Study On Key Technology Of Belt Polishing For Optical Materials

At present, the requirement for optical components is increasing greatly. In the modern optical system, the application of aspherial and freeform surface parts is more and more widely. Now, with the development of optical polishing method, the deterministic polishing technology is more important. But it is very difficult to fabricate the high deep concave surface, because the inside surface of such parts has small curvature radius, where some polishing methods are not attainable. So, the applications of this kind of parts will be limited. The optical belt polishing technology is characterized by high removal efficiency and good figuring ability. It has prominent advantages especially in processing high deep concave surface of the workpiece.The optical belt polishing method is further researched based on the early laboratory work. The work of this dissertation is as following.1. The problem of evident texture caused by low frequency vibration is solved after the optical belt polishing device is improved. The stiffness of belt polishing device is increased by improving the device of the cantilever, tensioning mechanism and idle wheel. The periodic impact on parts caused by the joint of polishing belt is weakened by the effective methods.2. The surface quality of polished flat glass is studied by the method of taguchi experiment. The experiment material of K9 glass plane is machined by grinding before experiment. Through selecting six control factors, the surface roughness value is measured after polishing machining.The obtained optimal parameters of the optical belt polishing are hardness of contact wheel of 70, load displacement of 0.05 mm, feed speed of 4 mm/min, step spacing of 0.1 mm, belt velocity of 0.63 m/s and apparatus offset angle of 30°. With the optimal parameters, the surface roughness of K9 glass plane is polished to about Ra12 nm.3. The figuring experiment is carried on plane specimen. The material of part is K9 glass. By the selected experimental parameters, the surface accuracy is improved from PV 0.45λ to 0.15λ after polishing 3 times. This result verifies the figuring ability of the optical belt polishing technology.4. The processing techniques of magnesium fluoride dome are studied. By swinging the polishing wheel in process, the part is polished on the normal direction of surface, and the roughness of surface is lowed.