The standard specifies a uniform method for programming function blocks, giving users the ability to program any brand of PLC in the same language.
Although the standard is not nearly as popular in the United States as in Europe, manufacturers are tooling up to promote it more here. The focus on function blocks makes programming much more modular, a feature that can make their products easier to use. “It gets away from what we call spaghetti codes, which is lots of ladder logic,” explains John Kowal, global marketing manager at Elau Inc., a manufacturer of packaging machine control systems in Schaumburg, Ill. “It’s not very modular, and it’s hard to troubleshoot.”
Ladder logic also is cumbersome in motion-centric applications, such as servo-driven bottle-labeling machines, which spin and move the bottle as they apply labels. “A proprietary PLC program is a real bottleneck for these guys,” says Kowal.
Another important ramification of the standard is that users can create libraries of pre-programmed function blocks and put them together in various ways like one would do with Lego blocks. “You don’t have to rebuild each of those individual blocks,” says Dr. Kenneth Ryan, director of Alexandria Technical College’s Manufacturing Automation Research and Education Center for Automation and Motion Control, in Alexandria, Minn. He is already developing training courses for PLC manufacturers to bring their sales and engineers staffs up to speed.
This ability could have tremendous value for the medical industry. Consider packaging machines for pharmaceutical manufacturers. “I can write code into a function block and lock it,” says Ryan. Once the company proves the block, and the Food and Drug Administration certifies it, it could conceivably be used again in other applications without having to go through another long and expensive certification process. Building control code from pre-certified function blocks could save a tremendous amount of time and money.
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