Grinding Optimization Model for Nanometric Surface Roughness for Aspheric Astronomical Optical Surfaces

• Main Authors: Jeong-Yeol Han, Sug-Whan Kim, Geon-Hee Kim, In-Woo Han, Sun-Choel Yang
• Format: Article
• Language: English
• Published: Korean Space Science Society (KSSS) 2005-03-01
• Series: Journal of Astronomy and Space Sciences
• Subjects: astronomical telescopes; aspheric mirrors; surface roughness; grinding optimization process
• Online Access: http://ocean.kisti.re.kr/downfile/volume/kosss/OJOOBS/2005/v22n1/OJOOBS_2005_v22n1_13.pdf

Bound abrasive grinding is used for the initial fabrication phase of the precision aspheric mirrors for both space and ground based astronomical telescopes. We developed a new grinding optimization process that determines the input grinding variables for the target surface roughness, checks the grinding error magnitude in resulting surface roughnesses, and minimizes the required machining time. Using the machining data collected from the previous grinding runs and subsequently fed into the multi-variable regression engine, the process has the evolving controllability that suggests the optimum set of grinding variables for each target surface roughness. The process model was then used for ten grinding experiments that resulted in the grinding accuracy of <ETC> =-0.906 ± 3.38(σ) nm (Ra) for the target surface roughnesses of Zerodur substrate ranging from 96.1 nm (Ra) to 65.0 nm (Ra). The results imply that the quantitative process optimization technique developed in this study minimizes the machining time and offers the nanometric surface roughness controllability superior to the traditional, qualitative, craftsman based grinding process for the astronomical optical surfaces.