Quality control

In engineering and manufacturing, quality control and quality engineering are used in developing systems to ensure products or services are designed and produced to meet or exceed customer requirements.

Quality control is the branch of engineering and manufacturing which deals with assurance and failure testing in design and production of products or services, to meet or exceed customer requirements.

Quality assurance
One of the most widely used paradigms for quality assurance management is the PDCA (Plan-Do-Check-Act) approach, also known as the Shewhart cycle.

Failure testing
A valuable process to perform on a whole consumer product is failure testing (also known as stress testing), the operation of a product until it fails, often under stresses such as increasing vibration, temperature and humidity. This exposes many unanticipated weaknesses in a product, and the data is used to drive engineering and manufacturing process improvements.

Statistical control
Many organizations use statistical process control to bring the organization to Six Sigma levels of quality, in other words, so that the likelihood of an unexpected failure is confined to six standard deviations on the normal distribution. This probability is 3.4 one-millionths. Items controlled often include clerical tasks such as order-entry as well as conventional manufacturing tasks.

Traditional statistical process controls in manufacturing operations usually proceed by randomly sampling and testing a fraction of the output. Variances of critical tolerances are continuously tracked, and manufacturing processes are corrected before bad parts can be produced.

Company quality
During the 1980s, the concept of “company quality” with the focus on management and people came to the fore. It was realized that, if all departments approached quality with an open mind, success was possible if the management led the quality improvement process.

The company-wide quality approach places an emphasis on three aspects :-
 * 1) Elements such as controls, job management, defined and well managed processes , performance and integrity criteria and identification of records
 * 2) Competence such as knowledge, skills, experience, qualifications
 * 3) Soft elements, such as personnel integrity, confidence, organizational culture, motivation, team spirit and quality relationships.

The quality of the outputs is at risk if any of these three aspects is deficient in any way.

Total quality control
Total Quality Control is the most necessary inspection control of all in cases where, despite statistical quality control techniques or quality improvements implemented, sales decrease.

If the original specification does not reflect the correct quality requirements, quality cannot be inspected or manufactured into the product.

For instance, all parameters for a pressure vessel should include not only the material and dimensions but operating, environmental, safety, reliability and maintainability requirements.

Industrial resources

 * Quality Progress

Scientific resources

 * Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement, ISSN: 0949-1775 Print, eISSN: 1432-0517

Academic resources

 * The Quality Assurance Journal, ISSN: 1087-8378

Notes & References

 * Godfrey, A. B., Juran's Quality Handbook, 1999. ISBN 007034003.
 * Pyzdek, T., Quality Engineering Handbook, 2003. ISBN 0824746147.
 * Pyzdek, T., Quality Engineering Handbook, 2003. ISBN 0824746147.