Manufacturing AUTOMATION

The modular PLC: Current applications and where the technology will be applied next

July 8, 2024
By Treena Hein

Powerful modular PLCs connect using globally-open industrial protocols, extending connectivity beyond a single manufacturer’s scope. (Photo: Omron Automation)

The modular PLC offers many benefits in a manufacturing plant, from flexibility, ease of upgrade/expansion and custom setups to simplified troubleshooting and enhanced system dependability.

Specifically, this type of PLC is an advantage in today’s manufacturing environment through its ability to connect to current fieldbuses and hardwired safety. This enables factories to start becoming more flexible, explains Thomas Kuckhoff, product manager of core technologies at Omron Automation, in a non-intrusive manner, “by integrating into existing architectures.”

Tyler Burke, product manager for industry management and automation at Phoenix Contact, explains that modular PLCs have seen wider adoption due to the shifting boundary between a PLC and a PC. He explains that devices with additional PC functionality are available on several of the most recent control systems, some coming with Linux preinstalled and some with Windows – and direct datalogging on these devices is one of the new capabilities made possible by this blending of PC and PLC.

“Additionally, it’s enabling the controller to run programs from many sources,” Burke points out. With modular PLCs, “customers have frequently logged data using open-source solutions before adding a graphical front end. Previously, a local PC would have been used to accomplish this kind of solution.”


Kuckhoff adds that modular PLCs which support multiple communication protocols set up companies for the future. They’re “suitable for tomorrow’s manufacturing environment,” he says, as they offer the flexibility to use plug-and-play hardware as well as drag-and-drop programming, allowing factories to integrate newer technology on their own schedule.

Burke agrees that the ability of modular PLCs to support multiple protocols ‘futureproofs’ devices, enabling them to keep up as demands and requirements change. Control systems are engineered to last over a decade, he says, so software needs to enable new applications and not hold existing control systems back. The fact that PLCs are slowly adding more PC functions, he says, makes the futureproofing all the more apparent.

Modular PLCs allow for scalability of and customization of automation when the manufacturer needs to expand operations. (PHOTO: Phoenix Contact)

Newest applications

Based on what Burke is seeing in plants these days, most of the latest modular PLC applications entail novel methods of data collecting or modification. “The push toward digitalization has resulted in increased data collection from devices in order to enhance machine efficiency and accurately anticipate problems,” he explains. “Applications have been seen where OEMs feed data to a database, including temperature and cycle counts. This enables them to keep an eye on a machine’s condition and alert clients when maintenance is necessary.”

In Kuckhoff’s view, the newest applications where modular PLCs are becoming anchors in automation architecture are the applications that require all three of the defining qualities of a truly modular PLC design: IO construction fluidity, programming software unification and PLC CPU flexibility. One example of this is in plants that are being updated or redesigned, where modular PLCs simultaneously communicate to a breadth of different fieldbuses required to connect to existing equipment and integrate higher-performing safety systems (e.g. devices on Fail Safe over EtherCAT). Other examples are plants where novel technologies are being integrated into new products such as electric or hydrogen-powered vehicles and batteries, or in manufacturing labs/design centers.

An example of how the modular PLC can empower faster adaption to new manufacturing scenarios can be seen in the area of high-speed/high-quality part traceability at high volumes. Kuckhoff explains that it’s now standard to use handheld scanners that quickly connect through open protocols and are intuitively integrated into a modular PLC. “In many food and beverage facilities, we have seen these handheld scanners be installed without interrupting downtime,” he says, “a result of the defining qualities of a truly modular PLC design.”

Not all alike

There is some variation of modular PLCs on today’s market, and Kuckoff notes the real source of power for modular PLC users is in the number of connections that they can access out of the box. That is, the top 25 percent of high-performing modular PLCs not only have hundreds of off-the-shelf IO part numbers for plug-and-play installation (while also having a single software with drag-and-drop programming).

And the very most powerful modular PLCs? They connect using globally open industrial protocols, extending connectivity beyond a single manufacturer’s scope, says Kuckhoff.

“By using EtherCAT, Fail Safe Over EtherCAT, EtherNet/IP, CIP Safety, IO Link, MQTT, OPC UA and SQL, all as each was intended to be used, the most-powerful modular PLCs have been designed to adopt new technologies quickly from the very beginning and without introducing undue complexity to the factory floor,” he explains. “Manufacturers of these modular PLCs know this all too well, and users can expect a lot of third-party connectivity guides and function blocks to help bridge the gap between manufacturers while maintaining the modular PLC off-the-shelf ethos.”

Modular PLCs support multiple protocols ‘futureproofs’ devices, enabling them to keep up as demands and requirements change. (PHOTO: Phoenix Contact)

As an example, Kuckhoff shares the story of a manufacturing team that needed to improve the reliability of the AC motors on their conveyor system. The existing modular PLC was able to accommodate the replacement of a previously-installed IP67 remote IO master with an IP67 remote IO master that communicates over IO Link. “The engineering team was able to use sensors already installed on the AC motors that were previously only showing if the motor was on or off through the current draw,” Kuckhoff explains. “The team modified the PLC program to use IO link to read the exact current draw of the motor. The team then pushed the update to the modular PLC during planned downtime. Now, the factory floor can trend the current load on the motors and set acceptable thresholds for operation, shifting maintenance from reactive to proactive.”

Kuckhoff notes that this solution was able to be deployed without any capital costs and without interrupting production, and calls it “textbook modular PLC.”

But while being able to leverage multiple manufacturers’ breakthrough technologies through open protocols is valuable with modular PLCs, Kuckhoff adds that what’s often more valuable is the confidence that new technology will quickly connect with the current design.

He explains that modular PLC manufacturers, due to the inherent design of using globally-open industrial protocols in the PLC development, stay very close to the standards that govern these networks. This ensures that factories have allies at the table when these networks evolve and that three of the defining qualities of a truly modular PLC design are not compromised during revisions.

Future applications

Looking at where the use of modular PLCs in manufacturing is headed, Kuckhoff says it’s an exciting time.

He first explains that there has been a lot of discussion around open networks, specifically about connecting to production assets and moving data from the factory floor to a central location for data analytics. However, use of this technology has been commonly limited to PLC programmers and factory floor technicians, leaving computer scientists out.

Kuckhoff therefore believes that over the next five years, modular PLC platforms will likely become more inclusive to those in the IT space, where the modularity to program using Python, JavaScript and C++ will become standard. “This not only allows for greater connectivity to the ever-growing data analytics space,” he says, “but also allows factories to invite all of their factory talent to contribute to automation design progress.”

Burke’s outlook for PLCs encompasses the fact that plant control systems are facing various current stresses, for example, the risk of cyberattacks. He therefore thinks devices will have more security features to restrict access. Overall, he foresees control platforms “evolving simultaneously to be more open than ever, with support for many protocols and languages, while also being more secure than ever.”

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