What Is Plastic Injection Molding?

Plastic Injection Molding is a technique used to shape plastic in the form of the object you’re aiming to produce. During the injection molding process, thermoplastic polymers are injected into a mold cavity. To do this, pellets of a material are heated so they can be injected into the cavity in a liquid state. This hot liquid is then left to cool in the mold so the part can properly set. Once one part is ejected from the mold, another cycle can promptly begin.

Although injection molding can also be used for metals and glass, it’s a particularly popular production process for manufacturing Plastic Parts.

The steps in an injection molding process cycle include clamping, injection, cooling and ejection.

During clamping, the injection mold is prepared for a cycle by tightly clamping the two halves that form the mold cavity into place. This ensures that the molded part will have a smooth appearance and ideally the molded part should have almost no line where the different halves came together, as this shows that the mold might not be clamping tightly enough.

Once the mold halves are clamped together, the mold is ready to form a part. Before the polymer is injected into the mold, the pellets are heated to form a liquid. The liquid polymer is then injected into the mold through a nozzle. This is the injection stage of molding process, which is the second stage in a four stage cycle.

Next, the part is left to cool in the mold for a predetermined amount of time. The cooling stage can take anywhere from a few seconds to a few minutes depending on the polymer being used to produce a part. While some polymers need hardly any time to cool at all, others can take a few minutes. It all depends on the part being produced.

Once a part has cooled, the injection mold is opened and the part is ejected from the mold. The mold will clamp again and prepare for its next cycle.

Because manufacturers know how long the cycle on their molds are, they can accurately predict the amount of parts a mold will produce every hour. This helps manufacturers know exactly how many parts they’ll be able to produce every day, week and month with a fully functional mold.