Injection Molding Basics

- Nov 13, 2017-

         Most solid plastic materials are produced by a process called injection molding. During the process of plastic injection molding, plastic resin pellets are heated until they melt. The melted liquid plastic is introduced, under pressure (injected), into a mold. The mold may be made up of any metal such as steel or aluminum. The molten form is then allowed to cool down and set into a solid form. The plastic material thus formed is then retrieved out of the mold.

         The actual process of plastic molding is just an expansion of this basic process. The plastic goes into a barrel or chamber by gravity or is force-fed. As it moves down, the increasing temperature melts the plastic. Then, the molten plastic is forcibly injected into the mold under the barrel with an appropriate shape. As the plastic cools, it solidifies. The plastic molded like this has a reverse shape of that of the mold. A variety of shapes can be produced by the process. The process of plastic molding is cheap due to the simplicity involved, and the quality of the plastic material is modifiable by changing the factors involved in the custom injection molding basics process:

– The pressure of injection can be varied to change the hardness of the final product.

– The thickness of the mold  affects the quality of the part produced.

– The temperature for melting and cooling determine the quality of the plastic formed.


         The major advantage of injection molding is that it is very cost effective and fast. Unlike a “cutting” manufacturing process, injection molding reduces the possibility of undesired sharp edges. Also, this process produces smooth and finished products that require no further finishing.