大口径SiC离轴非球面的高效磨削加工

Fast grinding of large SiC off-axis aspheric surface

研究了空间遥感器用大口径SiC离轴非球面的超声复合磨削加工工艺。分别对磨削原理、金刚石砂轮结合剂选择、机床选取、磨削参数设定等进行了分析,并设计和规划了磨削工艺流程。基于逆向工程原理建立了高精度离轴非球面模型,创立了激光跟踪仪精磨阶段在线测量大口径离轴非球面的工艺。结合工程实践对一口径为700mm×700mm的SiC高次离轴非球面元件进行了逆向工程建模和超声磨削加工试验,并利用激光跟踪仪进行了在线检测。经过3个周期(每个周期4h)的修磨,其面形精度PV值和RMS值分别由45.986μm和7.949μm收敛至12.181μm和2.131μm;与三坐标测试结果进行对比,其PV值和RMS值的偏差分别为0.892 3μm和0.312 8μm。实验显示,提出的磨削工艺实现了大口径SiC离轴非球面的快速精确磨削,其加工精度、效率以及表面质量都有了很大的提高。

A fast ultrasonic grinding for SiC off-axis large aspheres used in space remote sensors was researched. The principle of grinding, the selection of diamond grinding wheel bond, the selection of machine tool, and setting grinding parameters were analyzed, and the grinding process was designed. A high precise model of off-axis aspheric surfaces was established on the basis of the principle of reverse engineering, and the online testing method in fine grinding state for a large off-axis aspheric mirror by a laser tracker was established. Combination with an engineering example, the model of a large SiC off-axis asphere with the aperture of 700 mm× 700 mm was established by the reverse engineering principle, and it was grinded by ultrasonic method and measured by the laser tracker. After 3 cycles （4 hours per cycle of grinding）, the PV value（45. 986 μm） and RMS value（7. 949 μm） of the surface error are reduced to 12. 181 /am and 2. 131 μm, respectively. As compared with three coordinate testing results, the errors of PV value and RMS value are 0. 892 3 /am and 0. 312 8 μm, respectively. It concludes that the grinding technology realizes fast and high precise grinding for the SiC off-axis large asphere and improves its machining precision, efficiency, and surface quality.