自由曲面叶片数控加工刀具轨迹规划方法

研究了自由曲面叶片数控加工刀具轨迹规划方法。解决了两个问题:(1)叶片曲面建模过程中的布尔操作破坏了曲面参数域,从而在叶尖处造成冗余刀轨,并在叶根处有可能形成干涉;(2)叶片前后缘处曲率半径的剧烈变化导致步长计算容易超差从而造成啃切现象。针对问题(1),本文提出一种新的参数映射方法,将裁剪后的曲面参数域重新映射到一个规范化的参数域上去,并在新的参数域上规划刀轨;针对问题(2),本文提出一种改进的弦截法来计算走刀步长。该方法收敛速度快,且避免了对复杂函数的求导,计算量小。同时本文采用搜索解空间,并修改变量替换方式来避免该方法收敛于错误的解。仿真实例表明,本文方法达到了预期效果,在提高了加工效率的情况下,避免了啃切现象的发生。

On Toolpath Planning for NC Machining of a Free-form Blade Surface

During the toolpath planning for NC machining of a free-form blade surface,two problems need to be resolved:(1) the surface parametric field is destroyed by the Boolean operations during the modeling of the blade,leaving the redundant toolpath around the blade tip and resulting in the possibility of the gouge around the blade root;(2) the curvature of the blade changes sharply among the leading edge and the trailing edge which may result in the wrong tool step and the gnaw.For problem(1),a parameter mapping method is proposed.The parametric field is mapped onto a new normalized one and the toolpath is generated according to it;for problem(2),a modified secant method is proposed.This method converges quickly and avoids the derivation of the complicated function and take little computation time.It also avoids converging to the wrong solution by searching the solution space and modifying the iterative pattern.The simulation result shows that the methods proposed in this paper work well and the machining efficiency is increased and the gnaw is avoided.