科研之友
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摘要
In tool-path generation, the cutter contact (CC) contours and cutter location (CL) contours are basic elements. Invalid loops in these contours should be removed before planning the tool-path. According to the characteristic of intersection, all invalid loops can be divided into two cases: the general case and the degenerate case. A unified method for invalid two-dimensional (2D) loop removal is presented in this paper for both these cases. This method consists of four major steps: (1) finding all intersections in given polygons, (2) building the topology for each intersection point and grouping given polygons into complex polygons, (3) decomposing each complex polygon into simple polygons, and (4) extracting valid polygons from the simple polygons. The complex polygon decomposition operation is the decisive step of this method, and it is carried out as follows. First, the concept of virtual self-intersecting polygon and the criterion of priority exit-point direction determination are proposed to make sure that all general and degenerate cases can be solved in a uniform way. And then a set of simple polygons is obtained by traversing all the vertices in the complex polygon once and performing a series of tracing-direction-changing operations at each intersection point. This decomposition operation has a near-O(n) time-complexity, where n denotes the number of vertices in the complex polygon. In the extraction step, the concept of valid orientation is proposed; based on this concept, this method can be applied to both CC contours and CL contours, and then valid polygons are extracted by the criterion of invalid loop removal. The proposed algorithm has been implemented, tested with some general and degenerate cases, and applied in tool-path generation for the sheet metal incremental forming process. Performance tests show that this unified method for invalid loop removal is also robust and efficient.
- 出版日期2013-2
- 单位华中科技大学
