硬脆轴对称微结构表面的皮秒激光-超精密磨削链技术研究

Due to the superior properties in terms of light weight, miniaturization, integration to systems, the axis-symmetrical micro-structured optical functional elements have been widely applied in advanced optical systems. However, the tool wear problem in the diamond grinding process for the glass molding moulds has never been thoroughly solved, which always limits the improvement regarding the efficiency and accuracy and thus its optical performance. In aiming to solve this problem, this project firstly introduces pico-second laser as a pre-machining process featuring its high material removal rate and secondly, applies ultra-precision grinding as a final step machining featuring its deterministic high accuracy. Through this integrated pico-second laser and ultra-precision grinding processing chain, the Silicon Carbide(SiC)and Tungsten Carbide (WC) which are typical hard and brittle materials used as glass moulds, are investigated to machine with the axis-symmetrical micro-structured surfaces. Based on the fundamental study of the interactional mechanisms between the laser beam, grinding wheel and the materials, the micro-scaled material evolvement behavior in multi-modes is analyzed, then the mapping relationship between machining parameters and the multi-dimensional accuracies can be established. With the breakthrough of the bottle neck of grinding tool wear problem inhibiting the machining efficiency as well as the element accuracies, the processing parameters will be optimized according to the experiments of different typical workpieces. The research deliveries will no doubt present the theoretical and technological fundaments for the high efficiently and high precision machining hard and brittle axis-symmetrical micro-structured glass molding moulds. The study and research achievement of this proposed project will expand the application of hard and brittle materials in the field of the manufacturing field of micro-structured surface elements. Furthermore, the level of ultra-precision machining technology will be also accordingly promoted.

轴对称微结构表面光学功能元件以其小型轻量集成性好等特征在先进光学系统中得到日益广泛的应用，但是玻璃模压用超硬模芯的加工因工具磨损问题一直在限制其效率及精度的提高。本项目以碳化硅和碳化钨等典型玻璃模压用模芯硬脆材料为加工对象，以其轴对称微结构表面的高效高精度加工为目标，开展皮秒激光介入并协同超精密磨削的集成工艺链技术研究。通过分析皮秒激光及磨削工具作用下的多模式材料微观行为演变机制，建立起加工参量与被加工表面多维精度指标之间的内在关联。在突破该类元件传统磨削加工过程所存在的因工具磨损而影响加工效率与精度技术瓶颈基础上，完成典型元件的加工链工艺实验并提出过程参数的优化方案，从而为实现硬脆材料复杂微结构表面玻璃模压用模芯的高效率高精度制造提供理论依据并奠定技术基础。本项目的研究将拓展硬脆材料在微结构功能表面元件制造领域的应用范围，促进并提升硬脆及其它难加工材料的超精密加工技术水平。

轴对称微结构表面光学功能元件具有体积小、重量轻和集成性好等优点，在先进光学系统中得到了日益广泛的应用，玻璃模压加工可以实现其大批量低成本生产，而玻璃模压用超硬模芯的高效高精度制造是目前的瓶颈技术。本项目将超精密加工技术与皮秒激光能量束加工技术相结合，分别建立了适用于硬脆材料轴对称微结构模芯的皮秒激光加工系统和超精磨削加工系统。分析了激光加工参数对于加工结果的影响规律，计算了材料烧蚀阈值。进行了旨在提高材料去除效率和抑制亚表层损伤的激光加工参数正交优化。建立了激光去除函数模型，提出了基于零件几何特征计算激光加工驻留时间的烧蚀路径规划策略。在碳化硅和碳化钨上实现了菲涅尔微结构模芯的激光加工。从亚表层裂纹、加工硬化现象、工件内部残余应力三个方面，对激光加工的菲涅尔模芯微结构的亚表层损伤进行了检测分析。针对异形尖角的金属基和树脂基金刚石砂轮，分别使用旋转GC棒和钽块修整法实现了砂轮的精密修整。采用声发射监测技术实现了对砂轮修整状态的实时在线监测。通过压痕、刻划以及切入式磨削等基础实验揭示了材料损伤机理和材料表层及亚表层损伤机理。分析了砂轮磨损、砂轮振动及非均匀材料去除对工件微观纳米表面生成的影响规律。揭示了平行磨削轴对称工件表面波纹度特征的生成机理和分布规律，提出了表面波纹度仿真建模方法以及抑制表面波纹度的磨削参数匹配策略。研究了金刚石磨损机理并分析了砂轮微观和宏观磨损对表面生成的影响，通过刀具轨迹补偿，实现了典型轴对称微结构表面的超精密磨削加工(PV<0.8 μm, Ra<10 nm)。针对菲涅尔微结构模芯，开发了皮秒激光加工和超精密磨削加工协作接力的工艺链技术，微结构模芯的整体加工效率可以提高大约5倍，为突破硬脆材料轴对称微结构表面的高效高精度加工技术瓶颈，提供了新的解决方案。