Computer-Controlled Lapping System For Granite Surface Plates

Granite surface plates are traditionally finished by hand lapping, which is time consuming, strenuous, and costly. Surface quality and accuracies of such plates depend largely on the experience and skill level of the operator. in this study, a computer-controlled system is developed for ultraprecision lapping of granite surface plates. The system can easily achieve a high lapping efficiency and high flatness accuracy due to its capability of on-line measurement of flatness, optimization of the lapping process, and automation of the lapping operation. The system has been successfully applied to a number of granite surface plates, and the results show that a flatness error of less than 2 mum over a 1 x 2 m area is obtained. This paper also presents the principle of online measurement of flatness and experimental results based on the computer-controlled lapping system.