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3DAI
Free · runs in your browser · print-in-place or separate pin

Hinge Generator

Set the leaf size, thickness, knuckle count, pin diameter and clearance, add countersunk screw holes, and pick a print-in-place hinge or one for a separate pin. Drag the slider to open and close it in 3D, then download a flat STL that prints with no supports.

Loading the hinge generator...

How to make a 3D printed hinge

  1. 1

    Pick a hinge type

    Print-in-place prints already assembled, with cone pins between the knuckles. Separate pin leaves a hole through every knuckle for filament, a nail or a bolt.

  2. 2

    Set the size

    Enter the length, the width of each leaf, the thickness, how many knuckles, the pin diameter and the clearance, in mm or inches.

  3. 3

    Open and close it

    Drag the fold slider or press Play to swing one leaf about the pin. Warnings appear if a gap, pin or wall looks too thin to print.

  4. 4

    Download and print

    Save the STL (or a 3MF with each leaf as its own coloured object). It is already flat on the bed: print it as it is, with no supports.

The settings

TypePrint-in-place: 45° cones on the knuckles act as the pin, so the hinge prints in one go and turns straight off the bed. Separate pin: a through hole of pin diameter + clearance.
LengthAlong the pin, end to end. 10-400 mm.
Leaf widthEach leaf, measured from the pin centre to its outer edge, so the open hinge is twice this wide.
ThicknessLeaf thickness. It can be at most about half the knuckle diameter, so the leaves can fold shut.
KnucklesHow many barrels along the pin, alternating between the two leaves (3-25). An odd count puts the same leaf at both ends.
Pin and clearancePin diameter and the gap left between moving parts. 0.3 mm is the default; most makers use 0.25-0.4 mm.
Knuckle diameterAuto by default: big enough for the pin with 2 mm of wall, and for the leaves to fold flat. Type a size to override it.
Screw holesHoles per leaf, the hole diameter, and a 90° countersink diameter (0 for a plain hole).
StopFolds shut (0-180°, stops flat) or a right-angle stop (90-180°), for lids and flaps that should stay open.

Rules of thumb behind the warnings

The tool warns, but does not stop you, when a part looks too thin for a typical FDM printer with a 0.4 mm nozzle. These are rounded rules of thumb, not limits: a tuned printer or a resin printer can go finer.

CheckRule of thumbSource
Gap across layersAt least two layers (2 x 0.2 mm), or the parts can fuse. The cone gap measured from layer to layer is the clearance x 1.41.common FDM practice; makers report 0.2-0.4 mm hinge gaps (blog.circuit.rocks, Prusa forum)
PinAt least 2 mm for a printed pin, 3 mm is safer.amfg.ai FDM design tips; UZH FDM design guideline
WallsAt least 1.2 mm.Xometry FDM design guide (1.2-1.5 mm for supporting walls)

Rules of thumb, not guarantees: every printer differs. Sources are named only to credit where each rule comes from; The3DAI is not affiliated with or endorsed by them.

Need a custom part that is not a hinge?

Describe it and get a printable STL with AI: a bracket, a knob, a holder or a figure. Or turn a photo into a 3D model. The AI generators use credits; this hinge generator does not.

Describe it: text to STL →Image to STL

More free 3D printing tools

STL viewerScale STL3D print cost calculator

Hinge generator FAQ

Set the size at the top of this page, keep the print-in-place type, and press Download STL. Open the file in your slicer: it is already lying flat with both leaves on the bed. Print it without supports, then flex it gently a few times to free the knuckles. No signup and no install.
Most makers use 0.25-0.4 mm, and 0.3 mm (the default) works on a well-tuned FDM printer at 0.2 mm layers. If yours prints fused, go up to 0.35-0.4 mm; if it is wobbly, go down to 0.25 mm. Print a small clearance or tolerance test first if you are not sure what your printer can do.
Instead of a straight pin, each knuckle of one leaf has a 45° cone that sits in a matching cone-shaped hole in the next knuckle of the other leaf. A 45° slope prints without support, and the gap between the cones is the clearance you set. The hinge comes off the bed already assembled.
When the hinge has to carry weight or be very stiff. A piece of 1.75 mm filament, a nail, a steel rod or an M3 bolt is much stronger than a printed pin. The hole is the pin diameter plus the clearance; for a tight fit, set the clearance to 0.1-0.2 mm.
Both work. With an odd number, the same leaf has a knuckle at each end, which looks like a door hinge and holds a print-in-place hinge together from both sides. An even number gives each leaf the same number of knuckles. More knuckles share the load, but each one gets shorter.
It adds a small block on top of one leaf's knuckles, so the hinge opens from flat to a right angle and no further. Use it for a box lid or a flap that should stand up on its own. The default stop lets the hinge fold shut and stops it flat.
Print it flat as it comes, without supports, with at least 3 walls and 20% or more infill. Slow the first layer and avoid elephant's foot: squashed first layers are the most common reason a print-in-place hinge does not turn. PLA and PETG both work.
No. The hinge is built in your browser. Only the open-source geometry engine (manifold-3d) is downloaded once from a public CDN. No account, no credits and no watermark.