Rapid, Low Cost Living Hinges with 3D Printing

Posted August 30th, 2016 by Bailey Jones

We’re privileged to be featured in a 3D Printing Report that was presented at the annual IDSA International Conference. We detailed our experience in creating a flexible electronics housing.

Design Firm: Bright Product Development

Application: Functional prototype for consumer wearable product

3D Printing Technology: Selective Laser Sintering (SLS) – outsourced

SLS PrototypeSLS Prototype

Bright was contracted to design and prototype a new wearable product including a wristband with integrated batteries and electronics. This watch band by Reserve Strap extends the battery life of the Apple watch and integrates the electronics and batteries into a flexible wristband in order to charge the watch while you wear it. For aesthetic and functional reasons, it was decided to build an articulating frame using five living hinges between electronics compartments to provide the necessary flexibility to wrap around a user’s wrist.

3D printing was used to manufacture a functional prototype of the wristband because it allowed the prototype to be created quickly and at low cost. Using Selective Laser Sintering (SLS) with Nylon 11 EX material enabled the part to be produced with the living hinges, providing very similar functionality to the production part.

living hinge partLiving Hinge Production Part

While the final production part would be made of injection molded PP, the prototype was 3D printed in nylon. The prototype unit was designed to conform to guidelines for 3D printing living hinges in nylon. A key guideline was the minimum wall thickness requirement for SLS nylon. This posed a challenge because the final part design called for living hinges which were slightly thinner than could be produced using SLS. To resolve this, the 3D printed hinges were manually filed down to the final part dimensions.

The 3D printed prototype enabled the performance of the prototype to be tested quickly and with low prototyping cost. In fact, when the 3D printed part was inserted into the TPE sleeve, the product was indistinguishable from the final product.

The SLS process is especially suited to living hinges since nylon is one of the few plastics that can withstand repeated bending.  Although Bright did file down the wall thickness in the hinge area after printing it, they discovered that the minimum SLS build thickness of .025” provided for an adequately functioning hinge without any further modification.

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