Andy Banaczyk, head of maintenance at Rock-Tenn, said they had to physically test each interlock until they located the fault. “This was a real time-waster,” according to Banaczyk. The programmable logic controllers (PLCs) controlling the printing plant were obsolete and too expensive for upgrade with the original manufacturer, so Banaczyk took it upon himself to replace one of the PLCs with a PLC and touchscreen from AutomationDirect (www.automationdirect.com). This project went so well, Banaczyk decided to replace all the printing plant’s obsolete PLCs.
The Rock-Tenn plant prints more than 900 huge rolls of paper each month. It prints the outside of pasteboard cartons that will contain beer, yogurt, drink pouches and other products. The process is continuous: As one feed roll is emptied, a mechanism cuts the paper and splices on the waiting end of another full feed roll. The same thing happens at the other end. With so many heavy moving parts, safety was paramount, so the entire press was ringed with safety gates and interlocks.
Although Banaczyk was technically capable of designing, engineering, programming and installing new PLCs and monitors himself, the size of the project and the consequent time commitment were daunting. So he decided to call in outside help: first, W.L Smith Electronics (www.wlsmithelectronics.com) in Jacksonville, Fla., and then Expert Automation Design (EAD, www.eanda-technical.com) in Seminole, Fla. He asked WL Smith Electronics to design, build and supply many of the control enclosures, and program many of the PLCs.
After some of the controls had been changed, Banaczyk wanted to add inter-PLC communications and data transfers to allow the PLCs to share status information.
The new PLCs included DirectLogic D2-260 and D0-05 models connected to C-More touchscreens, all from Automation Direct. The plant also replaced many of the pushbuttons, selector switches and indicator lights with Automation Direct-supplied units. Banaczyk didn’t have the original PLC code and had no way to convert the old code, so engineers rewrote the control and safety code for each new PLC. Using DirectSoft programming software helped this to be a fairly simple and straightforward task, he said.
For example, Banaczyk implemented a voice-broadcast system using the audio capabilities of the AutomationDirect C-more touchscreen. He recorded many messages tied to specific actions or operations. When the press starts, for example, three voice messages are heard in succession: “Caution—Stand back! Hands up! Starting the press!”
An Ethernet network links all the PLCs in the building, with a few minor exceptions. Authorized personnel can access any linked PLC and monitor its status or make changes to the logic from any of several PCs around the plant. The entire system is also tied to a PC running DirectSoft software, which allows Internet access from web browsers.
All PLCs pass and exchange data among themselves as needed over the network in a peer-to-peer network configuration with no PLC as a master. This results in a more reliable system as there is no single point of failure.
Another benefit: The updated Safety System, reduced unnecessary stoppages dramatically.
“I couldn’t count the number of stoppages we used to have,” Banaczyk said. “I just know it was a nightmare before, and no problems now.” And when the rare stoppage occurs, the new automation system announces exactly where the fault is at the main control panel.
CASE APPLICATION: Click here to read about the intersection of motion and logic control. Includes a look at a machine-builder for the printing industry.
Renee Robbins Bassett, firstname.lastname@example.org, is Managing Editor for Automation World magazine.