Extracting cutter/workpiece engagements in five-axis milling using solid modeler

Abstract

Predicting cutting forces in milling process simulation requires finding cutter/workpiece engagements (CWEs). The calculation of these engagements is challenging due to the complicated and changing intersection geometry between the cutter and the in-process workpiece. In this paper, a solid modeling based methodology for finding CWEs generated in five-axis milling of free form surfaces is presented. The proposed methodology is an extension of the solid modeler based three-axis CWE extraction method given in [21]. At any given instant of the five-axis tool motion, the velocity vectors along the cutter axis may move in directions that do not lie in the same plane, and therefore the cutter envelopes need to be approximated by spline surfaces. Considering the spline surface approximations, the CWE methodology described in [21] does not work properly for the five-axis milling. Therefore in the proposed method, the in-process workpiece is used instead of the removal volume for extracting the CWEs. A terminology the feasible contact surfaces (FCS), defined by the envelope boundaries, is introduced. To extract the CWEs at a given cutter location, first the BODY entity, obtained by offsetting the FCS with an infinitesimal amount, is intersected with the in-process workpiece. Then, the resultant removal volume is decomposed into faces. Finally, the surface/surface intersections are performed between those faces and the FCS to obtain the CWE boundaries. To be used in the force model, the CWE boundaries are mapped from Euclidean 3D space to a parametric space defined by the engagement angle and the depth-of-cut for a given tool geometry.