Jon Hills, a mechanical design engineer who had graduated from Brown University and studied furniture design at the Rhode Island School of Design, needed high quality prototypes for the 2016 International Contemporary Furniture Fair (ICFF) Studio competition. With the deadline approaching fast, Jon was facing a problem – building the five Catenary Stool prototypes on his Makerbot was going to be far too slow and extremely expensive. On a friend’s advice, Jon contacted InterPRO and spoke with Dan Straka, InterPRO’s General Manager, about the challenge Jon was facing.
Jon’s novel stool design had to be both beautiful and functional, with enough strength to support a person’s weight and withstand the wear and tear of being stacked and roughly handled. After reviewing the 3D printed materials that were available, InterPRO determined that the required impact strength and rigidity could not be achieved with any 3D printing technology.
Dan suggested another approach: split the stool into three pieces, create cast urethane prototypes using RTV rubber molds and assemble them after casting. InterPRO has strong experience in creating cast urethane prototypes from 3D printed patterns.Dan showed Jon how casting would create stronger prototypes with excellent surface finish at much lower cost.
“Material science really drives the functionality of a part. With the urethane casting process we were able to use a very strong material with high impact resistance, and there were no design concessions for Jon’s stool. Manufacturing the design in thirds also saved Jon time and money”
– Dan Straka, InterPRO.
The material InterPRO suggested PTM&W’s PT-8976, a casting resin with very high impact strength. The PTM&W material would produce a very durable final part without any design concessions needing to be made. Jon gave InterPRO the go, with a deadline of 4 weeks before the ICFF competition.
InterPRO build the SLA pattern on a large-frame SLA-7000 overnight and the surfaces were sanded smooth by hand. The RTV silicone rubber molds were then built and final part production began. One week after receiving Jon’s CAD file, all the the pieces were cast and the five stools were ready to be assembled.
The painted and finished stool arrived on schedule right before the ICFF show started on May 14th.
Jon was really happy with the results and glad to discover that low-volume production with RTV molding and casting cost him far less than if the parts had been 3D printed.