Pin hinge (print-in-place)

Two interleaving leaves and a captive pin, printed pre-assembled.

A pin hinge is a knuckle (barrel) hinge whose two leaves interleave along a shared axis, with a captive pin running through every knuckle. The pin has an enlarged cap at each end that’s trapped in a pocket inside the outer knuckles, so it can’t slide out — yet the whole thing prints pre-assembled and articulates with nothing to snap together. The clearances that let it turn are plain geometric offsets; about 0.3 mm is a sound FDM default.

Two parts or three. *Separate* is the default: the pin is its own part, held by a cap at each end that sits in a pocket inside the outer knuckles. It cannot fall out, and if you snap one you can print another. *Captured* grows the pin into leaf A instead — the hinge arrives as two parts, there are no caps or pockets to print, and there is nothing that can work its way loose over time. Reach for captured when the hinge is small, when it will be opened often, or when you simply do not want a third part on the plate.

Match the leaf thickness to the barrel. The barrels rest on the bed and the leaves are centred on the pin axis, so unless a leaf is at least as thick as the barrel is wide it hangs *above* the plate — 2.5 mm up with a 3 mm leaf on an 8 mm barrel (the default leaf is as thick as the barrel, so it starts flat), which leaves a palm-sized area under each leaf printing over nothing. The Properties panel says so when it happens. Raising Thickness to the Barrel Ø drops the leaves flat and costs nothing in how far the hinge folds; leaving it as it is works too, as long as you turn supports on.

A lid that closes: On a wall. Flat leaves are centred on the pin axis, so folding one leaf onto the other puts it where the other already is: at the defaults the hinge stops at about 96°, not far enough to close a lid. For a lid, set Mount to *On a wall*. Each leaf becomes a plate for a part’s back wall, with a 45° gusset under every knuckle so nothing overhangs, and the axis stands far enough out from the walls that the knuckles clear both parts. Print the box and the lid side by side, open side up, back walls facing, and it folds 180° to close. Two things decide whether the lid lands on the box: the two back walls stand the Walls apart distance the Properties panel shows, and the axis sits halfway between the two rims, so set Leaf length to half the box’s height plus half the lid’s. Then use Attach to in the Properties panel to make leaf A part of the box and leaf B part of the lid. For a box of its own, the Enclosure generator’s Hinged lid places and sizes this hinge for you, and stands the lid’s leaf clear of the box so nothing rubs as it shuts — a hinge placed by hand on parts of different heights lies against the box’s back wall over the last few degrees. Thickness, Leaves reach the plate, Print supports and Print it shape flat leaves only.

1. Open the Generate panel from the left sidebar and choose Pin hinge (under Hinges & joints).
2. The whole hinge drops in as one pre-assembled, editable part. The parameters open in the Properties panel, where you set them.
3. Pick the Mount: Flat leaves for a hinge on its own, or On a wall for a lid that closes onto a box.
4. Set each leaf’s length, the hinge length, and the leaf thickness.
5. Set the knuckle count and the pin and knuckle diameters, then pick a fit — or Custom to set the clearance gap yourself.