Working Principle and Operation of Plastic Moulding Machine

Plastic moulding machine processing equipment is developed on the basis of rubber machinery and metal die-casting machines. Since the emergence of polymer injection moulding technology and simple moulding equipment in the 1870s, as an industry, it did not develop rapidly until the 1930s. Plastic moulding processing equipment is gradually commercialized, and IMM injection molding machine and extrusion moulding have become industrialized processing methods. Blow moulding is the third largest plastic moulding method after injection moulding and extrusion, and it is also the fastest growing plastic moulding method.

1. The working principle of plastic moulding machine

The working principle of the plastic injection moulding machine is similar to that of a syringe for injection. It uses the thrust of the screw (or plunger) to inject the plasticized plastic in the molten state (that is, the viscous state) into the closed mold cavity. The process of obtaining products after curing and shaping. Injection moulding is a cyclic process, each cycle mainly includes: quantitative feeding - melting and plasticizing - pressure injection - mold filling and cooling - mold opening and taking out. After the plastic parts are taken out, the mold is closed again for the next cycle. For more plastic auxiliary machinery, please contact us.

2. Operation of plastic moulding machine

(1) Clamping the mold: The mold plate is quickly approached to the fixed mold plate (including slow-fast-slow speed), and when it is confirmed that there is no foreign matter, the system is turned to high pressure, and the mold is locked (maintaining the pressure in the cylinder). 

(2) The injection table moves forward: the injection table advances to the designated position (the nozzle is close to the mold). 

(3) Plastic molding equipment: The screw can be set to inject the molten material at the front end of the barrel into the mold cavity at multiple speeds, pressures and strokes. 

(4) Cooling and pressure holding: According to the set various pressures and time periods, the pressure of the plastic moulding machine barrel is maintained, and the mold cavity is cooled and formed at the same time.

(5) Cooling and pre-moulding: the products in the mold cavity continue to cool, while the hydraulic motor drives the screw to rotate, pushing the plastic particles forward, and the screw retreats under the control of the set back pressure. When the screw retreats to a predetermined position, the screw stops rotating, the injection cylinder is loosened and retreated according to the setting, and it is expected to end. 

(6) The shooting table retreats: After the pre-moulding, the shooting table retreats to the designated position.

(7) Mold opening: The template retreats to its original position (including slow-fast-slow).

(8) Ejection: The thimble ejects the product. The basic requirements of a plastic moulding machine are plasticizing, injection and moulding. Plasticization is the premise to realize and ensure the quality of molded products, and in order to meet the requirements of moulding, injection must ensure sufficient pressure and speed. At the same time, due to the high injection pressure, a correspondingly high pressure is generated in the mold cavity (the average pressure in the mold cavity is generally between 20 and 45MPa), so there must be a sufficient clamping force. It can be seen that the injection device and the clamping device are the key components of the injection moulding machine.

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