purchased alternative was required. This identified a new series of issues, as any pre-existing components would not only have to meet the feature specifications and cost requirements, but also be compatible with the framework and model we would be building ourselves. A large amount of research time was allocated to this, as the success of the project depended on the parts coming together correctly. As a result, appropriate products were found for almost every section, and even where this was not the case, solutions to the design problems were found. Having finalised and optimised the design, and obtained the CAD drawings for any outsourced parts, a SolidWorks model of our final product was developed and assembled in full working order. From here, finite element analysis was carried out using estimations of the expected loads to determine whether our printer would function and operate in the expected manner, and allow for any necessary corrections to be made. Fortunately, our design was found to be structurally sound, and was therefore at a suitable stage to be put into production if required.
Conclusions Overall we believe our project has been successful, as the product we designed provided an adequate solution to the design problem, and met with the entire initial criterion. The market and product research we worked from confirms that our final design is suitable for product release and the testing we carried out on the structure itself verifies that building the printer is practically achievable, and would result in a fully functional 3D printer capable of meeting the requirements of an individual user. If our design is evaluated against our initial customer requirements and design parameters, they are met (in general) to the highest degree achievable within our budget and time constraints. The final version of our product can still be seen to closely replicate the concept drawing we initially selected, demonstrating that our concept generation methods were carried out effectively. The fact that some alterations and improvements were implemented is also a positive indication of our project as it illustrates on- going thought and optimisation, which is vital for product development. There were however issues with the project as a whole due to an overestimation of our own capabilities and the practicalities associated with the building of a 3D printing device. These limitations were not recognised at an early stage, and resulted in a large amount of wasted time and a lack of directed research, which had negative consequences on our progress. As soon as these issues were overcome, our project ran relatively smoothly, as each task was undertaken in stages to ensure all relevant and necessary undertakings were completely correctly and in full. On the few occasions that we did not adhere to this schedule, it did cause problems as it
generated confusion with the finer details, resulting in 2 different values being used for heat bed dimensions, and therefore certain sections had to be entirely redrafted. We were fortunate however in the outcome of this, and also in locating compatible parts that we had previously failed to realise could not be self produced, an oversight that could have sacrificed the entire project. With the exception of these drawbacks, which in many cases actually benefitted the project by encouraging us to re-evaluate certain areas to attain even better results, our project ran smoothly and produced a fully producible 3D printer capable of every feature we desired from it.
Future Work Sources: 26-35
3D printing presides at the forefront of technology; it is set to revolutionise the production process within manufacturing, allowing product innovation and customisation to occur at increasing speed. Research within the field is vast, with innumerable applications, including advancement regarding the input materials. Examples of such include bio-printing (including nano-medicine), in which bones, cartilage, organs and synthetic tissues for drug distribution and tissue scaffolding are created. Moreover, there is research into materials and machines that will allow the application of 4D printing in the future (appendix 37), however, the current capability of 3D printing on a widely applied scale is found in the production of prototypes within manufacturing, rather than objects of professional quality or of biological importance. Due to the design criterion, the printer described within this report is a very basic representation of the revolutionary technology currently being produced and adapted; the design is incapable of such innovative concepts described above, without a design overhaul being implemented. Significant improvements/alterations could however be applied so as to extend its working capabilities. Firstly, general improvements include increasing the feed rate so as to produce a more time efficient design; implementation includes redesigning the extruder so that the number of gear teeth is either reduced for the driven gear or increased for the driver gear. Furthermore, the step size could be decreased so as to improve the finish and accuracy of the design; allowing the creation of intricate designs. Other general improvements include incorporating: filament spools so as to increase the smoothness of the filament feeding into the extractor whilst reducing manual input, a blanket to place over the heating bed whilst it is warming so as to increase the speed of heating and thus time efficiency, a form of alarm so as to show when the bed is of working temperature and finally the attachments of fans. The use of a fan to cool the top of the hot-end and extruder reduces damage of the ABS components that make up the extruder, thus increasing the extruder and x-carriage component lifetime. Furthermore, a fan which can be controlled to cool the printed PLA will allow for more intricate designs to be created; the overhang performance is improved as well as the overall general quality as even smaller step sizes may also be implemented. Currently, printers are only capable of producing a product of constant colour/material. This constraint may be removed by altering the extraction process so that the extruder can be programmed to create a mixture of colours or materials subject to the designers specification. Although this technology is under experimentation for low cost printers, various designs can be found on thingiverse that already implement this. One already tested example involves creating a multiple extractor setup with a single hot-end combining nozzle, allowing for a blend of the filament materials to be produced (appendix 38). For a design that requires two unmixed materials, a dual extruder may be utilised. Another design (appendix 39) allows for the extraction of PLA and PVA - PVA can be used as a support for any overhang within the design and dissolved in water to leave the final product, thus allowing for more complicated designs to be created. All of the alterations described above would require research and experimentation in order to be implemented, thus increasing the cost of the 3D printer. Despite this, a combination of improvements (including those stated above), as well as many more general alterations, could be considered within optimising the design, so as to allow for the most relevant and cost effective solutions. In summary, 3D printing is an ever-evolving technology, for which the design described within this report represent only the very early stages.
