PLA creep

Is PETG substantially better than PLA+ when used in a friction-locked hinge joint?

I’ve assembled a rig for photogrammetry and focus stacking to capture intricate 3D images of insects and other biological specimens. However, I’m facing an issue: the hinge joints are slipping under the camera's weight, which you can see in the attached photographs. I suspect that the PLA+ material of the arms is experiencing creep due to the pressure from the locking nuts. Interestingly, the arms still feel solid after they collapse, which takes anywhere from 30 minutes to 2 hours.



So far, the only approach I've taken to address this issue is using neoprene washers on the axial thrust surfaces of the hinge joints (drawing below). Since I don't have experience with PETG, I wanted to reach out to this forum to see if anyone thinks that PETG has sufficient creep resistance to resolve the problem. I am also open to any other recommendations.



Thanks,
Mike

Maybe. Rubbing two pieces of PETG together does have more of a stick-slip feel than PLA. But PLA should be fine if you enlarge the friction surfaces, and not have the annoying stick-slip feel when adjusting it. Surface finish also matters. Sand them flat for good surface contact, but leave sanding scratches for a bit of grippy texture. Around 120 grit is best, I think.

Thank you, dekutree64. I think the issue might not be just simple friction between the arm components. It seems that the PLA is gradually deforming under the pressure of the locking nuts, which in turn reduces friction as the deformation lessens the pressure. It doesn't look like slip-stick is contributing to the problem, since the collapse appears remarkably smooth when observed through the camera.

There is no direct contact between the PLA parts as there are neoprene washers between the pressure surfaces to enhance friction. While these washers may contribute to the problem, given Neoprene's poor creep behavior, their thinness makes it unlikely that they are a major factor.


(Annotated drawing that should have been used in the previous posting.)

I am currently looking to substantially redesign the arms using a positive lock indexing mechanism.

Mike