Cable management is often an afterthought when designing new machines or retrofitting existing systems. Cables are bundled and cable trays are added to keep them in place, but the impact of the required wiring is often overlooked until the design process is nearing completion, when costs and overall equipment footprint become apparent. During commissioning, engineers may spend more time wiring the system, inspecting cables during troubleshooting, and incurring additional costs due to the lack of adequate cable lengths.
Evaluating cabling before commissioning offers significant benefits beyond providing better enclosures and a cleaner factory floor. Strategic cable management planning during the design phase can result in a cleaner system, reduced cable count, and the elimination of potential points of error and failure.
The most effective cable management strategy begins with selecting intelligent components. Engineers should minimize cabling requirements in their applications when selecting input/output (I/O) terminals, fieldbus systems, motion control devices, and other machine components.
Figure 1: Single-cable technology provides power and signals to HMI hardware, servo systems , and other field components through various connector types, thereby minimizing cabling issues. Image source: Beckhoff.
Reduce cable demand
It's important to remember that most cabling in a factory environment is used to provide power or network signals. While it involves a lot of work, it's simple to implement and doesn't require connecting sensors, control cabinets, or other equipment.
In most cases, the excess cabling is due to shortcomings in industrial equipment and networks, rather than the control engineers. For example, traditional Ethernet-based fieldbuses, such as EtherNet/IP or Profinet, require multiple managed switches. This often results in the inability to connect cables directly from the control cabinet to field components without using cascading switches or hubs. Consequently, this necessitates configuring more hardware for the system and introduces additional points of failure. Similar issues arise when powering machines.
When attempting to improve cable management in a system, selecting suitable fieldbuses and individual components that use fewer cables is necessary to accomplish the task. Engineers should first consider fieldbuses and I/O systems, prioritizing those that offer flexible topologies and reduce the need for switches.
EtherCAT industrial Ethernet systems offer flexible topologies without the need for additional nodes. EtherCAT can also integrate various third-party devices, from drives to I/O and field devices, and share data with the main controller. Furthermore, EtherCAT allows for easy data collection from legacy devices configured with other protocols without reconnecting cables back to the controller. Integrated hardware and software gateways enable data access from various fieldbus and industrial Ethernet systems to the EtherCAT network.
Choosing a fieldbus based on these factors is only the first step in a long journey. The network delivers optimal results when used in conjunction with components designed to reduce cabling. Single-cable technology (OCT) and pluggable I/O terminals are two key components.
Power and data are provided using single-cable technology.
While it is difficult to completely eliminate all cables in the field, the number of cables can be significantly reduced; single-cable technology provides an important tool for achieving this goal.
Over the years, various products have been introduced to provide power and signals through a single cable. Since 2003, Power over Ethernet (PoE) has been the IEEE Ethernet standard IEEE 802.3, and this technology has been applied in industrial applications. Other types of cables combine power with USB 2.0 and Digital Video Interface (DVI) signals for Human Machine Interface (HMI) hardware. There are also types of cables that can power and receive feedback from servo drives, or directly from a control cabinet or distribution module to a servo motor with an integrated driver. Because these cables can span over 100 meters, they must be provided with robust wire sheaths to ensure they can withstand the abrasion of industrial environments and reduce the likelihood of damage and potential points of failure.
For example, EtherCAT can power applications from 24 to 400Vac or 600Vdc and carry current up to 64A, providing two voltages for EtherCAT slaves and connected sensors or actuators. In this case, the two voltages—US for system and sensor power and UP for actuator peripheral voltage—are electrically isolated from each other, and each voltage can provide up to 3 amps of current to the connected components.
Streamlined motion architectures (such as distributed servo drive systems) can be daisy-chained, but may require separate distribution modules. However, some power distribution modules can supply signals from the control cabinet to up to five drives. EtherCATI/O modules with an IP67 rating can be installed externally to the cabinet and close to the machine, thus limiting cabling to a smaller area while providing signaling and power to multiple EtherCATI slaves.
EtherCATP (EtherCAT Ethernet Communication with Power Supply, ECP) technology supports a variety of connector families, including ECP (EtherCAT with integrated 24Vdc power supply) and ENP (EtherCAT Ethernet without power supply, no integrated 24Vdc power supply). These designs are very similar to the trapezoidal power core element used for power supplies. ECP cables are suitable for EtherCAT environments with high voltage requirements. ENP cables can be used with any Ethernet-based protocol, such as EtherNet/IP or Profinet, as an open solution. Both reduce cabling when used with components powered via single-cable technology.
Figure 2: Some pluggable I/O terminals are half the size of traditional hardware, and by eliminating point-to-point wiring, they also reduce points of failure while minimizing footprint.
Pluggable I/O terminals reduce cabling within the cabinet.
Besides eliminating field cables and switches, simplifying control cabinet cabling makes the system cleaner and reduces points of failure. Cabinets become cluttered when there are many I/O points, complicating cabling and increasing the likelihood of errors. Direct insertion of wireless I/O terminals into signal distribution boards is a significant advancement.
Using prefabricated cables with connectors featuring dedicated plugs for power and control signals, cabling is distributed from the wiring board to plug-in terminals. This method offers a particularly good return on investment for integrated production machinery. It aims to eliminate point-to-point cabling within cabinets through compact, application-specific electromechanical designs. By embedding I/O systems into the machine, machine manufacturers and end-user manufacturers can also minimize cable management efforts, labor costs, and potential wiring errors.
These pluggable terminals are typically more compact than DIN rail-mounted I/O, requiring up to 50% less space in some cases. This reduction in wiring also results in a corresponding reduction in equipment footprint, a definite benefit of the pluggable terminal approach.
This demonstrates how fieldbus and I/O technologies can effectively alleviate cable management issues in electrical enclosures. However, board-based I/O systems are best suited for new installations rather than retrofits. Single-cable technology reduces field cabling, whether in brownfield or greenfield applications.
Intelligent cable management and intelligent machine design
Innovative networking technologies eliminate unnecessary cabling. If these factors are considered early in the retrofitting or new machine design process, engineers are far less likely to face cable management problems later on. These cable reduction strategies are still emerging technologies. While they already offer many benefits, functionality will continue to increase as the technology matures.
Plug-in I/O terminals and single-cable solutions enable engineers to build control cabinets, significantly reduce wiring, and leverage single-cable designs to achieve fieldbus architectures that simultaneously power and provide data.
The automation industry is rapidly generating simpler products for every step of the engineering design and implementation process. Cable management should not be a field for hindsight.
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