Plastic Injection Molding Process Explained

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Plastic parts are manufactured from the injection molding process, which is also one of the most common molding processes. This process needs a mold, raw plastic material, and an injection molding machine to make all sorts of complex plastics of different shapes and sizes. The process is a simple 4 step procedure that will take about two to three minutes to complete.

Stage 1 – Clamping

The first step is to combine both the molds and secure them so no liquid can leak when the plastic material is injected into them. This is done by a hydraulic-powered clamping machine that forces both halves together and attaches them to the injection molding machine. The time required during the clamping stage is usually dependent on the size and power of the machine.

Stage 2 – Injection

This is followed by raw plastic pellets put into the injection molding machine that melts then with heat and pressure. Once melted, the hot plastic liquid is injected into the mold quickly and with high pressure to fill up all the spaces and not leave any air bubbles. The injection time is also dependent on the pressure of the machine and the thickness of the plastic liquid.

Stage 3 – Cooling

One of the reasons to inject quickly was that the molten plastic starts to cool down as it touches the mold. You need to let the mold rest for a bit to cool down as it cannot be ejected right away. There also are instances when the molten liquid would shrink during the cooling stage. So, when there’s any visible shrinkage, try and inject some more molten plastic liquid to fill the gaps up. The cooling of the liquid depends on the plastic you’re using and its thermodynamic properties.

Stage 4 – Ejection

A blue plastic cap

After the liquid has cooled, you can eject the solid plastic part from the mold using the ejection system present at the back of your mold. Sometimes you might also need to apply a lot of force has the solid plastic could have stuck to the mold. You can also use a release agent to remove the plastic part easily. This was the simple process of plastic injection molding.

You can also get your custom plastic parts by contacting us. We are a company that specializes in plastic injection molding along with 3D printing and rapid prototyping services. Take a look at all the unique designs we have made for our past clients and request a free estimate now.

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