Perfect Hinge (fully printed, no hardware) 40mm

A Hinge that can be printed in a single step. The main size is 40mm that fits general tapered head screws. 

What makes this hinge perfect ?
3D printed hinges are generally fragile due to a few inherent limitations. Firstly, it’s challenging to make the hinge robust without significantly increasing its size. Secondly, when a metal pin is incorporated, the knuckles often become the weak point. This is because metal is much stronger than plastic, so despite the presence of a metal pin, the overall fragility can still be high.
 

So, how can one achieve maximal strength in a hinge with constrained size using 3D printing? If both the pin and the housing are thin, the hinge will be weak. Conversely, if both are thick, the hinge will be too bulky. My approach was to distribute the strength between the pin and the knuckles using a variable size pin. Prototyping has shown this to be a promising strategy: it allows for stronger components within a compact area. By balancing the variable thickness between the pin and the knuckles, you achieve the benefits of both a thick pin and thick knuckles without excessively enlarging the hinge.
 

Naturally, the Young's modulus of thermoplastics means that a printed hinge cannot match the strength of a metal hinge of the same dimensions. For a plastic hinge to approach the strength of a steel hinge, it would need to be at least 80 times thicker. However, the combination of a variable shaft and a wedge-like shape results in a hinge that is significantly stronger relative to its size and material.

That hinge was awarded as Runner Up Prize int the Instructables 3D printing Contest summer 2016 :)

Notes:

Please print the hinge standing vertically. You can use drywall screws, like I did on the picture above. Otherwise the countersunk hole is diameter 4mm (1/8"). Just force the hinge for its first opening and enjoy.