On machining dynamics of flexible parts

Solid modellers are now well established for computer aided design of mechanical parts. Machining applications, however, remain limited to geometric tool path planning. The physical aspects of the process are largely ignored. Success in actual machining, however, depends on consideration of cutting forces, torques, part and tool deflection, chatter, tool breakage and wear. This paper reports research progress towards a comprehensive simulation of the physical machining process of thin flexible parts. The system is based on extensions to a commercially available solid modeller. Cutting tool location data (CL-DATA) files along with an initial solid model of the workpiece are inputs. Each tool motion is segmented into short steps along the path and angular increments of spindle rotation. At each simulation step, immersion of the cutting tool teeth with the part is calculated. This information is then used by a machining process model to calculate cutting forces and tool/workpiece deflection. Up to five-axis motion is supported using a sweep representation of the tool swept volume. Flexible tools are modelled as cantilevers; flexible parts are created as solid models, are meshed and are dynamically solved using finite element analysis. The mesh is updated as material is machined away from the part.