Living Hinge Design 3

[kenay503]

Has anyone ever had any experience designing a living hinge out of Delrin? I need a tough material that will be resistant to automotive fuels.

 

[insideman]

DElrin is not suitable for living hinges. Use polypropylene only.

 

[kenay503]

Polypro is too soft for what I need. I only need the hinge to survive a few cycles, once it is assembled, it will not be unassembled.

 

[patprimmer]

While PP makes the "best" live hinges, any plastic that can form linear crystals (ie any plastic that makes good fibres) can make a reasonable live hinge. Nylon can work if it's other properties are OK. It will have limited hinge life compared to PP.

Regards

eng-tips, by professional engineers for professional engineers
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[Demon3]

I agree with Pat. Also, if you don't know nylons have very good resistance to automotive fluids such as gasoline / petrol. You can find a comparison of chemical resistance for many common thermoplastics at

http://www.rtpcompany.com/

Nylon becomes much softer and with better elongation to beak only after some time exposed to humidity in the air. That means it's not a good idea to flex the hinge straight from the mold, better to wait. Also you can speed up the flexibilisation by dipping it in water for some time.

 

[Pud]

Hi Kenay503,

Have a look here - goes through design of hinges - worked example of hinge in acetal - non mouldable though!

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

Rgds

Harry