Quality control

For other uses of this term, please see Quality Control (disambiguation).

In engineering and manufacturing, quality control and quality engineering are involved in developing systems which ensure that products or services are designed and produced to meet or exceed customer requirements and expectations. These systems are often developed in conjunction with other business and engineering disciplines using a cross-functional approach.

History

Though terms like 'quality engineering' and 'quality assurance' are relatively new, the ideas have existed just as long as the very art of tool manufacture. Simple tools made of rock or bone were subject to familiar modes of failure. They could be fragile, dull where they should be sharp, sharp where they should be dull, etc. When the first specialized craftsmen arose, manufacturing tools for others, the principle of quality control was simple: "let the buyer beware" (caveat emptor).

The first civil engineering projects, however, needed to be built to specifications.

Craft and tradespersons

During the Middle Ages, guilds took the responsibility of quality control upon themselves. All practitioners of a particular trade living in a certain area were required to join the corresponding guild, and the guild instituted punishments for members who turned out shoddy products.

Royal government purchasing material were interested in quality control as customers. For instance, King John of England appointed a certain William Wrotham to supervise the construction and repair of ships. Some centuries later, but also in England, Samuel Pepys, Secretary to the Admiralty, appointed multiple such overseers.

Prior to the extensive division of labor and mechanization resulting from the Industrial Revolution, it was possible for a workman to control the quality of his own product. Working conditions then were more conducive to professional pride.

The Industrial Revolution led to a system in which large groups of men performing a similar type of work were grouped together under the supervision of a foreman who also took on the responsibility to control the quality of work manufactured.

Quality Assurance has developed a good deal during the last 80-90 years (in about 20 year intervals) from its inception to the current state of the art.

Wartime production

During World War I, the manufacturing process became more complex, and the introduction of large numbers of workers being supervised by a foreman designated to ensure the quality of the work, which was being produced. This period also introduced mass production and piecework, which created quality problems as workmen could now earn more money by the production of extra products, which in turn led to bad workmanship being passed on to the assembly lines.

Due to the large amount of bad workmanship being produced, the first full time inspectors were introduced into the large-scale modern factory. These full time inspectors were the real beginning of inspection quality control; and this was the beginning of large inspection organizations of the 1920s and 1930s, which were separately organized from production and big enough to be headed by superintendents.

The systematic approach to quality started in industrial manufacture during the 1930s, mostly in the USA, when some attention was given to the cost of scrap and rework. With the impact of mass production, which was required during the Second World War, it became necessary to introduce a more stringent form of quality control which can be identified as statistical process control (SPC). Some of the initial work for SPC is credited to Walter A. Shewhart of Bell Labs.

This system came about with the realisation that quality cannot be inspected into an item. By extending the inspection phase and making inspection organizations more efficient, it provides inspectors with control tools such as sampling and control charts.

SQC had a significant contribution in that it provided a sampling inspection system rather than a 100 per cent inspection. This type of inspection however did lead to a lack of realisation to the importance of the engineering of product quality.

For example, if you have a basic sampling scheme with an acceptance level of 4%, what happens is you have a ratio of 96% products released onto the market with 4% defective items – this obviously is a fair risk for any company/customer – unless you happen to be one of the unfortunate buyers of a defective item.

Postwar

After World War II, the United States continued to apply the concepts of inspection and sampling to remove defective product from production lines. However, there were many individuals trying to lead U.S. industries towards a more collabrative approach to quality. Excluding the U.S., many countries' manufacturing capabilities were destroyed during the war. This placed American business in a position where advances in the collabrative approaches to quality were essentially ignored.

After World War II, the U.S. sent General Douglas MacArthur to oversee the re-building of Japan. During this time, General MacArthur invited two key individuals in the development of modern quality concepts: W. Edwards Deming and Dr. Joseph Moses Juran. Both individuals promoted the collaborative concepts of quality to Japanese business and technical groups, and these groups utilized these concepts in the redevelopment of the Japanese economy.

Late twentieth century

In the late twentieth century, the extremely low tolerance of failure of such devices such as manned spacecraft, nuclear power plants, or life saving drugs created extremely refined approaches to quality control that place heightened constraints on managers developing such projects. In space exploration, victories or failures of quality control produce dramatic results- either the Space Shuttle Challenger disaster or the victory of the Mars Exploration Rovers after a high failure rate of probes to that planet. Studies of the Challenger and Columbia disasters highlight the nature of the friction between quality control and managers attempting to achieve aggressive schedules. It is a friction that has become familiar to high stakes technology product development when rigorous software testing or clinical trials of new drugs reveal product weaknesses.

Quality control: Encyclopedia BETA

Contents

Quality control

History

Craft and tradespersons

Wartime production

Postwar

Late twentieth century

See also

External links

References