Research For High Efficiency Machining Programming Of Complicated Mesh Surface

With the development of reverse engineering, 3D printing and other new design and manufacturing technologies, mesh surfaces are becoming more and more popular in numerical control(NC) machining. The measurement data in reverse engineering is represented by triangular mesh surface in most cases. Therefore, the machining of triangular meshes with high efficiency and quality becomes very important. Main contents and achievements are as follows:1. A contour packing algorithm based on skeleton line is proposed in this dissertation. The free-form contour of product needs to be rotated when it is packing on raw materials. The characteristics of the machining boundaries have not been considered in existing rotating algorithm and the boundaries are rotated by equal angle-interval. The convex and non-convex characteristics are expacted to be paired when polygons are packing. An endpoint of the skeleton of a packing contour means a cnvex characteristic of the packing contour. Inspired by this, a contour packing algorithm based on skeleton line is proposed. The parking area of materials is discretized based on a bottom-left and the lowest gravity center strategy. The packing contour colliding algorithm is also improved in this research. Experimental results show that the packing time is reduced and the material utilization is improved using the proposed algorithm.2. A boundary extraction algorithm for the machining area detection is proposed based on morphological image processing in this research. Z-map models are commonly employed in machining programming and simulation. Using traditional approaches, boundaries cannot be extracted precisely from a Z-map model. The image boundaries can be improved by morphological image dilation since the holes and gaps can be filled. Inspired by this, a boundary extraction algorithm for the machining area detection is proposed based on morphological image processing. Firstly, the Z-map model is transformed into a binary image with a slicing plane. The binary image is then dilated and the boundary pixels of the dilated image are extracted and coded. Finally, preferable accurate boundaries are generated. Experimental results show that the machining area boundaries extracted by this algorithm are more precise and smoother than those using traditional Z-map methods.3. A parting line extraction method based on heuristic searching strategy is proposed in this research. The characteristics of the mesh surface between two adjacent slices have not been considered in slicing pating line extraction method. According to the disadvantages, a parting line extraction method based on heuristic searching strategy is proposed. The parting points are gained by slicing method and then the parting point are linked by heuristic searching strategy. The cost functions of heuristic searching strategy are normalized.The parting line of a triangular mesh extracted by this method is composed by mesh edges. Experimental results show that the parting lines extracted by this algorithm are more precise.4. A starting location controlled 3D tool path generation based on methodology of harmonic map is proposed. 3D tool path can improve the efficiency and quality of numerical control(NC) machining. Harmonic map method is an important approach for 3D tool path generation. However, the starting locations of the tool paths are not located in the expected point and the tool paths are non-uniform in most cases. A generation algorithm of 3D tool path based on methodology of improved harmonic map was proposed. Experimental results show that this algorithm can solve the problems that the start of the tool paths are not located in the expected point and that the tool paths are non-uniform.