Improving the Accuracy of Machined Parametric Surfaces Using Cutting Force Synthesis and Surface Offset Techniques

Abstract

Prediction of machining errors and compensation for these errors during the tool path generation stage can improve the product quality significantly. A traditional approach would be machining a few parts, followed by a measuring process to estimate the errors, and finally using a scheme to compensate for the errors. In this paper two approaches are used to avoid trial runs. In the first approach prediction of the deflection of the cutting tool (based on modelling of the cutting forces) at certain points distributed on the design surface is calculated. An inverse operator is then applied to these errors to calculate a compensation vector at each point. A variable offset geometrical model was developed that uses these vectors to build the compensated surface. A detailed simulation analysis for the proposed compensation scheme is presented for different surface shapes in both up and down milling. The second approach is based on improving the roughing strategy by leaving a uniform thickness layer during the roughing phase on top of the finished surface. This leads to more uniform distribution of the cutting forces that may improve the accuracy of the finished surface.