Automatic Recognition and Construction of Draft Angle for Injection Mold Design

In the injection molding process, plastic products are difficult to demold due to friction force between the cavity and products, thus, finished products might be deformed or damaged. Therefore, designers should add a draft angle to the geometric surface of products, which is parallel to the unloading direction, in order to help the products eject smoothly from the cavity. This study uses CAD software as the main architecture to develop the function of automatic draft angle recognition and construction. The study is divided into three stages. First, the geometric features of products are identified in the CAD model by induced algorithm, then the quilts to be added in the draft design are determined and classified. Finally, draft angles are created in different ways according to different surfaces. An algorithm suitable for automatic draft recognition and construction, as well as the constraints of automatic creation of draft angle, is proposed. The feature recognition algorithm of this study can automatically inspect 90% of the surfaces to be drafted, and the automatic creation of draft features can economize 80% of required mouse clicks, thus, effectively increasing draft angle design efficiency, and preventing errors in mold design and manufacturing.