Grinding strategies for machining the off-axis aspherical reaction-bonded SiC mirror blank

Abstract

Demand for large-scale off-axis aspherical mirrors is increasing in next-generation space-borne optical imaging systems. In this paper, a variable-axis single-point grinding strategy is developed for precisely, cost-effectively figuring silicon carbide (SiC) mirror blanks that have high-order high-gradient off-axis aspherical surfaces on a precision five-axis machining center. The grinding strategies also include tool path generation/optimization, feeding direction control and wheel wear reduction/compensation. Applying the developed grinding strategies, by only one grinding cycle, a near-circular 372-mm SiC mirror blank is successfully grounded to 7.8 m in peak to valley, which is comparable to the reported machining accuracy of the BoX ultraprecision grinding machine. Moreover, the wheel need not have to be dressed during the whole grinding cycle due to the rotary ultrasonic grinding method. Therefore, this paper offers an efficient and economic solution for grinding off-axis aspherical and free from surfaces to micron-level accuracy, thus significantly decreasing the subsequent lapping/polishing production cycle time. 2014 中文 Optics Letters.