Toolcraft Plastics - Moulding Your Ideas

Our vacuum forming design tips for you.

Last month we gave you some injection moulding design tips, this month it's time for vacuum forming. As you probably know, here at Toolcraft we have longstanding experience of designing plastic parts for the vacuum forming process - here are some of the things to bear in mind.

Draft angles

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 depths

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.

maximum pocket depth

Undercuts

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.

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 »

Vacuum_forming_design_impossible_undercut
impossible undercut

possible undercut

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

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 !

We hope these short tips will be useful to you. Have a look at our help pages for an explanation of the vacuum forming process, including advice on vacuum forming material selection and vacuum forming material specifications. Don't forget that vacuum formings can be designed with a range of useful features. And when you're ready to make use of our design expertise to benefit your own projects, contact us.

With best wishes,

Sonja van Leeuwen, Marketing Coordinator
Toolcraft Plastics (Swindon) Ltd, Tel: 01793-641040