Influence of the edge effect on mirror shape in spin casting and the cause analysis

摘要

This paper attempts to study the abnormal bulge generated near the contact position between the mould and the surface of the mirror blank produced in spin casting. The generation of this phenomenon, which is named the edge effect, will significantly affect the shape accuracy of the mirror blank. Therefore, it is necessary to explore the causes of the edge effect and the method of its elimination. Through setting different contact angles, a simulation of the spin casting process was conducted to determine the relationship between the generation of the edge effect and the wettability between the glass melt and the mould. And then, the proportion of the raw materials of the ceramic fibre that is used to make the mould in spin casting has been changed in the experiment, so that the contact angle between the glass melt and the material of ceramic fibre was reduced from 140.489 degrees to 75.642 degrees. After using the mould that has been modified wettability for processing mirror blank, no edge effect happened, and the shape accuracy of the mirror bank was also improved.