Voronoi-diagram-based linking of contour-parallel tool paths for two-and-a-half-dimensional closed-pocket machining

Abstract

Contour-parallel tool paths for machining milling features are formed by linking the offsets. Determination of links between offsets and the sequence in which the offsets should be traversed is a major problem. Results of efforts to link tool paths from academic researchers and developers of commercial computer-aided manufacturing (CAM) systems have shortcomings which include the fact that the linking strategies (a) are not based on clear geometric principles, (b) are not optimal, (c) do not consider technological factors such as the amount of slotting, overmilling, mode of cutting, and (d) are either not gouge-free or use tool retractions to avoid gouging. To overcome these shortcomings, this paper presents a linking algorithm which employs segments on the Voronoi diagram as links. The technological factors, hitherto ignored in previous research are considered and their optimality is ensured by employing guidelines which were mostly developed through observations of tool paths generated from a general test bed. Multiple solutions obtained after pruning out unfeasible solutions can be evaluated by users using geometrical (total tool path length) and technological (amount of overmilling, slotting, etc.) considerations or a combination of the criteria. The implementation of the algorithm is tested by generating tool paths for two two-and-a-half-dimensional (2 1 / 2 D) milled features. When compared with those obtained from some commercial CAM systems, they are shorter by 5 to 31 per cent.

Smooth contour-parallel tool path generation for high-speed machining through a dual offset procedure

“…For Fig. 14a, according to [20], the total tool path length is about 11,200 mm; while for Fig. 14b, this value is about 12,123 mm, 8 % longer than that of Fig.…”

“…Park et al [19] developed a data structure called a "TPE-net," and based on that, they presented a linking algorithm which guarantees "zero" number of tool retractions. Hunduja et al [20] proposed an algorithm which employs segments on the Voronoi diagram as links. Dai et al [21] presented a graph model-based pathlinking algorithm for dental restoration.…”

“…The pocket example as shown in Fig. 14 is first used by Hinduja et al in [20]. It is a 2 1 / 2 D pocket with 14 protrusions, the cross-sectional shapes of which are trapezoidal, rectangular, and circular.…”

“…The width of the pocket is about 270 mm and height about 190 mm. As in [20], the cutter radius and the path interval are both 3 mm; in our test program, the two parameters are also set to be 3 mm. Figure 14a shows the tool path generated by the Voronoi diagram method, and Fig.…”

“…14b, all the sharp corners have been rounded. In [20], the offset tool paths are linked by line segments. To compare the tool path length, we have also linked the paths with line segments.…”