3-D Laser Processing using In-process Measurement and Control of the Processing Depth

Abstract

This paper proposes a 3-D laser processing system with, in-process monitoring and feedback control of the processing depth, which enables us to process an intended shape with accuracy. While in the conventional methods the processing depth is estimated by the predetermined relation to the processing conditions and determined on post-processed measurement, in the proposed system the processing depth is obtained in real time from the propagation time of AE (acoustic emission) signal caused by laser processing. The system consisted of a Q-switched Nd:YAG laser and an AE sensor attached on the back of the specimen is applied to process a shape with its depth changed stepwise by 150μm to lmm for silicon nitride ceramic. The formerly developed laser processing method using rotating beam, named "laser-endmill", and AE signal detection synchronized with the beam rotation are employed. As a result, local overprocessing is prevented and accuracy of form less than an error of 50μm compared to the designed one is achieved.