By Jason Vander Griendt

June 25, 2016 at 8:14 am

Moulds used in the plastic injection molding process

Injection molding is a production process used for manufacturing plastic parts and commodities. It works via thermosetting and thermoplastic elements. Plastic injection is used to produce a broad range of plastic products, ranging from plastic PCB electrical enclosures to chairs, toys, and even lego!

Plastic Injection Molding Process

Plastic injection molding is a very quick method of producing intricate shapes that can be formed from both thermosetting and thermoplastic polymers. Injection molding requires the polymer to be heated until it is molten. It is then forced under pressure into a mold. How can you tell if injection molding has been used to produce a plastic item you have in your possession? Injection moulded parts can sometimes be distinguished by a “sprue point”, which is a small bulge on the object formed due to a small blemish in the mold where the plastic got spread into a cavity. Also, if the sides of the cast don’t match perfectly together, a thin line may also be visible on the body of the object.

Along with plastic extrusion, injection molding is one of the principal methods for manufacturing plastic products. Once molds are created for the process, a vast number of pieces can be created very quickly. This technique lends itself well to companies who need to produce a high volume of products including the likes of high-precision engineering parts and disposable customer items due to the economies of scale.

Most thermoplastics are suitable to be used for injection molding purposes. Injection moulding also requires a variety of other ingredients for the process to be successful. Some of the most used elements in the process are Polypropylene PP, Acrylonitrile-Butadiene-Styrene ABS, Polycarbonate PC and Nylon PA.

Injection moulding accounts for a notable percentage of all products manufactured from plastic. In fact, the products that are produced through the injection manufacturing process range from tiny parts used in other products to large objects like car bumpers and wheelie bins, you name it. Injection molded parts are used in almost almost all manufacturing sectors. The flexibility of producing objects of different shape and sizes has helped pushed the boundaries of what’s possible to design in plastics. Furthermore, it has helped to replace many traditional components previously made from materials such as steel or other heavy metals because of the ease of production of plastic parts, low cost and light weight.

Learn more: Troubleshooting the plastic injection molding process

How Does Injection Molding Machine Work?

Injection molding machines work by adding plastic granules by means of a container into a warmed barrel. These granules are then liquified utilizing radiator groups and the frictional activity of an accompanying screw barrel. The plastic is then infused through a spout into a mold cast where it cools and solidifies to the shape setup of the mold pit. The mold is mounted on an adjustable plate. When the part has hardened, the plate opens, and the part is shot out utilizing ejector pins.

After an item is developed in a CAD design program, a moldmaker forms a mold from steel or aluminum which is accuracy-machined to be exactly the same as the design. We recommend prototyping your product via 3d printing before getting a mold created in order to see in advance if there are any design flaws that need rectifying before mass production. Creating the molds is often the most costly part of the process, and as such we have designed a system to help our clients crowdfund their product creation – it’s much easier than getting external funding and leaves you in control of the process.

Parts to be created via the injection molding process must be precisely designed for this purpose. The material utilized for the part, the shape and components of the end product, the material of the mold, and the properties of the manufacturing machines available should all be considered. For further advice or a quote on manufacturing your next plastic product don’t hesitate to get in touch!


Related article:

How much does it cost to do injection molding?

Where to find injection molding machines for sale

Jason Vander Griendt

Jason Vander Griendt is a Mechanical Engineering Technician with years of experience working at major companies such as SNC Lavalin Inc, Hatch Ltd. Siemens and Gerdau Ameristeel. He is the CEO of JCAD – Inc., a company he started in 2006 after seeing a gap in the market for businesses who could assist clients through the entire product design and manufacturing process.

Jason has been featured in Forbes, has had his businesses analyzed and discussed in multiple start-up books, was a previous winner of the Notable8 Digital Innovator of the year award, and is a regular guest on business panels and podcasts. Email Jason at or follow him on LinkedIn.

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