High Efficient Precision Conditioning of the Electroplated Diamond Wheel and Grinding of Fused Silica Glasses

Abstract

Generally, the fine abrasive diamond wheel is used to the precision/ ultra-precision grinding of large-size optical glasses, but there're some disadvantages, such as the frequent wheel conditioning, uncontrollable surface accuracy, and low processing efficiency. Coarse abrasive diamond wheel can implement a higher surface accuracy machining with large grinding ratio. However, to achieve precision grinding, efficient precision conditioning is very critical. The electroplated diamond grinding wheel(grit-size 151 μm) is rough trued using the Cr12 steel. The gathering heat speeds up the diamond wear, so the run-out error of grinding wheel is quickly down to below 10 μm. Combined with electrolytic in-process dressing technique(ELID), cup-shaped diamond roller is applied to precision condition the electroplated grinding wheel. The wheel's run-out error drops to within 6 μm, and the axial gradient error is reduced from 6 μm to 2.5 μm. By the wheel wear morphology and the Raman spectral curve, the conditioning mechanism is analyzed. In different wheel truing stage, the fused silica is surface ground respectively. Using the high run-out error grinding wheel, the optical glass is mainly removed in the form of brittle fracture. When the run-out error and axial gradient error reduce, the fused silica glass is ground mainly as plastic removal, with the surface roughness Ra 19.6 nm and subsurface crack depth 2 μm. Thus, the well trued coarse abrasive grinding wheel can be considered for precision machining optical elements.