Plastic injection molding is a process used in fabricating items from cell phone cases, water bottles, or even automotive parts. Almost all of the plastic items we use currently were made using the plastic injection molding process. Currently, companies have geared their manufacturing efforts to assist in making plastic parts for masks to help battle the COVID-19 outbreak. While they may be a current mainstay in manufacturing, they are nowhere near new and have been around for quite a while. 

A Little History of Injection Molding

The first injection molding machine was patented in 1872 by John Wesley Hyatt and his brother Isaiah. The machine looked different back then and was simplified, resembling a hypodermic needle that used a plunger to inject plastic through heated cylinder into a mold. The progress in the industry was slow at first making collar stays, button, and hair combs. In 1903 they used the first soluble form of cellulose acetate that was less flammable than cellulose nitrate which led to usage in powder form. 

How Does it Work?

An injection machine is made up of three primary components – the feed hopper, the screw and the heated barrel. Plastic granules for the part are fed into the heated barrel by a hopper. Plastic that is placed in the hopper is usually in powder or granular form although some resins, for instance silicone rubber, may be a liquid and might not entail heating. The material is then melted utilizing the frictional action of a reciprocating screw accompanied with heater bands. The molten plastic is then injected through the nozzle and into a mold cavity – it may seem easy, but injection molding is actually a very complex process. While in the mold cavity, the material cools and solidifies to the configuration of the cavity. When the part has hardened, the moveable platen that the mold is mounted opens and the part is ejected using ejector pins.

Buying an Injection Molder

Are you in the market for an injection molder? Buying one used could be a way to keep your output going for less money. HGR has used injection molders for sale like Engel, Cincinnati Milacron, Sumitomo, and more. Browse some our inventory here or see what’s on sale in our upcoming online sales event.