It only looks like magic until you know how it's done. Whether it's slight of hand, unfamiliar technologies, juggling, invisible networks or other forms of prestidigitation, new tricks always seem alien and unworkable until you learn their inner workings. The same was true for many wireless tools and methods, but acceptance has grown along with familiarity — as it always does.
As long as data is communicated correctly, safely and securely, does it matter if you can't see a wireless network doing its job? Heck no. Likewise, most old-time control engineers never saw their pneumatic valves and relays actuate either, but they still trusted their equipment because they were intimately familiar with how it worked, and very often had installed it themselves. Now, the same is becoming true for wireless.
SEE ALSO: Is Wireless the Right Solution?
Freedom from Wear
The Johnson Controls automotive seat plant in Tlaxcala, Mexico, has 43 carts that move around a carousel as they pass through a urethane process. The line's communication cables that transmit monitoring and control data were wearing out, breaking and causing unplanned downtime. Johnson's engineers needed a more durable, non-intrusive way to establish real-time communications between their carts and supervisory control system, including delivering data to its field office PC and managing permissions on a urethane-injecting robot on the line (Figure 1).
System integrator Adepi and distributor Risoul y Cia worked with Tlaxcala's staff, and together they implemented 1743 I/O modules on 23 carts, which were linked via IHN radios and an IHN master that can transfer data at 300 Mpbs to a PLC platform. The I/O modules and PLC are from Rockwell Automation, and the radios are from ProSoft Technology.
"High data-rate radios were the best option for wireless communications between each of the carts and the PLC, based on our testing results and presale technical support provided onsite," says Adrian Torres, Johnson's project leader.
Because the radio-enabled I/O and PLC optimized speed and reduced cable wear on Tlaxcala's urethane-injection process, its remaining carts were scheduled to get wireless components earlier this year. Johnson is also evaluating a similar solution at its U.S. facility.
Besides preventing wear and tear on hardwiring by reducing the need for it in the first place, wireless frees up operators and technicians to move more easily in and around their machines and process applications. It lets them change parameters more directly and efficiently without having to communicate as often with a centralized control room or other detached supervisory stations.
For example, Paper Converting Machine Co. in Green Bay, Wis., had two hardwired HMI pendants mounted on its printing presses and lifts, but it recently added radios to make one HMI wireless. This allows operators to walk around the presses, which makes them easier to set up and adjust while they're running, mostly printing on film or paper for packaging. After adopting an earlier IEEE 802.11 Wi-Fi radio, PCMC migrated to wireless local area network (WLAN) access points and radios from Phoenix Contact. The WLAN also uses Wi-Fi and 200 mW of output power to send 300 Mbps to PLCs on the presses.
"Customers asked for a wireless interface, so in 2010 we integrated fully guarded radios with ranges that weren't too long to monitor channels on the presses. The biggest issue was providing wireless, but we needed communication speeds of 1 second or less, and got 200 ms to 700 ms, which was enough because our monitoring, setup and adjustments don't have to be in real time," says Jordan Koplien, electrical engineer at PCMC, which is a division of Barry-Wehmiller Companies. "The wireless pendant allows operators to see the process web itself, including both sides of the web around its central impression drum, which is a two-sided cylinder with printing heads on each side."