Page 46 - MetalForming August 2012

Tooling Technology
Coating Makes Drawing Stainless
Painless
Beset with galling and cup tearing, Penn United Technologies sought a solution for drawing stainless-steel cups. The metalformer found one: a physical-vapor-deposition (PVD) tool coating.
Metalformer Penn United Tech- nologies, Cabot, PA, produces laminations and complex parts to exacting specifications. In many cases, stainless steel comprises the part material. For difficult stainless-steel forming, the company has chosen to employ a physical-vapor-deposition (PVD) tool coating.
The coating (from Phygen Coatings, Inc., Minneapolis, MN) prevents galling while maintaining critical part toler- ances, and also enables operations such as drawing to proceed tear-free. And the coated tools exhibit increased life, allowing for more productive part runs without the need for stoppages to replace or repair worn tools, according to company officials.
In two plants, Penn United lever- ages state-of-the-art stamping presses, ranging from small bench machines to 300-ton workhorses, with bed sizes to 96 by 42 in. To meet required high part volumes, presses churn at speeds
To form stainless-steel parts such as these for a medical customer, Penn United Technologies had to overcome issues with galling and part tearing. A new tool coating fit the bill, and increased tool life exponentially.
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to 2000 strokes/min. Parts produced on these presses are destined for cus- tomers in medical, defense, aerospace, automotive, hardware, electronic and other markets. Penn United also designs and fabricates stamping tool- ing inhouse.
Finding Answer
to Improve Stainless Draws
The company produces many parts stamped from stainless steel. Demands in dealing with this material have pre- sented challenges. For example, in 2004 Penn United was struggling to deep-draw cups in a progressive die. Trying to draw the cups in a four-station die on a 100-ton mechanical press, the company could not consistently complete the drawing operation without galling or tearing the 0.003-in.-thick Type-304 part material. Perhaps a tool coating was the answer. Jim Marraccini, project engineer at Penn United, recalls the challenge.
“This part, a 0.5-in.-dia., 0.5-in.-deep
cup for a medical device, often would tear,” he says. “We make about 50,000 of these parts in a run and probably 10 times that annually, so we needed a fix.”
The company searched for a solu- tion, and eventually identified a coat- ing for its affected carbide tools. That initial solution, however, didn’t last long. “Our initial coating selection last- ed for about 15,000 hits before we needed to pull the tools for repair,” he says. Back to the drawing board, which put Penn United on the doorstep of another tool coater—Phygen Coatings.
“What’s the problem with forming stainless steel?” asks Dave Bell, Phygen president. “Stainless has significant chrome content, and tool steel also contains chrome. What happens when you combine similar metal alloys under high forming pressures and heat? The alloys weld together. You need to pre- vent that from occurring.”
For this and subsequent tool chal- lenges at Penn United, Phygen employed