电镀金刚石砂轮高效精密修整及熔融石英磨削试验研究

大尺寸光学玻璃元件主要采用细磨粒金刚石砂轮进行精密/超精密磨削加工，但存在砂轮修整频繁、工件表面面形精度难以保证、加工效率低等缺点。采用大磨粒金刚石砂轮进行加工则具有磨削比大、工件面形精度高等优点，然而高效精密的修整是其实现精密磨削的关键技术。采用Cr12钢对电镀金刚石砂轮(磨粒粒径151 μm)进行粗修整，借助修整区域聚集的热量加快金刚石的磨损，可使砂轮的回转误差快速降至10 μm以内。结合在线电解修锐技术，采用杯形金刚石修整滚轮对粗修整后的电镀砂轮进行精修整，砂轮的回转误差可达6 μm以内，轴向梯度误差由6 μm降至2.5 μm。通过对修整前后的金刚石砂轮表面磨损形貌成像及其拉曼光谱曲线分析了修整的机理。对应于不同的砂轮修整阶段进行熔融石英光学玻璃磨削试验，结果表明，砂轮回转误差较大时，工件材料表面以脆性断裂去除为主；随着砂轮回转误差和轴向梯度误差的减小，工件表面材料以塑性去除为主，磨削表面粗糙度为Ra19.6 nm，亚表层损伤深度低至2 μm。可见，经过精密修整的大磨粒电镀金刚石砂轮可以实现对光学玻璃的精密磨削。

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

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 Ra19.6 nm and subsurface crack depth 2 μm. Thus, the well trued coarse abrasive grinding wheel can be considered for precision machining optical elements.