Perfect Hinge (fully printed, no hardware) 40mm

prusaprinters

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 fragile, for most of them. There's some reasons for that. First, you can't make the hinge beefy unless increasing drastically its size. Second, when a metal pin is added, the knuckles became the weak point because metal is way stronger than plastic, and the overall fragility increases despite of the metal pin. So the question is : how to get maximal strength with a constrained size fully printed hinge ? If the pin and the housing are thin, the hinge will be weak, if both are thick the hinge will be too big. So my guess was to distribute the strength between the pin and the knuckles around a variable size pin. The prototyping showed that it was a pretty good idea: you get stronger parts in a small area. As the variable thickness is balanced between the parts, you get the perks of a thick pin and a thick knuckle while that parts are not thick all along their shape. Obviously, the young modulus of thermoplastics does not allow to get the same strength as a metal hinge of the same size, as the printed part should be at least 80 times thicker to approach the reference strength of a steel hinge. But the variable shaft trick combined to a wedge-like shape produce a pretty strong hinge for the size and the 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.