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Figure 1 - Comparison Chart of 3D printers (Markershed)
Figure 2 - Snippet of 3D printer comparison chart showing only DIY systems (additive 3d)
Figure 3 - EDMC Design Template for a Hybrid Stepper Motor (reprap.com)
Figure 4 - Stepper Driver dimensions (avrstmd.com)
Figure 5 - Comparison of filament types for FDM (tridprinting)
Biased Scores 10 4 3 1 9 8 6 7 2 5 55
1 2 3 4 5 6 7 8 9 10
Able to print in 3 dimensions Print resolution Print size Print speed Robust Ease of assembly Ease of maintenance Lightweight Low cost Ability on different terrains
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10 Scores x 0 0 0 0 0 0 0 0 0 1 x 0 0 1 1 1 1 0 1 1 1 x 0 1 1 1 1 0 1 1 1 1 x 1 1 1 1 1 1 1 0 0 0 x 0 0 0 0 0 1 0 0 0 1 x 0 0 0 0 1 0 0 0 1 1 x 1 0 0 1 0 0 0 1 1 0 x 0 0 1 1 1 0 1 0 0 0 1 1 1 1 1 1 1 1 x 0 1 x Totals 9 3 2 0 8 7 5 6 1 4 45
Normalized Scores 18.18% 7.27% 5.45% 1.82% 16.36% 14.55% 10.91% 12.73% 3.64% 9.09% 1
Figure binary 6 - Formalised w eighting of customer requirements
20.00% Normalised Score 15.00% 10.00% 5.00% 0.00%
Customer Requirement Figure 7 - Graphical display of binary weighted customer requirement matrix
Figure 8 - Design Concept 1
Figure 9 - Design Concept 2
Figure 10 - Design Concept 3
Figure 11 - Design Concept 4
Figure 12 - Design Concept 5
Figure 13 - Design Concept 6
Figure 14 - Design Concept 7
Figure 15 - Design Concept 8
Figure 16 - Design Concept 9
Figure 17 - Design Concept 10
Figure 18 - Design Comparison Chart
Customer Requirement Able to print in 3 dimensions Print resolution Print speed Ease of assembly Ease of maintenance Ability on different terrains
3 4 6
10 10 10
1.82 1.82 1.82
8 6 9
0.58 0.44 0.65
10 7 8
0.55 0.38 0.44
8 8 9
0.15 0.15 0.16
8 6 7
1.31 0.98 1.15
10 8 7
1.46 1.16 1.02
10 8 8
1.09 0.87 0.87
8 10 8
1.02 1.27 1.02
9 9 8
0.33 0.33 0.29
9 6 6
0.82 0.55 0.55
9.11 7.95 7.96
Figure 19 - Spreadsheet ranking design concepts
Figure 20 - Selection of potential TRIZ solutions (source: University of Southampton, http://www.southampton.ac.uk/~jps7/Lecture%20notes/TRIZ%2040%20Principles.pdf)
Figure 23 - Graph showing parameter optimisation curves
Figure 21 - Graphical representation of results from QFD analysis
Figure 22 - Optimisation model of customer requirement design merit
Design Variables Weight of moving object Weight of nonmoving object Length of moving object Length of nonmoving object Area of moving object Area of nonmoving object Volume of moving object Volume of nonmoving object Speed Force Tension, pressure Shape Stability of object Strength Durability of moving object Durability of nonmoving Temperature Energy spent by moving Power Waste of energy Waste of substance Loss of information Waste of time Amount of substance Reliability Accuracy of measurement Accuracy of manufacturing Manufacturability Convenience of use Repairability Adaptability Complexity of device Complexity of control Level of automotion Productivity
Normalised Importance 7% 6% 5% 4% 3% 2% 1% 0%
0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0
Parameter value as a ratio of upper constraint
Figure 24 - Vanguard Model of Cost Analysis
