Where Wire & Cable Is Used in a Robotic System

A robotic cell can contain several completely different cable applications. The wiring inside a stationary control cabinet may have very different mechanical requirements from cable traveling through an energy chain or routed along a six-axis robotic arm.

Because these functions can exist within the same machine, there is no single universal "robot cable." Cable selection should begin with the electrical requirements and the mechanical motion at the exact point where the cable will be installed.

Flexible Cable vs. Continuous-Flex Cable vs. Robotic or Torsion Cable

These terms are sometimes used interchangeably, but they should not be treated as the same thing. The difference is especially important in robotics, where a cable may experience millions of bending cycles or repeated twisting around a robot joint.

Flexible Cable

Flexible cable is designed to bend more easily than a typical fixed-installation cable. That can make it useful for machine wiring, installation around equipment, maintenance applications or situations involving occasional movement.

However, a cable being described as flexible does not automatically mean it is designed for continuous repetitive bending.

Continuous-Flex Cable

Continuous-flex cable is specifically engineered for repeated motion. These cables are commonly used in cable carriers, energy chains, gantries, pick-and-place equipment, automated machinery and other applications where the cable bends repeatedly in a controlled motion.

Conductor stranding, insulation, jacket construction and the way the cable components interact internally can all affect flex life.

Robotic and Torsional Cable

Some robotic applications add another mechanical stress: twisting. A multi-axis robot may rotate a cable around its longitudinal axis while simultaneously bending it.

A cable designed for millions of repetitive bending cycles in a linear cable carrier is not automatically suitable for torsional movement on an articulated robot. When the cable will twist, the manufacturer's torsion rating or stated robotic application should be reviewed rather than relying only on a continuous-flex designation.

This distinction is one of the most important considerations when specifying cable for robotics.

Continuous-Flex Control Cable for Robotics and Automated Machinery

Control cables carry signals and power between machine components, actuators, relays, switches and other devices. When those connections move repeatedly, a standard control cable may not provide the mechanical life required by the application.

Continuous-flex control cables are used in applications such as robotic cells, moving machine sections, gantries, material-handling systems and cable carriers.

One example is Belden 7401W MachFlex flexible control cable , a cable from Belden's MachFlex family intended for demanding motion applications.

Another option is Alpha Wire 852605 Xtra-Guard Flex continuous-flex control cable . Alpha's Xtra-Guard Flex family is designed for applications where repeated flexing is part of normal operation.

The correct control cable still depends on conductor count, AWG, voltage, shielding, environmental exposure, bend radius and the specific type of movement.

Continuous-Flex Cable for Gantry Robots, Linear Axes and Cable Carriers

Cartesian robots, gantry systems and other linear-motion equipment often route cable through an energy chain or cable carrier. Unlike a six-axis robot, the dominant stress in these systems is frequently repetitive bending along a defined path.

This is a classic continuous-flex application. The cable must tolerate repeated travel while maintaining the manufacturer's required minimum bend radius.

A product such as LAPP 8910044 ÖLFLEX FD 890 continuous-flex cable provides an example of a cable intended for cable-chain and continuously moving power/control applications.

Cable-chain suitability should still not be confused with torsion capability. A cable can perform very well in repeated linear motion without being intended for repeated twisting around its own axis.

Servo Motor and VFD Cable in Robotic Systems

Servo motors and variable-frequency drives are common throughout robotics and automated manufacturing. Their cabling must handle motor power while also operating in an electrically noisy environment created by rapidly switched drive signals.

Shield construction, grounding, insulation, voltage rating and cable geometry can all be important when connecting drives and motors. When the motor or cable itself moves, the mechanical requirements become just as important as the electrical ones.

Belden 29502F high-flex VFD cable is an example of a VFD cable designed for applications requiring increased flexibility and resistance to demanding industrial environments.

In a robotic system, VFD or servo cable may be used between drives and motors, on moving axes or in machinery where both motor power and repeated movement must be accommodated. The exact motion requirements should always be checked against the manufacturer's cable specifications.

