Zhong Bo, Wu Wei, Wang Jian, Zhou Lian, Hou Jing, Ji Baojian, Deng Wenhui, Wei Qiancai, Wang Chunjin, Xu Qiao
Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900, China.
State Key Laboratory of Ultra-Precision Machining Technology, Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong 999077, China.
Micromachines (Basel). 2023 Mar 27;14(4):737. doi: 10.3390/mi14040737.
A large-aperture silicon carbide (SiC) aspheric mirror has the advantages of being light weight and having a high specific stiffness, which is the key component of a space optical system. However, SiC has the characteristics of high hardness and multi-component, which makes it difficult to realize efficient, high-precision, and low-defect processing. To solve this problem, a novel process chain combining ultra-precision shaping based on parallel grinding, rapid polishing with central fluid supply, and magnetorheological finishing (MRF) is proposed in this paper. The key technologies include the passivation and life prediction of the wheel in SiC ultra-precision grinding (UPG), the generation and suppression mechanism of pit defects on the SiC surface, deterministic and ultra-smooth polishing by MRF, and compensation interference detection of the high-order aspheric surface by a computer-generated hologram (CGH). The verification experiment was conducted on a Ø460 mm SiC aspheric mirror, whose initial surface shape error was 4.15 μm in peak-to-valley (PV) and a root-mean-square roughness (Rq) of 44.56 nm. After conducting the proposed process chain, a surface error of RMS 7.42 nm and a Rq of 0.33 nm were successfully obtained. Moreover, the whole processing cycle is only about 216 h, which sheds light on the mass production of large-aperture silicon carbide aspheric mirrors.
大口径碳化硅（SiC）非球面镜具有重量轻、比刚度高的优点，是空间光学系统的关键部件。然而，SiC具有硬度高、成分多的特点，这使得实现高效、高精度、低缺陷加工变得困难。为了解决这个问题，本文提出了一种新颖的工艺链，该工艺链结合了基于平行磨削的超精密成型、中心流体供给的快速抛光和磁流变抛光（MRF）。关键技术包括SiC超精密磨削（UPG）中砂轮的钝化和寿命预测、SiC表面凹坑缺陷的产生和抑制机制、MRF确定性和超光滑抛光以及计算机生成全息图（CGH）对高次非球面的补偿干涉检测。在直径为460mm的SiC非球面镜上进行了验证实验，其初始表面形状误差峰谷值（PV）为4.15μm，均方根粗糙度（Rq）为44.56nm。经过所提出的工艺链加工后，成功获得了均方根误差为7.42nm、Rq为0.33nm的表面误差。此外，整个加工周期仅约216小时，这为大口径碳化硅非球面镜的批量生产提供了启示。
