Microcutting Force Prediction by Means of a Slip-line Field Force Model

Abstract

Mechanical micromachining is a very flexible and widely exploited process, but its knowledge should still be improved since several typical phenomena play a role on the microscale chip removal (e.g. “minimum chip thickness effect”, microstructure influence on cutting forces, stable built-up edge, etc.). Several models have been developed to describe the machining process, but only some of them take into account a rounded-edge tool, which is a typical condition in micromachining. Among these models, the slip-line field model developed by Waldorf for the macroscale allows to separately evaluate shearing and ploughing force components in orthogonal cutting conditions, therefore it is suitable to predict the cutting forces when a large ploughing action occurs, as in micromachining. The present work aims at objectively verifying the cutting and feed force prediction performance of the Waldorf model within typical microscale cutting conditions (uncut chip thickness lower than 50μm and comparable in size to cutting edge radius) in its original version and in a modified version considering the partial effective rake angle. A suitable set-up, especially designed for microturning conditions, has been used in this research to measure forces and chip thickness. Tests have been carried out on C38500 brass (CuZn39Pb3) with different cutting speeds and different ratios between uncut chip thickness and cutting edge radius.