The process of injection moulding starts with plastic pellets that are made from a mixture of inorganic and organic polymers, along with additives to boost the melting process. These tiny pellets are mixed into a hopper. This first step commences the journey of making products from pellets, followed by the next step that is the preparation of plastic.
The pellets are introduced onto the threads of a huge rotating screw, where they are continuously heated to melting temperatures, approximately around 400 degrees Fahrenheit. Simultaneously, the pellets are kept rolling as the process also requires force and friction. The giant rotating screw is designed to offer both force and friction. The pellets inside the giant rotating screw moves along its circumference and smash into each other. A good point to remember is that the higher quality plastic comparatively requires a higher temperature to melt.
Now, as all the necessities are fulfilled, i.e. heat, force and friction, the pellet starts to melt and the subsequent process of filling begins. At the same time, the screw constantly directs the molten plastic alongside its threads towards a valve. Maintaining extremely high pressure, the valve emits the liquid plastic into a metal mould, prepared from the best quality metal having optimum heat resistant, until every cavity inside the mould is filled. After this step, a mould enters the next phase of product development .i.e. the Holding Phase. The filling and holding are the two most crucial phases in the plastic injection moulding process, because the quality of the product totally depends upon the execution of these processes.
Once the molten plastic is ejected into the mould, the pressure on the mould as well as liquid plastic is preserved until the liquid plastic condenses to a desired solid state. This step may take just a few seconds, or minutes because the metal mould expels the heat from the liquid plastic, and in sequence is cooled by cooling agents in its outer surroundings. By the time the part has cooled down, the screw regains its initial position, gathering the next batch of pellets from the hopper. After being cooled down, the newly manufactured product is then casted-out through so called ejector pins from the mould and is processed for secondary processes like decoration, sub assembly, or delivery.