Discrete applications have been integrating the concept of in-line quality control, but typically in an open-loop architecture where a system automatically monitors/measures certain variables, stops the line, and alerts an operator to make changes before too much scrap is run. Such systems also might automatically segregate out-of-spec products based on measurements most often provided by high-speed data acquisition and logic linked with machine
vision or other sensors.
In a closed-loop configuration, a logic device would use information analyzed in real time to send a message, actuate a change, and measure again in a self-correcting control/feedback loop.
Until recently, widely available tools didn’t have real-time capabilities to allow closed-loop changes in discrete processes, suggests John Leppiaho, senior manager for Proficy software, GE Fanuc Automation. “Most customers don’t know why equipment is down. The vision for automatic closed-loop correction is there, but we haven’t seen it in practice.”
The solution for many would be to better define product specifications and, as processes move away from a quality centerline, depending on the deviation, stop and fix the process. Doing so would improve overall quality and reduce waste, Leppiaho says. “Some product introductions can have 300 quality parameters; any ability to reduce new product cycle time is huge,” he explains.
Today’s software can offer tremendous advantages by using the S95-based data model, triggering Web reports and alarms from work-in-process issues and down time, allowing management by exception. Customers can create the specs in their data model so that if a process gets out of limits, an alert would be triggered. Such a setup can offer tremendous advantages. “This opportunity is like what HMI offered 10-15 years ago. Consider this HMI/SCADA software for the production level. Productivity gain potential at this level is huge,” Leppiaho says.
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