cost Able to print in 3 dimensions Print resolution Print size Print speed Robust Ease of assembly Ease of maintenance Lightweight Low cost Ability on different terrains Figure 25 - Table of Merit/Value Calculations
119.52 13.74 143.45 3.6 81.468 3.48 143.45 0.74 89.45 14.56 208.97 13.8 31.92 10.43 175.37 6.72 81.46 2.08 57.53 4.84
16 14 12 10
14.56 13.74 13.8
8 6 4 2 0 0 50 100 150 4.84 3.48 2.08 0.74 3.6
Cost Figure 26 - Cost/Merit Trade-Off Plot
Description Inputs: Stepper # of steps Full/half stepping Drive Gear Teeth Driven Gear Teeth Diameter of Pinchwheel Feedstock Diameter Filament Diameter Motor Speed Motor Speed
Value 200 0.5 11 39 6.2 3 1 10 66.66666667
Units steps teeth teeth mm mm mm rpm steps/s
Outputs: Steps/mm of feedstock Steps/mm of filament Flow rate of feedstock Ideal Head Feedrate Ideal Head Feedrate
72.8120334 8.090225934 6.471801129 8.240396154 494.4237692
steps/mm steps/mm mm^3/s mm/s mm/min
Figure 27 - Spreatsheet calculating print speed from gear data (RepRap.com source: ref 18)
Figure 28 - Heated bed platform design (panucatt)
Figure 29 - SolidWorks drawing of printer framework
Part No. Required
Figure 30 - Plastic part list for printer framework
type M12 M12 M12 M10 M10 M8 12mm diam rod 8mm diam M8 M8 Length,mm 496 376 551 460 356 404 376 404 475 225 amount 2 2 2 2 2 1 2 1 2 1 Total 17 pieces
Figure 31 - Metal part list for printer framework
Figure 32 - SolidWorks model of extruder
Figure 33 - Parts required for extruder section
Figure 34 - Final combined SolidWorks model
There are 4 stepper motors in the 3d printer, 3 to control movement in X, Y and Z directions and one to feed the wire. In the extruder (left) the motor drives a bolt which then forces plastic through heating coil onto the plate.
X Direction Motor drives threaded rod (light green) which moves extruder (pic above) dark black rod is smooth rod to increase stability of the extruder. Pulley mounted on a motor is 2 times larger than pulley on the rod (in diameter, and number of teeth) therefore increasing the speed.
Y Direction Motor is driving threaded rod ( same as X direction), pulley on the motor is 2.5 times bigger than one of the rod for increased velocity. Then, through another set of pulleys, motion is transferred to another threaded rod. Both pulleys are the same in this case, as we want both of rods to move at same velocity.
Exactly the same as as in Y direction, but this time pulley on motor is SMALLER than pullkey on rod because that increases precision, and we dont need high velocity in vertical direction (just to lift the plate step by step)
Figure 35 - Flow Chart describing operating mechanism of our printer
Figure 36 - Tabulated Results of Finite Element Analysis
4D printing includes multi-material prints w hich have the ability to transform to a desired shape, directly after the printing process; this is essentially self-assembly of programmable materials so as to allows for optimization for d esign constraints and joint folding. Figure 37 - Explanation of 4D Printing
Figure 37 - Multiple extractors with single combining nozzle
Figure 38 a and b - Examples of colour blending in 3D printing