Reducing Waste, Defects, and Rework with SPC

Steve Wise
By Steve Wise | November 13, 2020
Vice President of Statistical Methods

Fact checked by Stephen O'Reilly

Statistical process control (SPC) is everywhere in manufacturing. Why? Because it just works. And I promise to explain. There may still be some folks who either don’t know about it or are intimidated by the concept of SPC. If you’re one of those, please check out this blog from a little while back. It’s good background on SPC and why we manufacturers use it.
In short, that blog covers just about everything you need to know about SPC (and you can check out our website here, too, for even more info), so I won’t go into great background detail here. Suffice it to say this about SPC: “Manufacturers are only as good as their processes. Your organization is judged by the quality and volume of products that your processes produce. But there are struggles, most notably:
  • Reducing scrap, waste, defects, and rework
  • Improving product quality
  • Eliminating variation in processes
  • Maintaining compliance with regulatory and customer requirements”
SPC on the Plant Floor 
And that’s why I’m writing this blog—to talk about how SPC can help you reduce scrap, waste, defects, and rework by focusing on what really matters.

To Start

As I state in the aforementioned blog, SPC is the “methodology for measuring and controlling quality during the manufacturing process.” We at InfinityQS are known as the SPC experts in the manufacturing industry.
So, I thought it only fitting that we take the opening statement, “SPC just works,” and expound on that.


When it comes to reining in your manufacturing operations, no matter what part of the process you’re talking about, you’ve got to measure it.
What gets measured we pay attention to. What doesn’t get measured is ignored.
Think about it. We all tend to clean the house when we’re expecting company. It’s only natural. You want to put on a good face. And we all love a clean house. When we know we’re being judged (or someone has an eye on us), our behaviors change…usually for the better.
Continue with that thought. When something gets measured in manufacturing, we pay attention to it—and we start asking questions. Which brings me to “toast points.”
What's Gets Measured

Toast Points

What is a toast point, you ask? A toast point is a little brown toasty mark left on a tortilla, or similar product, which denotes that the item has been lightly toasted. It adds a bit of flavor and it looks appealing through the clear wrapper. And here’s the kicker—these things are measured. Oh, you better believe it.
Are there enough of them on the item? Is there an ideal number of toast points? What about size? How do I measure a toast point? What happens when/if there are too many or too few? Can I control the number? Can I do something with toast points to differentiate my tortillas from my competition? What systems can we put in place to ensure more ideal tortillas come off the line? Do the ingredients, recipe, cooking equipment, or process set points make a difference? Can I make more money by focusing on toast points? And, finally, do toast points even matter?
For our purposes here in this blog, toast points are all the fine details of your manufacturing process. Whatever they may be. There are answers to all these questions, of course—but finding them requires something very important: data.

Data is the Key

Whenever I think of data, I think of statistical process control. Hand in hand. Why? Because SPC is driven by data. SPC is the premier method to understanding the unknowns in your processes. Tackling broad topics like waste reduction, defect elimination, and rework avoidance requires focusing on those “toast points” in your operations.
You have to pay attention to the data.
Pay Attention to the Data

Swimming Upstream

There are a thousand reasons why data is so important to SPC…and to your business. The most obvious one I can think of is money. Let’s start with the example of finding a defect in your product. What do you think is the most expensive place to find a defect? Finding out from the customer, of course—the flawed finished product! The product is sold, it’s “out there in the field,” and being used. And a consumer complains. They find something wrong with your product and complain about it. I won’t even go into the uses of social media when it comes to customer complaints. We’ve all heard the nightmare stories…and why we have to avoid them.
When a customer finds a problem with your product in the field, all sorts of data have to be collected to find out why and how that problem got out of your facility (and past your quality control system) and into someone’s hands. So, where do we start to look for the root of the problem? Upstream.
And where’s the least expensive place to find a problem? Right at the source. As a colleague once told me, “Fail early.” Makes sense in this context, right? You want to find your failures early in the manufacturing process, so you can fix them before they propagate and get out into the world.

Who’s Your Customer?

So, if you think of a product going through all of the steps in your manufacturing process, every step is a potential source of defects, right? The further upstream we catch them, the closer we get to the source that's creating them.
In my early years in manufacturing, we were taught the concept that every operation has a customer. Your customer is the person that's receiving whatever it is you're giving them—the next step in the process. If you’re responsible for creating widget A in the manufacturing process, then the person who receives widget A from you and adds to it, or changes it somehow (and passes it on)—that’s your customer…and so on downstream.
The point here is this: satisfy your customer and give them what they need. What’s the old saying? “Watch the pennies, and the dollars take care of themselves.” Keep a close eye on all the steps in your manufacturing process—each and every one—and chances are your finished product will reflect that.
SPC in Manufacturing

Even Then It’s Too Late

But even if you operate in such a fashion—making sure your “customer,” the next step in the manufacturing process, gets what they need to push the product to it’s final, “selling,” point—it’s still too late when you find a defect. Why? Because by then a defect can potentially be part of the process. Indulge me for a moment. Perhaps an example will help here: if you’re the person doing the rough cut on a spindle, and you make a hundred of those things and hand them off to someone to do the finished cut, well, you may potentially have to go back and rework or throw away all that work when a defect is found. You need to find defects before a hundred, or a thousand, of whatever it is you’re working on are created and passed along in the manufacturing process. And it’s easy to see how the problem is compounded if the defect makes it through a number of steps in your process.
However, if during your rough-cut operation, you were checking for whatever it is that your customer (the next step in the manufacturing process) will be looking for, you would have caught any defect much sooner. So, you almost have to put yourself in the mindset of your customer, become their eyes and ears. That's going to get you closer to the source of any defects. So, what am I getting at with this? Simply that customer feedback improves efforts.
What this all means to me is that reducing waste, scrap, and rework—these are all just symptoms, by-products. What we’re really trying to do here is eliminate defects. Defects are the underlying disease.
And the best tool for eliminating defects is SPC.
SPC in Manufacturing

Treat the Disease

To find the source of a defect, you have to ask the right questions. And what dictates, what drives us to the right questions? Well, that's the data that you're gathering.
The data will tell you what the next questions need to be. And then you go collect data to answer those questions, and then that data will tell you what's the next level of questions you've got to ask. And so on.
Questions expose, or data expose, the right questions to ask. They provide manufacturers with the treatment you need to cure the defects sickness.
In my Life of Data blog series, I talk about working toward asking the right questions, gathering the right data, to find out all you can about the step or the process you’re focusing on—because “only through proper evaluation can data help you discover ways in which you can improve, uncover problems, and perhaps even avoid potential problems.” That’s the key to SPC, in my opinion.
In the next blog in this series, I’ll look more at the importance of data, as I delve into the top advantages of statistical process control. Please join me.
Read the other blogs in this series:
Take advantage of the technology at your fingertips today: contact one of our account managers (1.800.772.7978 or via our website) for more information.


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