基于临界约束的四轴数控加工刀轴优化方法

针对自由曲面四轴加工中复杂刀具运动导致的干涉和刀具运动不连续等现象,提出一种基于临界约束的刀轴优化方法。基于刀具与工件约束曲面之间的相对位置关系,利用曲线上的点搜索算法确定切触点处的临界刀轴矢量,并计算当前切触点刀轴摆动的可行域;以切削行内所有切触点的刀轴可行域为基础,建立当前切削行内无干涉且相邻刀轴变化最小的刀轴矢量优化模型,实现了自由曲面四轴加工无干涉刀轴矢量的光顺控制。整体叶盘四轴加工试验表明,利用此方法获得的刀轴矢量可以显著改善机床运动的连续性,并避免刀具干涉的产生,提高了加工质量。

Tool Orientation Optimization Method in Four-axis CNC Machining Based on Critical Constraints

To avoid interference and to keep smooth tool movement in four-axis machining of free-form surface,a critical constraint based tool orientation optimization method is presented.According to the geometric relationship between the cutting tool and the constraint surface,critical tool orientation for every cutter contact point is determined by using point searching algorithm,then the tool orientation feasible region can be determined based on the critical tool orientation.When tool orientation feasible region for every cutter contact point is generated,an optimization model is built in order to get interference-free and smooth tool orientation.With the presented method,smooth and interference-free tool orientation along tool path in four-axis machining can be generated.To demonstrate the validation and advantages of this innovative approach,examples of four-axis milling bilks are rendered,and the results are compared to those obtained by existing method.This approach can improve machine tool movement and avoid tool interference,thus to improve machining quality of free-from surface.