Injection moulding

A look at the plastic injection moulding machine and its process

Since the patenting of the first injection moulding machine in 1872, the injection moulding process has come a long way.

We have long moved on from producing only small products such as buttons and hair combs, to now including every imaginable industry including medical, automotive, and aerospace.

What is an injection moulding machine?

A plastic injection moulding machine, also called an injection press, is a piece of production equipment that is used to produce plastic items via a moulding process.

The typical setup of a moulding machine consists of a hopper, an auger or screw conveyor with heating and temperature control elements, and the mould tool.

The mould tool can be further divided into the sprue, the runner, the gate and the cavity.

Let’s take a look at the uses of these parts and the moulding process.

Injection moulding

What is the injection moulding process?

Injection moulding process consists of six, easy to follow steps that result in your finished product:

• Clamping
• Injection
• Dwelling
• Cooling
• Opening
• Ejection

1.      Clamping

The mould has to be clamped shut to contain the pressure of the molten plastic as well as to seal any coolant channels that may pass through sections of the mould.

2.      Injection

The injection moulding process begins at the hopper. The granules or resin are fed into the hopper which directs them into the auger. The auger, which is heated to a controlled temperature, pressurises the plastic as it is being melted and forces it into the mould tool.

Some machines may carry a ramming tool instead of an auger.

The molten plastic enters the mould tool via the sprue, which is a nozzle from the auger that is fit snug against the opening of the moulding tool. The molten plastic then travels through the runner which is simply a passageway that guides the molten plastic.

The molten plastic then reaches a narrowing, known as the gate and from here is injected into the cavity. The cavity is the moulding of the finished product being manufactured.

plastic injection moulding

3.      Dwelling

Dwelling is the process of increasing the pressure of the molten plastic in the cavity to ensure that all the areas are totally and uniformly filled.

4.      Cooling

The plastic in the cavity is then cooled for it to harden. Moulds can be air-cooled but it is much more efficient and effective to utilise a coolant such as water to control the rate of cooling of the finished product.

5.      Opening

After the part has solidified, the clamps are opened to reveal the finished product.

6.      Ejection

This is the removal of the finished product from the mould. This can be done manually or automatically such as with an air blast system.

Some mould tools carry multiple cavities for the production of multiple parts from a single injection. These usually carry cold slug wells at the turning points of the runners. These cold slug wells capture the colder molten plastic to reduce the risk of inconsistencies in the finished product.

If you have any questions about injection moulding machines, contact the proven experts at Applied Machinery. One of Australia’s largest and most respected dealers of machinery, they can provide you the best advice as well as the best quality moulding machines in the business.

What is an injection moulding machine?

Everything You Need to Know About Injection Moulding


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