How to build a vacuum forming mould to fit your own plastic parts

Being able to build your own parts is not only handy and allows you to achieve something you’re immediately proud of but also helps you save money. Whilst it is now common for people to be able to make things out of wood and metal, making parts from plastic is not as common.

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Vacuum forming

Forming involves using heat and vacuum to move plastic over simple moulds. This process is very economical. Building a mould for a vacuum former requires some technical thinking. Instead of producing a mould that is an accurate representation of the part, you are producing a form that the part will sit on. Therefore, this means the mould will need to be slightly smaller than the part required, and that the corners and bends will need to be slightly bigger.

What to use

The best material to produce a mould is medium density fibreboard (MDF) as it is extremely versatile and strong enough to withstand the pulls of a vacuum former band. If the part you are building is a replica, then you should begin by taking the replica apart, and accurately tracing and cutting out these parts on the MDF using a bandsaw. Sand the parts down, either by hand or with a belt sander. Layer up each individual part until happy with the design, and then superglue together. You do not want the pieces to come apart, so using a nail gun to attach the layers after supergluing is recommended.

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Any edges can be routed with a round-over bit. Smooth all uneven surfaces. Add any holes, e.g. screw holes, but remember these should be larger than the originals. Also, ensure each vertical surface has at least 2 degrees of a draft between the base and the top of the surface so that the tool can be released from the plastic easily. To review a typical range of vacuum forming products go to

On completion of the forming, the part should be shaped using bandsaws and sanding. Getting the hang of producing a mould that accurately creates the desired part can be tricky, but on completion, there is a great satisfaction in seeing the final product, and the advantage of being able to use the mould again and again.