ACS produced these custom in-ear devices utilising a 100% digital production workflow that includes 3D Systems' Figure 4 Standalone 3D printer (Credit: ACS Custom).
3D Systems' Patrick Dunne (Vice President, Advanced Application Development) likes to sidle up next to me at a trade show and produce an item from his pocket from a project he’s working on with great glee. The most recent example was not much to look at, geometrically speaking, but it felt nothing like any other 3D print. Because it wasn’t a 3D print, it was pure silicone, enabled by 3D Systems’ Figure 4 technology and its application, eggshell moulding.
Eggshell moulding is a sacrificial technique where a thin mould is printed and then a material is injected into the mould with the resulting mould then broken away. It’s a technique many resin-based 3D printers offer, and its advantages in the ability to o er the pure forms of materials like rubber and silicone have numerous applications.
Two years ago, one company that caused something of a splash in eggshell moudling was Collider Tech. The Tennessee company, founded on the vision of an ex-Shapeways employee, finished runner up at the prestigious TechCrunch event Startup Battle eld. However, all is quiet with Collider, their social media hasn’t been updated in over a year and they haven’t replied when TCT has reached out.
Whereas 3D Systems now has customers buying Figure 4 standalones specifically to run eggshell moulding. ACS Custom is one such firm. The UK-based production house for custom hearing protection, in-ear monitors and other communication devices is using two Figure 4 Standalone systems to produce eggshell moulds.
“ACS were already doing eggshell moulding,” explained Colin Blain, Advanced Applications Engineer at 3D Systems. “But we went through a Figure 4 benchmarking process with them and it was a win on every level where we were twice the speed, we could achieve much thinner wall thickness and our resolution was better. Plus the cost of ownership for both hardware and materials was lower.”
As a result of the enhanced workflow, ACS has realised a 4X increase in capacity and 2X increase in efficiency while reducing material consumption by 50% and labour cost by as much as 80% on one part.
“The Figure 4 Standalone, and the overall collaboration with 3D Systems, has totally exceeded our expectations,” said Andy Shiach, Managing Director, ACS Custom in a press release. “By transforming our workflow with Figure 4, our company is being elevated to a whole new level. We have been able to dramatically increase production capacity and efficiency through our ability to nest multiple parts on the same build plate – producing more parts in the same amount of time. These results are amplified by the incomparable surface finish allowing us to deliver high quality product to our customers. The strength of the technology coupled with the expertise of 3D Systems’ team has made a significant impact on our business.”
3D Systems Figure 4 standalone.
The process
Creating the eggshell moulding is relatively simple; a CAD user creates a positive o set on the external surface of the model, then removes the original CAD to leave a hollow shell. The resulting shell is, typically in the Figure 4’s case, 0.3 mm thick. The CAD designer will then add features to allow the injection of the material and some vents to prevent air pockets.
In ACS’s case, that shell is then printed using Figure 4 standalone and the specific eggshell moulding resin 3D Systems has developed. A material like silicone can then be injected in using a syringe and the shell is then broken o with ease by hand thanks to the elastomeric properties of the usual end-use material.
Such is the growing popularity of the technique, 3D Systems is working on ways to reduce those steps:
“We’re looking at including this as a workflow feature into our 3D Sprint software product,” Colin told TCT. “It would give people that don’t have access to the native CAD the ability to do eggshell moulding at an STL level. The workflow in 3D Sprint would also include placement of the injection and venting features as well as the actual kind of shelling process itself.”
An eggshell moulding update to 3D Sprint would go down well with ACS who are already sold on the software.
“3D Sprint is an invaluable part of our workflow,” explained Dan Bennett, Technical Director at ACS Custom. “It includes so many useful tools which help us prepare and optimise the CAD data, and manage the entire print process. 3D Sprint has been instrumental for us to increase efficiency and productivity, and ultimately reduce time-to-part.”
ACS Custom’s current workflow is 100% digital production. ACS 3D scans a customer’s ear, imports that data into design software to design the end part, and 3D prints an eggshell mould which is then cleaned and filled with silicone. Once the silicone is set, the mould is broken away, and electronic components are added to complete the device.
In the last four years, the 3D printing of elastomeric materials like TPUs has come a long way, far enough for the likes of New Balance and Adidas to use in production of training shoe midsoles. However, what’s also been evident at any 3D printing trade show in the past few years is that there is a desire to process pure medical-grade silicone in a quicker and more efficient way, the likes of Wacker have launched 3D printing machinery specifically to tackle this requirement.
“Direct 3D printing the elastomeric materials are pretty good but most of them is still somewhat lacking in rebound and tear strengthen and some require additional thermal post curing to get the end- use properties,” explained Colin. “If you’re looking for a food/medical grade silicone or rubber part in a specific colour and shore hardness then eggshell moulding is a really good fit. Real-world applications like that of ACS go a long way to prove this.”
