Development of an in-Process Sensor for Surface Roughness by Laser Beam

Summary

The basic development of a new type of in-process sensor for surface roughness measurement is described. It is based on the principle that the reflected laser beam which is obtained from one condensed and directed on to a machined surface moves in accordance with the small displacement given by surface roughness. For detection of the movement a photo diode array is utilised. Roughness in circumferential direction having 2 µm amplitude and 50 µm wavelength could be measured at the speed of 500 mm/s. The optical and electronic composition of the apparatus is described and some examples of the measurement are shown. These suggest that the system would make it possible not only to measure the surface roughness but also to identify the effect of structural vibration on the machined accuracy, to detect the existence of a micro-scratch on the surface, to trace the wave-form of the chatter marks which remain on the surface, and so on, by in-process measurement.