Plastic Injection Molding Machine And Expert System

Since 1930's, plastic injection molding machine (PIMM) technology and equipment has developed, and become a kind of very important, representative plastic processing method and equipment. Plastic parts are used widely. PIM technology and equipment have been existing for forty years, which is proven that PIMM electrohydraulic technology level is the key to improve PIMM quality and satisfy the demand for high quality plastic parts. On the other hand, the quality of plastic parts is relative deeply to raw material, the choice of molding equipment, the setting of plastic technics parameters, matrix and environment condition in the manufacture of plastic parts by plastic injection machine molding equipment. Skillful special knowledge and practical experience are required to assure the quality and to avoid to cause defect, however, those are difficult for general technology personnel and workers to master and apply into the practical manufacture in short term. Expert system (ES) classifies all kinds of experience and knowledge into repository that is very easy to extend, makes use of reasonable ratiocination mechanism, and applies them into production soon. On the basis of preconditionshown above, electrohydraulic technology and the application of ES in PIM manufacture in this paper. Relative design programs are suggested.In chap 1, the author briefly reviews development of PIMM. The author believe that increasing demands for plastic parts and adaptable processing equipment satisfying with the demand of new material are the motive force of PIMM, and world energy shortage, the tendency of steel replaced by plastics, press processing replaced by injection processing are the historical source to promote development of PIMM, spreading microcomputer and the development of electrohydraulic proportion technology and the application of expert system are the key to improve PIMM.In chap 2, the author discusses system configuration and processing character of modern PIMM, theoretically suggests relevant control strategy of each loop to satsfy with the demand of molded parts quality. As the master computer, industrial control computer is adopted to processing data and really process controlling, and is able to communicate with another master computer, to realize global control.In chap 3, on the basis of objective of PIM, the author analyzes main factors effecting molded parts, including plastic material character, mold quality, equipment and process control. The relevant measure taken theoretically is given.In chap 4, the 2D digital electrohydraulic flow-pressure control servovalve is applied to PIMM. PIMM hydraulic pressure system requires speed control in the motion of plastic cylinder and press control during keeping the press. Usually, the speed control of hydraulic press executing elements adopts flux valves with press compensation (the overflow valve is often used to save energy), and the pressure control is achieved by overflow valves. In fact, these control functions are achieved individually by the overflow valve and the press valve, so the system structure is complicated and expensive, the 2D digital electrohydraulic flow-pressure control servo valve can take on the control of flux and press, and thus the integral system has easy structure and is easy to maintain, and the ratio of capability and price is high.In chap 5, the idea of expert system (ES) applied in the field of PIMM is proposed.lt is composed of three sub-systems of molding process control. The construction and reasoning mechanism are given. By applying expert knowledge, it is important and helpful to reduce reject rate and time of testing mold.