Growing a ‘Living Hinge’ with 3D Printing

One of the most fascinating examples of how far 3D printing has advanced is its ability to produce truly functional parts such as living hinges.

A living hinge, also known as a flexible hinge, is a thin, flexible piece of plastic that joins two rigid plastic parts or panels together. 

Living hinges are designed to be flexure bearing to allow for constant flexing of the part. Because flexible hinges are cheap to manufacture they are very common in disposable packaging (such as in egg cartons or baby wipes packs) and when properly designed, they should last the entire life of the product.

Hinges designed for polypropylene and polyethylene materials should follow a standard set of design guidelines to create a fully elastic hinge that will stand the test of time. The basics of good hinge design include a generous radius at the bottom of the hinge and a smaller recess at the top to enable easy folding-over and to prevent excess stress building up on the long side during folding.

As we began to mention in our previous posts, Objet's Connex multi-material 3D printer is the only 3D printing technology that is able to 'grow' living hinges as an integral part of a rigid model. The Objet Connex system jets a series of photopolymer resins with different mechanical and dimensional properties (and can even mix these in numerous proportions) during the print session to create a whole range of flexible and rigid parts  – with the more flexibly material laid down for the living hinge and the rigid material laid down for the solid panels. 

The box in the above picture features 5 separate living hinges printed in Objet TangoBlack material with the panel walls printed in the rigid Objet VeroWhite. The box folds together and has a snap-fit lid. The entire box is printed in a single build with no assembly or gluing required.

Living hinges created on Objet's Connex 3D printing systems can be used to accurately test and prototype:

• Caps and packaging
• Clips
• Left and right clamp shells

The power of such 3D printing technology is that it enables the prototyping process to match the speed and accuracy of computer led mass-production. Products that require the use of living hinges can now be designed on the CAD software and then verified in your hand within only a few hours. Haven't got your recess and radius angles just right? No problem. Simply tweak the CAD design and print again. Any design faults can now be fixed without hassle and well before a company invests in full scale production.

You can read more about the rapid prototyping of 'living hinges' right here.