Check Sheet - Function - Check Sheet For Defect Cause

Check Sheet For Defect Cause

When a process has been identified as a candidate for improvement, effort may be required to try to identify the source of the defects by cause.

This type of check sheet consists of the following:

• One or more columns listing each suspected cause (for example machine, material, method, environment, operator)
• One or more columns listing the period during which process outputs are to be observed (for example hour, shift, day)
• One or more symbols to represent the different types of defects to be recorded—these symbols take the place of the check marks of the other types of charts.

Note that the defect categories and how process outputs are to be placed into these categories must be agreed to and spelled out in advance of constructing the check sheet. Additionally, rules for recording the presence of defects of different types when observed for the same process output must be set down.

When the process distribution is ready to be assessed, the assessor fills out the check sheet's heading. For each combination of suspected causes, the assessor actively observes the process. Each time the process generates an output, he or she assesses the output for defects using the agreed-upon methods, determines the category in which the defect falls, and adds the symbol corresponding to that defect category to the cell in the grid corresponding to the combination of suspected causes. If no defects are found for a process output, no symbol is entered.

When the observation period has concluded, the combinations of suspect causes with the most symbols should be investigated for the sources of variation that produce the defects of the type noted.

Optionally, the cause-and-effect diagram may be used to provide a similar diagnostic. The assessor simply places a check mark next to the "twig" on the branch of the diagram corresponding to the suspected cause when he or she observes a defect.