基于超精密车削表面衍射光斑分布特性的金刚石刀具磨损在线监测研究

In the field of diamond turning of large optical components, the issue of the optical characteristics deterioration caused by tool wear is one of the major factors restricting the performance of optical components. Aiming at the technical problem of the on-line monitoring of tool wear during diamond turning, this project proposes a novel method for the on-line monitoring of diamond tool wear by establishing the mapping relationship between the diffraction characteristics of ultra-precision turning surface and the wear characteristics of diamond tool. The influence mechanism of surface microscopic topography on the distribution characteristics of diffraction spots is revealed at the nanoscale by using finite-difference time-domain method, and the effects of tool wear on the surface microscopic topography and the diffraction spots are comprehensively discussed based on the theoretical and experimental researches. Furthermore, this project builds the mapping relationship between the diamond tool wear and the distribution characteristics of diffraction spots, and chooses the intensity ratio of the high order diffraction spot and the 0 order diffraction spot as the evaluation index of tool wear condition. Finally, the non-contact on-line monitoring of submicron diamond tool wear is accomplished. The research results have the important theoretical significance and engineering value in improving the machining quality and efficiency, as well as lowering the manufacturing cost of the large optical components, which can be promoted and applied to the ultra-precision machining process of large-size aluminum mirrors and optical roller mold.

在大型光学元件的金刚石车削加工领域，刀具磨损所导致的加工表面光学特性恶化问题，已经成为制约光学元件使用性能的主要因素之一。本项目针对金刚石车削加工中刀具磨损在线监测这一技术难题，通过建立超精密车削表面衍射光学特性与刀具磨损特性之间的映射关系，提出一种新的金刚石刀具磨损在线监测方法。采用时域有限差分法，在纳米尺度上揭示表面微观形貌对各级次衍射光斑的影响机理，从理论和实验两个方面综合研究刀具磨损状态对表面微观形貌和衍射光斑的影响规律。在此基础上，建立金刚石刀具磨损量与衍射光斑分布特性的映射关系，并将高级次衍射光斑与0级衍射光斑的强度比值作为刀具磨损状态的评价指标。最终，实现亚微米级金刚石刀具磨损量的非接触式在线监测。本项目的研究成果对于提高大型光学元件的加工质量和加工效率并降低制造成本具有重要的理论意义和工程应用价值，可以推广并应用到大尺寸铝反射镜和光学辊筒模具等金刚石车削加工中。

在大型光学元件的金刚石车削加工领域，由刀具磨损引起的加工表面光学缺陷已经严重制约了光学元件的使用性能。本项目以提高金刚石车削元件的加工精度和表面质量为出发点，通过构建刀具磨损量与衍射光斑分布特性的映射关系，提出一种非接触式金刚石刀具磨损在线监测方法。在加工表面衍射光学特性分析方面，本项目采用矢量衍射理论及其计算方法，建立了纳米尺度表面微观形貌仿真模型；分析了表面微观形貌特征及入射光波长、入射角对衍射光斑分布特性的影响；揭示了金刚石车削表面衍射光斑的产生机理和变化规律。研究结果证明了不同类型的纳米结构表面具有相似的衍射特性；当采用较小的入射波长和入射角度时，高级次衍射光斑强度会更大。在金刚石刀具磨损特性方面，得到了不同磨损状态下金刚石刀具刃口形貌；研究了刀具磨损量对表面塑性侧流现象及刀具边缘隆起高度的影响；建立了加工表面功率谱密度与刀具磨损量的映射关系。磨损的刀具将会导致更多的材料塑性侧流行为，进而导致未去除材料的堆积高度增大，加工表面粗糙度也将相应增大，周期性特征也更为显著。在加工表面衍射光斑测量方面，设计并搭建了加工表面衍射光斑测量平台；建立了刀具磨损量与衍射光斑分布特性的映射关系；设计了衍射光斑强度与角度提取算法；提出一种金刚石刀具磨损状态的评价指标，即高级次衍射光斑与0级衍射光斑的强度比；开发了金刚石刀具磨损在线监测软件系统。该系统不仅可以提供金刚石刀具磨损状态提示功能，包含刀具无磨损、轻微磨损以及严重磨损三种状态信息，而且还包含了加工表面微观形貌预测与评估功能。研究结果表明：在一定条件下，即使金刚石车削表面粗糙度Sa的变化小于2nm，高级次衍射光斑强度也会增加将近5倍。本项目的研究成果为光学元件的超精密加工过程的在线监控提供了新的技术手段，具有重要的学术与现实应用价值，可以推广并应用到更多金刚石超精密车削加工领域。