Viewing Statistical Results

  1. On the home view, go to the Reports tab and select Statistics on the left pane.

  2. On the SPC Configuration window, enter the following parameters: Number of Subgroups, Subgroup Size, and Frequency.

  3. Select the plus icon in the upper-right corner of the screen.
    The SPC Variable window shows the new variable.
    Configure the new SPC Variable.

  4. On the SPC Variable window, select Calculate.

  5. To show the statistical results, on the SPC Variable window, select the View box.
    The View box shows the date and time which the statistics results have been done.
    The statistical results are displayed through a histogram, the XBar-R chart, and the XBar-S chart.

    When all calculations on the filtered results are done, they are sent to the Web HMI and ToolsTalk 2.
    The statistics results are locally saved on a Temporary Internet Files folder (not saved on the controller).

    Statistical results can be displayed only on the Web HMI.

Histogram

A histogram is a series of rectangles, each proportional in width to the range of values within a class and proportional in height to the number of samples falling in the class. A Gaussian curve follows the trend of the rectangles. A histogram reveals the amount of variation that any process has within it.
The histogram is useful because it emphasizes and clarifies trends that are not readily discernible in tables.

XBar-R Chart

The XBar-R control chart shows both the mean value (XBar) and the range (R) of a subgroup. This is the most common type of control chart using indiscrete or continuous values. The XBar part of the chart shows any changes in the mean value of the process while the R part shows any changes in the dispersion of the process.
This chart is particularly useful because it shows changes in mean value and dispersion of the process at the same time, making it a very effective method for checking abnormalities in the process.

XBar-S Chart

The XBar-S control chart shows both the mean value (XBar) Chart and the standard deviation (S) for each subgroup.
The XBar-S chart is identical to the XBar-R chart except that the R (range) is replaced by an S (standard deviation).

Calculated Statistical Values

In the Web HMI the calculated statistical values are displayed in information boxes below the histogram, the XBar-R chart, and the XBar-S chart.

The calculated values depend on the chart on which they are read.

The calculated statistical values are:

  • Min = minimum value for all collected sample values

  • Max = maximum value for all collected sample values

  • Mean =

  • Mean+3Sigma = + 3*stdDev

  • Mean-3Sigma = - 3*stdDev

  • Cp (in XBar-R chart the value is based on range, and in XBar-S chart the value is based on sigma)

  • Cpk (in XBar-R chart the value is based on range, and in XBar-S chart the value is based on sigma)

  • Center line = in Range part , and in Sigma part

  • Target (if available the target value for the monitor)

  • Standard deviation = Total overall standard deviation = stdDev