Just as there's more than one way to skin a cat, there's more than one way to successfully revive a relationship — including rejuvenating solid, older machines and equipment with innovative, younger control systems and capabilities.
Just as human relationships evolve in ways both subtle and obvious, familiar automation and control devices often can be applied in new ways and in settings where they hadn't been used before. So, while there's nothing like new friendship and discovering automation's advantages over manual processes, even old buddies and long-time automation users find they can renew their relationships with their machines and equipment with some new functions, usually enabled by newer controllers, better software, improved data processing, more pervasive networking or a suitable combination of each, depending on the needs of a particular application.Improving PLCs
RockTenn's printing plant in Jacksonville, Fla., goes through more than 900 huge rolls of paper per month, and prints the outsides of pasteboard cartons that will contain beer, yogurt, drink pouches and other products. The plant's press is 14 ft wide and nearly 150 ft long (Figure 1), and was built by Cobden Chadwick (now Chadwick Web Processing), based in Heywood, U.K. The paper is threaded through the machine and around a huge temperature-controlled cylinder. After printing, the paper passes through a dryer and an inspection station, and then is re-rolled. The now-obsolete PLCs monitored and controlled the entire press from a central location.
The plant's automation systems became increasingly unreliable as the obsolete and costly PLCs generated too many false alarms, and couldn't give feedback about problem locations or provide diagnostics. "To find a fault, the plant's staff had to waste time physically testing each interlock until they could locate it," says Andy Banaczyk, RockTenn's maintenance director, who initially replaced one of the old PLCs with a new PLC, touchscreen and software. This initial project went so well that Banaczyk decided to replace all the PLCs in the plant and add communications to let them share status data, but knew he would need some help.
RockTenn's management, general manager Greg Hoag and plant manager Peter D'Angelo, supported the plant's improvement and upgrade, so Banaczyk enlisted help from system integrators W.L. Smith Electronics, which built enclosures and programmed PLCs, and Expert Automation Design (EAD), which retrofitted legacy PLCs, migrated older PLC programs to newer software, and implemented a new data network. They selected their hardware primarily from AutomationDirect.
"We didn't have the original PLC code and had no way to convert the old code, so we had to rewrite the control and safety code for each new PLC," says Glenn Erickson, EAD's president. "However, using DirectSoft programming software made this fairly simple and straightforward. For example, Andy implemented a voice-broadcast system using the audio capabilities of the C-more touchscreen, and recorded messages tied to specific actions or operations."
Some of the PLCs control temperature, safety systems and press operations, while others monitor press operations, but now all of them can pass and exchange data as needed in a peer-to-peer network with no PLC acting as a master device. This configuration allows the new systems to be more reliable because there's no single point of failure, Erickson adds. So far, RockTenn's plant has gained 30 new PLCs with nearly 2,500 corresponding I/O points. The plant also replaced many of the former pushbuttons, selector switches and indicator lights.
Though the new PLCs replaced almost all the plant's existing controls, an old stepper-control PLC still controls the impression rollers and ink rollers, but it's scheduled to be replaced soon, too. All of the other automation systems for the physical components of the ink-supply system have been upgraded already.
"We set up a communications system, so all the PLCs in the building, with a few minor exceptions, are linked by Ethernet. We can call up any linked PLC and monitor its status or make changes to the PLC logic, all from any of several PCs around the plant," Erickson explains. "The entire system is also tied to a PC running DirectSoft, which allows Internet access and enables any authorized person to log in, monitor the system, or make changes. This has reduced downtime and service calls."
Because the press is ringed with safety gates and interlocks, this upgrade project also included the safety system. "This further reduced unnecessary stoppages to the point they can now be counted on one hand during a 12-month period," Banaczyk says. "I couldn't count the number of stoppages we used to have. I just know it was a nightmare before, and now we have no problems."
When a rare stoppage does occur, the plant's new automation system announces at the main control panel where the fault is located on the press. "With fewer safety system faults and quick resolution of fault causes, this item has dropped off the charts as an area of concern," Erickson adds.