7 steps for injection molding of twin screw extruder

Writer： admin Time：2020-02-24 14:23 Browse：℃

1. Heating and pre-plasticizing

Driven by the drive system, the screw conveys the material from the hopper forward and compacts. Under the mixing and shearing effects of the heater, screw and barrel outside the barrel, the material gradually melts. A certain amount of molten plastic has accumulated in the section, and under the pressure of the melt, the screw slowly retracts. The retreating distance is adjusted depending on the amount required for one injection of the metering device. When the predetermined injection amount is reached, the screw stops rotating and retracts.

2. Mold clamping and locking

The mold clamping mechanism pushes the mold plate and the movable mold portion of the mold mounted on the movable mold plate and the mold movable mold portion of the movable mold plate to close the mold and lock it, so as to ensure that sufficient clamping force can be provided to lock the mold during molding.

3. Advance the injection device

When the mold clamping is completed, the entire injection seat is pushed and moved forward, so that the injection nozzle of the injection machine and the main runner of the mold are completely fitted.

4. Injection and holding pressure

After the mold clamping and the nozzle completely fit the mold, the injection hydraulic cylinder enters the high-pressure oil and pushes the screw forward to the barrel. The melt accumulated in the head of the barrel is injected into the cavity of the mold with sufficient pressure. The plastic volume shrinks. In order to ensure the compactness, dimensional accuracy and mechanical properties of the plastic parts, it is necessary to maintain a certain pressure on the melt in the mold cavity to supplement the material.

5.Relieve pressure

When the melt at the mold gate freezes, the pressure can be released.

6. Return of injection device

Generally, after the pressure relief is completed, the screw can be rotated and retracted to complete the next feeding and pre-plasticizing process. (In the current general situation of injection molding, the action of the injection seat withdrawing from the main gate of the mold has been canceled. This action is performed when molding materials that are more salivated, such as PA).

7.Open mold and eject plastic parts

After the plastic parts in the mold cavity are cooled and shaped, the mold clamping mechanism is opened, and the plastic parts in the mold are pushed out.