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Defect Concentration Diagram: Definition, Examples

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defect concentration diagram

Concentration diagram of Cholera deaths 1854 in London (John Snow (1813-1858))

A defect concentration diagram is a visual representation—usually, a diagram or map—which shows all defects or problem areas in what is being analyzed. As a research tool, it may began as a blank diagram or picture, in which problem locations are marked down as they happen or are discovered.

It may be the drawing of a product, the map of a city, the diagram of a motherboard, or any other map on which trouble-spots can be marked down. Sometimes it is simply a photo taken by a digital camera, which can be marked up as faults are noted. Ideally, the defect concentration diagram will show the product or situation from multiple angles.

The diagram, when completed, can help researchers or quality control analysts determine whether there is a pattern in defects. Patterns or trends, when noted, allow a manufacturer to correct defects, reinforce areas, or change processing methods.

Defect Concentration Diagrams in Statistical Process Control

Defect concentration diagrams are one of the seven major tools (sometimes called the ‘magnificent seven’ in statistical process control. The other six are histograms, check sheets, pareto diagrams, cause and effect diagrams, and scatter diagrams.

Example of the Defect Concentration Diagram in Use

In World War II, allied engineers used defect concentration diagrams to find out where their airplanes needed reinforcement. A defect concentration diagram was made showing the location of bullet holes in the fuselage of returning planes, and from that plans were made for which parts of the fuselage needed to be reinforced.

In factories, a quality control inspector uses defect concentration diagrams to plot problems found in defective products. For a furniture company, this might be misaligned pieces, rough unfinished patches or other aesthetic issues. A defect concentration diagram gives immediate feedback as to what is going wrong, and allows the inspector to make quick conclusions about which part of the process may be lacking.

A defect concentration diagram can also be used by a company to plot problems arising after purchase. For instance, a defect concentration diagram in which Apple plots all the issues with returned iPhones would show problematic hot spots that designers should pay attention to in future releases; for instance, the battery, ear phone jack, and, for certain releases, the home button.

References

Braun, John. Statistics Course Notes: Into to Statistical Process Control
Retrieved from http://www.stats.uwo.ca/faculty/braun/oldcourses/ss316b/notes/SPC/spcintro.pdf on January 27, 2018
Math 405 Class Notes: Methods and Philosophy of Statistical Process Control
Retrieved from https://classes.engineering.wustl.edu/2012/fall/ese405/405chapter5.ppt on January 26, 2018
Walker, Elshennawy, Gupta, & Vaughn. The Certified Quality Inspector Handbook
Retrieved from https://books.google.com/books?id=jF5_E4naG58C on January 26, 2018

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