Suppliers had questions about using printed composite tooling in a shop environment. Will it melt and degrade over time if it gets hit with weld flash coming off of welding guns? What kind of adhesive should be used to join two pieces together? Should the 3D-printed part get a special coating if it has to go through the high-temperature ovens in a paint shop?
Repair procedures for printed tools presented another challenge. Unlike metal tools, composite tools can’t be fixed by welding on a replacement part.
“We’ve been working with GM and its supply base trying to figure out the optimal way to go,” says Whitman. Production facilities can print new parts as needed or pre-print replacements to have on hand. Stratasys has also been helping suppliers develop temporary solutions, such as using aluminum or metal strips epoxied or bolted in place on the broken tool until the permanent replacement is printed.
Although GM and its suppliers are finding most of the answers they need as they work through their projects, there is one remaining issue that will take more time to resolve.
“If we have certain critical large tools carrying heavy weights, we will do a finite element analysis (FEA) model,” says Lentine. The FEA predicts a tool’s properties, like deflection and reaction to stress. “The FEA with the Stratasys process is complicated and there’s less confidence in it, because [the printed tooling] isn’t an isotropic material or an injection molded plastic. It’s built up in layers and in tool paths, so it is actually not homogenous.”
Stratasys is developing solutions in conjunction with some software partners. “One of the things that we’re still working on as a company is getting to a full characterization of the materials so that we know their strength and stiffness, especially with fiber-loaded materials,” says Whitman. “There isn’t a simulation solution available right now to say that we know exactly how this material behaves and we know how it’s going to fail.”
Because of the uncertainty, engineers design the printed tools to be a little bulkier and stronger than might otherwise be necessary. Once more FEA information becomes available, that additional safety factor will probably be reduced.
3D’s Automotive Future
There was some pushback when GM first engaged with suppliers on AM tooling. Suppliers said they weren’t sure that they wanted to adopt it, and they didn’t have confidence that it could work.