Tips For Selecting flexible cable

Nov. 2, 2000
Selecting the right cable for a job is a matter of comparing old problems with new requirements.

By Harry J. Pizutelli
Olflex Wire and Cable Inc.
Fairfield, N.J.


Robot 900 cable from Olflex withstands the torsional stress from the bending and twisting motions in robotic applications. Torsional stress tests subject the cable to well over two million cycles, and flexing tests to more than five million cycles.

CRF cable jacketing resists acids, alkalis, and chlorine. It is applied mainly in cutting, milling, and grinding applications that use harsh cooling and lubricating fluids such as Skydrol and Blassocut.

Diverse automated manufacturing applications require flexible wire and cable to work in numerous environments and withstand millions of cycles. Continuous flexing, bending, and exposure to solvents and oils can shorten the life of the cable. Increasingly, cables must withstand such harsh conditions and the stresses and strains of widely varying applications.

These rising demands are due in part to the increase in speed and sophistication of automated equipment. For instance, in linear motion applications, cables must continuously flex back and forth in a C-track where the required bend radius may be as much as ten times the cable diameter. Worse yet, cable for robotic equipment is twisted clockwise and counterclockwise through angles ranging from 90 to 360°, and must be able to withstand high torsional stresses. However, specifying the proper cable for each application dramatically increases the life of the cable and the efficiency of the equipment where it is installed.

The first step in specifying cable is to consider the environment where the cable will be used. This dictates the jacketing material.

Then, specific factors of the application determine the type of flexible cable suited for the job. Following are the basic categories of flexible cable along with some common applications.
  • Continuous flex cable is intended for high-speed automated equipment such as industrial robots, pick-and-place machines, automatic handling systems, machine tools, and conveyor systems. Fine wire copper conductors ensure that the cable can withstand millions of flex cycles.
  • Flexible control cable permits easier handling and installation in confined areas. A variety of jacketing materials make it suitable for dry, damp, and wet conditions, as well as harsh environments with oils and chemicals.
  • Continuous flex cleanroom cable is halogen free, does not shed surface particulates or out-gas harmful chemicals, and its jacket does not hold a static charge that can attract dust, aerosols, water, and contamination.
  • Torsional robotic cable is designed for twisting and bending applications, without failure or fatigue, generally for more than two million cycles. It must satisfy flame, voltage, and aging requirements as well as withstand longterm twisting.
  • Servocable combines three different conductor types in one jacket for power, signal, and control to servomotors to obtain precision positioning over large or small distances. Power conductors and signal pairs are made of fine stranded copper conductors insulated with elastomeric compounds. Signal pairs are shielded with aluminum foil and a tinned copper drain wire.
  • Flexible data bus cable is used in manufacturing environments in device-level networks that connect plant floor devices to control systems. It includes Profibus, Interbus, and DeviceNet cables that support data rates to 1 Mbit/sec.
  • Flat festoon and round cable is specially intended for crane and conveyor systems. Neoprene or PVC jacketing makes it ideal for use in rugged outdoor applications such as construction machinery and dockyard installations.
  • European wire, cable, and cordage, better known as harmonized cable, is ideally suited for electronic and electrical equipment designated for export to European countries. The cable adheres to European Committee for Electrotechnical Standardization (CENELEC) guidelines, while complying with CE directives.

For cleanroom applications, continuous flex conduit made from a halogen-free polyurethane material does not shed particles and does not out-gas. Polyamide strain-relief connectors and bushings for clean rooms are shed-free, halogen-free, antistatic, and do not out-gas.

The signal pairs in servocable are shielded with aluminum foil, a tinned copper drain wire, and an optional tinned copper braid under the standard polyurethane outer jacket. Most servo cables can operate in temperatures from –30 to 80°C.

Cable tracks provide rigidity for unsupported lengths of cable and maintain alignment in continuous flexing applications. Inside track widths range from 0.59 to 9.84 in. to accommodate a wide variety of cable sizes.

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