The application of tool path compensation for the reduction of clamping-induced geometric errors

Spherical-tipped locators and clamps are often used for the restraint of workpieces within machining centres. For structurally rigid fixtures and workpieces, contact region deformation, slip, and lift-off are the predominant modes of workpiece displacement. Experimental evidence obtained thus far indicates that this displacement can be severe during clamping. In addition it can be a significant source of geometric error. However this error can be reduced significantly through tool path compensation. This paper describes two different techniques that can be used to determine workpiece displacement during clamping. The first applies eddy current displacement sensors to measure workpiece displacement online. The second applies an analytical model to predict workpiece displacement during clamp actuation. This paper also shows how workpiece displacement data can be used to compensate tool paths prior to machining. Lastly this paper describes an experimental study used to validate both techniques.