Statistical process control/statistical quality control software is closing the loop by working online, identifying and fixing problems before an operator is aware any problem exists.

Software for statistical process control and statistical quality control (SPC/SQC)—once used exclusively offline for analysis—now integrates with control and human-machine interface software. Online responsibilities include providing alarms or even fixing problems before an operator knows any problems exist.

"Traditionally, manufacturing and quality control functions have been separate," says Ralph Rio, Cimplicity Manager, GE Fanuc Automation (Charlottesville, Va.). "Operators ran the machines that make products and, hours or days later, an inspector looked for flaws in the products. This lag time between production and inspection allowed bad products to get through the process, causing rework, scrap, and/or custom returns. This wreaked havoc on production schedules and costs."

Greater integration means "operators can control and monitor both production and quality processes automatically," he says.

Ken Dingman, ABB Automation (Rochester, N.Y.) global manager, Information Management Products, agrees. "An SPC package should be able to analyze data and perform the statistical computations in the background. When an 'alarm' condition occurs (such as a run alarm), an event should be generated in the control system so that the operator is aware of it. This will allow for immediate attention" to avoid deviation in product quality.

An example of how SPC charts can prevent errors includes compensating for tool wear on a metal-cutting machine. The SPC software detects when parts grow in size. Before the upper control limit is reached, says Mr. Rio, software identifies the trend, creates an alarm to notify an operator, then before the part gets out of "spec," automatically adjusts the cutting tool's position to compensate for the drift.

Applications extend far beyond machine tools into almost any industry.

Daryl Walther, of Rockwell Software's (West Allis, Wis.) HMI Business Unit, Rockwell Automation, says, "Controlling a process is essential for producing quality products, so virtually all processes can benefit from SPC." Rockwell Software once charged for the SPC module, but views it as "core functionality" for HMI so includes it at no additional cost. The software "collects samples from the process, analyzes the data for SPC trends, and displays SPC charts, all in real time," Mr. Walther says.

It's not just integration that makes this class of software functionality more valued, it's more power.

ABB's Mr. Dingman says, "One of the important areas of SPC is multivariable SPC [MSPC]. Currently, typical Shewhart analysis only considers one variable at a time and whether it is within its control limits. What it does not address is the effect that multiple variables in combination can have on product quality." For example, two variables might be in control individually, but interact in such a way that moves product outset specifications. "Multivariant SPC would identify these interactions and indicate when product is made out of specification," Mr. Dingman says.

Important requirements for implementing online SPC/SQC applications, according to David McCaffrey, product development manager, MDC Technology Ltd. (Teesside, U.K.), are:

• A server to perform MSPC model calculations;
• Easy interfacing to plant data;
• An internal historian for logging trends of model inputs, outputs and alarms;
• Distributed client software to allow monitoring of model output and alarms either in real time or retrospectively; and
• Embedding of MSPC client software and alarms into the same operator environment as the factory control and alarm system.

Fisher-Rosemount Systems (Austin, Tex.) embeds MDC products into the DeltaV automation system. In addition to interfaces with more than 200 distributed control and SCADA systems, MDC touts 10% reduction in batch cycle times, 4% improvement in product quality, and up to 5% in increased profitability to customer processes.

Real-time operation and MSPC aren't the only functionality users have demanded from SPC/SQC software vendors. Other major trends include:

• Easier interfaces (set-up, alarming, and correction) for non-statistically inclined users, with re-emphasis on solving problems, rather than analyzing;
• More sophisticated modeling tools so problems can be identified and corrected earlier, before product moves outside spec;
• Better data storage and retrieval, in part, using standard tools, such as web-enabled software, ActiveX, and Object Linking and Embedding (OLE) for Process Control; and
• Integration and information exchange with other software, throughout the enterprise.

Brad Klenz, senior quality technology specialist in the Quality Center at SAS Institute (Cary, N.C.), points to SPC software set-up as a potential source of grief when implementing these systems.

Building on Mr. McCaffrey's suggestion of a central server, Mr. Klenz recommends a "Quality Data Warehouse" for enterprise quality improvement. Such a warehouse collects data from and makes it available to systems such as SPC, enterprise resource planning, manufacturing execution systems, manufacturing resource planning, and laboratory information management systems.

Meeting the analytical needs of the manufacturing enterprise requires proper data aggregation, correct subgrouping, allowing for multiple sources of variation, sufficient structure for traceability, and support for measures of uncertainty, Mr. Klenz says.

Central storage allows access and analysis, resulting in decisions that improve the quality of processes, products, and services.

Making SPC and SQC data available to all levels of the enterprise, brings a multiplicity of benefits, explains USDATA Corp. (Richardson, Tex.) chief software architect, Mitch Vaughn. Availability allows users to automate product routing; classify based on quality, production line, plant or enterprise analysis; and achieve ISO 9000 compliance. Data integration also allows for easier tracking of rework and repair and ability to provide electronic delivery of quality information to customers, Mr. Vaughn says.

Competition's tougher than ever. "Customers expect tighter quality, faster delivery, and more flexible production," says MDC's Mr. McCaffrey. SPC/SQC online tools—when fed with reliably sensed data in real-time—can help with ahead-of-time, in-spec, lower-cost deliveries that customers demand.

For 47 companies involved in SPC/SQC, go to www.controleng.com/buyersguide . For additional SPC/SQC vendors also see www.qualitymag.com/buyguide.html.