Lofting-based spiral tool path generation algorithm for milling a pocket with an island

Abstract

To improve the machining efficiency and cutting force stability for milling a pocket with an island, a lofting-based spiral tool path generation algorithm is presented. First, the machining area undergoes partition based on lofting lines through the profile vertices, and isogonal lofting lines are assigned according to the sub-area angular weight. Linear interpolation is proposed to get equal-spaced points between internal and external lofting points, and these interpolation points are circumferentially connected to form a spiral polyline. Next, control vertices that follow an exponential function distribution are inserted. Using these control vertices, a B-spline curve of any order can be defined. Finally, a spiral tool path for machining a pocket with an island is obtained. The algorithm can control the machining efficiency and machining precision by adjusting shape factor, lofting line number, and B-spline order according to specific processing requirements, and it can be directly applied to a machining center with a Non-uniform rational B-spline (NURBS) interpolation function. The experimental results show that, compared to contour-parallel, the Cn continuous B-spline curve tool path has an obvious advantage on tool path length, machining efficiency, cutting force continuity, and workpiece surface quality.