Time-Optimal Connection Between On-the-Fly Drilling Trajectories and Rest Boundary Conditions

This paper presents a new algorithm, capable of handling five degree-of-freedom (axis) positioning and details the generation of connection trajectories into and out of the closed cubic spline trajectory, which is used for repeating on-the-fly laser drilling passes. These connection trajectories have to either start from a rest state and blend into the closed cubic curve with the correct position, velocity, and acceleration boundary conditions or they have to leave the closed cubic spline with the aforementioned boundary conditions and proceed to a rest state. The position assumed at the ‘rest’ condition is not constrained. The conducted simulation and experimental benchmarks reveal a successful reduction in total machine drilling cycle time and reduced process vibrations transmitted to laser optics causing misalignments. The algorithms developed have been tested in a target application involving the laser drilling of cooling hole arrays on gas turbine engine combustion chamber panels. The novelty, in this paper, is concurrent planning of five-axis time-optimal movements and direct minimization of the total travel time, which also consider knowledge of the machine kinematics and process constraints, in order to improve the productivity and part quality in five-axis laser drilling operations.