Shop develops self-leveling clamp: General Industry Coverage

The goal of every workholding setup is the same: holding and supporting the part so it doesn’t move during machining. This is especially challenging when machining thin-wall, near-flat, die-cast components, which can easily distort under clamping forces that would be relatively small for parts with larger dimensions.

Die-cast aluminum automotive parts are being used more frequently because they help lighten the weight of vehicles without sacrificing strength. In many cases, they’re cast into near-net shapes, which minimizes machining and improves productivity.

Courtesy of Jesel

A blueprint of the die-cast aluminum engine cover showing the five clamping points.

Jesel Inc., Lakewood, N.J., a valve-train components manufacturer, had a machining requirement for finishing small die-cast aluminum engine covers. Due to the thinness of the casting, 0.150 ” to 0.250 ” between machine sides, and a 0.005 ” parallel flatness requirement, a standard fixed-point fixture clamp could not effectively hold the part.

Fortunately, the components were cast with clamp pads (some die-cast aluminum parts no longer include them in the die-cast component to minimize weight). As a result, Jesel was able to develop its own self-compensating, or self-leveling, clamp to attach to those pads. The self-leveling feature, which moves the clamp in both directions until both sides of the clamp contact the surface, allows for casting thickness variation.

This clamping allows for the use of more clamps than just the ones used at the three primary point locators because the self-leveling design does not force the part out of its position. As a result, even with the added force from additional clamps, the part is less likely to distort in machining.

The self-leveling clamp for this particular application is approximately 2 “×3 “×3 “. It is basically a mounting block with an internal, dual-acting piston, a clamp screw on one side and a clamp button on the other.

“It will clamp both sides of any feature within its range of about 0.100 “,” said Ray Frattone, director of manufacturing for Jesel. “It solves the problem of having to use separate, adjustable work supports in addition to the clamp because it adjusts to the casting and does not force it up or down from the three primary point locators. These work supports typically require skill and time to execute properly. With our clamp, tightening one screw is all that is required.”

All areas of the casting shown in the photo on page 31 require machining. The casting is first located on its three primary tooling points and then clamped on the tabs in five places (the three primary point locators and two additional clamp pads) by tightening five screws with a ¼ “-drive air driver.