7 steps in plastic injection molding
1. Heating, pre-plasticizing
The screw drives the material from the hopper forward and compacts under the drive of the transmission system. Under the mixing of the outer heater, the screw and the barrel, the material is gradually melted, at the head of the barrel. A certain amount of molten plastic has accumulated, and the screw slowly recedes under the pressure of the melt. The distance of the retreat is adjusted depending on the amount required for one injection of the metering device, and when the predetermined amount of injection is reached, the screw stops rotating and retreating.
2. Clamping and locking
The clamping mechanism pushes the template and the mold part of the mold mounted on the movable template and the mold part of the movable template to be closed and locked, so as to ensure sufficient clamping force to lock the mold during molding.
3. The injection device is moved forward
When the clamping is completed, the entire injection seat is pushed and moved forward so that the nozzle of the injection machine completely conforms to the main gate of the mold.
4. Injection, pressure retention
After the mold clamping and the nozzle are completely fitted to the mold, the injection hydraulic cylinder enters the high pressure oil, pushing the screw forward relative to the cylinder, and the melt accumulated in the head of the cylinder is injected into the cavity of the mold with sufficient pressure due to the temperature decrease. To shrink the volume of the plastic, in order to ensure the compactness, dimensional accuracy and mechanical properties of the plastic part, it is necessary to maintain a certain pressure on the melt in the mold cavity to supplement the material.
5. Pressure relief
When the melt at the mold gate freezes, the pressure can be relieved.
6. Injection device back
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 injection molding, the action of the injection seat to withdraw the mold main gate has been canceled, and this action is performed for a material with a relatively serious flow pattern such as PA).
7. Open the mold, top out the plastic parts
After the plastic parts in the mold cavity are cooled and shaped, the clamping mechanism opens the mold and pushes out the plastic parts in the mold.