自由曲面三坐标加工走刀步长的确定

Determination of Step Length in Three-Axis NC Machining of Free Form Surfaces

对三坐标曲面加工中由于离散直线逼近导致的加工误差问题进行了研究．从分析刀具的三维线性包络运动出发，得出了适用于多种类型刀具的加工误差估计的通用表达式，该误差在曲面法线方向定义，是较精确的轮廓加工误差．在此基础上，得出了能较严格满足给定精度要求的走刀步长计算式，给出了提高算法效率的措施，并以实例验证了该算法对误差控制的效果．

The machining error in three-axis machining of free form surfaces leaded by discrete linearapproximation is studied. By analyzing the three-dimensional linear enveloping movement of cutters,an expression used to estimate the machining error and being suitable for various types of cutters isobtained. The discussed machining error is considered in the normal direction of the surfaces, thus theexpression can give a satisfied estimation to the actual machining error of the surfaces. The formulafor determining rational step lengths based on given accuracy is then derived, and the methodsimplifying the calculation of the algorithm is developed. The effect of the algorithm on error control isverified.