Single use - Plastic Hinge?

[ttx]

Hi,
We are designing a plastic enclosure to encase a circuit board. The part will be injection molded - possibly ABS or Cycloloy. The part is a "clam shell" design that is intended to snap shut once and not be reopened. We have been struggling a bit trying to determine if the hinge design that we have will work. There seems to be a fair bit of information on the Web regarding living hinges-but not single use hinges. We definitely don't want a living hinge and don't want to use Polypropylene or Polystyrene. Does anyone have any insight to share on single use hinges? Any information or sharing of past experiences would be appreciated.

Thanks.

Best Regards,

JW
Tactex Controls Inc.

 

[patprimmer]

I already answered this. Please don't double posts as it wastes time and bandwidth and it causes confusion and inhibits full interaction of responses.

Why don't you cut and paste any responses in the least responded to thread to the more popular one, then red flag the least popular thread yourself.

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

 

[Chris1001]

Hi JW,
Styrolux or KResin (SBS transparent resins) are good for single use hinges. Follow usual design guidelines, ie good land areas either side of the hinge. Never gate close to or on the hinge.

Another possibility is Eastar polyesters (PET based copolymers) their ability to cold draw could give a good hinge. Good combination of clarity & toughness also.

 

[ttx]

Chris1001,
Thank you very much for responding. I have been having a difficult time finding anyone with experience in this area.

Cheers!

JW

 

[ornerynorsk]

Why a single use hinge? Is it for tamper evidency?

 

[ttx]

ornerynorsk,
Without going into too much detail....
We needed an enclosure for electronics that was:
-easy to assemble for our production department.
-able to provide us the strength that we required. (living hinge materials ie. Polypropylene are to soft)
-a snap fit, not intended to ever be opened.

After much research, we settled on ABS/Polycarbonate. The funny thing is....you can open the enclosure and because of the Polycarb - it fractures somewhat - but doesn't break.

JW