The invention relates to a manufacturing method of the master die cavity which is used to shoot up forming die. It can prevent the edge of the die cavity from over buffing. An auxiliary gripper is utilized to protect the master die cavity while buffing. The auxiliary gripper has a center hole, and its shape is corresponded to the edge of the die cavity. The manufacturing method includes the following steps that the corresponding fixed structure and location structure are forming at a die cavity rough blank and auxiliary gripper. The auxiliary gripper is located at the die cavity rough blank by the location structure. And the relative relation of the auxiliary gripper and the die cavity rough blank is kept in constant by the fixed structure. The composite unit formed by the auxiliary gripper and the die cavity rough blank is practiced electro discharge machining programming by an electrode. The required master die cavity is made in the concave center of the die cavity. The composite unit is practiced buffing programming. Then the fixed structure is loosened. The auxiliary gripper is moved away from the master die cavity, so that the intact and satisfactory master die cavity is gained to practice the subsequent programming to shoot up the forming die. |