Pushing Rapid Prototyping Materials to the Limit

Just a couple of years ago, few people expected their selective laser sintering machine or a 3D printer to make prototypes that were physically and functionally analogous to production parts. But the increased sophistication of rapid prototyping (RP) equipment and a host of companies wanting more functionality from their parts are pushing the science behind commercially available RP materials.

Alex Morgan, a material scientist at the University of Dayton Research Institute, is making polymer-based parts for the defense and aerospace industries which demand high heat, solvent and electrical resistance. That’s because many of the companies he works with not only want to review RP parts for size, shape and weight, but often seek to test their production-readiness.

“What I think you’re going to start seeing as a trend is being able to make a rapid prototype design with the final resin that you would actually go into production with,” Morgan says. “This is where selective laser sintering and 3D rapid prototyping become production tools.” He suggests that if the resin used for prototyping is that intended for the final part, then if the part run is small enough, then the prototyping equipment can be in lieu of, say, injection molding.

This situation provides both a challenge and an opportunity for both RP polymer makers and machine vendors alike. That is, RP polymer makers and equipment builders don’t want to have too specialized materials and capabilities because that might limit their markets, but they do want to be able to provide greater levels of optimization for their current and prospective customers. For example, what were once considered niche material applications in aerospace, biomedical implants and electronics appear to have broader industry appeal.

“The industry’s been developing a lot of new materials during the last five years and all of them have been in response to customer requests across the industry,” says David Rosen, director of the Rapid Prototyping and Manufacturing Institute (RPMI) at Georgia Institute of Technology.

Rosen projects several key material advancements in the next few years, including more age-resistant stereolithography material chemistries that behave much more like injection molding thermoplastics and more polymers with nano-materials to improve mechanical properties in selective laser sintering processes. In the world of 3D printing, Rosen says all major manufacturers are developing machines to accommodate numerous materials and a full range of colors without the need for post-processing. “You’re going to see multi-material capabilities, where you’re not just mixing two materials, but printing with multiple materials at the same time,” he says.

The ability to print a product’s housing and all of the electrical connections in one go is “not that far away,” in Rosen’s estimation. The biggest challenge is developing printer heads capable of using high-viscosity fluids, which Rosen says will “revolutionize these technologies.”

Stephen Danforth, a materials science and engineering professor at Rutgers University, sees more advancements coming for formable metals, particularly aluminum oxide, stainless steel or tool steel. He notes the electron beam melting system, the EBM 400, introduced by ARCAM, which builds parts out of titanium, as a big first step in this trend.

“I don’t see making a million spark plugs a year using rapid prototyping,” he says. “But if the Army or NASA needs 500 of something, or if there’s an application where you want to customize 500 or 100 parts for a particular buyer, then RP may be very useful.”