Opportunities for Innovation
The speed with which 3D tooling can be produced also provides opportunities for innovation. When Schniepp was employed at GE Aviation a decade ago working on FRP parts for a new Boeing program, he says that the 12- to 14-month lead time for the Invar tooling accounted for half of the 24- to 28-month long project. “We would have to lock in our part design 12-plus months ahead of first delivery just so we could get the tool in time!” he muses. “That really limits the amount of design optimization you can do… . If we had today’s technology, we would have had a lot more freedom to do additional design work and optimization.”
Faster tooling also gives companies the ability to rapidly change product designs. “Imagine that you are a boat manufacturer. Your product is highly aesthetic, but your competition comes out with a boat that is almost identical,” says Hedger. “3D molds give you the potential to pivot in the middle of the year and produce a completely new product line without missing a beat.”
Kunc adds that 3D-printed tooling can also provide features that are simply not possible with traditional tooling, including embedded sensors and active heating elements. For example, in 2017, ORNL collaborated with TPI Composites in Scottsdale, Ariz., to additively manufacture a test mold for a wind turbine blade. Previously, the molds were created by making a plug, casting a female fiberglass mold over it and then running resistive wire across the back for heating. Kunc says the process was laborious and could result in hot and cold spots on the mold if the wires weren’t spaced correctly. “Instead, the additive process allowed us to design channels through which we could blow hot forced air to create really nice, uniform heat along the bottom of the tool,” he says.
Equipment innovations are also on the horizon. ORNL and Cincinnati are experimenting with a BAAM that has been modified to print multiple materials. Kunc says that in the future it may be possible to generate a single tool from multiple materials – for example, switching from non-reinforced polymer to fiber-reinforced polymer or from a soft structure to a rigid structure.
To gain widespread acceptance, 3D-printed composite tooling solutions have to address three main challenges: thermal expansion, temperature tolerance and tool life. 3D-printed thermoplastics have a large coefficient of thermal expansion (CTE), which means they expand and contract with temperature changes. Another passible issue is limited layer-to-layer adhesion. This is because while FRP beads of material bond to each other across the X,Y plane of each extruded layer, fibers don’t generally cross from one layer to the next (in the Z direction), leaving a weaker, non-reinforced bond.