How does injection moulding work?

It’s one of the most popular and efficient manufacturing processes in the world and produces for a huge number of the products you use every day. Plastic injection moulding is capable of producing large volumes of high-quality, identical items in a short time. Products that are produced range from precision engineering components to regular household items.

Yet many of us have no idea how plastic injection moulding works, or what’s involved in producing products.

The variety of shapes, sizes, strength and types of thermoplastics that can be used in injection moulding mean that the process accounts for a significant proportion of plastic products produced today.

Cost-effective prototyping with 3D printing

The first step of in the injection moulding process is the development of a mould that will form the liquid plastic into the required shape. Thanks to advances in computer aided design (CAD) technology, much of the prototyping can be conducted digitally. However even now the success of injection moulding depends on the skill of an industrial designer or engineer, and a mould/tool maker to produce a perfect mould.

3D printing can also be used to create a prototype mould, or if the product is suitably simple, the finished mould can be printed. With current technology, there are disadvantages to 3D printing as the moulds are not as durable as those made of steel or aluminium. They can typically only last for hundreds of cycles instead of the millions their metallic counterparts can handle. Additionally, due to the layered nature of the 3D printing process, the mould will not have the smooth finish that metals produce. The choice of mould depends on the component volume and purpose.

Turning plastics into components

Once the mould has been created and thoroughly tested, it is ready to begin creating components.

The most common thermoplastics used in injection moulding are:

• Acrylonitrile-Butadiene-Styrene ABS
• Nylon PA
• Polycarbonate PC
• Polypropylene PP

The plastic component granules are fed into a heated barrel where they are melted into a liquid which is then guided through a nozzle of the injection moulding machine into the cavity of the mould which fills with liquid plastic, taking on its shape. This molten plastic cools rapidly and becomes solid after only a few seconds. The mould then opens and ejects the newly formed component and the process is repeated.

The speed of the cooling and efficiency of the process once a mould has been created allows large component producers such as Essentra Components to provide exceptional brand quality and reliable part quality due to the identical nature of each component.

See below for some of the plastic injection moulded products on offer from Essentra Components.