Optimization of the process chain for mirrors made of silicon carbide

Different grades of silicon carbide (SiC) became an established material for structures as well as optical mirrors in space-borne applications. But the manufacturing still causes high efforts and restrains an extension of application in further fields. The research project MirrorFab aims for a qualification of an optimized process chain for manufacturing mirrors made of Cesic (R). Cesic (R) consists of a matrix of SiC reinforced with chopped carbon fibers. There is a space qualified Cesic (R) manufacturing process and an established network for the supply chain The project addresses the required gain in efficiency and flexibility in the manufacturing capabilities. The consortium covers the major parts of the process chain It aims for increasing the performance of each manufacturing technology. Additionally, the consideration of the complete process chain enables a holistic optimization approach. This paper deals particularly with the process optimization of the grinding step after infiltration. The benefit of the use of an ultra precision grinding machine for mirrors in the range of 200 mm is evaluated. This paper presents the results of a systematical study on the influence of the grit size, the type of bond as well the major machining parameters on the surface roughness and the grinding forces, when machining the material Cesic (R). A major finding is, that the use of ultra fine grinding wheels does not result in a superior surface quality compared to the use of a D46 grinding wheel with resinoid bond.