Plastic is an incredibly versatile and relatively inexpensive substance. The term ‘plastic’ applied to any of 7 different basic types of compounds among which there are literally hundreds of different variations. The list of plastic products is almost unending. If a tool design can be created to form it from plastic, there is a good chance it can be mass-produced.
Several different methods are employed to manufacture plastic parts. The process of plastic injection molding is one of the most common. Fabrication companies that produce parts using this method typically receive basic feedstock in pelletized form. The manufacturing process can be divided into three basic steps.
Large quantities of plastic pellets are often positioned above the injection molding machine in a hopper that provides a gravity feed. When the machine is producing parts the bottom of the hopper supplies pellets to a horizontal screw-typed conveyor system. A turning auger moves a steady flow of feedstock toward the injector.
Heating units that surround the barrel of the conveyor chamber begin elevating the plastic temperature to the melting point. During this stage, the liquified plastic is also being pressurized in a chamber. The outlet of the chamber is much like a hypodermic syringe with a nozzle that feeds into the molding tool.
Tools for injection molding are often arrangements of two heavy metal halves that, when brought together, form the molding cavity. The pressures and temperatures used to move the molten plastic require heavy hydraulic machinery to position and hold the tool halves in place as a part is molded. The plunger injects the required volume of liquid plastic into the mold and the tool remains sealed to cool and re-solidify the plastic part. When the part is ready, the tool halves separate, and the part is ejected.
Strolling down almost any store aisle will demonstrate how prolific plastic has become. From tools and toys to containers and coat hangers, plastic is truly part of the fabric of modern life.