There are a number of factors that determine whether or not a production tool should be 3D printed. “End-of-arm tooling, lift assist devices, measurement devices – a lot of those things are over-engineered and over-built in aluminum or steel. They’re heavy and not as functional as they could be. Those are the kinds of applications that we are looking at when we meet with an OEM like General Motors or a supplier of theirs,” says Russell.
GM is currently working with its tooling suppliers on various AM projects. One supplier is studying whether a lighter weight, printed, end-of-arm tool design for a robot can reduce the cycle time in a certain sub-assembly cell. Another used AM to produce a small hand tool to check metal studs that were coming into a plant. “The studs needed to interface with another piece of metal, but they were coming in bent and [workers] never had anything to check them with,” explains Lentine. Using 3D printing, GM quickly produced multiple checking tools and distributed them to the plants as a fix for an ongoing problem.
“Once the designers have an idea of the design principles and the design guidelines, they are actually the best at creating new geometries,” says Lentine. “They really know how to look at a part and put it together a little differently. So there is a learning curve, but it’s not too steep a learning curve from what we’ve experienced.”
Lentine says suppliers’ questions about working with AM composite tooling came from their knowledge and understanding of what is required to build a tool for a GM production assembly plant.
For example, they needed to figure out how the printed tooling and metal tooling differ in stress-strain curves, durability and fatigue properties. They wanted to learn about the tooling’s dimensional capability: would it be accurate when printed, or would it need machining? Will thermal expansion be an issue? Can a tool be designed in Michigan’s cold, dry winter work effectively in a production plant in the south?
Torque requirements were another concern. “All of our assembled components with steel and aluminum have torque requirements to ensure that the bolt is actually being pulled and creating compressive forces on two plates being pulled together. But it’s different with plastics, because the same torque requirements will likely strip the plastic out,” says Lentine. (The solution is to insert Hewitt coils or install threaded metal inserts into the part.)