AFR, CL Fast Computation And Dynamic Interpolation For CAM: Research And Implementation

The thesis studies three key problems of CAM: automatic recognition of machining features, tool path fast computation and dynamic NC interpolation. The theoretical results are implemented and verified at the CAM platform, IE-CAM, developed by our team. Acquiring machining features from CAD model is a key for computer integrated machining systems, while feature recognition is one of the most promising methods. Getting tool paths from machining features is called tool path computation, which in the case of a pocket, is generally done in three steps: offsetting the contour of the pocket, sewing up the gaps between tool paths and eliminating over-cuts. The thesis develops a fast algorithm to deal with over-cut detection. NC interpolation, converting tool paths into movement of the machining tool, is the key for high speed & high precision machining. The key points in the thesis are as the following.Recognition of interacting machining features implemented by using hash tables. When machining features interact, they break each other. Recognizing these features has always been a hot topic. The proposed method successfully recognizes broken holes and slots. All holes are classified by their direction, and distributed sorted into hash tables with their center points as the keys. In this way, all broken features from the same hole are collected into one entry. The original hole then can be identified with simple rules. In the case of slots, all bottom and side faces of slots are classified per normal direction and sort along the direction into a hash table. Again, faces from the same plane are combined, yielding complete slots.A sweep plane algorithm is designed to eliminate over-cuts in tool paths of arbitrary pockets with islands. All safe tool paths can be reported in O(n log n+ k log n) in time, where n is the number of vertices of the tool paths, and k the number of intersection points.The problem of jerk elimination in high speed machining is tackled by Pythagorean hodograph quintic spirals. Formulas of the shortest PH curve for...