Essentially, it’s the process of heating plastic resin pellets and forcing the melted plastic into a mold cavity. Once the plastic has cooled, the part is released and then the process begins all over again.
There are three main parts in an injection molded plastics machine – the mold, the clamping unit and the injection unit. It is the clamping unit that holds the mold together during the plastic injection and the cooling process.
Plastic material in the form of small pellets are fed into the injection unit and then heated to a molten stage (transforming from a solid state to a liquid). After reaching the right temperature, the hot molten plastic is forced into the mold. Either a screw or a ram controls the pressure and speed of this phase of the injection molded plastics process. The short phase between the injection and the cooling of the object into its solid form is referred to as the “dwelling” phase. This step ensures that the mold cavities are completely filled before cooling begins.
This process allows manufacturers to produce more complex and intricate shapes that would be too difficult or costly to machine. The injection molded plastics process also allows many parts to be created at the same time with the same mold. Other advantages include high production rates, low labor costs, high repeat tolerance, and very little need to do anything to finish the part after it is molded. The unused plastic pellets and runners can also be recycled for future molds so there is virtually no waste.