Where Metal Injection Molding Makes Sense

When you commit to producing 7.5 million parts for an industry as demanding as automotive, you better know what you’re doing.

That job, recently undertaken by the Metal Injection Molding arm of Phillips Plastics, demonstrates the confidence that the Wisconsin company has in its ability to meet customer needs, no matter how demanding.

Phillips, which has been molding plastic parts since 1964, launched its metal injection molding (MIM) operation in 1996. “Our company founder, Bob Cervenka, has always been technology driven, and he believed that this new MIM process could complement our existing business,” recalls Mike Magnine, a sales representative for Phillips and former application engineer at its MIM facility in Menomone.

Filling a Void

What Cervenka saw was a technology that could produce strong, highly-complex parts at a cost as much as 50% less than CNC machining or investment casting. Over the years, Phillips has completed more than 350 MIM projects for industries ranging from automotive and medical to firearms and telecommunications.

“The sweet spot for MIM involves parts quantities from 100,000 to a quarter million,” says Tony Pelke, the engineering manager at the Phillips MIM plant. “But we’ve had jobs for the auto industry involving more than 5 million parts and a couple for cell phones that have run more than four million.”

As Pelke explains it, engineers should think about MIM if they have a complex part that could fit inside the spherical diameter of a golf ball, or tennis ball at the largest. Most MIM parts weigh less than 30 grams, and Phillips has made some as small as 0.013 to 0.375 grams. Think of hinges on cell phones, high-precision surgical clamps or triggers for firearms.

MIM allows you to produce intricate parts with little or no secondary machining. What’s more, the material density and mechanical properties are typically 98% of wrought steel. Tolerances can be held to as little as +/- 0.0005 inches, with secondary machining.

“The light bulb really goes on for engineers when they realize that they can consolidate or reduce the number of parts with MIM, which eliminates costly and time-consuming assembly and machining steps,” notes Magnine.

A Powerful Partner

Consistency and quality assurance are also essential, and very early on Phillips partnered with materials giant BASF, which supplies the metal/polymer feedstocks for the MIM process. Phillips routinely works with more than 15 different powder metal alloys, and BASF also will develop special alloys for high-volume Phillips customers.

At its 35,000-square-foot MIM plant, Phillips maintains seven injection-molding machines. Robots load molded “green” parts onto conveyors headed for debinding ovens, where 90% of the polymer binder is removed. The final operation, sintering, removes the secondary binder, and final density is achieved. Phillips offers batch debinding and sintering for large parts and special alloys, such as titanium, and well as continuous debinding and sintering to boost throughout for smaller parts and stacked components.

“Interest in MIM is spreading fast among design engineers,” says Pelke, who urges engineers to contact Phillips as early as possible. “Let us critique the design for optimal quality and cost-efficient production.” If need be, too, Phillips metallurgists can recommend the best powder metal alloy for the application.

MIM business is growing rapidly at Phillips, adds Pelke. As a result, the company is installing a new $2.5 million continuous debinding and sintering furnace. That investment will double the company’s capacity to serve its MIM customers.