Trajectory Planning Of Optical Surface Polishing Based On Small Tool Head

Optics plays an important role in the large system of human development.Optical research occupies an important position in the research of human basic and engineering application science.Optical components are the necessary carrier and necessary tool to realize optical functions.More and more rotating aspheric and free-form optical elements are widely used in modern optical equipment.Higher machining precision is required for the surface quality of optical elements,and how to improve the machining quality has become a key research direction.Trajectory planning of computer-controlled polishing technology for small tool heads based on Preston equation,the local removal rate of the polishing process of spherical tool heads was derived.The geometrical relation in polishing process is established,the velocity distribution and pressure distribution are obtained by using Hertz contact theory,and the local removal model is constructed.The removal model was verified by experiments and the applicability of Hertz contact theory was analyzed.The influence of the ratio change between the curvature of the polishing head and the curvature of the surface on the removal model and trajectory planning should be considered in surface polishing.It is analyzed that under certain polishing parameters,the proportion range of workpiece surface curvature radius and surface curvature radius is within r_tool<r_c<20 r_tool,r_tool<r_m<20r_tool,the change of elliptical spindles a and b in the polishing contact area has obvious influence.The change of spindle affects the change of polishing contact area and pressure.The changes of each parameter in the above contact area comprehensively affect the depth change of the removed contour.In the method of obtaining the trajectory of the surface by projecting the two-dimensional trajectory onto the three-dimensional surface,the above changes are the influential factors that cannot be ignored.Trajectory planning process in terms of size of track spacing consider two main factors that caused by the projection line spacing between the trajectory of change,the curvature changes caused by the contact area,the synthetic curvature of the projection distance and polishing head contact area change of two factors influence on trajectory planning,trajectory planning algorithm is proposed based on the concept of overlap rate,realize the curvature and track spacing between quantitative control.The Archimedes spiral was selected as the basic trajectory line in the trajectory planning of the turning surface,and according to the characteristics of Archimedes spiral trajectory,its pitch was modified by the trajectory planning algorithm to realize the variable pitch control.The trajectory planning algorithm is used to simulate the surface and compare the polished surface quality before and after modification.Simulation analysis shows that the trajectory of different overlap rate is different from that of polished surface,and quality evaluation criteria are proposed to determine the best overlap rate.The trajectory planning analysis was carried out for the planar workpiece,and the overlap rate was 60%when the best surface quality was determined by simulation.Through experimental verification,the measured surface Ra reached 0.0854?m.Under the condition of constant force polishing,the closer the curvature radius is to the radius size of the polishing head,the larger the removal amount will be.Uneven removal amount of the polished surface appears in the above trajectory planning method.In view of the uneven phenomenon,equal removal amount control methods are proposed,such as stepwise equal overlap rate method and speed control method.Simulation analysis of the two methods of polishing surface quality,the speed control algorithm surface quality is better than the stepwise overlapping rate control method,through the experimental verification of the speed control algorithm surface quality reached Ra0.0776?m.