Study On The Key Techniques Of Computer Controlled Lapping For SiC Aspheric Mirrors

With the development of space optical technology, the manufacturing of space optical element faces challenge. In recent years, Si C become the preferred material for manufacturing space optical mirrors because of the high specific stiffness and specific intensity. But the hardness of Si C is very high and Moh's hardness is 9. Through form grinding, the wear rate of the grinding wheel is very high and the machine can't bring the precision superiority into full, so that the working efficiency is low and it's hard to improve the manufacturing precision. These become the bottleneck problem of the Si C mirrors manufacturing. Computer Controlled Optical Surfacing(CCOS) plays an important role in figuring polishing for optical element. Using CCOS to lap Si C aspheric mirrors can achieve three body grinding instead of two body grinding. It can solve the problem of grinding wheel wear effectively in superhard material grinding. Meanwhile, it can reduce the precision demands of the machine and there's a hope to advance the efficiency and precision of accurate grinding. With the goal of improve the precision and efficiency of accurate grinding for Si C aspheric mirrors, we do the research aiming at removal function modeling of CCOS lapping, the influence factor of removal function stability, the optimizing of lapping tools, the control of edge effect and so on, and have these major research content:1. The research about the stability of removal function. Study the influence of different lapping tools on the material removal rate of Si C to choose the lapping tools for high material removal rate. Based on the Si C aspheric mirror, we study the changing law of misfit between lapping pads and the surface of the mirrors by simulation and analysis. Combining with the wear rate of the different lapping pad's materials, optimize the lapping tools and feed speed of the machine through lapping process to keep stability of removal function through lapping Si C aspheric mirror.2. The research about controlling edge effect. Study on the changing law of the material removal on the edge with overhang distance of the lapping pads. Provide the choosing basis of the overhang distance to control the ‘warping edge'. Learning from smoothing polishing, propose a new method using large lapping pad to control ‘warping edge'. The experiments of controlling ‘warping edge' are done on the ?130mm plane circle Si C workpiece and the Si C aspheric mirror with the stadium shape, and we get good result.3. The study on the lapping for Si C aspheric mirror. Introduce the method to measure off-axis aspheric mirror by using coordinate measurement and the processing principle of measured data. Study the measuring results of the different measuring paths, and then provide reference frame for the choice of the measuring program. Introduce the lapping process of Si C aspheric mirror, and expound the key technology in different process during the lapping.