Removal of the single point diamond turning marks by spiral sine trace bonnet polishing process

Single point diamond turing (SPDT) technology has been widely used in the high precision optical surface processing field. However, the micro-nano texture which is mainly composed of turning marks remain on the turned surface will affect performance of optical systems. Therefore, it’s necessary to remove the turning marks for improving the surface quality. Removal of the single point diamond turning marks was studied in the paper. It was found that the removal efficiency was highest when the polishing direction was perpendicular to the turning marks. A new polishing trace called spiral sine trace was presented based on the finding. The design principle was introduced in detail. Contrast experiment of different polishing tracks consisting of spiral sine trace, spiral trace and raster trace utilizing bonnet polishing was carried out. Result shows that the improvement effect of micro-nano texture in spiral sine trace was obviously superior to two other kinds of trace. A germanium aspherical surface manufactured by SPDT was smoothed by spiral sine bonnet polishing. The results shows that the roughness of surface Ra reduce from 1.28 nm to 0.4 nm before and after polishing, the regular turning marks transform to random micro-nano texture, and above all, the surface figure accuracy isn’t damaged during the smoothing process.