No abstract

As an optical hard brittle material, glass-ceramic is widely used in radome, astronomical telescopes, and laser industries. However, an efficient method for machining optical free-form surface of glass-ceramic still needs to be studied by academia and industry. In this study, a laser-assisted fast tool servo machining device for glass-ceramic is developed. The theoretical stiffness of semicircular flexure hinge in the device is calculated by flexibility matrix method. The displacement output characteristics of the device are verified by simulation and displacement measurement experiment. Static and dynamic temperature measurement experiments of glass-ceramic are carried out respectively. The free-form surface morphology of glass-ceramic is obtained through machining experiment. Laser-assisted fast tool servo machining can reduce surface roughness by 24.4% and tool wear by 35.7% compared to conventional machining, which fully proves that the laser-assisted fast tool servo machining device can obtain higher machining quality of optical free-form surface.

Glass-ceramic is a typical hard and brittle material that is difficult to machine. In order to improve the surface quality of laser-assisted fast tool servo machining optical free-form surface of glass-ceramic, the effects of spindle speed, feed speed, piezoelectric frequency and laser power on the surface roughness were investigated. Firstly, the Taguchi method (TM) was used to establish the orthogonal experiment, and the contribution rate of each machining parameter to the surface roughness was obtained through variance and signal-to-noise ratio (S/N) analysis. The order of the influence degree of each parameter on the surface roughness is as follows: laser power> spindle speed> feed speed> piezoelectric frequency. The optimal machining parameter combinations obtained for the TM experiment are as follows: spindle speed 50rpm, feed speed 0.01mm/rev, piezoelectric frequency 8Hz, laser power 75W. The range of surface roughness reduction obtained by comparing laser-assisted machining (LAM) with pure fast tool servo (FTS) machining is 38.75%~58.77%. The Box-Behnken Design (BBD) in response surface methodology (RSM) was used to design experiments and a regression model for surface roughness was established through RSM. The deviation between the surface roughness predicted by the regression equation and the experimental value is less than ± 6%. The influence law of various machining parameters on surface roughness was studied through three-dimensional response surface. RSM optimized the minimum surface roughness with a desirability of 99.43%. The optimal combination of machining parameters optimized through RSM is as follows: spindle speed 53.71rpm, feed speed 0.02mm/rev, piezoelectric frequency 6.73Hz, laser power 72W. This paper is the first to combine LAM with FTS for machining optical free-form surface of glass-ceramic. This study provides a reference for laser-assisted fast tool servo machining and the research methods of surface quality.