Jumat, 16 Mei 2014

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.

Chocolates, futuristic plastic chairs, dustpans and even shoes may be made by injecting some material into a mold. Molds are designed by designers and engineers and then handed over to a moldmaker to transform the design into a metal mold, which is finally precision-machined. The process, which has been around since the middle of the 19th century, is extremely versatile and gives rise to an infinite number of widgets and parts for sewing machines, automobiles and rocket ships.

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.

The starting material, whether polymer, metal or thermoplastic, is pulverized into a fine dust and, in the case of metal, mixed with what is called a binder to produce what is called feedstock. The feedstock is fed through a hopper and passed through a heater while being fed through a tube by a linear actuator. The material is melted into a liquid and then fed into a mold and then cooled.

The range of objects that can be manufactured using this technology is amazing. There are a lot of parts that one would not intuitively think were made this way. Even the parts for the machines that do the injecting and molding have injected and molded parts inside them.

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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