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What Issues Need Attention In The Pre-injection Phase?
Original: | Author: Jasmine of DGMF | Publish Time: 2014-09-01 | 6380 Views | Share:
What issues need attention in the pre-injection phase?


First, screw speed

1. The melting of plastic is generally due to the heat generated by the rotation of the screw, so the speed of the screw is too fast, it has the following effects:

Thermal decomposition of plastics;

Shortening of glass fiber (fiber-reinforced plastic);

Worn screws or heating barrels.

2. The setting of the rotation speed can be measured by the size of its circumferential speed (circumferen-tial screw speed): the circumferential speed n (speed) * d (diameter) * π (circumference rate)

Generally, for low-viscosity plastics with good thermal stability, the peripheral speed of the screw rod rotation can be set to about 1m / s, but for plastics with poor thermal stability, it should be as low as about 0.1.

3. In practical applications, we can reduce the screw speed as much as possible, so that the rotary feeding can be completed before the mold is opened.

 

Back pressure

1. When the screw rotates and feeds, the pressure accumulated by the melt glue advanced to the front end of the screw is called back pressure. During injection molding, it can be adjusted by adjusting the ejection pressure of the injection hydraulic cylinder. :