These simple and graceful hinges have been designed with FreeCAD.

The print-in-place design provides ready to use, fully functional and strong enough hinges for many uses. No need to add a metallic pin.

Open the FreeCAD .fcstd file, adjust the parameters in the 'Dimensions' spreadsheet and generate your customized hinge. When some parameters combinations are impossible, FreeCAD will either ignore your choice or just crash.

Vertical play has to be set just above your printing layer thickness in order to have an empty layer between the two leafs.
Pin play has to be set according to the precision you can get from your printer and also depends of your nozzle size.

These hinges are intended to be printed vertically, so I put an angle between the two leafs to bring more stability during the printing.

Once printed, you must force or knock them a little to make the leafs rotate. If it's too hard or if the hinge breaks, increase the pin play.

An STL file is given as an example.

Feel free to use and share this design. Good design is hard work, donations are welcome.

Changelog:

Updated on Apr. 20th, 2020:

• Simplified some sketches
• fixed a bug due to redundant constraints

Updated on Apr. 12th, 2020:

• Improved design to increase the folding angle
• fixed a bug that appeared after a FreeCAD update