How to build a control card

Control charts are line charts that are built on the basis of certain measurement data on the performance of a product or process at different time intervals. They allow you to consider the dynamics of changes in indicators, and due to this, further control the process itself.

Instruction manual

1

Control charts differ from ordinary rulers only in additional horizontal lines. These lines indicate the control boundaries (upper and lower) of statistically permissible changes in the considered or measured value, as well as the average size of all measurements.

2

Draw the top and then the bottom of the graph. To do this, create a line of average values, and then identify certain (maximum permissible) boundaries of these values ​​in the form of the maximum possible decrease in the indicator in question and increase.

3

Note the changes in the value in question on the graph. Points that are applied as changes on the control map can be formed not only as a result of direct measurements of a specific process indicator, but also by the total value of a group of certain indicators that were obtained at the same time interval. For example, such a total indicator may include the average size of a group of measurements, the value of deviations, the average value of defects per unit of production and the percentage of defects.

4

Determine the change in indicators on the control card in accordance with time. Thus, you can find out exactly when and how the process changed and thereby develop a basis for further management. For example, if the control card shows some single case of the value going beyond the control boundaries, then there is no need to take any action to adjust the process in question. But if the control card reflects the asymmetric shift of the indicator in question (over a long time interval) in relation to the average value line, then this process requires urgent intervention and the adoption of certain corrective actions.