IMPROVEMENT ON PRODUCTIVITY FOR MACHINING CENTERS - EFFECTS OF TOOL PATHS ON PRODUCTIVITY

The productivity of machining centers is affected not only by the effe ctive feed rates and average tool per- block travel studied in the fir st report, but also by the generated tool paths, especially the variat ion of moving vectors of the tool. In this paper, first of all, the fa ctor of productivity evaluation is defined extensively to the case of multi-F code, and furthermore expressed as a function of the time cons tants, feed, average per-block travel and the moving vectors of the to ol. The expression of the factor shows that the smaller the time const ants and the average variation of moving vectors, the higher the produ ctivity is, and the longer the average per-block travel, the higher th e productivity is. Then with feature-based work models, namely, spline surface, slope, boss, island and pocket, being exemplified, the produ ctivity of those NC programs generated by I-DEAS CAM tool is analyzed by the self-developed NC program simulator in two patterns of tool pat hs, namely the contour line and zigzag. The results show that in most cases, the productivity of the tool path in contour line pattern is hi gher, and the productivity of machining with a tool of smaller diamete r is higher when the cutting power is kept constant. The theoretic and simulative studies on the tool path will contribute to the developmen t of new CAM tools.