A Step-by-Step Guide
1. Clamping:
The process begins with the mold, which consists of two halves: the stationary platen and the moving platen. The clamping unit closes these two halves together, applying significant pressure to keep them tightly shut during the injection process. This clamping force is crucial to prevent the molten plastic from leaking out.
2. Injection:
Next, the injection unit comes into play. Plastic material, typically in the form of pellets, is fed into the barrel of the injection unit. Inside the barrel, a screw rotates, heating the plastic to a molten state. Once the plastic has reached the optimal temperature and consistency, the screw acts like a piston, injecting the molten plastic into the mold cavity at high pressure.
3. Holding:
After the mold cavity is filled, the holding phase begins. The injection pressure is maintained during this phase to pack the cavity completely and compensate for any shrinkage that occurs as the plastic cools. This ensures the part replicates the shape of the mold accurately.
4. Cooling:
While the holding pressure is maintained, the cooling process begins. Coolant, typically water, circulates through channels in the mold, allowing the plastic to solidify. The time it takes for the part to cool depends on factors like the type of plastic, the wall thickness of the part, and the mold temperature.
5. Ejection:
Once the part has cooled sufficiently, the mold opens. Ejector pins, located within the mold, push the solidified part out of the mold cavity. The ejector system is carefully designed to ensure the part is released cleanly without damage.
6. Repeat:
After the part is ejected, the mold closes again, and the cycle repeats. This continuous cycle allows for the efficient production of a large number of identical plastic parts.
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