How to the Barrel Temperature of an Injection Molding Machine

2021-11-08

How does the injection molding machine accurately and effectively control the barrel temperature? The temperature control of the barrel of the injection molding machine uses a microcomputer control loop to select a suitable control algorithm to complete the control of the heating jackets outside the barrel of the injection molding machine. To ensure that the working temperature of each section in the barrel can be maintained within the set range according to the process requirements, precise temperature control is beneficial to improve product quality and the utilization rate of raw materials in precision injection molding, which is a very important indicator.

The temperature control object of the barrel of the injection molding machine is a nonlinear, uncertain, strongly coupled and large hysteresis system, which is one of the control difficulties. For this type of object, there is still a lack of a unified and effective control method, and the conventional PID control method cannot meet the requirements of high-precision injection.

Injection molding machines produce different products, with different pre-molding amounts, different ambient temperatures, and different production cycles, and their barrel temperature object model parameters are different. There is a strong coupling phenomenon between the temperature control of each section of the barrel, and it is necessary to achieve complete decoupling control is very difficult. In addition, the object is still a large hysteresis system, and conventional control methods will inevitably have large overshoots and oscillations. Therefore, it is necessary to study adaptive temperature control strategies to achieve high-precision temperature control.

In the plastic injection molding machine process, temperature control mainly includes the temperature control of the injection molding machine barrel, nozzle and mold. The injection molding machine barrel temperature is the heating temperature of the barrel surface. Because the injection molding machine barrel wall is relatively thick, the selection of the thermocouple detection point is very critical, and the temperature curves at different detection points have large differences. Therefore, two-point parallel detection, that is, setting thermocouples on the surface and the depth of the injection molding machine barrel at the same time, will obtain a relatively stable temperature curve, which is conducive to the accuracy of temperature control.

The injection molding machine nozzle temperature directly affects the shear flow when the melt passes through, and has a great impact on the quality of the product. Therefore, the control accuracy of the injection molding machine nozzle temperature is required to be higher. Mold temperature refers to the surface temperature of the injection molding machine mold cavity in contact with the product, which will significantly affect the injection molding machine mold filling, cooling and pressure holding process.

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