Wanted to experiment with a new way to do flexy things. I’m still working through different filaments to see which one seems to do best.
BambuLab Matte filament seems to work well.
Generic PLA (Sunlu) was too stiff and cracked.
BambuLab basic PLA was ‘ok’, but doesn’t seem to be as resilient as matte PLA.
The model is posted here.
It’s an experiment and I’m sure I’ll get some low ratings. It’ll be worth it FOR SCIENCE!!!
Edit: I like the caterpillar more.
It looks neat, gonna give that a test print soon.
Do you mind if i use this method in something I’m doing?
I don’t mind at all! Would be great actually. I’m really curious to see how others use it. I’m working on a caterpillar that uses the same method.
For the sake of disclosure, this way of flexing seems inherently fragile, but it has a very interesting feel.
A bottom layer of .2 is very flexible. .4 is a bit stiffer but seems a bit tougher. I think I’m going for .2 for now until complaints arise lol.
FWIW I tried PETG and while it’s more ‘springy’ once it reaches the deformation point it just snaps instead of deforming. For this design it doesn’t have an upside imo.
If you put the “flex-layer” as a bridge in the middle of the parts, the flexibility would be constrained in both directions and breaking it would be harder.
If you spin this further and put a 1-2mm zylinder in the middle of the parts it will be flexible im all directions (at least with petg, as I think pla will be too bridle for this).
Maybe worth to give both ideas that a try. 
My main concern with moving the spine to the middle would be printability issues, especially if it’s distributed for ‘mass consumption’. You’d have to count on getting really good adhesion on the 1mm wide ‘ribs’, especially accounting for dirty plates, collisions with the nozzle while printing the middle, etc… 
I tried a few versions with petg and I did not think it made that much of a difference. Past a certain point it just snaps instead of deforming like PLA does. I think the ideal material would be TPU, but I don’t have any on hand to try.
Yes that where also my concerns, but of course you have to make them a little bit thicker (>2mm) otherwise it is likely to fail.
If it works reliably it will open new possibilities for PiP mechanics. I have something in mind which I maybe want to try when I find the time for
This is my Idea I had in mind. It’s just a concept, but it works surprisingly well. A flexible compliant print in place mechanism.
Maybe it can be further adapted for some robotics stuffs and similar.
Ooo that’s super cool! The fact that the movement is effectively reversed is really interesting… The first thing that popped in my head was the flexible fingers of a robotics gripper. Might work even better in TPU! I found it to be super tough for the caterpillars.
Thx 
I think with TPU this thing would be really hard to print, since there is a bridge through the whole part for the bowden mechanism to work and I never get consistent tpu bridges 
If you cross over the bowden, it will move in the same direction, but comes with a few design constraints. Also a 4-way movement should be possible but then only with a 1:1 ratio.