Ball-and-socket joint

A captive ball on a stem inside a socket, for multi-axis motion.

A ball-and-socket joint captures a ball on a stem inside a socket whose top opening is narrower than the ball, so it swivels freely yet can’t pull out — the joint for desk-lamp arms, phone mounts, and poseable figures. Like the pin hinge it prints pre-assembled: the ball floats in the cavity by the clearance gap all round, so it comes off the plate free. About 0.3–0.4 mm is a sound FDM default.

Turn one joint into an arm. Set Joints above 1 and the same ball-and-socket unit stacks into a flexible arm — a camera mount, a coolant nozzle, a lamp gooseneck. It still prints in place: every ball arrives already captured in the socket below it, so the whole arm comes off the plate articulated with nothing to assemble. Each joint adds friction as well as reach, which is what lets a longer arm hold its pose — if yours sags, tighten the fit rather than shortening it.

Stacked cups are coned underneath. In a chain every cup after the first stands on the stem below it, and a flat cup bottom would be a wide disc printing out over a thin stem. Cup taper cones it off the stem instead — measured from horizontal, so 45° and up needs no support. It is capped automatically so the cone can never cut into the ball cavity, and the panel tells you when a request was capped or was too steep to be worth coning at all. Set it to 0 for the old square base.

1. Open the Generate panel from the left sidebar and choose Ball joint (under Hinges & joints).
2. The ball-and-stem and the socket drop in as editable parts. The parameters open in the Properties panel, where you set them.
3. Set the ball and stem radii and the stem length above the socket.
4. Set the socket opening radius (kept narrower than the ball) and the wall, then pick a fit — or Custom to set the clearance gap yourself.