Encoder, Feedback, Sensor and Signal Cable

Robotic motion depends on accurate feedback. Encoders, resolvers, limit switches, proximity sensors and other devices continuously report position and operating conditions back to the controller.

These signals may operate at relatively low levels and can be located close to motor and drive wiring. In those environments, shielding can help manage electromagnetic interference when the connected equipment and installation require it.

For moving signal and data applications, Alpha Wire 86502CY Xtra-Guard Flex shielded continuous-flex data cable provides an example of a multi-pair cable designed for repeated movement with foil and braid shielding.

Cable selection for encoder and sensor systems should also consider pair configuration, capacitance, shielding, conductor size, connected-device requirements and the motion profile.

Industrial Ethernet Cable for Robots, PLCs and Machine Vision

Industrial Ethernet is increasingly used throughout automated manufacturing for PLC communications, machine vision, sensors, controllers, remote I/O and networked production equipment.

The cable required for a stationary Ethernet drop can be very different from the cable required on a moving robotic axis.

High-Flex Industrial Ethernet

Ethernet cable installed on moving equipment must maintain its electrical transmission characteristics while repeatedly flexing.

Belden 7938A Cat 5e high-flex industrial Ethernet cable is an example of a shielded Ethernet construction intended for high-flex industrial communications applications.

Applications may include moving network connections, machine vision, robotic equipment and automated machinery when the cable's published ratings match the required motion and network performance.

Stationary and Occasional-Flex Industrial Ethernet

Not every Ethernet connection within a robotic cell moves continuously. Cabling between PLCs, sensors, network switches and stationary machine components may require industrial environmental resistance without needing continuous-flex construction.

LAPP 2170893 ETHERLINE industrial Ethernet cable is a 22 AWG shielded Cat 5e construction supporting PROFINET, EtherCAT, EtherNet/IP, Power over Ethernet and PoE+. It carries a 600V UL AWM rating and is intended for fixed installation and occasional flexing rather than continuous robotic movement.

That distinction illustrates an important point: an industrial Ethernet cable can have robust electrical ratings and resistance to industrial environments without being a continuous-flex robotic cable.

Robot Dress Packs and Cable Management

A robot dress pack organizes and routes the cables and other utility lines traveling along the robot arm. Depending on the system, the dress pack can contain motor power, feedback, Ethernet, control wiring and additional service lines.

Cable management is critical because the cable's installed path determines the mechanical stress it actually experiences. Even a correctly selected continuous-flex cable can have its service life reduced if it is installed below its minimum bend radius, pulled too tightly, allowed to rub against nearby equipment or forced into motion for which it was not designed.

When evaluating cable for a dress pack, consider the movement of each robot joint rather than simply classifying the entire robot as a continuous-flex application. Some sections may bend repeatedly while others may experience significant torsion.

For twisting sections of articulated robots, verify that the cable manufacturer specifically supports the required torsional motion. Do not assume that every cable marketed for cable carriers or continuous flex can also tolerate repeated twisting.

Cable Requirements by Robot Type

Six-Axis Articulated Robots

Articulated robots can produce some of the most complex cable movement because several joints may rotate in different directions. Cable may experience bending, twisting and changes in bend radius as the robot moves through its work envelope.

Dress-pack routing, torsion capability and strain relief are therefore particularly important.

Cartesian and Gantry Robots

Gantry systems usually move along linear axes. This makes continuous-flex cable designed for energy chains and repeated linear bending especially relevant.

Travel distance, acceleration, bend radius and cycle count should all be considered.

SCARA Robots

SCARA robots combine rotary and linear movement. Depending on cable routing, sections of the system may require continuous-flex performance while other areas can be subjected to rotational movement.

Collaborative Robots

Collaborative robots can place additional emphasis on compact routing, small cable diameters and tight installation spaces. Power, data, sensor and end-of-arm-tool connections still need to be evaluated according to their individual motion requirements.

