Léonie Hilsdon & Mark Elvy on going beyond design validation with 3D printing
When it comes to speed and cost effectiveness, little beats 3D printing for validating designs. However, optimising designs for prototyping often means having to re-validate for production. How should designers bridge this gap? Here, three relevant technologies are presented along with expert guidance on how to enhance designs to shorten product development times.
The cost of additive manufacturing (AM) reduces daily. By eradicating the tooling component, production cycles are truncated and become more cost effective. Roadblocks to considerations, such as certification, are becoming fewer – indeed, Carbon’s new EPX 86FR material has a V0 rating from UL. Specifying materials and part applications helps any service provider to understand specific requirements and recommend the best solution. Wall thickness, accuracy and part stability are major contributors towards cost and lead time. Designing for AM from the start removes any issues; and the earlier that estimates are compared between AM and traditional methods, not just using cost, the better.
Printing with stereolithography (SLA) is a popular prototyping method. Technology and materials are improving all the time. The large-bed Stratasys Neo 800 printer has very high tolerances thanks to its laser process, claiming an accuracy to 0.1mm, even for parts over 300mm. When designing for this process that produces detailed prints with the look and feel of traditional thermoplastics, engineers need to factor in support structures for thin walls and understand that part stability is compromised if wall thickness is less than 0.2mm in the X/Y axis and 0.4mm in Z plane. A good service provider will advise whether a part will produce a perfect print first time and work through any necessary changes before anything is printed.
HP’s 3D printing for production process, Multi Jet Fusion (MJF), takes the next step in moving into production parts. This laser sintering technology has an accuracy of +/- 0.3% over 100m. The advantage here is that there are no support structures to consider and recommended optimum wall thickness is 0.4mm. Viable end-use materials enable the production of moving, complex parts; and part consolidation of previous multiple-part assemblies is a more cost-effective production process.
Carbon’s Digital Light Synthesis (DLS) printers have been designed solely for scale production using high-specification materials. They are promoted as being the most accurate of the three examples presented here. Each ‘slice’ – 100µ in the Z axis – comprises pixels, 75 µ in the X and Y axes. Although this precision promotes excitement, there are considerations when it comes to designing parts with thin walls. Support structures are required, and the print bed is much smaller as it has been designed for speed.
The Bigger Picture
Taking into account the above examples, what’s the overall message? Given the constant challenges in supply chains, sustainability, material prices, shipping and stockholding, using the same processes for design and manufacture must converge. It is incumbent on all design engineers to think differently: “Can this part be made without the need for tooling?” If it can, engineers will have longer to improve the design before it’s frozen to be sent to the toolmakers. In fact, they can continue to improve the design after they receive their first order of a specified quantity of parts.
Léonie Hilsdon & Mark Elvy are with Paragon Rapid Technologies