Information about Plastic injection Moulding

The manufacturing process that produces packaging, plastic tote boxes, bottle caps, wire spools, automotive dashboards, and other plastic products is called injection moulding. In fact, it is the most common part manufacturing method. Manufacturers can perform injection moulding using a variety of materials including common thermosetting and thermoplastic polymers, metals, confections, elastomers, and glasses. Usually, they feed the raw materials into a heated barrel, mix it, and force it into a mould cavity where it can harden and cool to the shape of the cavity.

Learn more about plastic tote boxes

An industrial designer or engineer designs the product while a toolmaker or mould maker fabricates the mould from metal, usually aluminium or steel. With the help of modern technology, manufacturers can now produce a wide variety of parts, from the tiniest components to entire motor vehicle body panels. To facilitate the moulding process, manufacturers must take into account the following:

1: The materials used for each part or component

2: The desired features and shape of each part

3: The materials used for the mould

4: The properties of the moulding machine


Typically, the moulding process is very fast in fact, manufacturers can produce complex designs from thermosetting and thermostatic polymers within a very short time. Due to the flexibility in size and shape, this manufacturing process accounts for a huge proportion of all plastic parts and products used today. As the most preferred plastic parts manufacturing process, injection moulding is the favoured process for producing components such as

1: Containers for housing all sort of different products and recycling boxes. As well as products like DVD cases.

2: Automotive parts like car bumpers or interior compotents.

3: Electronic housing and battery casings. Housing for electronic compotents like Telephone handsets, TV cabinets and Power tool housing.

4: Bottle caps

5: Combs

6: Syringes

And many other plastic products, which are used everyday both in the home and at work.

The Moulding Cycle

The sequence of events during the moulding process is called the injection moulding cycle. It begins when the mould closes, followed by the injection of the material into the metal cavity. Once the cavity is full, a machine applies pressure to compensate for material shrinkage. Once the plastic component is sufficiently cool and firm, the mould opens and the machine ejects the part. Some of the common moulding variations include:

Sandwich or co--injection moulding

Fusible core moulding

In-mold lamination

Gas assisted moulding and Water assisted injection

Injection-compression moulding

Microinjection moulding and Microcellular moulding.

Outsert and insert moulding

Power injection

Lamellar moulding

Reaction injection

Low pressure injection

Structural foam injection

Rubber injection

Thin--wall moulding


The principal enemy of injection-molded components is stress. When one melts a plastic resin containing long strains of molecules, the force and heat of the extruder forces the molecular bonds to break temporarily. The pressure forces the resin into the mould cavity in every crack and crevice. As the molecules press through each feature of the mould, they turn, distort and bend to form the desired shape. This intense pressure may exert tremendous stress, which in turn locks into the component. Components or parts with too much stress can easily crack, warp, fail, or cause other problems.

Like any other manufacturing process, injection moulding can create defective parts. Therefore, it is important to troubleshoot and examine each part or component for defects and address any defects appropriately.