网格曲面数控加工编程分型线提取算法

Determination of parting line for NC machining of mesh surface

针对复杂网格曲面分型线提取精度和效率不高的问题,根据非封闭自由曲面和封闭自由曲面的拓扑信息和几何特点,提出了2种基于投影方法的分型线提取算法。对非封闭模型,首先将模型投影到平面并重新三角网格化,然后提取投影三角网格的边界,最后以平面三角网格的边界为检索信息在原始网格中检索得到自由曲面的分型线。对封闭模型,根据模具分模的几何原理,提出通过建立封闭自由曲面凹模和凸模离散几何模型的方法提取封闭自由曲面的分型点,然后通过一环邻域点搜索法对分型点排序,得到分型线。实验结果和数据分析表明,两种方法可以精确、高效地提取非封闭和封闭自由曲面的分型线,并可以确保分型点都是三角网格曲面的顶点。

In order to improve the extraction efficiency and precision of the parting line of complicated mesh sur- face, it presents two approaches according to geometric characteristics of non - closed and closed models. For non - closed model, it projects and triangulates the model on a plan, and extracts the boundary of the new mesh. Searching the corresponding point of the boundary point on the model, it determines the parting line of the non - closed model. For closed model, it establishes the discrete geometrical models of male die and female die accord- ing to the principle of parting mold, applies the parting points to determine the intersection of the geometrical models of male die and female die. Finally it sorts the parting points to yield the parting line. The results from demonstration cases show that parting line for models of freeform surfaces can be easily determined and design ef- ficiency be greatly improved, all the parting points be the vertexes of the triangular mesh.