Statistical Process Control Explained - TigerStop

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Statistical Process Control Explained

To improve, one must measure, and continue to measure on a consistent basis. – Spencer Dick, President, TigerStop LLC


Statistical process control, also known as SPC or “How not to fall out of the sky in a burning ball of flames,” is used when one wants to measure the outcome of a process. In other words, statistical process control guarantees that parts and components used for things like airplanes are within specifications. Because who wants to pummel to the earth in a heaping ball of flames? Not us. SPC is used in a wide variety of industries and most frequently in industries that have federally regulated manufacturing, like the aerospace industry (for obvious aforementioned reasons).

SPC is also used in lifesaving applications by surgeons when measuring the survival rates in bypass surgeries, for example. Basically, SPC is important in any application in which you want to accurately measure outcomes.

Think of SPC like your Fitbit® or Jawbone®, which measures and tracks how many steps you are taking in a day, in addition to your heart rate, caloric consumption, and so forth. Whenever you want to measure the outcome of a process (walking) and set a goal (weight loss, fitness) you typically use a form of SPC. The best way to find success is to set measurable goals and track those goals.

So What Does This Mean for My Shop?

Let’s look to our friends at Wikipedia for further clarification:

Statistical process control (SPC) is a method of quality control which uses statistical methods. SPC is applied in order to monitor and control a process. Monitoring and controlling the process ensures that it operates at its full potential. At its full potential, the process can make as much conforming product as possible with a minimum (if not an elimination) of waste (rework or scrap). SPC can be applied to any process where the “conforming product” (product meeting specifications) output can be measured. Key tools used in SPC include control charts; a focus on continuous improvement; and design of experiments.  An example of a process where SPC is applied is manufacturing lines.

So, why don’t more manufacturing shops use SPC?

That’s a good question. If your manufacturing shop wants to meet or exceed customer expectations, you should have some type of statistical process control or quality control process put in place.


In a cabinet manufacturing shop, for example, quality is being able to produce accurately cut cabinet components over and over again. It is being able to do so quickly and without any mistakes that make their way down the production line to be found on the assembly table. It’s producing parts that don’t have to be reworked and don’t have to be thrown into the scrap bin. Quality is being able to set an accurate process in place and repeat it over and over again.

Identifying Issues

If you’re tracking your progress using SPC, it’s easy to see where in the manufacturing shop problems are occurring. Such problems may arise in the following areas, among others:

  • Machine problem
  • Personnel problem
  • Process problem

If there is a significant amount of variation in a particular component, ask yourself: Is it because your operator cannot accurately read a tape measure (personnel problem)? Is it because the saw is inaccurate and needs to be recalibrated (machine problem)? Or is it because the quality control team has not yet been put in place in the factory (process problem) and only some parts are being checked for accuracy before they’re shipped out the door?

SPC helps you answer these types of questions.

Statistical Process Control


Using a product like the TigerSPC in conjunction with a TigerStop automated length measuring system helps eliminate such problem areas. Using a TigerStop pusher or stop system allows your operator to quickly and accurately cut, drill, press, etc. parts over and over again. TigerSPC calipers can then quickly measure those parts, up to 16 feet in length to ensure quality control. Taking a random sample of your cut parts with TigerSPC calipers ensures that your personnel and machining areas are of the utmost accuracy.

If, for example, you’re manufacturing airplane parts, a federally regulated manufacturing process, and want to ensure that the holes you just bored into a component are equidistant, you can use TigerSPC to do so. With its easy-to-use snap-in jaws, you can change from holes to miters to overall measurements in seconds without losing calibration. All TigerSPC jaws and appliances are machined to ensure the same zero point, so no recalibrating for different setups.

Using automation to help with quality control and statistical process controls is a huge time and money saver.

Learn more about TigerStop products and TigerSPC.