Anisotropy of surface roughness in diamond turning of brittle single crystals

Abstract

This paper deals with an investigation of the effect of crystallographic orientation and process parameters on the surface roughness of brittle silicon single crystals in ultraprecision diamond turning. The process parameters involve the depth of cut, feed rate, and spindle speed. Experimental results indicate that anisotropy in surface finish occurs when the cutting direction relative to the crystal orientation varies. There exists a periodic variation of surface roughness per workpiece revolution, which is closely related to the crystallographic orientation of the crystals being cut. Such an anisotropy of surface roughness can be minimized with an appropriate selection of the feed rate, spindle speed, and depth of cut. The findings provide a means for the optimization of the surface quality in diamond turning of brittle silicon single crystals.

Keywords:

• Anisotropy
• Arithmetic roughness
• Process parameters
• Brittle regime
• Brittle–ductile transition
• Chip formation
• Critical depth of cut
• Crystallographic orientation
• Degree of roughness anisotropy
• Ductile regime
• Optimization
• Periodicity
• Surface roughness
• Variation
• Ultraprecision diamond turning

Acknowledgments

The authors would like to express their sincere thanks to the Ultra-precision Machining Centre of The Hong Kong Polytechnic University for the use of their equipment. They would also like to express gratitude to Mr. T. W. Chung and Mr. K. L. Man for their technical support of the research work.