Custom-tailored: engineers put aside standard clamping scheme and outwit complex geometry of workpiece.

Author:Smith, Kyle
Position:Workholding

Two automotive components with complicated geometry couldn't outsmart the engineers at ESE LLC when machining in a traditional orthogonal workholding fixture was not possible.

The Lapeer, MI, company specializes in providing customers with solutions for their custom manufacturing applications from complete turnkey projects to stand-alone fixtures, gages, or special machines. ESE makes extensive use of Roemheld power workholding products supplied by Cart Lane Roemheld Manufacturing Co. of Ellisville, MO, in custom workholding fixtures for machining centers, presses, broaches, and other manufacturing equipment.

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In this project, ESE was assisted by George Campbell, power workholding engineeringmanager of Cart Lane Roemheld, in choosing the most effective power workholders for this application. Using 3D solid modeling soft ware, the engineers at ESE were able to design modular workholding fixtures, holding four parts each (Fig. 1, one variation). This orientation allowed for better utilization of machine tool spindle time along with simplified custom details and reduced assembly time. With the unique geometry of the parts, it could not be machined in a customary orthogonal workholding fixture, but minimizing the number of time-consuming fourth axis rotations was desired.

A rotated top assembly (Fig. 2), unlizing Roemheld Size No. 2 double acting swing clamps, provided reduced tool lengths and increased tool clearances. These double acting hydraulic cylinders moved custom clamp arms 90 degrees, allowing the operator full access to the part locating details when undamped, yet provided significant clamping force across from the part datums while clamped.

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With the experience ESE gained machining prototype components from the customer supplied forgings and information derived from finite element analysis, it was determined that the workholding fixtures would require more than just a standard datum clamping scheme.

In this application, the machining forces exerted on the part were outside of the clamped area. As a result, part deflections of several hundred microns were demonstrated during the prototype machining and computer analysis.

ESE was then able to design an auxiliary hydraulic circuit for the single acting threaded body cylinders (Fig. 3) to be used as dampeners for the undamped portions of the part in their initial design. This information up-front prevented expensive rework after the fixture details...

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