My attempt of making a hinge. I do not know how strong it is but it works for now at least. It a openscad thingi so you can mod it. It only hinges at 90 deg but that is what i needed ;-)

Print the part in one go (standing up makes them a bit stronger). They overlap a bit so the create support for each other while printing. I used 3mm abs to keep them together (melting the ends so that they won't slide out)