I am trying to design a living hinge for a small business card box.

Printing with layer lines parallel to folding axis yields a strong print but the hinge fails. I have tried to modify the hinge with little success and changing print orientation does not help me either.

Attached are images of the area.

Any help is greatly appreciated.

Thanks

(Note: I prefer working in metric but the person who it's being made for began in imperial and wants imperial measurements)