DYNAMIC EFFECTS OF CIRCULAR AND NONCIRCULAR LASER SHAPING

A laser finishing technique has been developed which allows tangential impingement of a high-power laser beam on the apex of a rotating cyli ndrical workpiece. Previous studies have shown that sub-micron R-a sur face roughness can be achieved on polymethyl-methacrylate and Si3N4 wi th a material removal rate up to 5 mm(3) s(-1). This technique can als o be used for the shaping of non-circular and discontinuous profiles a t high machining speeds. This paper presents steady-state and dynamic models for the beam-material interaction that can be used to estimate the surface texture and dimensional accuracy of laser-shaped parts. Th e steady-state analysis relies on conformal mapping to transform the c ircular workpiece profile into a semi-infinite domain for an energy ba lance solution. The dynamic model incorporates disturbances due to var iations in laser power, beam mode, rotational agreement with R-a measu rements for variation in rotational speed, feed and beam power compare d with previous beam kinematics models and static finishing. Compariso n of estimated overlap profiles with profilometry measurements showed good correlation in the periodicity of surface roughness. Sensitivity analysis showed that feed has the greatest influence on R-a in the ope rating range of fine finishing, whilst rotation speed and feed have th e greatest influence on the material removal rate. Simulation results of octagonal profiles showed decreasing straightness error with increa sing laser energy density of the laser beam. The dynamic simulation mo del showed improved agreement with straightness error and sharp corner features of the profiles compared to the static simulation model. (C) 1997 Published by Elsevier Science S.A.