Jahnel Kirk, Michels Robert, Wilhelm Dennis Patrick, Grunwald Tim, Bergs Thomas
Department of Fine Machining and Optics, Fraunhofer Institute for Production Technology IPT, 52074 Aachen, Germany.
Chair for Manufacturing Technology, Tool Machine Laboratory (WZL), RWTH Aachen University, 52074 Aachen, Germany.
Micromachines (Basel). 2023 Dec 14;14(12):2240. doi: 10.3390/mi14122240.
Glassy carbon provides material characteristics that make it a promising candidate for use as a mould material in precision glass moulding. However, to effectively utilize glassy carbon, a thorough investigation into the machining of high-precision optical surfaces is necessary, which has not been thoroughly investigated. This research analyses the process of material removal and its resulting surface integrity through the use of nano-scratching and ultra-precision grinding. The nano-scratching process begins with ductile plastic deformation, then progresses with funnel-shaped breakouts in the contact zone, and finally concludes with brittle conchoidal breakouts when the cutting depth is increased. The influence of process factors and tool-related parameters resulting from grinding has discernible impacts on the ultimate surface roughness and topography. Enhancing the cutting speed during cross-axis kinematic grinding results in improved surface roughness. Increasing the size of diamond grains and feed rates leads to an increase in surface roughness. An achievable surface roughness of Ra < 5 nm together with ductile-regime grinding behaviour meet optical standards, which makes ultra-precision grinding a suitable process for optical surface generation.
玻璃碳具有一些材料特性，使其成为精密玻璃成型中用作模具材料的有前景的候选材料。然而，为了有效利用玻璃碳，有必要对高精度光学表面的加工进行深入研究，而这方面尚未得到充分研究。本研究通过纳米划痕和超精密磨削来分析材料去除过程及其产生的表面完整性。纳米划痕过程始于延性塑性变形，然后在接触区出现漏斗形破裂，最后当切削深度增加时以脆性贝壳状破裂结束。磨削过程因素和刀具相关参数对最终表面粗糙度和形貌有明显影响。在交叉轴运动磨削过程中提高切削速度会改善表面粗糙度。增大金刚石晶粒尺寸和进给速率会导致表面粗糙度增加。实现Ra < 5 nm的表面粗糙度以及延性域磨削行为符合光学标准，这使得超精密磨削成为生成光学表面的合适工艺。
