Creating Living Hinges

By Kevin Gunn
Time Required: 1–3 Hours 
Difficulty: Easy

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I have a particular interest in discovering new ways to push the limits of material fabrication with my laser cutter. In this guide I’m going to give you an overview of living hinges that will allow you to make bends (and springs!) in a single piece of rigid material. Wood and acrylic are particularly amenable to this technique, and the result has an artistic aspect that’s pretty cool as well!

More importantly, I’m going to try to add a bit of theory to this so that you can extend these techniques in new and better ways.

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Steps

Step #1:

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What does it mean for a material to be rigid in the sense I'm using the term? A rigid material is one that has very limited ability to bend over a given length of that material
Acrylic is RIGID. Very, very little flexibility, but it's a beautiful material. So how do we get it to bend?
The acrylic sample that I cut here has the ability to fold easily from fully open (flat) all the way to fully closed (180 bend) in either direction. It also can act as a spring along its length.
How does this work? Head to the next step for the physics and geometry of it.

Kevin Gunn

12 Responses to Creating Living Hinges

Kevin Gunn on December 12th, 2011 at 5:38 pm said:

It’s a 40W Full Spectrum Engineering “Hobby” Laser. For 1/4-inch acrylic I find I need 100% power (at 15mA) and 20-25% speed with 2 passes (30% with 3 passes also works). The laser cuts smaller pieces (near the exit port of the beam) than larger pieces (where the optics are far from the point of origin), thus the variation. I’m happy with the laser, though, and I recommend it strongly for hobbyists since the “Deluxe” version ran me only $2500. For production runs I’d want something bigger/faster/stronger, but it’s a BIG jump in price.

I’ve done a few tests on kerf, but nothing too exacting, and my notes appear to be incomplete. I may try to run a test on acrylic later today and will post the results if I do.
Kevin Gunn on April 10th, 2012 at 1:06 pm said:

Extruded acrylic (Optix brand, if I recall correctly).
Patricia Muñoz on June 27th, 2014 at 11:10 am said:

In our research group we have been working in making materials flexible through laser cutting and making practices with our students and designing objects for patients with mobility issues. We have made two small books (in spanish). You can download the first one, free of charge, from this link http://edicionesdelaforma.blogspot.com.ar/2012/10/la-flexibilidad-en-la-generacion-de.html
Hope you enjoy it.
- Alex on December 11th, 2015 at 7:08 am said:
  
  That’s interesting, thanks!
Rachel Trewartha on March 29th, 2016 at 4:20 pm said:

Would this “triple zig” design work alright if the width of my plexiglass is only 2mm?
Jim Wesley Colovos (James diSi on April 13th, 2017 at 10:50 pm said:

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Brian Wagner on April 14th, 2017 at 4:08 am said:

Try using the inkscape extension written by my good friend Mark. http://www.thingiverse.com/thing:203940
DrXenocide on April 14th, 2017 at 4:57 am said:

I made a customizable generator for OpenSCAD: https://www.thingiverse.com/thing:1736879
And another that can use any character you want: https://www.thingiverse.com/thing:1745322
Mr_Productive on April 18th, 2017 at 11:23 am said:

Actually flat pieces 3D printed with PLA make amazingly good springs if the radius of the bend is large enough. You can control the strength of the spring by how wide the piece is, how many layers you print and the thickness of each layer.
- Greg Harley on April 20th, 2017 at 1:14 pm said:
  
  This article inspired me to try printing one with my Ultimaker, here’s the result: https://youtu.be/70QyKsuYAH0
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