Binder Jetting Follows in Footsteps of Metal Injection Molding

For Smith Metal Products of Center City, Minnesota, additive manufacturing seems likely to become the new possibility arising out of a new possibility.

The company is a provider of metal injection molding (MIM) that was launched by nearby plastics injection molding provider Plastic Products Company. MIM and plastics molding have enough in common that the knowledge and resources of the parent company provided a valuable advantage when the new company was launched 20 years ago, but MIM and plastics are also different enough that the two disciplines needed, and now have, different organizations and facilities.

Now, similarly, MIM provides a valuable starting point for the metal AM capability Smith has invested in: binder jetting. The company has begun using an Innovent binder jetting machine from ExOne. Early successes, plus the seeming promise of this capability, hint at the prospect that this advance might also become the seed of a larger and more structured commitment to the capability.

For now, AM is serving Smith Metal by helping to move MIM forward.

How MIM and AM Help One Another

Conservative about the changes it makes, Smith Metal watched AM for years before beginning with it. According to General Manager Todd Jensen, the point came at which “we were turning away enough bridge production opportunities to know we needed this capability.” MIM, which requires a mold, is inherently a high-volume process. AM, which thrives at the smaller “bridge” quantities prior to full production, is a natural complement.

And MIM in turn complements binder jetting. Thanks to the volume of metal powder Smith already purchases for MIM, its binder jetting benefits from material pricing better than other AM users obtain. In addition, the same sintering furnaces already in use for MIM parts can perform this same step for binder jetting. Metallurgy expertise also transfers. MIM and binder jetting go together well.

Edward Jornlin is a recent materials engineering graduate hired to help the company advance and master the new capability. He is learning about the distinctive behaviors of binder jetting, including the ways shrink factor is different in AM versus MIM (in AM, for example, shrink can differ in XY versus Z), as well as the behaviors of different 3D printed part features during sintering. Meanwhile, Jim Beyer is learning about different behavior changes resulting from AM. The Smith Metal account manager has used the capability successfully to help customers commit to metal injection molding. On multiple occasions, delivering a metal 3D printed prototype of a component design to a customer enabled the company to arrive at full confidence in its design — enough to proceed into production. “The binder jetting pushed them over the finish line,” he says.

However, there is farther than this to go. That is, beyond prototyping, there is still the bridge production.

A Bridge Farther

One significant market for potential growth for Smith Metal, now that it has both MIM and AM, is medical devices. Specifically, there is opportunity here to provide production via AM on the scale of perhaps hundreds of parts for the initial trials necessary for new medical devices to win regulatory approval. In addition, there are opportunities in various markets to deliver work produced only through AM, never to be taken up by MIM, because the part design necessitates this capability. Inquiries about this kind of work have been coming to the company since it announced AM would be part of its services.

Meeting these opportunities for production through AM will require further steps. “We need to put a quality system in place around this capability. And we need to carry out production AM in a way that doesn’t overwhelm our other processes,” Jensen says. Further, the company will need to add more binder jetting capacity, an investment that seems likely to come.

Would the AM production capability then become as distinct from Smith Metal’s MIM work as MIM is from plastics molding? Maybe not. But within this company, the development and pursuit of a new and disruptive manufacturing capability does have a familiar feel.