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Coiled spring pins improve production of surgical instrument

19 February 2013

A medical device manufacturer was using a Swiss style CNC-machined knurled solid pin in a laparoscopic surgical device to drive the jaw movement at the distal end of the device. However, high insertion forces were causing the pins to bend, damaging the sub-assembly and generating metallic debris.

Following tests on the original assembly - which identified incompatibilities between the pin and host materials causing debris generation on insertion - Spirol recommended replacing the solid pin with a heat treated, 420 stainless steel light duty coiled spring pin. The flexibility of the coiled pin facilitates a low insertion force while providing adequate retention without protruding knurls damaging the hole and generating debris.

A light duty pin provides the appropriate balance of flexibility and strength for this application. Moreover, the fact that the pin is made from hardened 420 stainless steel provides the necessary corrosion resistance without risk of being damaged by the 416 stainless host material during installation. 

Subsequent testing of the coiled spring pins revealed a clean installation that required significantly less force - with no evidence of burrs or shavings and no damage to the sub-assembly. The Spirol coiled spring pin has permanently resolved all of the issues previously experienced and the manufacturer has also benefited from the cost reduction associated with switching from a CNC-machined pin to a roll-formed coiled pin.

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