Carrier systems that twist, from igus inc., can be used to handle cabling on robots. Modified inner and outer plate construction increases carrier flexibility.

The performance demands on electrical cables and hoses constantly increase. The shrinking size of equipment and facility space often mean cables must bend in a tighter radius. Requirements for higher productivity mean cables and hoses must reliably perform over longer cycle periods.

Cable carriers have often been used to protect these energy transmitting components of a motion system. To meet the increasing demands, though, carrier manufacturers are developing new designs and new materials to help users better manage their cables and hoses.

Handling the bends

The limiting factor in how tightly a carrier can bend is usually the cables or hoses it houses. Each type can only bend so far before they sustain damage, such as conductor breakage, plus cable entanglement and wear from back-andforth motion. The typical minimum bend radius of a high-flex cable is seven to ten times its outer diameter.

Shelves, separators, mounting brackets, and strain relief components like these from Kabel-Schlepp America, help reduce damage to cables and hoses in a carrier.

To solve these problems manufacturers are offering cables and hoses specifically for use in carriers. These offerings include power-supply cables with special extruded materials that fill in the space between the conductor bundles with a flexible, strong plastic inner core to hold the bundles in place.

The conductors in the cables may be twisted, braided, or bundled for extra resiliency. In addition, the cables and hoses have varying outer diameters, conductor counts, gauges, and transmission properties. Thus, users can select from cables with a small bend radius of five times (or less) the outer diameter.

Harnesses and conduit-support accessories are also available to handle and support cabling. Some vendors offer a complete system, with shelves, separators, mounting brackets, and strain relief components. In general, the conduit carrier should be at least 20% larger than the cable and hose bundle.

Users should also be careful to correctly match the bend radius to the application to prevent a condition known as the polygon effect. This happens when the bend radius is too tight and the carrier crimps as it bends, taking on a polygon shape before it fails. The manufacturer’s application engineers can offer selection advice.

Going around in circles

In other applications, rolling carriage systems provide the support carriers need. Such a system keeps all loading off the cable carrier, except acceleration and deceleration loads. From Kabel-Schlepp America, this increases system longevity.

New carrier designs accommodate the twists and turns found in some motion systems, such as articulated robots. In some of these carriers, the design of the linking plates’ inner and outer construction has been modified to increase the flexibility of the carrier along the rotating arc. Often the circumference is also adjustable.

Requiring little space, some of these designs handle circular speeds to 8 mps with a spiral configuration capable of coiling 540 degrees around. Chain width and bend radii are variable, and the conduits are accessible from either side of the carrier.

Going the distance

Travel distances for carrier systems are lengthening. Distances of 700 ft or more are no longer the exception. Depending on weight of the cables (fill weight), unsupported strength, and stability, a carrier can travel short distances without the upper portion rolling so far back, or sagging, that it touches the lower portion. On long travels, however, the carrier will sag until it runs on itself and possibly loses alignment. The usual solution to maintain alignment has been a guide trough. But this adds cost to the system. And, in other cases, there is not enough room in a facility to accommodate it.

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