Authors:
Chwan-Huei Tsai
Jian-Shiun Shiu
Department of Mechatronic Engineering, Huafan University, 1, Huafan Road, Shih-ting Hsiang, Taipei Hsien 223, Taiwan

This study proposes a new laser cutting method that uses the unstable fracture technique. In this method, a diamond blade is used to scribe a groove along the desired cutting path in an alumina substrate. A defocused CO₂ laser is applied to the substrate surface. As the laser moves a short distance, a short crack is generated through the edge of the substrate. When the laser direction is reversed, a great thermal stress is induced at the crack tip, causing the substrate to break along the scribed line. The acoustic emission signals produced during the fracture process were obtained to analyze the crack growth phenomenon. SEM photographs of the breaking surface were obtained to analyze the cutting quality. The relationship between the laser scanning speed and groove depth is discussed based on findings from the experimental results. The stress analyses via ANSYS were performed to characterize these complicated phenomena. It was found that the laser-cutting surface was free of micro-cracks and the surface quality was much better than that from mechanical breaking.