Tool path generation for machining free-form pockets with islands

In this paper, we propose a procedure for generating tool paths for machining free-form pockets with multiple islands. A pocket is assumed to have a pocket boundary and island boundaries defined by closed cubic B-spline curves. The pocketing procedure does not require the islands to be disjoint and to be enclosed by the pocket boundary. The pocketing procedure consists of five steps: (1) boundary approximation, (2) boundary merge, (3) profile offset, (4) loop removal, and (5) termination test. The input to the pocketing procedure is a set of closed cubic B-spline curves defining a pocket and its islands, together with the stepover size and the tool radius. The output of the pocketing procedure is the cutter location (CL) data of the three-axis NC milling machine to carve a free-form pocket within a given tolerance. The pocketing procedure is implemented in C on a SUN workstation. An NC simulation module based on the G-buffer method is also implemented to verify the CL tool paths.