Blow moulding vs injection moulding – what’s the difference?

These two methods of making plastic parts are widely used and both are cost effective. But it’s helpful when deciding which is suitable for a specific application to have an overview of the differences between them. So here’s a quick guide that should help.

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Blow moulding and its advantages

Blow moulding is somewhat similar to glass blowing. It produces an object that is hollow, and formed in one piece. The process can produce high volumes of items that are very uniform, such as bottles.

In general, machinery and production costs are lower with blow moulding. It produces pieces that are complete – if you think of the bottle, there’s no need to produce each half separately and join them. This means that blow moulding can make some shapes that would be impossible with injection moulding. From water bottles to automotive parts, blow moulding is ideal for items which are hollow and need to be produced as a whole.

Injection moulding and its advantages

This technique needs more engineering effort in terms of pre-production tooling and creating the moulds. In this process, the mould is injected with a liquid polymer which is under very great pressure and at a high temperature. Once cooled, the plastic parts are released.

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Plastic injection moulding http://www.meadex.co.uk has its own advantages. It’s an efficient and precise way to produce small parts in large volumes. It’s very flexible because changes in the material, or its colour, are easily made. And it’s efficient, with low wastage of materials.

Injection World magazine recently reported on the way that both hard and soft injection moulded plastics are taking weight out of cars – https://content.yudu.com/web/1rl19/0A1uufg/IWNovDec18/html/index.html?page=14&origin=reader. The use of inserted films, combined with injection moulding, means that objects can be produced and decorated in one process. Injection moulding allows surfaces such as high gloss, matte and semi-matte, so it lends itself to highly creative applications.

Each technology has its place. While injection moulding has more upfront cost in designing the mould, blow moulding tends to need greater supervision during production runs, to ensure that quality isn’t compromised by air leaks, streaks and wall thinning. The best course is to talk to an expert about your application to see which technique would be more suitable, and what new processes are available.