During production of parts in the plastic industry, it is important to meet certain tolerances, eg. given in the drawing.
For this purpose regular checks of specific characteristics of a sample, mostly at multiple parts, are carried out in practice.
The control chart is a curve, which shows for example the mean of the samples and its standard deviation.
Limit values can be added into the control chart for warnings and necessary interventions. If these limits are exceeded, measures or interventions in the process can or must be taken.