Kinematic compensation of repetitive errors for non-circular laser shaping

This paper presents an approach for kinematic compensation of the laser shaping process which is capable of achieving improved dimensional accuracy for non-circular profiles. In this approach, a plug-in repetitive controller is added into the existing position servo loop to improve tracking of the desired sinusoidal trajectory and subsequently reduce tracking errors. The effect of tracking errors on different dimensional error modes in the non-circular shaping process is identified. Simulation models are developed for testing the performance of the repetitive controller in shaping various non-circular profiles with different operating parameters such as oscillating amplitudes and sampling time. Simulation results show that better tracking performance can be obtained with the addition of the repetitive controller. Experimental results include fabrication of single-harmonic-term profiles such as triangular, square, hexagonal and octagonal profiles and multiple-harmonic-term profiles such as diamond-shaped profiles in polymethyl methacrylate with both control algorithms. The non-circular profiles are measured through optical CMM to determine the dimensional accuracy in edge straightness, angularity, parallelism and feature size.