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Case Study 5

Part name: M73 frame

Material: cold-rolled steel or 6061 aluminum

Thickness: .092

Challenge: To fabricate a family of parts from two different materials, with some part numbers requiring multiple secondary operations, while minimizing overall cost to the customer.

Solution: Often the task of minimizing cost involves finding a balance between high-speed production rates and high tooling costs. Here, we were lucky enough to produce the frame in-the-flat from each material with one die with one set of details. The progressive blanking die was a robust 4-post precision die set that produced a part with 12 holes, a slot, and the complete external profile, with accuracy of the location of these features relative to one another on the order of +/- .001.

With this many punches, if the die went out of time because the material misfed, or because a pilot punch broke, or because the pilot distorted the hole used for location, the resulting breakage of punches would be very expensive; to avoid this, we used an extremely accurate CNC servofeed.

Secondary operations included forming a bearing race, which required an excellent surface finish; this was accomplished in the steel frame by forming the ball race after plating, and with the use of a high-pressure forming liquid. Another secondary operation necessary on some frames was a 90 degree bend; this was a challenge in 6061 aluminum, which has a tendency to fracture under severe forms. This was avoided by heating the workpiece just before it entered the forming die, which used a camming action to create the form, minimizing shearing forces within the material.

Other secondary operations performed on various members of this family of parts included tapping, engraving, and bead-blasting, all of which were done in-house. Some part numbers required as many as eight secondary operations.