Cables are often the last component to be considered when designing moving machines or equipment. It shouldn’t be this way, because they supply the electric power and electronic signals vital to almost all modern motion designs. That’s why cables compromised by extreme temperatures, chemicals, abrasion, or EMI can bring entire systems to a screeching halt, costing both time and money. Following are some real-world questions from engineers in the field, answered by W. L. Gore & Associates Inc., Landenberg, Pa., for getting the most out of cables that must perform in tough environments.

80% of our cable failures happen at the backshell. Are there any new developments in this area?

The backshell of a cable — an end piece that joins the cable conductors with various connectors — can fail under EMI, excessive strain, a compromised environmental seal, and other issues. EMI is probably the most common issue — particularly because of how some cable shields transition to the backshell. Several new designs and process solutions address these issues. One way to combat environmental sealing problems is with moulds or to pot the inside of the backshell.

Ideas on how to increase cable life

Tangling occurs in applications where cables are in motion, particularly if they are in a cable chain or the cable is just moving. Packaging is critical; individual wires should be packaged into a round cable jacket, or at a minimum, a shrink tube or expandable sleeving should be used to hold the wires together. If the application involves continuous motion or repeated flexing with rests in between, be aware that moving cables generate kinetic energy: This kinetic energy results in the wires having to work to eliminate the stress. This can actually cause the cables to move, corkscrew, and tangle unless carefully managed. The most effective way is to package them into a planar cable, also called a flat cable. Planar cables are revolutionizing the linear motion, high-flex arena because they take individual round constructions and eliminate the need to put dividers and shelves into a cable chain to keep round constructions from tangling.

Though a full answer to this question would require more information, here are a few tips. First, identify the mechanical constraints. In a flexing application, the type of motionis the first thing to classify. Is it a rolling flex, torsion, or tick-tock motion, or is a person attached to it? If it’s a rolling flex which encompasses 75% of automated motion applications.

 

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