Tips for Avoiding Cabling Failure
POSTED 01/22/2024 | By: Emmet Cole, A3 Contributing Editor
Cabling is a key component of industrial motion control and automation systems. Responsible for transmitting power and data, cabling connects components within machines such as industrial robot arms. Cabling also enables machines to communicate with each other, exchanging the information required to make flexible, data-driven manufacturing possible.
Cabling is also the most common point of failure in motion control and automation systems.
In part, that’s because cables are often required to move to perform their function, which is why it’s so important to consider physical length, bending radius, and durability requirements from the outset.
Overuse and mechanical stress are common causes of failure that can be avoided by selecting the right cable for your application, says Matt Burns, technical marketing director, at Samtec, a leading manufacturer of connector and cable products with its headquarters in New Albany, IN.
"Different applications have different requirements. It’s important to specify whether your application requires cabling to move and how much. Movement creates additional stresses on cables, as do high vibration environments.”
Exceeding a cable’s minimum bending radius can cause cracks and breaks in cable insulation and conductors. While allowing for movement, it’s also important to try and achieve the shortest possible cable length. Unnecessarily long cables will increase signal loss, degrading signal integrity and reducing overall efficiency.
Cables are being asked to transmit more data than ever, says Matthew Simons, director at Alysium-Tech GmbH, a leading supplier of cable assemblies and interconnects specialized for machine vision applications, with its headquarters in Nuremberg, Germany.
“If you look at speeds of transmission given the total data volume to be transferred, it has increased exponentially over the years. Applications like high-speed vision for quality and control applications, demand rich depth of color, higher resolution and larger areas of interest, which all create a significant volume of data to transmit through your assembly. As data rates increase further, this becomes more demanding.”
The main challenge, explains Simons, is ensuring that cables meet the industrial requirements, such as high flexibility, robustness, vibration and dust resistance or higher temperature resistance, whilst achieving perfect data transmission properties.
“Consider a welding application with a camera mounted on the robot arm. In such applications operation at high temperatures is required. There are flexing requirements including torsional loads. Longer lengths are required, as the computer is typically located away from the robot.”
In addition, the welding process creates significant electrical noise, so the cable needs to have the highest EMI (electromagnetic interference) protection and EMC (electromagnetic compatibility) properties.
“Ensuring that all these requirements are reliably realized in the smallest form factor, with the best product handling ability, for the best price, is Alysium’s primary goal. We work as closely as possible with our customers to ensure that they get the most suitable cabling for their specific requirements,” says Simons.
For many straightforward applications standardized solutions such as DB9 or HDMI cables will work, says Samtec’s Burns, but “everyday cabling” should be avoided when it comes to advanced, high-speed, high-bandwidth automation and motion control.
“When it comes to the high-speed, high-performance applications that we typically deal with, we develop application specific cabling solutions based on a collaborative design effort with our customers and partners. We propose the best solution depending upon their application requirements.”
It’s a risk to use consumer-grade cabling in industrial environments because application specific requirements have not been considered in their design, warns Alysium-Tech's Simons.
“Consumer grade cables and connectors have been built for consumer applications, like connecting an external hard disk drive to your PC at your desk. The benefits of the utilization of these standardized protocols are obvious: they are widespread and standardized, manufactured in large quantities, hence economical in terms of cost performance, and familiar. The deployment of standard materials in the radically different environment of a production facility is however unlikely to meet industrial expectations.”
The most obvious physical difference between consumer and industrial products are elements like screw locking, which enable a cable to be robustly connected to a device. The differences in design considerations exceed these standard elements, however.
“Externally, the consumer and industrial cabling may look relatively similar, but the design steps considered in their creation are very different. To take just one example, in consumer electronics, the pins are typically held together in the contact assembly by press fit. We use molded contact assembly so that the pins are fixed, meaning that the pins stay in position, even if larger cables are used (for longer lengths) or greater forces are applied during vibration or acceleration.”
Since cables are being expected to carry more data than ever before across high speed networks, “less than perfect cables” are no longer up to the task, says Ted Brunk, Global Sales Manager, Quabbin Wire & Cable Co., Inc.
“At higher speeds, the entire capability of the cable is used. A cable that is not quite to specification won’t work. When we are designing cables for automation applications, the flex life and environmental requirements have to be met without compromising the electrical performance.”
As the Internet of Things (IoT) and the Industrial Internet of Things (IIoT) continue to expand the reach of ethernet, cable designers must remain flexible and be in constant search for new materials, Brunk notes.
“The days of having a ‘set’ product line are over. The biggest challenges — and rewards — will go to manufacturers who are able to provide flexible cables and flexible manufacturing processes. Single Pair Ethernet cable will eventually reach the outer edges of all networks in factory, process and building automation, but many two-pair and four-pair cables will still be used as the backbone leading up to the edge of the network. All these cables must be built with the suitable conductor insulations, shielding and jacket insulations to survive and protect mission-critical communications.”
For more information and cabling tips, check out this guide from the A3 archive.