Packing pressure control for energy-saving servo injection molding based on Fuzzy-PID controller

To face the increasingly serious energy crisis, how to develop high-precision products with better energy-saving characteristics by injection molding machines is one of the main research directions in the industry of plastic molding. This paper presents a new energy-saving design of servo injection molding system with servo motor-driving fixed pump and servo solenoid valve. Such a structure can guarantee the manufacturing precision and lower the cost. In the study, a Fuzzy-PID controller for the packing pressure in the injection process was designed based on the mathematical model which was established and revised according to the new system. Additionally, numerical examples are presented by Matlab. Results showed that the new Fuzzy-PID controller is able to reduce the error of packing pressure tracking effectively. Furthermore, the new designed system is good-robust and more stable than the traditional PID controller.

I. Intrduction

Plastics are widely used in industry as one of the basic materials. Comparing with other materials, plastics have many advantages, i.e., lighter weight, easier processing, and better mechanical/chemical properties. Since 1976 plastics have surpassed steel, copper, and aluminum in combined volume and become the most widely used materials in the US. Injection molding is one of the most versatile and important manufacturing processes which are capable of mass-producing complicated plastics parts with excellent precision. In the modern plastics industry approximately 80% plastic merchandise are produced by the injection molding system especially in recent years during which more and more plastic products are in great demand due to the expansion of domestic and international markets for automobiles, electronic appliances, building materials, food and medicine industries.