20 April 2018 Noncontact on-machine measurement system based on capacitive displacement sensors for single-point diamond turning
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Abstract
On-machine measurements can improve the form accuracy of optical surfaces in single-point diamond turning applications; however, commercially available linear variable differential transformer sensors are inaccurate and can potentially scratch the surface. We present an on-machine measurement system based on capacitive displacement sensors for high-precision optical surfaces. In the proposed system, a position-trigger method of measurement was developed to ensure strict correspondence between the measurement points and the measurement data with no intervening time-delay. In addition, a double-sensor measurement was proposed to reduce the electric signal noise during spindle rotation. Using the proposed system, the repeatability of 80-nm peak-to-valley (PV) and 8-nm root-mean-square (RMS) was achieved through analyzing four successive measurement results. The accuracy of 109-nm PV and 14-nm RMS was obtained by comparing with the interferometer measurement result. An aluminum spherical mirror with a diameter of 300 mm was fabricated, and the resulting measured form error after one compensation cut was decreased to 254 nm in PV and 52 nm in RMS. These results confirm that the measurements of the surface form errors were successfully used to modify the cutting tool path during the compensation cut, thereby ensuring that the diamond turning process was more deterministic. In addition, the results show that the noise level was significantly reduced with the reference sensor even under a high rotational speed.
© 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)
Xingchang Li, Xingchang Li, Zhiyu Zhang, Zhiyu Zhang, Haifei Hu, Haifei Hu, Yingjie Li, Yingjie Li, Ling Xiong, Ling Xiong, Xuejun Zhang, Xuejun Zhang, Jiwang Yan, Jiwang Yan, } "Noncontact on-machine measurement system based on capacitive displacement sensors for single-point diamond turning," Optical Engineering 57(4), 044105 (20 April 2018). https://doi.org/10.1117/1.OE.57.4.044105 . Submission: Received: 8 November 2017; Accepted: 3 April 2018
Received: 8 November 2017; Accepted: 3 April 2018; Published: 20 April 2018
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