A living hinge is a thin flexible hinge (flexure bearing) made from the same material as the two rigid pieces it connects, rather than cloth, leather, or some other flexible substance. It is typically thinned or cut to allow the rigid pieces to bend along the line of the hinge. The minimal friction and very little wear in such a hinge makes it useful in the design of microelectromechanical systems, and the low cost and ease of manufacturing makes them quite common in disposable packaging.
Plastic living hinges are typically manufactured in an injection molding operation that creates all three parts at one time as a single piece, and if correctly designed and constructed, it can remain functional over the life of the part. Polyethylene and polypropylene are considered to be the best resins for living hinges, due to their excellent fatigue resistance.
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Using the Protomold cross section as a template, these different thicknesses should work well for different prototyping methods to make hinges. Cast urethane, 'PP like' resin 0.8mm, CNC polypropylene 0.5mm, molded polypropylene 0.3mm, SLS (nylon 12 PA) 0.3mm.
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