Design advice for automotive heatstake assemblies.

There is no set formula for determining size, quantity or positions of stakes but the number and design of heatstakes used to join a thermoplastic assemblies together will depend upon;-

 1) Total strength required.


 2) Support under the heatstake.


 3) Available access for the Heatstaking tools


 4) Aesthetics - The balance and general finished appearance.


 5) Moulding restrictions sink marks


 6) Provision for a safety margin

Further considerations

Keep the stake positions away from heat sensitive components including thin sections of a moulding (particularly vertical walls which may be nearer to the Hot-Air delivery point that the stake being heated).  

Leave adequate room to enable approach of the system and don’t forget that the headed stakes take up more room once they have been processed.  

Ensure there are equal sections around the area being processed. When a hole is placed at the edge of a moulding and there is little or no material on one side, this thinner section will melt away resulting in a total failure of the assembly method.  

Do not mould stakes on thin material sections unless there is no other alternative, and where there is no option, keep the thickest section of the stake under 70% of the base moulding thickness.

PHASA design engineers can evaluate your part  and offer advice to optimise the design for heatstaking and assembly.


A free design guide is available by filling in the form on the contact page.



To discuss your individual requirements call us on +44 (0)1638 561 478


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Phasa Limited
10 Victoria way
Studlands Ind Est
United Kingdom

Tel: +44 01638 561 478
Fax: +44 01638 667 310

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