Monitoring future production

Once a reliable set of control limits are determined they can be used to monitor future production.

  1. On the Analyse-it ribbon tab, in the Report group, click Goto dataset.
  2. On the Analyse-it ribbon tab, in the Dataset group, click Filter.

    The filter is removed from the dataset and the additional data after the improvements were implemented is shown.

  3. On the Analyse-it ribbon tab, click Return to analysis.
  4. Select the Known process parameters check box.
  5. Select the Vary for each process change option.
  6. In the Parameters grid, alongside the Production phase, in the Mean edit box, type 8.647, and in the SD edit box, type 0.429.
  7. Clear the Advanced out-of-control rules check box.
  8. On the Analyse-it ribbon tab, in the Process Control group, click EWMA.
    In the analysis task pane, a new panel Control Chart (Moving Average) is added.
  9. Click Recalculate.

Control limits for the production phase are computed based on the process mean and standard deviation computed during the OQ stage.

Xbar-R control chart with process phases(click to enlarge)

The EWMA control chart is more sensitive to detecting small shifts in the process mean than the Shewhart control chart and is an alternative to the advanced control rules. Small drifts in the process mean may indicate a drift in the calibration of the automated colorimeter that is used to control the amount of copper in the plating pool.