Living Hinge

[Jiten Patel]

Hi All,

I have been playing about with the living hinge for boxes etc. Does anyone have a formula for figuring out the amount of lines needed for a particular sized curve? So say I want to make a box that was 100mm in depth and I wanted the living hinge to be 100mm, how many lines would it need to do it.

Also is there an optimum distance they need to be apart in order to work?

Trial and improvement is all good and well, but there must be some science behind it?

Any help would be great.

Jit

[Chuck Stone]

Jit .. I downloaded a project that had a living hinge in it and it was on 1/8 material.
So I copied that into other files and never adjusted the size. I might have to copy
and paste to extend it, but I never changed the original size/spacing. I figure that
if it worked, why mess with it?

I never got into the science.. and I don't know that it wouldn't vary a lot by material,
and even vary between different pieces of the same material. So.. I don't really have
any answers you were looking for .. just an idea for a workaround.

[Duncan Crawford]

Hi, Jit

These days I cheat on those hinges-- finally bought the CorelDraw macro 'FlexIt' from laserjumpstart. Don't know if there's more than a lot of empirical work codified in it, and it's all hidden at any rate, but it has various adjustable settings for material flexibility and a couple of hinge patterns, so number and spacings of lines can be varied, and it deals with material width automatically. At the least it's been a good starting point and what it produces can be fine-tuned manually once you try a sample cut in your material. That's how I got the hinge on the wine bottle box posted here a week or two back-- started with the default/medium flexibility setting, then stretched the result so the lines were just a bit farther apart so the final hinge would be more durable in my particular 3mm Baltic birch. I've done the same for 5mm plywood, but haven't tried other materials as yet.

duncan

[Jiten Patel]

Thanks for the replies and suggestions. Guess I will have to tinker with it until I get it....or just buy the macro.

Thanks again.

[Glen Monaghan]

Never saw any serious analysis, but you'll have to adjust for material properties and probably no avoiding experimentation for each material and intended use. Certainly, you need to adjust the number, size, and/or spacing of slots according to the thickness/flexibility/brittleness of the substrate, as well as for how much hinge action you want, plus desired durability. There's also a tradeoff with cutting time, since more and longer slots require more time to cut than shorter and fewer slots, and it can be surprising how quickly the time difference adds up. Common acrylics, being rather brittle, will require more slots and closer spacing for similar hinge action and durability than will similar thickness baltic birch.

[Edward van Mierlo]

Hello, I did some research on this not too long ago and found this:
http://www.deferredprocrastination.c...attice-hinges/
I'm affraid I did not try this math, but it looks like the guy has made quite a study of the matter.
Good luck!