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.

1. Set the ball and stem radii and the stem length above the socket.
2. Set the socket opening radius (kept narrower than the ball), clearance gap, and wall.
3. Generate: the ball-and-stem and the socket drop in as editable parts.