Living Hinge
I recently designed a product with living hinges. After a bit of googling I had found 2 articles which seemed pretty authoritative.
https://www.3dhubs.com/knowledge-base/how-design-living-hinges-3d-printing
https://www.matterhackers.com/news/living-hinge:--design-guidelines-and-material-selection
Reading these, I thought I was out of luck because the only material I have is PLA and these guides recommend to other materials. I thought I would give it a shot anyway and got some great results after a little trial and error. I wanted to share these findings in case anyone else can make use of the info.
Hinge Design
The guidelines in the articles above show that the hinge section becomes thin with a curved radius. I guess the logic is to replicate how living hinges are injection moulded. I followed the diagram exactly and found the the hinge fold was a angle and was difficult to control. Instead I played around with various thickness and profiles and found one that works really well. A 2mm wide x 1mm tall section with a V groove half way through (i.e. 0.5mm deep) works really well. The material I used was https://rigid.ink/products/abs-1-75mm-3d-filament-0-03mm-tolerance-1kg-roll PLA white.
See attached image.
After Printing
I let the print cool down before removing and then heated up the bed to 75 deg C. I then pushed the hinge down onto the bed to heat up the hinge for about 30 seconds. This makes it very easy to fold back and forth and I continued to do this while it cooled down.
The result is a living hinge that works really well. I haven't fatigue tested the design yet. So far it doesn't feel like it would fail anytime soon.