Dispatches from the front (Pre-release Report) - Summer's coming edition


#1

One of the things that lasers do really well is make very thin cuts in things. That makes something called a “living hinge” practical for all sorts of projects. Living hinges allow materials that don’t usually bend, curve or fold easily. One of the things that most amazes non-laser people is seeing things bending that ought not to. Putting those together is a marriage made in heaven and gives you a little extra “Wow!” to help explain why the wait for your Glowforge was worth it.

Since the winter has finally left (:crossed_fingers:) the Northeast, it seems appropriate to break out the sunglasses and what better way to hold them when you’re not wearing them or to hold your regular glasses while the shades are on your face than a sunglass case made from a living hinge?!

Obrary Designs has some nice pre-formatted projects you can download. Some are free and others have a nominal fee. Similar to how I expect the Glowforge catalog to work. Taking a shortcut so as not to have to map out the whole living hinge case, I grabbed their sunglass template.

It comes with a wood pattern as well as one for cutting out the felt lining. The lining was simply a rectangle that presumably is glued in the center of the case before forming it. But it is short on the ends and side leaving more wood exposed than I’d like and making it look as if it were an afterthought. I copied the pattern for the case, deleted all of the living hinge cuts and narrowed it 1/8" on either side and then cut that out of my felt.

That lets the felt completely cover the interior of the case and perfectly fits the curves and the tab closure. I think it looks better. The felt I used was craft store polyester with an adhesive backing.

The wood pieces I cut out of 1/8" Proofgrade Maple Plywood. I used plywood because living hinges flex better with the non-homogeneous grain that is a result of the plies vs the unidirectional grain of a solid wood.

Coming out of the 'forge it’s a little smokey and this is where the Proofgrade masking and pre-finishing come in handy. And where it poses a couple of “gotchas”. The masking means I won’t have to sand it which can be tricky with living hinges - catch an edge and you break a hinge piece and the whole thing is ruined. But that masking means weeding lots of thin little strips of masking material from the wood.

Fortunately duct (or Duck brand) or Gorilla tape has a higher grab than the masking. It’s a matter of placing several (3 per side) strips on the masking, rubbing it down and then pulling both the Gorilla tape and masking off.

You do have to give it a start sometimes by peeling back the Gorilla tape a bit, starting the peel of the masking, pressing the Gorilla tape back down to grab those loosened ends and then pulling the Gorilla tape off and along with it the masking.


Short work to weed the living hinge.

Then it’s time to prep the interior and the glued portions of the end pieces with a little sanding to get the finish coat off the wood to allow for maximum glue adhesion.

The ends are two pieces that form an end-cap. The inner portion is set back about 1/8" or so to allow the body of the case to wrap around and held in place with a bit of glue. Getting that inner piece lined up just right would be a challenge except the inner end piece is cut out of a piece the same size as the outer end piece. That leaves a ring the exact shape and size of the outer piece. So it’s a simple matter (after sanding the inner & inside of the outer piece) to glue up the smaller inner piece and place it inside the ring and sandwich together with the outer piece. Once the glue dries (a couple of binder clips work as great clamps) the inner ring pops off (if you didn’t let glue seep out from under the inner piece :slightly_smiling_face:) and it’s ready to glue to the body.


Place a line of glue 3/4 of the length of the body from the larger horizontal strip up towards the tab end. If you glue the whole thing the hinge won’t open :stuck_out_tongue_closed_eyes: This is why I narrowed the felt by 1/8" on each side. It leaves the wood exposed on the very edge to rest on the inner ring.

Use a couple of rubber bands to act as clamps until the glue dries. I start with a wood glue (Titebond) to seal the wood and then a stripe of Crazy Glue (isocyanoacrylate glue). I may add a couple of 23ga pins to “nail” it to the end piece inner disks if I decide it needs reinforcement but I’ll see how it stands up to a bit of use first.


Weekly Highlights for the Week Ending April 22nd, 2017
Living Hinge D&D Boxes
#2

nice work !


#3

Totally Tubular Dude! :grin:
(I have been waiting a long time to use that.)


#4

Oh, it’s beautiful! Now I want to do a living hinge–haven’t tried that yet…


#5

So nice! Thanks for all the photos and detailed construction tips.


#6

Beautiful!
Thanks for the step by step!


#7

I loved this whole post! And you did an amazing job of documenting the step by step. Thank you!


#8

That is an awesome write up which makes me anxious to make a case like yours. The detail that you used is great. Thank you. :grin:


#9

Wow, thank you for the excellent step by step write up - and also for mentioning Obrary. They have a TON of great projects, including some stacking boxes and storage solutions that I’ve been wanting to try.

Your project came out beautifully! In your experience with living hinges, do you find them to be relatively strong and/or stable? I feel like I’ve read a few mentions that they can be a tad fragile, but maybe that’s situational?


#10

Can’t wait for my forge. Thanks for the tip on the gorilla tape to help with all the peeling.


#11

Very nice! I really love the felt lining and the adjustments you made for it. Any reason that you didn’t line the sides as well?


#12

Very Nice :slight_smile:


#13

They’re not an issue for static loads like boxes and things like @marmak3261’s match box. I haven’t done a ton of stuff with flexing hinges where it’s opened & closed a lot. The backing material (felt, cotton or linen, etc) should help a lot. Some materials are less well suited for them - solid wood, acrylic. There’s also a balance between too many cuts and too few. There’s some decent math out there for calculating optimums based on curve radius and other factors as well.

Just that I don’t see glasses having much scratch/wear coming from the ends/corners of the frame vs wanting full coverage for anywhere the lenses might contact the case. It would be a simple matter to add them by cutting out the smaller circles of the end pieces from the felt too.


#14

Seems like a better way of forming a curve would be to cut V wedges out of the inside but not quite all the way through. That way you would get a smooth surface on the outside. It might be difficult to get the depth just right with a laser though. DiBond can be curved that way by milling with a V shaped bit, leaving the aluminium skin and a thin layer of the plastic core to do the bending.


#15

I knew this was process was done in wood but never thought of doing it with DiBond! Great idea! :slight_smile:


#16

Excellent documentation. Bookmarking for sure! :bookmark:


#17

Yes, superb documentation. It was a delight to read. :military_medal:


#18

This post has really helped me think through living hinges again and do a little more research and just plain analysis of where stress is occuring. One thing with automatic living hinge makers is that they are not necessarily designed for special uses, more generic. It takes some manual tweaking, but I believe I understand a little more and can address both the acrylic and wood versions of the stamp container/dispenser.

Looking at the living hinge above, notice that the edges have kerfs going into the wood far along. My mini tabs only had a very short line at the corner and thus didn’t have enough flex at the edge around the tabs. I think I can fix this now. Thanks for all the discussion.


#19

Crossing fingers for you :crossed_fingers: