Process control charts identify special-causes of variation that need to eliminated to
bring the process under control, so the results are predictable and can be used to determine
the ability of a process to meet customer specifications.
During the installation period of a new automated colorimeter for controlling the
copper content in the plating process control charts can be used to identify
special-causes of variation that need to eliminated to make the process perform
predictably. The Xbar and R charts plot the mean and range of the copper
concentration in the plating pool respectively.
(click to enlarge)
Inspecting the plots you can see special-cause variation is present in the
- There is a point dated the 03/01 on the R chart with high variation.
- There are 2 further points dated the 11/01 and 13/02 on the Xbar chart.