Plastic Injection Molding Basics

The use of plastic plays a major role in our day-to-day lives. Many plastic products are created through a process called plastic injection molding, which involves the use of an injection molding machine, raw plastic and a mold. From toothbrushes to automotive parts, plastic molding services produce everyday items that most people don't often think about. Below, learn about how plastic injection molding works and its everyday applications.

Injection Molding Process:
Plastic injection molding is a very short process that usually lasts between two seconds and two minutes, depending on the product. There are four stages of the process: clamping, injection, cooling and ejection.

In the clamping stage, the two halves of the mold are held together in the injection molding machine using a clamping unit and enough force to keep the mold secure. The injection stage occurs once the mold has been clamped in place, during which the raw plastic material is injected into the mold. The material typically starts out as pellets or a fine powder, is fed into the machine and melted by heat and pressure, then injected into the mold. Once the plastic is in the mold, it begins the cooling stage, solidifying and taking the shape of the desired mold. The ejection stage is the last part of the process, which involves opening the mold once enough time has passed for the plastic to cool.

When the four stages of the injection molding process are complete, the part is separated from the runner (feed channel), depending on the type of material, often put through a plastic grinder to be recycled into new pellets.

Possible Defects:
Although the process and stages of custom injection molding can be as quick as just a few seconds, precision and accuracy are critical when it comes to such factors as time, pressure, temperature, moisture and force. Possible defects that can occur in a molded plastic product include flash, which occurs when the clamp force is too low and molten material seeps out of the molding area, warping and unfilled sections.

Everyday Applications:
The materials used for plastic injection molding vary greatly in strength, weight, texture, flexibility, cost, thermal stability, heat resistance and many other factors. The time it takes to create a plastic molding, as well as the pressure and temperatures, depends on the type of material used for that product. Examples of common, everyday products that require plastic injection molding include: automotive components, food packaging, toys, eyeglass frames and lenses, kitchenware, zip ties, chair seats, food containers, bottles, pens, cosmetic packaging, syringes, gutters and much more. The most common applications are plastic housings, which are thin-walled enclosures used for such products as power tools, consumer electronics, among many others.