The Injection Molding Manufacturing Process

By Henry A. Parker


Think about injection molding and your mind immediately goes to plastic army men and other tiny toys and accessories that toddlers love to cram in their ears, nose, throat, etc. The process, injecting fluid material into a mold, applies to all sorts of other materials, too. Metals, glass, confections, polymers and elastomers can all be molded and then custom machined to produce everything from a jelly snakes to car doors.

Mobile phone covers, toy bricks, plastic forks, styrofoam cups, metal scissors and the fans that go inside computers to keep them from overheating while you are playing Candy Crusher, all of these items are fashioned using IM technology. The process, which was first used in the mid-19th century, is amazingly versatile and yields gizmos and widgets for everything from kitchen gadgets to the International Space Station.

One use for the IM process to which we can all relate is in the production of toy soldiers and collectible military miniatures. There are miniature troops to match practically every war in history. The price of the piece often corresponds to the seniority of the figure. The Duke of Wellington, for example, will cost more than his minions, although Richard Sharp would probably fetch a pretty penny.

Electric toy train enthusiasts are avid consumers of IM technology. Where do you think the little toy trees and little toy engineers and signalmen come from? The amount of authenticity and detail that goes into making these items is breath-taking. Built to last, these pieces are often manufactured from molded metal so they are sufficiently robust to be passed down from generation to generation.

To manufacture parts from metal, the starting material is first ground into a fine dust and then combined with a binder to form a feedstock that is fed through a hopper into a heated tube. The mixture is pushed through the tube using a linear actuator, something that looks like a screw. The material then goes into a mold, is cooled and then ejected.

The vast range of objects that can be produced using IM is astounding. The injecting and molding machines are themselves built from parts that are the product of IM technology.

The industry relies on a vast number of other industries for its survival. Software, polymers, additives and the molding machines themselves are all related industries. It is going to be fascinating to see how this industry stands up to new developments in 3D printing technology.




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