Process Superstition Is a Poor Substitute for Process Awareness

Getting the most from real-time SPC charting

Published: Friday, October 19, 2012 - 08:38

Papering the walls with printed charts might impress visitors, but anyone who wants to get the most from SPC charting must make the right chart available in the right place at the right time. Consider the weekly or monthly quality review meeting. The right people may be in the room, and the right charts may be shown, but as much as a month may have passed since the data have been gathered. Not much can be done to address something that happened six days or six weeks ago.

Likewise, if charts are simply displayed on a bulletin board in a hallway or the lunch room, they will probably not be helpful to workers trying to understand recent process changes. Charts must be accessible and visible; they must be in the right place to be useful. Of course, regardless of where a chart is displayed, selecting the correct chart type is critical. The skill of discerning when to use an individuals chart rather than a p-chart can be addressed through SPC training, but either chart will be less valuable when it doesn’t reflect recent or real-time data.

In many plants, it is this last point that undermines the value of their SPC charting efforts. The benefits of real-time SPC charting are many:

• Correctly deployed real-time SPC charts will improve workers’ overall process awareness. This awareness is not a one-time benefit but builds over time. Process operators begin to see patterns and learn how to respond. It may be that one worker’s decision, based on immediate data, can prevent scrapping an expensive product. Without the data, visible and consumable in chart form, this kind of process awareness is less likely to develop over time. Process superstition is a poor substitute for process awareness.
• The right hardware and SPC software can address the many friction points that occur when trying to deploy real-time SPC charts. These friction points can inhibit a worker’s use of the charts. One friction point is simply the location of the display. Another can be the complexity of navigating to the correct chart. Finally, the data shown on the chart might be behind current production and therefore not that helpful to the operator. Each of these can be addressed. Lighter, thinner, and more rugged display screens make it easier to position them so they are easily visible and do not interfere with work. These screens can be distant from the computer in situations where it is not practical to have a PC nearby. As for navigating complex software, in the ideal situation the user does not have to interact with the software; it can be configured to keep the right display with current data updated all the time. At the very least, it should be easy for the operator to quickly change between different setups. Many applications can run in a limited feature mode so the operator sees only what he needs for the job.
• Real-time SPC charting can empower workers to take action. When an operator is not sure about what is happening, she is less likely to make changes. Watching a control chart fluctuate over time can build confidence in how a process works. The chart with its control limits may function as a safety net; the worker may suspect a problem, but when the chart confirms a signal, he gains confidence in taking corrective action, rather than letting a process continue to degrade.

All of these outcomes will contribute to process improvement, efficiency, and savings of time and money.

A large manufacturing plant was working on the problem of product losses generated by unplanned shutdowns of the production line. A shutdown was often caused by failing electric motors. Data from the motors were gathered automatically and a real-time SPC charting solution was deployed. Because there were several motors, each one generating amperage data, the solution required multiple SPC charts. These charts were summarized and ranked based on the number of out-of-control conditions. Experience had shown that motors almost always showed out-of-control signals prior to failing. The motors most likely to fail filtered their way to the top of the list. Since the list constantly refreshed and operators could see the list and easily view associated charts, they could start a planned, orderly shutdown so the offending motor could be replaced before it caused quality issues. The number of expensive unplanned shutdowns was reduced dramatically, creating significant cost savings and demonstrating the benefit of having the right chart available and visible, in the right place, at the right time.

Without real-time SPC, a defect or failure may be the first indication that something has gone wrong in the process, and without SPC data, decisions about correcting the problem are simply best guesses. The advantages of real-time SPC charting are clear, and have become most manufacturers’ secret weapon to stay competitive in their markets and provide quality products that not only meet their customers’ requirements but also help them identify problems in the processes faster.

In this example chart from CHARTrunner Lean SPC charting software, the benefits of detecting a problem early are clearly demonstrated. If no intervention had occurred, it is clear the process was headed into a state where scrap or rework might have resulted.

The benefits of understanding data in real time are clear, and rapidly improving technologies, including SPC charting software, render real-time charts immediately accessible for analysis. With charts that are constantly updated by emerging data, an operator can immediately identify issues that would otherwise result in wasted resources and defective products.

After all, saving money and time will be far more impressive to your customers—both internal and external—than any wallpaper display of weeks-old charts.

About The Author

Steve Daum

M. Stephen Daum is director of development for PQ Systems. Prior to assuming responsibility for development, Daum was the lead programmer on PQ’s statistical software products, a position he took in 1985. Daum has more than 20 years of experience with control charts and control charting software and has shared that experience through presentations, training, and educational sessions for organizations throughout the United States, England, and South Africa.