In this study, the effect of specimen thickness on machining characteristics and deformation mechanism of laser forming for plastic material with YAG laser were made clear by the experimental analysis. Each specimen with different thickness can be bent to 90 degrees under proper machining conditions. The optimum laser power, in which bending angle takes a maximum under the same feed condition, increases with an increase of specimen thickness. In the case of thick specimen, the deformation occurs without a delay between the beginning point and the end one of irradiation just after finishing of laser scan. On the other hand, thin specimen is deformed from the beginning point of irradiation during laser scan at a small number of laser scan, since the rigidity of thin specimen is lower compared to that of thick specimen. Consequently, the bending angle per one laser scan is small in the case of thin specimen. However, the bending angle per one laser scan becomes larger at a large number of laser scan. Because it is considered that the increase of rigidity of specimen leads to the stable deformation, since the hardness of irradiated area increases with an increase of laser irradiation.
