High-performance grinding of a 2-m scale silicon carbide mirror blank for the space-based telescope

Abstract

Silicon carbide (SiC) is a competitive candidate material for building the space-based reflecting mirrors. However, SiC is also a typical difficult-to-machine material due to its extreme hardness. When SiC workpiece is machined by grinding, the wheel wears rapidly which leads to a deterioration of surface form accuracy. Grinding efficiency also becomes extremely low due to the frequent truing and dressing of grinding wheels. To achieve high-performance grinding process capable of producing accurate surface at high grinding efficiency, an ultrasonic vibration-assisted fix-point grinding technology was developed in this study. Wheel wear observation indicated that the wheel needs not to be dressed during the whole grinding cycle. Moreover, a laser tracker was used to achieve an on-machine measurement of the surface form error. A CNC tool microset was adopted to evaluate the wheel wear amount. On the basis of the above two results, surface form error could be predicted before grinding, and thus, an inprocess compensation of surface form error was carried out. Using the above-mentioned grinding strategies, a SiC mirror blank with an aperture diameter of 2 m was successfully ground to a form accuracy of 18 μm in peak-to-valley (PV). Therefore, this work provides an efficient and economical solution for grinding the large-scale SiC aspherical surfaces.

Study on Damage of 4H-SiC Single Crystal through Indentation and Scratch Testing in Micro–Nano Scales

“…Space-based astronomy telescope [13], grating [14] Device Large band gap, high temperature, high frequency…”

On-Machine Precision Form Truing and In-Situ Measurement of Resin-Bonded Spherical Diamond Wheel

“…However, ultra-precision grinding is only possible provided that a periodic form truing of the diamond wheels is conducted over the whole grinding cycle [3,4]. The resin-bonded spherical diamond wheels are especially beneficial for obtaining better ground surface quality but are more susceptible to wear [5]. A high-efficiency on-machine precision form truing process and a form-truing error in-situ measurement method are therefore necessary to reduce the influence of grinding wheel wear on the resulting accuracy of the grinding surface profile, thus allowing for efficient and precision grinding of complex surfaces of hard and brittle materials [6].…”

Development of a Novel Three Degrees-of-Freedom Rotary Vibration-Assisted Micropolishing System Based on Piezoelectric Actuation

“…For optical systems to continually exhibit high hardness, strength, and light weight, SiC ceramic is an ideal material for building space-based optical information collection systems. It also has inherent properties such as low thermal distortion, toxicity, and potential cost relative to other conventional materials [1,2]. However, the processing of SiC into a practical surface topography presents a challenge resulting from its high hardness and brittleness [3,4].…”