I’ve tried a few different materials, standard resins were too brittle for action figure ball and socket click joints (like modibots). When I print ball and socket click joints, the pieces fit well but I run into the rag doll effect, where the sockets rub smooth very quickly and the printed action figure will not hold its pose. Has anyone had this problem? What materials or other methods would be good to avoid this problem? All suggestions welcome!
Second question - I really admire the kaiyodo revoltech joints - which snap strongly into different positions, but I’m not sure how to replicate those - or even if any of formlabs materials would hold up over time.
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I’ve used Durable and Tough 1500 for ball & socket joints with 3-5 times installation/removal cycles. The parts do loosen more quickly than machined delrin but it hasn’t been an issue for the weight of my parts. Formlabs has a white paper where they measured the coefficient of friction of different materials and provide starter clearances for different types of fitments. You can search online for “[White Paper] Engineering Fit: Optimizing Design for Functional 3D Printed Assemblies”.
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Many thanks for the feedback and the reference - that helps a lot!
This was tremendously helpful - here is the relevant excerpt from the paper:
Durable Results: In this test there was an inflection point between 0.2 mm and 0.3
mm of allowance where the ball and socket becomes easier to separate. Between
0.0 mm and 0.2 mm, the ball moves smoothly in the socket but stays in position. The
interference fit in this range would be ideal for articulated figurines, which need to
keep their orientation. Above 0.3 mm, the ball is slightly loose and moves freely in
the socket. Below 0.0 mm, the ball could not be inserted at all.
Tough Results: The ball and socket model was also printed in Tough Resin, but
could not be inserted by hand because of the high friction and high strength of
the material. Durable is better suited for a ball and socket geometry due to its
wear resistance.
Why not just buy a bunch of Revoltech joints, and design the figure to use those? Kaiyodo sells the joints by themselves.
