Fourslide Stamping of Stainless Steel Spring for the Medical Industry

Fourslide Stamping for Increased Spring Rate

Springfield Spring & Stamping worked with the design engineering team from a world-renowned medical device company to develop a stronger and more consistent spring for a surgical stapling device. The spring component was originally designed as a fourslide stamping with a large radius. The radius on the spring acts to compress (flatten) and release as the surgeon uses a scissor-type action with the stapling device during the surgical stapling procedure.

The first generation spring in the device was made from Type 301 spring tempered stainless steel material (185,000 KSI). The spring did not possess the strength (spring-rate) the new generation device required. The part’s shape could not be altered. Cosmetics were very important and the edges of the spring needed to be smooth and burr-free.

Springfield Spring & Stamping changed the material to 17-7 PH high tensile stainless steel (210,000 KSI). Raw material is ordered to an exact +/- .003 wide strip with a #5 deburred edge. Parts are formed on a fourslide machine. The parts are precipitation hardened at 900-degrees F for one hour in vacuum. The vacuum hardening process ensures a bright and consistent surface finish. The part’s final hardness after precipitation hardening is increased to 260,000 KSI. Parts are tumbled in mazor and a citric acid passivation cleaning is performed as the final process. The part spring rate increased by over 35% and the surgical stapling device met all of its fit and functionality specifications.

Project Specifications
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Product Description
This stainless steel spring is used within a surgical stapling device.

Processes (Primary) Processes (Secondary)
Prototyped and Tested
Material Selection: Change material from 301 Full Hard stainless steel to 17-7 Stainless steel or Condition C temper
Fourslide Stamping
Precipitation Hardening (@ 900ᵒF in Vacuum/Final Hardness Becomes 260000 KSI)
Passivation Cleaning (Citric Acid Passivated)

Overall Part Dimensions
Raw Material(±.003" Strip)
#5 Deburred Edge

Tightest Tolerances Material Used Material Finish
+/-.003 17-7 PH High Tensile Stainless Steel (210000 KSI) Precipitation Hardened

The Spring Rate is Increased by Over 35%.
Edge condition of final part much smoother.
Bright silver finish aesthetically pleasing in a medical environment.

Industry for Use Standards Met Product Name
Medical Customer Supplied Specifications Stainless Steel
Surgical Stapling Device Spring