Vacuum forming v injection moulding

If you need plastic parts, you have two options for manufacturing them. Knowing which of the processes is most suitable for your products will help you to make time and cost-effective decisions.

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Injection moulding

Injection moulding is a four-step process that uses melted plastic to create plastic pieces inside an injection mould. Once cooled, the screw-driven injection moulding machine extrudes the finished object. This process enables identical parts to be manufactured quickly and cheaply.

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Vacuum forming

In the vacuum process, a heated plastic sheet is sucked into a mould using a vacuum. Once set hard, the object can be removed and trimmed by hand. This process costs significantly more than the injection moulding process, making this form of production more suitable for low to medium runs.

Which process is best for your needs?

A simple overview of the processes involved will go some way towards helping you to decide which is best for your products. Using the vacuum process is not as versatile as using injection moulding, as any shaping only happens in one plane. With injection moulding, the shapes you can form are infinite; however, injection moulding relies on a high degree of precision throughout the process, from the design and manufacture of the tool itself to the right choice of material and skilled machine operation.

With the vacuum process, a company such as can create more sophisticated shapes, products and special features that injection moulding cannot match.

The vacuum process can also create hollow forms with much thinner walls than those created using an injection moulding tool. In terms of finishing, injection moulding has low scrap rates unless the runners are left to cool, when the objects must be removed by hand and reground. Using the vacuum method, each shape must be cut from the sheet and the waste reground for future use.


Whichever process you choose, both types of manufacture can be used to produce high-quality plastic products. Plastic injection moulding allows for high production runs, full automation and low unit costs, whereas the vacuum process offers low startup costs, fast prototyping, and is ideal for repeat jobs using aluminium casings. In determining the right process for your job, you should also consider your design and engineering costs, your budget, and the timeframe in which you need to work.