五坐标数控加工的理论误差分析与控制

对五坐标曲面加工中由离散线性运动逼近理想刀具轨迹所引起的理论加工误差进行了较严格的分析。基于五维线性包络运动分析，得出了适用于多种类型刀具的加工误差估计的通能表达式。该误差是三维意义下较严格的刀具包络成型误差，综合考虑了零件表面的局部几何形状、刀具的形状尺寸与刀轴控制参数、走刀进给方向、机床旋转/摆动机构参数以及走刀步长的影响。在此基础上，分析了减小加工误差的措施，给出了能较严格满足给定精度要求的走刀步长估计算法，有效控制加工误差并提高刀具轨迹质量。

ANALYSIS AND CONTROL OF THE THEORETICAL ERROR IN FIVE-AXIS NC MACHINING

The theoretical error in five axis NC machining,which is resulted from approximating the perfect continuous tool path with discrete linear segments,is strictly analyzed.An expression used to estimate the theoretical error and suitable for various types of cutters are given.The error estimate is accurately obtained from the three dimensional enveloping movement of cutters.The infouences of the local geometry of part surface,the shape and dimensions of cutters,the control parameters of cutter axis,the feed direction,the structure parameters of swing mechanism and the step length have been considered in the obtained expression.Then,the measures to decrease machining error are analyzed,and the algorithm for determining rational step lengths based on assigned accuracy is derived.As a result the machining error can be controlled effectively and the quality of tool path can be improved.