This technical information has been contributed by
Connecticut Spring and Stamping

Stamping Company Coins Cost-Effective Solutions for Critical Medical Components

Engineering and Technical Services

By eliminating the quality issues that its customer had been experiencing with a previous supplier’s work, Connecticut Spring and Stamping reportedly reduced the customer’s per-part cost by approximately 50 percent, ultimately saving “hundreds of thousands of dollars” over the course of the year. The customer had been experiencing significant problems with the production of a stamped jaw for an endoscopic clip applier, a medical instrument that applies titanium clips to blood vessels to close them off during endoscopic surgery. The client’s supplier was stamping the jaw and then machining a groove into the stamped part, but its machining operation was unable to hold the required tolerances. The client also wasn’t able to achieve the level of surface finish required for medical parts that are inserted into a body cavity.

“They were experiencing a 25% part rejection rate on incoming inspections, and about 12% rejection of the completed surgical instruments,” said Steve Dicke, vice president of sales and marketing at CSS. “After initial discussions, we felt as though we could take the application and, rather than machining a groove, which is where the staples are driven from, we could actually coin the groove into the jaw. We felt it would give them a higher-quality part with tighter dimensions than they were currently getting, which would give them 100% quality for incoming inspections.”

Produced from 420 stainless steel as a single-piece component, the stamped jaw is one of the most critical components within the clip applier, and therefore must be held to very tight tolerance requirements. Connecticut Spring and Stamping accomplished this through a combination of direct engineering involvement and design recommendations. “Together, we developed a different configuration for the component that was only capable of being produced with stamping,” said Mark Labbe, a manufacturing engineer at CSS. “We worked with them very closely, and they changed the part several times. As they added new features, we had to re-engineer it because all of the parameters changed. They had to dimensionally change the part to make it function correctly, and we had to configure it to whatever they needed.”

Although its customer designed the jaw, CSS assisted with part design and handled the tooling design–ultimately developing sophisticated tooling to coin the part multiple times in a programmed fixture. The tooling produced a coined jaw capable of holding stack up tolerances less than 0.001 inch.

Connecticut Spring and Stamping’s use of a coining process also enabled its customer to design into the part an enhancement that wasn’t possible with the machining process–an enclosed end that achieves better clip closure. “They couldn’t machine it in that fashion because the machining had to add the groove in from the end,” Labbe explained. “So there was an opening on the end of the part. By coining it, we could actually close up the end so that the part had a better feature. Coining is a stamping process where you cause material to flow into a shape under high pressure, similar to forging, but it’s a cold process. We started with a stamped part, but the coining allowed us to do all of the critical features in one operation.”

Although changing to another manufacturing process was key, the resulting design improvement was expedited by CSS’s close interaction with its customer. “I think the product design improvement came about through a collaboration with the customer, and the fact that they didn’t realize how tight we could hold the tolerances, and that we could fold up the end as consistently as we did,” Dicke maintained. “They recognized the improvement to their design and made the modifications based upon the collaboration. They would have been happy without the product design improvements, so it came as an additional benefit.”

By the time they were through, CSS had helped its customer go from a 25% part rejection rate to zero rejections, while significantly reducing the cost of the parts by using a stamping process. “The tooling cost is not necessarily less, but the per-piece cost goes down significantly when you go from a machined part to a stamped part,” said Dicke. “Processing time is much slower when you’re machining it, so the stamping process saved them time and money in the long run.”

“We saved them hundreds of thousands of dollars with the parts we made for them in one year, if you consider the cost of the part times the volume of the parts,” Dicke added proudly. “Each finished instrument costs several hundred dollars, so it was very expensive to dispose of the other supplier’s rejected instruments.”

This technical information has been contributed by
Connecticut Spring and Stamping

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