Hybrid Laser-Polishing Process for Machining Silicon Carbide

摘要: Silicon Carbide (SiC) is considered one of the best candidate materials for mirrors or structures for space optic applications because it has excellent mechanical and chemical properties, such as low density, high strength, low thermal expansion and superior chemical inertness. To fabricate optical elements, the work material needs to be polished and satisfy the requirements of accurate form and surface roughness at the same time. Given the micron-scale rate of material removal, however, the polishing is one of the most time-consuming processes. Furthermore, the extreme hardness and brittleness of SiC make it difficult and costly to fabricate for applications using conventional machining processes such as milling or turning. There have been previous studies to investigate polishing SiC, including hybrid approaches of polishing SiC that employ external energy sources such as ultrasonic vibrations, magnetic fields or plasma. However, most of these efforts have been focused on roughness improvement. In contrast, improving the material removal rate (MRR) has not received much attention. Laser beams have frequently been adopted in hybrid manufacturing as the best assistive energy source to improve MRR. However, the laser beam has not yet been adopted as an assistive energy source for polishing. A novel hybrid polishing process, namely laser assisted polishing (LaPol), was developed in this study to improve the MRR of polishing SiC, by combining a CO2 laser source with a conventional mechanical polishing process. For the first time a laser beam was synchronously irradiated through a rotating custom-made hybrid tool and focused …