单晶锗微结构的超声振动辅助微切削加工

Ultrasonic vibration assisted micro cutting of micro-structures on single crystal germanium

摘要:

为解决单晶锗微结构元件超精密金刚石切削加工的技术难题,提出采用超声振动辅助切削技术提高单晶锗的临界未变形切屑厚度,并推导了微结构切削中切屑厚度的理论计算公式. 进行微圆弧金刚石刀具的振动辅助微切削实验,研究临界未变形切屑厚度随振幅的变化规律,分析微槽表面加工质量和切屑形貌等. 分析4.5 μm和10.0 μm深的十字槽、矩形凸台等微结构的加工质量,针对微槽边缘的加工损伤问题,采用“切深递减”同时结合横向进给的工艺方法. 实验结果表明:微槽切削中切削深度的理论计算值存在较大的误差,应选用直接测量法；振动辅助切削的临界未变形切屑厚度随着振幅的增加而增大,最高达到了704 nm,是普通切削深度的5.2倍. 与普通切削相比,振动辅助加工可以在一定程度上降低微槽表面粗糙度. 采用振动辅助微切削技术能够在大切深条件下加工出具有较高表面质量和轮廓精度的微结构,能够有效解决微槽侧面加工损伤问题,微槽表面粗糙度R_a值低至3.09 nm.

Abstract:

To realize the ultra-precision diamond cutting of micro-structured single germanium components, the vibration assisted diamond cutting was adopted to increase the critical undeformed chip thickness (CUCT) of brittle germanium, and the theoretical equations were derived for calculating chip thickness of micro groove. By micro cutting tests with micro arc shaped diamond tool, the influence of vibration amplitude on CUCT was analyzed, and the surface roughness of micro groove and morphology of chip were also studied according to the experimental results. Accordingly, the machining quality was evaluated during cutting cross-shaped groove and rectangular boss with depths of 4.5 μm and 10.0 μm. For the sake of removing damage near the edge of groove, a technological process was adopted and conducted by applying cutting-depths decreased gradually and cross feed together. According to the experimental results, the cutting depth of micro groove was suggested to measure directly because of the higher values calculated by theoretical equations. The CUCT was found to increase with the increase of vibration amplitude and reached 704 nm, which is almost 5.2 times of that without vibration assistance. It was also observed that the surface roughness could be decreased when applying vibration assisted cutting. Moreover, vibration assisted cutting was proved to have excellent performance on machining micro structures with high accuracy under large cutting depth. The adopted technological process was able to remove the surface damage and generate smooth surface with R_a 3.09 nm.