Wiring Harness News WHN Sept-Oct 2020 WHN Sep-Oct 2020 - Page 29

INDUSTRIAL INFO-TAINMENT Wiring Harness News SEPTEMBER/OCTOBER 2020 29 Strain-Relief: Design Tips for Durability and Aesthetic Appeal By Christian Brown fictiv ______________________________ You reach over to plug in your phone, and you feel that spark – and not in a good “I love this product!” kind of way. The wire is broken, and yet another charging cable is about to make its way to a landfill, while you have to make a midnight run to the store to be ready for your 6 a.m. Skype conference with Japan. For such a simple idea, strain relief designs have a huge impact on users, right or wrong. And it’s not only in consumer products where we can blame gorilla-like users; even NASA has these issues. When you need your cables to last a long time, how can you create a reliable connector? Can you do this without demolishing that beautiful aesthetic your team has worked so hard on? The following tips will get you the answers you need, and still have you out the door in time for happy hour. Why Do Good Cables Go Bad? Tight bends in the cable near the connector cause high stress, fatigue, and failure. The stiff connector interfaces with a very flexible cable, and the point of contact ends up taking the brunt of the movement. Every tug is concentrated on a single point. Strain is inversely proportionate to the radius of curvature – a fancy way of saying the tighter the bend, the more risk of failure. An easy way to visualize this is to take two paper clips out of your desk drawer and straighten them (for those who want a more detailed, scientific approach, check out the work done by The Royal Institute of Technology in Sweden). With the first paperclip, try bending the wire around a pencil, straightening it, and repeating this several times. The paperclip will bend easily, and is unlikely to break. With the second paper clip, make tight bends, back and forth, and see how many times it can be bent without breaking – my personal best is five repetitions. The lesson is clear: repeated tight bends = failure. The Solution? Strain Relief Strain-relief on cables offers mechanical support to the cable, pro- _____________ Continued on page 31