What is it: The Demerit Chart is a control chart to chart products with more than one kind of possible defect. Some defects have very serious consequences on the performance of the product and some that are not so serious, Demerits are assigned and weighted accordingly to the serious of the defect. Demerits are than described as a defect of a product multiplied by its weight. The various types of defects or non conformances of a product are usually classified into three different categories, as follows:

• Class A - Critical: a nonconformity that will result in a hazardous or unsafe condition when used or obstruct the full capabilities of the product
• Class B - Major: a non-conformance that is likely to result in a failure or retard the use of the product in its end use
• Class C - Minor: a nonconformity other than critical or major that is not likely to affect the usability of the product in its use

Class A defects will then have the highest Demerit weighting and Class C defects will have the lowest Demerit weighting.

Why use a it: Demerit Control Charts helps us to find samples with large numbers of nonconformities as well as large numbers of critical nonconformities. The chart calculates the demerits as the weighting factor times the number of that particular nonconformity in the sample. A tool that can be used to chart the severity of defects from one batch to the next, and using the power of control chart conditions are able to trend out of control conditions.

Where to use it: Usually used at the last inspection station of the manufactured product.

When to use it: To monitor and or correct out of control processes.

How to use it: Enter the batch size of each sample taken. Classify the various types of defects into three different categories. Class "A" Defects- Critical (Very Serious), Class "B" Defects- Major (Serious). Class "C" Defects- Minor (Not Serious). Once each defect is classified, a weight is given to each class depending on its severity. The most common weights used today are 100 for As, 50 for Bs, 10 for Cs. Than enter the three non conformances types detected in each batch. Use control charts out of control criteria to detect out of control conditions in the process. The template will provided will automatically chart the Demerits for assessments of out of control observations.

 Name Format Preview (Click to enlarge) Demerit Control Chart Template Microsoft ExcelFormat Demerit Control Chart Example Microsoft ExcelFormat
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