Formation of plastic material has been generally performed by injection molding, compression molding and so on. These methods are effective for mass production, but need expensive molds. On the other hand, a laser beam makes it possible to deform a material by the thermal stress. Therefore, a flexible precision deformation is possible with YAG laser because of its easy handling and good condensation. This laser forming method without a mold can be applied to a trial production or a large variety of products in small lots. In this study, machining characteristics and deformation mechanism of plastic with YAG laser were made clear by the experimental analysis. Bending angle increases rapidly in cooling process after laser irradiation and takes the largest angle under a certain energy density. Higher feed rate leads to an unstable machining, so proper slow feed rate and low power condition are recommended in order to obtain the better machining result. It is also possible to deform a continual curve surface by giving the feed perpendicular to the scanning direction. Furthermore, in the case of plastics, bending direction can be controlled by selective coating of paint on the top or bottom surface of the specimen with one-side laser irradiation.
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