Optimization of scanning path under ion beam cleaning process based on thermal effect

Abstract

Ion beam figuring (IBF) is an advanced machining technology for high precise optical component. For brittle materials with high thermal expansion coefficient such as KDP crystal, thermal effect is an intractable problem due to the accumulative heat introduced by incident ions on optical surface. Asymmetrical heating induces rapid changes of thermal stress and once the thermal stress exceeds the mechanical strength, the component may crack or break. In this paper, the number of scanning rows was factorized to various combinations with times of scanning and the number of moving rows. Temperature field and thermal stress of each combination were simulated using finite element analysis software ANSYS. Comparing with the results, the much better combination was found. With optimized scanning path, peak of thermal stress is lower than that of traditional scanning path. Especially, peak of tensile stress on X-distance and Y-distance were reduced obviously. At last, a law for optimization was established: when times of scanning and the number of scanning rows are equal or approximately equal, the thermal stress appears lower.