How the Process of Injection Molding Works?

How the Process of Injection Molding Works?


The process is quite short, usually between two seconds and two minutes, and it usually involves the following stages:


Before injecting the material in the mold, you need to secure the two halves using the clamping unit. The other half adheres to the injection molding equipment and the other slides.

This clamping unit is then forced the mold halves together and then uses enough force to close the mold as you inject the material. The amount of time needed to close and clamp the frame will depend on the machine. If you are using bigger devices, it will require more time.


The plastic or any material you want to use is then fed into the injection molding equipment and pushed towards the mold via the injection unit. This part of the process includes the melting by heat and pressure. The liquefied plastic is then injected in the mold fast and then increasing the pressure packs and holds the material.

The shot is a termed given to the amount of material being injected. It is not easy to calculate the exact injection time. But it can be estimated using the injection pressure, injection power, and the shot volume.


The liquefied plastic in the mold will start to cool down once it gets in contact with the mold surfaces. When the plastic starts to cool down, it will solidify and shaped into the needed part. But, during cooling, they might shrink. The packing of material during the injection stage lets the additional material to flow into the mold and reduce shrinkage. You cannot open the mold until it completed the cooling time, which is estimated from the different thermodynamic properties of the material as well as the part’s wall thickness.


This is the last stage of the process wherein the cooled part is ejected from the mold. If you open the mold, a mechanism is applied to loosen the piece on the mold. Force is used to carefully remove the part because, during cooling, the part shrinks and sticks to the frame. To facilitate ejection, you can spray a mold release agent on the mold surfaces before injecting. You can estimate the time of opening the mold and ejecting the part using the dry cycle time of the machine.

After completing the last cycle, some post-processes are needed. You need to trim the excess material that has occurred during cooling.

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