On-line determination of the grain angle using ellipse analysis of the laser light scattering pattern image

Abstract

Under fixed cutting conditions, the surface finish roughness is correlated to the grain angle. However, the means of determining the grain angle automatically and accurately is still a challenge for on-line control of the router. It is therefore necessary to develop a new technology to determine the grain angle accurately and automatically. In this research, a laser light scattering pattern was used to accurately determine the grain angle. The light scattering pattern image was a quasi-ellipse caused by the grain direction and tracheid effect. A new modified Hough transform ellipse analysis technology was adopted to determine the ellipse parameters that could be used to determine the grain angle. The results indicated that the measured grain angle using the method proposed here was accurate and effective. The measured grain angle coincided with the real grain angle. There was an insignificant difference between the measured grain angle of Japanese beech (Fagus crenata blume) and that of sugi (Cryptomeria japonica D.Don) under two machining conditions that gave planed or sawn finishes. However, the accuracy of the measured grain angle of sugi was better than that of Japanese beech for the planed finish, the accuracy of the measured grain angle of Japanese beech was better than that of sugi for the sawn finish, and the accuracy of the measured grain angle for planed samples was better than that for sawn samples of both sugi and Japanese beech.