Virtual workpiece: workpiece representation for material removal process

In this paper, an efficient methodology to generate a virtual workpiece (VWP) is presented. VWP is a workpiece in a virtual environment in which the geometric, kinematic, and thermo-mechanical effects of the process and resources can be reflected. VWP encompasses not only the macro-information corresponding to the shape of the “virtually” machined intermediate workpiece, but also the micro-information, such as the surface roughness, scallop heights, chatter mark, etc. To represent VWP, swept volume (SV) of geometrically defined cutters is generated first by envelope profiles which are calculated by the intersection of the Tool map with the Contact map of the tool moving direction. Then SV is tessellated to conduct elementary 1D Boolean subtraction of SVs from the IPW. The Boolean subtraction is realized by means of an efficient ray-triangle intersection test using Barycentric coordinates. Finally, VWP is reconstructed as a triangular mesh (STL, stereolithography data format) from the orthogonal triple-dexel model (TDM) which predicts machined surface quality, such as surface roughness, gouging and sharp edges and is reused for further operations, e.g., tool path generation, simulation and geometric metrology, etc. To demonstrate the validity of VWP modeling, several material removal processes, e.g., milling and micro-EDM operations, have been tested and the proposed approach has been proven to be applicable to enhance the quality of NC simulation and verification.