Welding Robots

Robotic welding environments can combine repeated movement with heat, abrasion, weld spatter and high levels of electrical noise. Cable construction and routing must therefore address both mechanical movement and environmental exposure.

Pick-and-Place Systems

Pick-and-place equipment can run extremely high cycle counts. Even when the movement is relatively simple, continuous repetitive motion makes flex life and bend radius important selection factors.

Common Causes of Cable Failure in Robotics

Many premature cable failures in automated machinery are mechanical rather than purely electrical. Understanding those failure modes can help prevent downtime.

• Conductor fatigue: repeated bending can eventually break conductor strands if the cable is not designed for the required cycle life.
• Jacket cracking: repeated motion, temperature or incompatible oils and chemicals can damage the cable jacket.
• Abrasion: rubbing against robot components, cable carriers or nearby equipment can wear through the outer jacket.
• Excessive torsion: twisting a cable that is intended only for linear flexing can damage conductors, insulation or shielding.
• Incorrect bend radius: routing a cable tighter than the manufacturer's specified minimum radius increases mechanical stress.
• Shield damage: repetitive movement can degrade shielding if the cable construction is not intended for dynamic service.
• Improper strain relief: pulling forces transferred directly into conductors or terminations can cause premature failures.
• Environmental attack: oils, coolants, chemicals, heat, UV exposure or weld spatter can damage cables not designed for those conditions.

How to Select Cable for a Robotic Application

A useful cable specification should describe both what electricity or data the cable must carry and what will physically happen to the cable during operation.

1. Identify the Type of Motion

Determine whether the cable will remain fixed, move occasionally, flex continuously in a controlled direction, twist around its axis, or experience a combination of bending and torsion.

2. Determine the Electrical Requirements

Identify the required voltage, conductor size, number of conductors or pairs, current, shielding and signal or communications requirements.

3. Define the Mechanical Requirements

Review minimum bend radius, travel distance, speed, acceleration, expected cycle count and, for rotating applications, the required degree of torsional movement.

4. Evaluate the Environment

Consider operating temperature, oil, coolant, chemicals, abrasion, UV exposure, moisture, weld spatter and any other conditions the cable may encounter.

5. Consider Signal Integrity and EMI

Motors and variable-frequency drives can generate electrical noise. Encoder, feedback, instrumentation and data circuits may require shielding or specific cable geometry based on the connected equipment.

6. Verify Required Approvals and Ratings

Confirm the applicable UL, CSA, NEC, voltage, flame and equipment requirements for the installation.

Do not select a robotic cable based solely on voltage and conductor size. For example, a 600V cable may satisfy the electrical requirements of an application while still being unsuitable for continuous flexing or torsional movement.

Examples of Cable Types Used in Robotics and Automation

These examples illustrate different cable constructions and application types. They should not be treated as interchangeable. The correct cable must be selected according to the electrical, mechanical and environmental requirements of the specific robotic system.

Choosing the Right Cable Can Reduce Robotic System Downtime

Cable is often a relatively small component of a robotic system, but a cable failure can stop an entire production cell. Using ordinary flexible cable in an application that actually requires continuous flexing or torsion can lead to conductor fatigue, intermittent signals, damaged shielding and unplanned maintenance.

The most reliable approach is to treat cable movement as part of the original specification. Determine whether the installation is fixed, occasionally flexing, continuously flexing or torsional, and then select a cable whose manufacturer supports that type of service.

Robotics also frequently requires more than one cable family. The same cell may use continuous-flex control cable, VFD cable, shielded feedback cable, high-flex Ethernet and stationary industrial communications cable.

Need Help Selecting Cable for Your Robotics or Automation Application?

Ramcorp Wire & Cable can help source continuous-flex, control, VFD, industrial Ethernet, instrumentation and specialty cables for robotics and automated machinery.

If you have an existing cable, send us the manufacturer and part number. For new applications, provide the conductor size and count, voltage, shielding requirements, required length, type of motion, minimum bend radius, torsion requirements and operating environment.

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