Study on discrete form algorithm of cutter location surface in CNC milling of freeform surface

Abstract

A novel discrete form algorithm of cutter location surface is proposed to produce 3D tool paths in computer numerical control (CNC) 3-axis milling of freeform surface. As compared with the normal form algorithm, it can be applied to the complex curve surface and irregular shape cutter. The research objective is to identify the discrete form algorithm of cutter location surface. First, the cutter working surface and the machined curve surface were dispersed to be two-point clouds, respectively. Next, the tangency mode of their point clouds was established to produce the cutter location surface. Then, CNC milling experiments were carried out to identify the machined form errors for discrete and normal form algorithms. Finally, the effects of discrete form parameters and workpiece surface posture were investigated on the discrete form accuracy. Experimental results show that the machined form errors for the discrete form algorithm is identical to that for normal form algorithm, but its large form errors are mainly distributed on the large workpiece slope location. On decreasing searching interval and lattice grid size, the discrete form accuracy increases. Moreover, the workpiece surface posture greatly influences the discrete form accuracy, but there exists such a workpiece surface posture that the best discrete form accuracy may be achieved. It is concluded that the discrete form algorithm is feasible to produce the cutter location surface for CNC milling of freeform surface by controlling lattice grid size and searching interval and choosing a suitable workpiece surface posture.