A STUDY ON NC-CUTTER PATH GENERATION FOR SUBDIVISION SURFACES

本文提出了细分曲面模型的三轴数控刀具轨迹自动生成的切片和精加工刀具轨迹生成方法和算法。首先确定满足工业要求的细分方案，然后确定工艺方案。其次，采用由切削公差和刀具参数决定x/y方向网格间距的Z-map模型，由极限细分曲面建立网格点，以减少计算机内存的使用，提高计算速度。针对工件，提出了一种平头米尔斯铣刀片切刀位轨迹生成方法，通过生成覆盖网格并建立Z-map模型，计算刀触点和刀位点，调整刀高，得到每片切片的刀位轨迹。对于精切刀位轨迹的生成，采用球头铣刀，通过计算极限曲面与Z-map模型之间的投影点的刀位接触轨迹，然后将其偏置为刀位轨迹，从而得到精切刀位轨迹。最后给出了具体的实现方法和实例。对于这两种路径，我们计算了极限曲面的曲率半径，以避免过切。在参数设置没有问题的情况下，所有这些刀具路径都是自动计算的，并且实现表明这些路径是快速生成的。

In this study we proposed methodologies and algorithms of slice-cut and finish-cut tool path generation through which a 3-axis NC cutter path can be generated for subdivision surface model automatically. At the beginning, suitable subdivision scheme in order to satisfy industrial requirements, and then a process planning is determined. Next we employ a Z-map model that grid interval of x/y direction can be decided by cutting tolerance and tool parameter to set up mesh points from limit subdivision surface in order to reduce the use of computer memory and raise the computing speed. For work pieces we present a slice-cut tool path generation method with flat-end mills, we generate a cover mesh and set up a Z-map model for it, calculated their cutter contact points and cutter location points and adjust the cutter height to achieve tool paths for every slice. For finish-cut tool path generation we use ball-end mill, and achieve the path by calculating the cutter contact paths with projection points between the limit surface and the Z-map model, and then offset them to cutter location paths. Finally we implement the method and present some examples. For these two kinds of paths, we calculated curvature radius of the limit surface in order to avoid gouging. All of these cutter paths are computed automatically if there is no problem in parameter setting for the desired NC path plan, and the implementation shows that these paths are generated rapidly.