Plastic Injection Molding Components

Plastic injection molding is a process that affects our day-to-day lives in a great way. From zip ties to automotive dashboards, gutters to electrical components, injection molding produces plastic parts that many people don't even think about. While the process is quick, it involves precision and accuracy regarding the amount of pressure, the temperatures, force, friction and many other factors.

There are four stages of the injection molding process: clamping, injection, cooling and ejection. The required equipment includes an injection molding machine, a mold and raw plastic material. Below, learn about the different components that come into play throughout the injection molding process.

Clamping Unit:
Before the plastic is injected into the mold, the mold must be held in place securely. The two halves of the mold are securely fastened to the clamping unit of the injection molding machine. The front and rear halves of the mold, called the mold cavity and mold core respectively, are pushed together with enough force to keep the mold closed throughout the injection and cooling process. Depending on the machine, the plastic material and the product, the time required to clamp the mold varies. Once the cooling stage is complete, the mold can finally be opened by the clamping motor or hydraulics.

Injection Unit:
The raw plastic material that is injected into the mold typically begins the process in the form of pellets or a fine powder. The material is then melted and injected through the injection unit. The raw plastic is poured into the injection unit through the hopper, which is a large container with an open bottom that feeds into the barrel. The plastic is heated and melted as it moves toward the mold, then quickly injected into the mold.

Molding:
The mold base keeps the mold in place with support plates. Once the material has heated and melted in the injection unit, it flows through the nozzle and into the sprue bushing, which channels the material into the mold. Other channels include runners that deliver the material from the sprue to the mold cavities. Each runner has a gate, which directs the flow of molten plastic into the cavity. After the cooling stage, the ejector bar in the mold base works to push the solidified plastic part out of the mold cavity.

Materials:
The raw plastic materials used in the injection molding process vary in strength, texture, cost, heat resistance, thermal stability and other factors. Certain types of material work better for different products. Acrylic, for example, is used for knobs, lenses signs and shelves. Cellulose acetate is used for eyeglass frames. Polypropylene is often used for automotive bumpers and covers, bottles, and crates. Other applications for plastic injection molding services include kitchenware, chair seats, fuel system components, cosmetic packaging, pens, food containers and much more.