Research On Plasma Transferred Arc Surface Modification System And Key Technology For Complex Die&mould Surface

The surface properties of die directly affect the quality of product and service life of die&mould. It is estimated that 80% of die failure is surface damage. According to different structure and service condition, the mould is subject to different external loads and complex form of stress, all which apply on the surface. As a result, the mould surface is more prone to injury than internal part. Plasma Transferred Arc(PTA) has the characteristics of high energy conversion efficiency, low cost of facility and installation, low requirements for production environment and conveniently carrying, which has great advantages when used for metal surface strengthening and modification. However, existing plasma surface modification equipments mainly concentrate on the processing of plane parts or simple curved surfaces. It is lack of corresponding solutions for automatic processing of complex die&mould surface.To solve the problems discussed above, this paper designed a PTA surface modification system for complex die&mould surface. According to the characteristics of the PTA processing technology, the system uses a 6DOF(degree of freedom) robots as movement executive mechanism, together with self-developed control software, can drive plasma torch to perform three-dimensional offline trajectory and different surface treatment with different processing methodIn hardware system, an industrial personal computer is chosen as the control center and interacts with PTA device and robot through data acquisition card, electric control module and network communication.In order to realize the offline automatic processing, this project designed and developed an offline control system. The system mainly consists of the processing control module and the off-line trajectory processing module. In the processing control module, based on the processing technology of PTA modification, a type of control text format that includes movement parameters and processing parameters is designed. Through the keywords paraphrase by self-made command interpreter, real-time collaborative control of PTA equipment and robot can be made. Off-line trajectory processing module developed a path generating function, which can control and adjust trajectory path, robot pose and PTA processing parameter according to the CAD model.In order to ensure the smooth implementation of processing and prevent the occurrence of accidents, this article elaborately calculated the robot working space based on the principle of kinematics and analysed the robot joint limiting displacement together with singular points through simulation validation, which can reduce the occurrence of joint limiting displacement condition effectively. A flexible work piece calibration method is proposed, which can realize rapid calibration of work piece with different characteristics. Besides, through the transformation of Euler Angle coordinate, robot pose can be improved and occurrence of singular points can be avoided in advance.Entity mould surface strengthening experiment results showed that the system can do PTA strengthening to complex curved surface effectively. The processed mould was of good surface quality, and the surface performance was improved greatly. The experiment not only testified the feasibility of offline automated processing using PTA surface modification system, but also verified the operability of complex mould surface treatment.