The Top 10 SPC Mistakes: Part 1

March 1, 2018
5 min read

Me: As you think about your organization’s manufacturing quality efforts—what you’ve overcome and what you hope to accomplish in the future—there is something you need to know.

You: What? Who? Me?

Me: Yes, you. No matter how long you’ve been playing this game, and I know many of you have been playing it as long as I have, you find that there are many pitfalls to implementing a statistical process control (SPC) system.

I’ve been doing this for about 30 years, and I’ve worked with and witnessed hundreds of SPC implementations.  Many have been very successful, virtually transforming plants and corporate cultures. A few have been less than successful. And many—most, actually—occupy the murky middle ground between success and failure. These deployments are usually characterized by an interesting mix of localized support and excitement, coupled with an undercurrent of corporate indifference.

You: Okay, I’m interested. Go on…

Me: Although many quality experts know what to do for a successful SPC implementation, few know what not to do. That is, not until the damage is done…and SPC failure ripples throughout the entire organization and the mistakes are made obvious.

To help ensure that your SPC money is spent wisely and that your system has the highest probability of success, I think it’s a good idea to take the right steps that all the experts in all the books discuss, but don’t commit the mistakes I’ll be listing in this blog series. Forewarned is forearmed.

So, without further ado, let’s start our rundown of the Top 10 Mistakes to avoid when using SPC…here are numbers 10 and 9.

10. Train everyone
It’s no secret that SPC is a tremendous cost-saving and process-improvement tool. The general perception is that the more people who know about SPC, the better. I hate to contradict, but it’s just not so. Years ago, I was a consultant and trained many professionals in statistical methods and their use. My customers were good people representing good companies. They had good intentions and they wanted the best for their organizations. Their ideals were no different when it came to SPC knowledge.

In their good intentions, they typically required administrative staff, sales people, and other support personnel to attend SPC classes. Most of these folks had rarely, if ever, set foot onto a manufacturing shop floor. The result was quizzical looks, excessive doodling, and eyes glued to newspapers. They eventually raised their eyes, and then their hands, and they posed questions like, “Why, exactly, am I here?” Quite frankly, most of those administrative and support personnel shouldn’t have been in the class in the first place.

My response has always been that companies should train the people who are going to be actively involved in the use of SPC—not everyone. So don’t train all of your people in SPC. Don’t waste your money. Make SPC training available for the people who will be directly involved in improving your processes. Let the rest read the morning newspaper over coffee, on their own time—not during an expensive training session.

9. Chart everything
You may have spent thousands of dollars on SPC training. Now that your people have attended classes and passed the tests, what do you do next? Full of enthusiasm after their training, some answer this question by charting everything—from the number of minutes on time cards to the number of days late for purchase requisitions, and everything gets placed on a control chart. (Unfortunately, people who are new to SPC are sometimes left to their own devices for how their newly acquired statistical knowledge should be applied.) But the problem is: When everything is important, then nothing is.

My recommendation is to only use SPC where it’s needed. Start on the manufacturing shop floor, and don’t bother applying statistical methods if there’s even a hint of questionable benefit. This is especially important in the beginning stages. If the initial SPC implementation is identified for its convenience, or because it’s an area of high production, and therefore better suited to using an X-bar and a range-control chart, then forget it. It will be viewed by operations folks—rightly or wrongly—as just another management botch job. In this scenario, there’s minimal likelihood of making a splash and proving that SPC is a great tool.

Don’t forget that you need the support and backing of operators, process engineers, and support personnel to help SPC use be accepted and grow. The first area you choose for SPC use shouldn’t be problem-free. It probably won’t be the most convenient, or the easiest place, for using control charts.

Instead, search out areas where scrap, rework, and other issues need to be resolved. Tap the shoulder of your local Six Sigma expert and find out where process control issues are most prevalent. Talk with quality engineers and support personnel to determine where problems exist and, therefore, can be solved. Believe me, if your first use of SPC isn’t successful and SPC doesn’t make a splash, you could be in for a very rough road ahead. In short, don’t apply a wonderful technology such as SPC unless there’s a need for it.

Join me next time for more of this list of Top 10 Mistakes to avoid when using SPC…for numbers 8 and 7: “Segregate control charts from manufacturing” and “’Pinching’ the SPC Coordinator.” ‘Til then…

top 10 sign on blue

Read the other blogs in this series:
The Top 10 SPC Mistakes: Part 2
The Top 10 SPC Mistakes: Part 3
The Top 10 SPC Mistakes: Part 4
The Top 10 SPC Mistakes: Part 5