Question regarding little tiny ball joints...

Hey, fellow Shapeways enthusiasts,

For kicks, I'm trying to work on a mini-figure model that would be compatible with Hasbro's Kre-o line. The parts I've designed are mostly complete, but I'm having a little anxiety about the ball joints on the shoulders and hips.

Has anyone here worked with similar joints?

I've intersected the spheres from the limbs and created little ports on the way to the hollowed out socket, but I'm not sure how wide a path I need to clear so that the joint can be pushed into place. I'm also trying to figure out if I should slope the pathway in one direction or another (like a ramp leading to the hollowed socket).

I hope that makes sense...I'm still just learning how to speak in 3D.

Any recommendations are much appreciated!

Thanks!

T.

The post Creating balljoints in SketchUp
by Drawn-Steel Hero might help you out.

Paul
[hr]

stop4stuff Modeller for hireShapeways Shop - Controller PendantTwitterYouTube​

[hr]

Thanks for the link. I'm checking it out. He's working on a much larger scale, so I wonder if that changes things.

Right now, I have it set up so that I'm going to be trying to push a 3.3mm sphere through a 2.8mm wide/.5mm thick aperture leading to hollowed out socket. I made the socket at 3.5mm (.2mm wider than the sphere joint), just in case it ends up tighter than intended in the printing process.

I guess my question is whether the plastics have enough give, or if I should widen/narrow that aperture.

But before I drop my seven bucks on seeing if this works, I thought I'd seek the wisdom of the masters.

I'd say do a trial run with different tolerances to see what works.
But if you don't want to do that make the parts as snugly fitting as possible, you can file down tight parts.
There's no remedy for loose parts though.

You can tighten up loose joints by painting thin layers of clear nail laquer, assuming that's ok with the plastic you are using. You can also dab the laquer onto assembled joints, but you have to remember to keep moving the part as and after it has dried off, or it ends up glued solid.

An other example:
You can also use this form with nylon material.
You make the ball a little bigger so it's a little jammed.
https://www.shapeways.com/model/3dtools/7873425/0/6?key=30830c8f31d03c0a2bfb5713cbd3d289

Yes the popcorn joint works and allows ball joints as small as 3mm diameter.
Use three tabs for optimal bendability vs. clearance space on the small joints.
The size of the slot between tabs can be as small as the minimum clearance (0.5 mm for nylon), you can experiment with even smaller values such as 0.3 mm, when used they will separate.
Between ball and socket I usually put a zero clearance for friction fit, for tighter joints a slight interference fit works.