Adjust Quality in Real Time

In closed-loop process control, controllers can make changes as needed to keep the process close to a quality setpoint. Discrete applications often measure quality offline, stop the process, make changes, and toss a bin of out-of-spec scrap. Is this disparity ending?

 

Mark T. Hoske

 

AT A GLANCE

• Close the loop on quality
• Reduce scrap, speed changeovers
• Automatically measure, adjust, repeat

In discrete applications, automation systems and quality control

systems are often separate, producing a time lag between quality analysis and actual production. Wouldn't it be great to monitor quality information in real time and feed corrective instructions back to the control system in a closed loop before the production line makes a bin-full of scrap?

Process control has been doing just that for years. But on the discrete side, most quality processes have been offline. Explanations and excuses are many, but technology has now caught up and can offer many discrete applications the opportunity to actuate changes and close the loop without operator intervention, saving time, materials, and effort.

A current example of closed-loop, real-time, in-line quality control for discrete processes can be found in CNC (computer numerical control) machines that measure, monitor, and automatically compensate for tool wear without operator intervention.

Detect, prioritize, notify

"Much of feedback control is analogous to tool-cutting quality control compensation," observes John Gerry, Expertune CEO and president. "Valves wear, heat exchangers foul, and the PID loops continually try to hold setpoint. Performance will deteriorate over time, which is where you need to have an on-line performance monitor to detect, pinpoint, prioritize, and notify the appropriate people."

Expertune's PlantTriage and similar packages from other companies alert decision-makers—through enterprise-wide, performance monitoring and diagnostics—about available eco