Contact zone analysis based on multidexel workpiece model and detailed tool geometry representation

Abstract

A new method for analyzing the tool-workpiece-contact area in cutting processes is presented. To gain enhanced knowledge about tool-workpiece interaction, determination of chip thickness, contact length and resulting cross-section area of the undeformed chip is of major interest. Compared to common simulation approaches, where rotation-symmetrically constructed tool geometry is used, the new method uses a detailed three dimensional tool shape model for an extended and more accurate contact zone analysis. As a corresponding representation of the workpiece and its time dependent shape-changes a multidexel model is used. To prepare the geometric tool model, the contained BREP topology is built up within the simulation system using data from a STEP-file. First of all functional parts of the tool like rake and flank faces and cutting edges are labeled for further processing. In a second step the identified NURBS-faces are discretized for the application in material-removal calculation. This way a mesh is built-up based on triangle elements which maps the geometry of each cutting edge into a 2D parametric representation. In relation to rake face, each node is described by its position on the cutting edge and its perpendicular distance to this edge. To perform contact zone analysis each cutting geometry and a multidexel model are intersected in discrete time steps corresponding to a tool rotation of about three degrees. The intersection point of each dexel and the cutting geometry is calculated. Parametric cutting geometry allows for a direct computation of local cutting depth and contact length for each involved point. Based on the local values of contact length and cross section area of the undeformed chip the characteristic values for the entire contact zone are calculated and used to predict mechanical as well as thermal loads caused by the cutting process. To demonstrate the application of the novel approach, prediction of forces in slot milling of 1.1191 steel is presented.