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Vacuum Forming Design Guide

Here at Toolcraft, we have longstanding experience of designing plastic parts for the vacuum forming process. Please see below for our brief design guide.

Draft anglesvacuum forming draft angle

When designing for the vacuum forming process you must add draft angles to all sides of your parts to ease removal of the plastic parts from the tool once they've been formed.


If you're forming over a male mould, add draft angles of at least 3 degrees, but if you're forming into a female mould, add draft angles of at least 5 degrees. For pocketed trays, the same draft angles will also need to be added to all sides of each pocket.

Possible depthsvacuum forming design pocket depth

For vacuum formed trays or parts with pockets, ensure each pocket depth is no more than 75% of the smallest width at the top of the pocket. Otherwise the material will stretch too far over the vacuum forming tool, causing excessive thinning and weak pockets.


vacuum forming design undercut


Try to avoid undercuts wherever possible, as parts with undercuts are difficult or impossible to remove from a standard vacuum forming tool after they've been formed.vacuum forming design possible undercut



However, it is possible to vacuum form undercuts if your part has an undercut at one end, but an equal angle at the other, so that the direction of removal of the part from the mould tool has an equal or greater angle than the undercut - see the the illustration >>


Another solution is use a split tool with side entrant tool that is removed first after forming, but this will increase the tooling costs - at Toolcraft, we look out for undercuts and will advise you on possible redesigns to keep tooling costs low.


Toolcraft Tip – Fast Vacuum Forming Mould Tools

vacuum forming resin cast tool

If you have an existing vacuum forming but no tooling, it's possible to make a plaster or resin cast of the product and use it to make a vacuum forming tool and parts within a matter of days ! Confused? Have a look at our Fish Fillet editorial !


If you need advice on a subject not listed above or you'd prefer to have your question answered specifically, please contact us.


We have a lot more vacuum forming advice for you to explore, or if you're ready to benefit from our excellent design service, just

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