Analysis of wear non-uniformity of pad in full aperture polishing

摘要

Full aperture polishing (FAP) is the key application process that realizes low damage and ultra-smooth surface in the fabrication of large plane optical element. The polishing pad plays a vital role as a significant part in FAP. When the material of element is removed, the contact surface of pad also appears non-uniform wear, which is detrimental to polishing accuracy and efficiency. In this work, wear density (WD) is proposed to characterize wear uniformity of pad, and relative wear (RW) is used to represent the wear degree. Based on the wear density distribution model, the effect of process parameters on the pad wear is investigated. It is pointed out that when the speed difference between the element and the polishing plate is 0.2r/min to 0.5r/min, the wear track distribution of pad is relatively uniform. Furthermore, the results showed that swing has the greatest influence on the wear non-uniformity, while the traverse velocity is the smallest. In order to reduce the serious local wear, the swing can be increased according to the diameter of the polishing plate. This provides a good guidance for the optimization of FAP process.