Short Run SPC Charts | Short Run Control Charts | Control Charts for Short Runs

Short Run SPC Charts (DNOM)
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Traditional SPC uses 20 or more data points to develop a control chart. So what do you do if you only produce three of this widget, then four of another, and then six of something else? The answer: Short Run SPC.

Short Run SPC (DNOM)

In short run SPC, we're making a few parts of different sizes, so we can't really use the actual measurements. Instead of evaluating the variation of each measurement, we use the variation of parts from a target value. These are also known as Deviation from Nominal (DNOM) charts.

So, if the first group of parts has a target value of 74mm, we measure each part and determine the variation from the target. If the next group of parts has a target value of 60mm, we measure those and determine their variation. Ideally, the variation from the target value will remain stable even though the parts vary in size.

QI Macros Short Run SPC (DNOM)

Since you're only doing a few parts at a time, it doesn't make sense to have a macro to handle short run SPC. So the QI Macros provide sheets in each of the Primary Control chart templates:

XmR Four Pak
XbarR Five Pak
XmedianR
c, p, u, and np attribute control charts

To access these sheets, click on Fill in the Blank Templates, then SPC Charts, then one of the chart templates. Then click on the tab title Short Run. Here is an example of the Short Run control chart tab in the XmR Four Pak.

In the QI Macros Short Run SPC templates, input your target values and measurement values into the yellow cells. You'll notice there are three parts at 74mm, five at 33.5mm, and seven at 22.5mm. The QI Macros will calculate the difference between the target and your data.

Short Run SPC X Chart Template in QI Macros for Excel

The "Difference" is used to create the control chart. Even though the pieces vary in size, the variation from target is in control:

Short Run SPC X Chart in QI Macros for Excel

I've only included the X chart, but the Range chart is also in control.

Short Run SPC isn't for everyone, but if your shop does a lot of small jobs, you might consider using short run charts to control the end product.

Watch this Short Run Control Chart Video

Here is a list of the worksheets in the control chart templates with links to more information:

Control Chart with Center Line based on the Average - uses the average of your data for the center line.
Control Chart with Rolling Data and Control Limits - graphs the most recent data points as defined by you.
Control Chart Center Line based on the Median (X charts only) - uses the median of your data for the center line instead of the average.
Short Run Control Chart - compares your data points against a target value for each point. For use when you are making a few parts of different sizes.
Horizontal Control Chart worksheet - for data organized in rows versus columns.
Control Chart with Fixed Control Limits - allows you to enter fixed or historical control limits.

List of control chart templates

To purchase the QI Macros

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If you already own the QI Macros, you can purchase an upgrade. You must purchase one upgrade for each license you own.

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Short Run SPC Charts (DNOM)

Short Run SPC (DNOM)

QI Macros Short Run SPC (DNOM)

Here is a list of the worksheets in the control chart templates with links to more information: