Toolpath Generation for Robotic Flank Milling via Smoothness and Stiffness Optimization

Robotic flank milling has outstanding advantages in machining large-scale slender surfaces. Currently, the paths for this process are mainly generated by optimizing redundant robot degrees of freedom (DoFs) on the basis of conventional 5-axis flank milling paths. This two-step framework, however, does not enable optimal robot kinematic and dynamical performance compared to the direct generation of 6-DoF robot paths, limiting the machining efficiency and effectiveness. This paper presents an optimization method to directly generate a toolpath with six DoFs for robotic flank milling. Firstly, the kinematic model of the milling system and the representation of the 6-DoF toolpath are established. Then, the standard geometric error for flank milling that conforms to the geometric specification is defined, and an efficient algorithm based on conformal geometric algebra is proposed to solve it. On this basis, the toolpath optimization model with toolpath smoothness and robot stiffness as objective functions is established. A sequential quadratic programming algorithm is proposed to solve this highly non-linear problem based on the lexicographic order of arrays. The simulations and experiments demonstrate that the proposed method has better efficiency, robustness, and effectiveness compared with the existing methods. Due to the improvement of smoothness and stiffness, the productivity, accuracy, and finish of the machining are all enhanced.

Automated summary

This paper presents an optimization method for directly generating a six-degree-of-freedom toolpath for robotic flank milling. By optimizing the smoothness of the toolpath and the stiffness of the robot, the efficiency, accuracy, and finish of the machining are improved.