Need Hard Durable material for use with living hinge? 1

[MarktheCoop]

Im not sure if such a material exists, but I need a hard durable material such as polyacetal that can be used with a design including a living hinge. Any suggestions would be greatly appreciated.

Thanks
Mark

 

[patprimmer]

Depending on the number of cycles of the hinge, but nylons can work in a live hinge, and I expect PET might also.

The live hinge principal works because the linear molecules align themselves fairly accurately across the hinge, parallel to each other and perpendicular to the axis of the hinge. This arrangement is instigated by flowing the material through the narrow gap that is the hinge, then it it enhanced by stretching the semi molten material (before the material is crystallised to a significant degree), by flexing the hinge as the mould is opened.

Synthetic fibres are also formed by stretching the polymer as it freezes, thereby aligning the molecules in the direction of the axis of the fibre. I would presume that any plastic that makes good fibres would be reasonable for making live hinges, but I acknowledge that PP is best at this.

Regards
pat pprimmer@acay.com.au
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[MarktheCoop]

I guess I should have included the cycles, the hinge will undergo a few cycles at most and remain closed once installed. The part is a special clip with anti-rotation and needs to be hard and durable to prevent being torn apart by the sheetmetal in which it will be installed.

From experience PP is much too soft and Polyacetal works best for this application, but it is too brittle to mold a hinge.


Thanks
Mark the Coop

 

[patprimmer]

Nylon should do it.

I guess you already have a mould that has done PP and acetal.

If it moulds both of those materials, it should mould Nylon OK.

I would try type 6 first as it is easiest to mould, if it is to soft, try 6.6.

both should be unfilled, and moisture conditioned after moulding, but before use


Regards
pat pprimmer@acay.com.au
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[Pud]

Hi Markthecoop,

Have a look here:

http://engr.bd.psu.edu/pkoch/plasticdesign/living_hinge.htm

All you need to know I think......


Rgds

Harry

 

[patprimmer]

Great info pud

it is being printed to be included in my hard copy information system as I type.

Regards
pat pprimmer@acay.com.au
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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.