Improving processes is the best way to boost quality, and statistical process control is showing the way.
A generation of engineers has grown up since statistical process control (SPC) became SOP in U.S. manufacturing.
SPC is the building block for total quality management, ISO standards, six sigma and a host of other methodologies to control variance and reduce waste in manufacturing processes. Food engineers have applied SPC in some fashion for a quarter of a century. Though its use is expanding, the number-crunching essence of SPC remains unchanged. “We keep adding more algorithms to meet more rigorous requirements,” allows Jeffery L. Cawley, vice president at Northwest Analytical Inc. (NWA), “but the core functionality is the same.”
The automotive industry was the first to apply statistical data to control processes, but many questioned the application in food, where inconsistent raw materials created variability nightmares. Food engineers overcame that roadblock, and the data mined from SPC is migrating to other users. Whether it’s the line operator or the CEO, users of SPC data are gaining a better understanding and control of their company’s products.
The same is true of customers. Part of the SPC evolution is delivering more user-friendly data to these data users. “A lot of our customers are asking us, ‘How can we get histograms, run charts and other analytical data on what you’re shipping on the Internet?'” reports a flour miller’s head of quality, who requests anonymity. “Right now all they would get is a line with ingredient declarations. Wouldn’t it be great to give them current averages for moisture content, protein, ash absorption and stability without forcing them to invest in the statistical training needed to read our data charts?”
Web browser access to data charts is a capability many software suppliers have added to their programs, among them NWA, GE Fanuc and Zontec (see related supplier’s list). Windows-based operating systems are another development in recent years that has expanded data accessibility.
“We went through three generations of our product,” beginning with a DOS-based application, says Warren Ha, Zontec’s president. “Most people have moved to Windows, particularly in the last two years. Compatibility is the big advantage, and once you learn one application under Windows, the rest should be fairly self-explanatory. The user interface is much better, and you can run multiple tasks.”
Rockwell Software originally offered the SPC module of its RSView32 HMI package as an add-on module, but today it’s part of the core functionality. “That change was definitely customer driven,” according to Darrell Walker, marketing manager. “Manufacturers insisted on the inclusion of the SPC function.”
As SPC has become more mainstream, more bells and whistles have been added to the basic packages. E-mail messaging, remote monitoring and alarm systems help broaden the audience for the data, but there is the potential for undermining one potential benefit: operator empowerment.
“If we empower operators in the appropriate manner, do we really need pagers carried by managers to go off?” asks John G. Surak, a professor at Clemson University and an expert on food applications of SPC. “We’re transforming these people to be able to monitor and analyze process data and take the appropriate action, including the decision not to make adjustments if a predictable cause for variation has occurred.
“You really want the operator to make the decision that a change has occurred that requires altering the process,” Surak continues. “If the process is out of control, operators should go through a decision tree to determine the appropriate corrective action. If all else fails, then you call the manager.”