九轴联动叶片双刀对铣高效加工的路径规划方法研究

The middle and large sized blade is easy to produce deformation because of the cutting force. Therefore the milling efficiency and precision for the blade would be influenced directly, which has become the bottleneck to limit the development of the blade manufacturing industry. The applicant and the research group developed a set of milling machine with twin-cutters for blade machining, in which the milling with nine axes simultaneous motion has been realized. Based on this machine, aiming at offsetting the cutting forces and reducing the deformation, a novel blade milling method with twin-cutters was approved by the applicant, but the force offset effect and the constraints between the paths of two cutters should be considered during the path planning, therefore, the path planning method is a novel planning problem with complicated objectives and constraints, which is also the theoretical basis and key technology to realize the blade machining with twin-cutters simultaneously. Based on the research on a path optimization algorithm, the algorithm for fitting and adjusting the cutter-contact points in the same line will be researched for the smooth of the cutter-contact points trajectory, and the optimization algorithm of the tool attitude in the feasible region will also be researched for the smooth of the tool axes. Finally, the path planning method for turbine blade milling with twin-cutters and nine axes simultaneous motion will be approved based the research on former algorithms, the simulation and cutting tests will be conducted to verify the theoretical research goal.

在自主研发九轴联动叶片双刀加工机床的基础上，以控制切削变形为目标，申请人及课题组针对中长型叶片粗加工提出了双刀对顶纵铣方法，在规划刀路时需考虑双刀切削力抵消的力学优化目标及双刀加工共用工件转轴的结构约束，这给路径规划方法提出了新问题。鉴于此，本项目基于牛鼻刀切削力建模，研究了切削力抵消效果的数学表征方法，提出了兼顾切削力抵消、残留高度及切削宽度的多目标路径规划算法；针对刀触点轨迹不平滑的问题，提出了基于最小二乘法的单行刀触点集等参数化拟合算法，考虑残留高度公差及叶片两侧对应刀触点沿行距方向等参数这两个约束，研究了拟合所得等参线的修正算法及基于此的刀触点再规划方法；考虑在共用工件转轴时双刀姿态间的约束关系，提出了双刀姿态的统一表征方法，研究了双刀姿态优化的多约束可行域求取方法，并以单行刀轴矢量平滑为目标，提出了双刀姿态在该可行域内的寻优算法；最终，拟针对汽轮机叶片进行加工仿真和实验验证研究。

叶片为汽轮机等透平机械的核心部件，具有细长薄壁的结构特点，加工过程易发生变形，提高加工精度存在一定的难度，且批量加工的效率低。本课题在自主研发九轴联动叶片双刀加工机床的基础上，以控制切削变形和提高加工效率为目标，针对中长型叶片粗加工和半精加工提出了双刀对铣加工方法，并研究了九轴联动叶片双刀对铣路径规划方法。.课题研究了切触点间参数增量的控制算法和对置切触点的同步规划算法，实现了双刀对铣刀路的多目标规划。基于机床后处理算法开发，考虑工件回转轴和双刀摆轴引起的非线性误差，对双刀对铣刀路实现了深入优化。研究了双刀轴矢量的统一表征方法，建立了双刀轴矢量可行域，提出了双刀加工可行域内双刀轴矢量同步平滑寻优算法。以恒定的表面进给速度和各进给轴伺服驱动能力为约束，研究了各进给轴进给速度的优化算法。基于切触点、刀轴矢量及进给速度的优化算法，开发了叶片双刀加工路径规划和程序输出软件模块。.针对1Cr12Ni2W1Mo1V材料典型汽轮机叶片，规划了叶片型面的双刀加工轨迹，并对加工过程进行了仿真分析和加工验证。叶片型面长度为633mm，回转直径为165mm，毛坯余量约3mm，粗加工切削厚度约2mm，半精加工切削厚度约0.6mm。计算了切削力引起叶片型面的最大变形量，与相同加工参数的单刀加工比较，双刀对铣显著减小了叶片变形量。加工结果表明，加工表面均布整齐的可见刀纹，叶背和叶盆型面的轮廓误差范围分别为[-0.029mm, 0.067mm]和[-0.029mm, 0.058mm]，满足加工精度要求，验证了双刀加工工艺和加工轨迹的可行性。同时，双刀加工的加工效率相对传统单刀加工提高约45%。.课题研究成果为多轴联动、多刀具同步加工的路径规划提供了思路，为实现薄壁叶片双刀对铣工艺奠定了理论算法基础，体现了一定的研究意义和应用价值。基于所研究的路径规划方法已对生产企业开展了软件定制开发服务，实现了成果初步转化。