Research On Figure Error Correctiion Technique In Ultrasonic-magnetorheological Compound Finishing

With the development of optical technology, more and more aspheric surfaces have been applied for many new requirements of the optical systems, and the surface figure accuracy and sub-surface damage has been required. To achieve deterministic removal, the computer-controlled polishing technology (CCP) for complex surface has been developed by various countries since last 60s. CCP had become an important method for ultra-precision machining. Because of the dimension of polishing tools and other factors, most existing technologies for optical fabrication can't be applied in the machining of concave aspheric surfaces with small curvature radius. The computer-controlled ultrasonic- magnetorheological compound (UMC) finishing which is the ultra-precision machining method for concave spheres with small radius and freeform surfaces. The figure error correction technology of UMC finishing has been researched in this paper, and the main aspects of the research are as follows:Firstly, dwell time algorithm in computer controlled UMC finishing was researched. Based on figure error, mathematical model of the removal function and the figure accuracy requirement, the proportional algorithm and Jasson- Van- Cittert algorithm were studied respectively. The unicursal pseudo-random polishing path was schemed to reduce the high-frequency errors left by small polishing tool.Secondly, the method of generating NC code automatically and processing simulation based on software UG was studied. Polishing path was built based on UG/CAM, and then the post-processor for UMC finishing device was developed using UG/Post Builder. The integrated simulation and verification (IS&V) system had been created. The correctness of the machine tool movement was simulated and verified.Finally, the figure error correction experiments were carried out. The executed code was generated combing the NC code and the dwell time. The power spectral density (PSD) was analyzed and the result indicated that the random polishing path could reduce the high frequency error.