Two-Piece Boxes Thanks To Laser-Cut Flex Hinges

It sounds like a challenge from a [Martin Gardner] math puzzle from the Scientific American of days gone by: is it possible to build a three-dimensional wooden box with only two surfaces? It turns out it is, if you bend the rules and bend the wood to make living hinge boxes with a laser cutter.

[Martin Raynsford] clearly wasn’t setting out to probe the limits of topology with these boxes, but they’re a pretty neat trick nonetheless. The key to these boxes is the narrow to non-existent kerf left by a laser cutter that makes interference fits with wood a reality. [Martin]’s design leverages the slot and tab connection we’re used to seeing in laser-cut boxes, but adds a living flex-hinge to curve each piece of plywood into a U-shape. The two pieces are then nested together like those old aluminum hobby enclosures from Radio Shack. His GitHub has OpenSCAD scripts to parametrically create two different styles of two-piece boxes so you can scale it up or (somewhat) down according to your needs. There’s also a more traditional three-piece box, and any of them might be a great choice for a control panel or small Arduino enclosure. And as a bonus, the flex-hinge provides ventilation.

Need slots and tabs for boxes but you’re more familiar with FreeCAD? These parametric scripts will get you started, and we’ll bet you can port the flex-hinge bit easily, too.

14 thoughts on “Two-Piece Boxes Thanks To Laser-Cut Flex Hinges

  1. Actually it wouldn’t provide that much ventilation since the way the hinge works means the inside curve is generally closed. | | -> \/
    No biggie i think, but just something to note.

  2. We’ve looked into this at our hackerspace. The technique is not as interesting or useful as you might think.

    (Note: Not commenting on the project, only living hinges in general.)

    A wooden hinge has to be fairly big to work. You can’t make, for instance, a wooden cover for a 1″ thick book (or even a 2″ book) with a living hinge because you can’t make a hinge that bends that far that quickly.

    If you actually use the hinge as a hinge eventually one of the links will break, ruining the effect. Of course this puts more stress on adjacent links, so this leads to a cascade failure.

    On the previous note, the hinge itself is fairly delicate and links can easily break from rough handling.

    You might get more useful effects by covering the hinge with a supporting material such as packing tape, or infusing the material with something that makes the wood more pliable. Covering the hinge with adhesive-backed leather, for instance would probably work.

    This is an interesting technique that’s not good for general use. Maybe useful for a display piece that’s never handled, but it won’t stand up to any sort of stress.

    1. Use water, perhaps, to soak the hinge, letting it dry while it is positioned on a halfway bent position? Intuitively I feel that should be possible.

      You can actually cut patterns for hinges that bend at different angles for curved sheets also; it doesn’t have to be limited to the above. I’m very interested in these but it seems few patterns are available so I’ll need to experiment.

      1. For solid wood, yes. But plywood? Unless the glue is waterproof, it’ll delaminate. I think most of that Baltic birch uses interior-grade glue, especially the thin stuff like 5mm (1/4″).

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