I keep experiencing a dead-hinge

livinghinge

#1

OK, getting very frustrated with trying this living hinge piece. Working on a cool shot glass holder for St. Patricks day and I must have snapped 10, WAAAAAAY before any serious bend (like 20 degrees). I am cutting this in :proofgrade: walnut ply and I have tried a linear pattern:
2018-03-15_21-59-47

And then I tried the cool interlocking spiral one that was posted on the forum recently that someone was showing wrapped around their wrist, and believe me it snapped way, way before that…;
2018-03-15_22-09-58

So here is my svg if someone can take a whack or explain what I don’t understand. (note with the spiral pattern I deliberately overflowed the sides otherwise when I tried cutting it down it didn’t successfully go to the edges so figured that wouldn’t work, so this wastes a few mm of surrounding wood.

Teeling Shot Holder spiral hinge.svg.zip (16.4 KB)

That should fold into this (realize the svg doesn’t have the cross brace, but that’s not the issue) and not sure why the render doesn’t have the holes on the top cut out (graphics bug?)


#2

I’m far from being a hinge expert, but I did find, when I cut one that wasn’t wanting to bend as far as it should, that spritzing it with a little water and working that down into the cracks with my fingers made it a lot more willing to bend into the shape I needed it to be. FWIW!


#3

I haven’t had good success with those multi-directional hinges. They’re really pretty, but they don’t bend in one direction as far as plain straight line hinge will, or at least one that limits the bend to one direction.

And for anything other than the straight line, you might have to extend the hinge and might not get quite as “tight” a bend. (At least that’s been my experience.)


#4

Thick walnut ply or medium? I tried to do a living hinge out of 1/4” Baltic birch ply the other day and it was not happy! I redid it in 1/8” ply and it was much, much happier. First living hinge since I’ve owned the laser - needed a box in under an hour. This thing is amazing.


#5

I have been staying with thin stuff for good hinge results.
Thin as in around 0.125 (1/8").
I have made some thicker, but they just were not springy (or merely broke when bent).


#6

I was working on a trebuchet from someone’s thingiverse file, and it used 1/4". I only had 1/8", so I doubled up. The doubled-up hinge, locked into place with tabs, feels very strong.




This one works for me in 1/8" BB ply (3-ply):
eighthINmaterialHinge2x3nAhalf


#7

Cool! :sunglasses:


#8

Reducing the scale of the pattern will give more points to share the flex. This is medium maple ply.

Resilient too, I have flexed this piece like it was a worry stone.


#9

ok, so I played with this instead of doing the work that I should have been doing.

Tried a single-shot version with your hinge pattern, failed, tried it again larger, and worked for a second, then snapped. I think it could work with some more tweaking. Tried the living hinge pattern that I posted (and that I know works for this 3mm BB ply). That worked, but I had to use clamps and glue to get it to stay.

Then tried it with the doubled-up hinge, and that version worked with no glue, although I still ended up gluing the ends of the two layers to each other.

(pardon the keg-cup shot glass, it’s the only one I had in the office.)

here’s my svg:


it has the small (light green, horizontal, top layer only) and larger (dk green, vertical, both layers) supports included. You can ignore the smaller support if you are doing the two-layer doubled-hinge version.


#10

OK, so that’s awesome, but I ended up with the bottom version of the 2 at the top which just snapped in the middle (actually looked almost exactly like that). BTW: that pattern produces a huge smoke plume in the backyard). Although this seems like regular ply rather than the Walnut :proofgrade:I’m using (which looks awesome). Why didn’t your’s snap? Do you wet them or something?

BTW: a solo cup of Teelings would be fantastic. For aficionados of whiskey (with an ‘e’ - which means Irish whiskey) Teelings is fantastic. Owned by the Teeling sons of the current Teeling’s owners in Dublin and finished off in rum barrels giving it a slight banana flavor. The tour is really nice and they really let you get into the guts of the distillery.


#11

Probably the difference in material… I’m using 3mm bb plywood; it’s only 3-ply but thats enough to have cross-grain, unlike the :proofgrade: ply with it’s manufactured core.


#12

That would be my guess. The PG’s MDF core is likely more prone to breaking the ends of its slices. I haven’t had good success with MDF living hinges so wouldn’t be surprised if that’s the issue here. (Assuming the PG one is cut with the grain.)