Early efforts to control the quality of production
During the Middle Ages, guilds adopted responsibility for quality control of their members, setting and maintaining certain standards for guild membership[citation needed].
Royal governments purchasing material were interested in quality control as customers. For this reason, King John of England appointed William Wrotham to report about the construction and repair of ships[citation needed]. Centuries later, Samuel Pepys, Secretary to the British Admiralty, appointed multiple such overseers[citation needed].
Prior to the extensive division of labor and mechanization resulting from the Industrial Revolution, it was possible for workers to control the quality of their own products. The Industrial Revolution led to a system in which large groups of people performing a similar type of work were grouped together under the supervision of a foreman who was appointed to control the quality of work manufactured.
Wartime production
At the time of the First World War, manufacturing processes typically became more complex with larger numbers of workers being supervised. This period saw the widespread introduction of mass production and piecework, which created problems as workmen could now earn more money by the production of extra products, which in turn occasionally led to poor quality workmanship being passed on to the assembly lines. To counter bad workmanship, full time inspectors were introduced into the to identify, quarantine and ideally correct product quality failures. Quality control by inspection in the 1920s and 1930s led to the growth of quality inspection functions[citation needed], separately organised from production and large enough to be headed by superintendents.
The systematic approach to quality started in industrial manufacture during the 1930s[citation needed], mostly in the USA[citation needed], when some attention was given to the cost of scrap and rework. With the impact of mass production required during the Second World War made it necessary[citation needed] to introduce an improved form of quality control known as Statistical Quality Control, or SQC. Some of the initial work for SQC is credited to Walter A. Shewhart of Bell Labs, starting with his famous one-page memorandum of 1924[citation needed].
SQC includes the concept that every production piece cannot be fully inspected into acceptable and nonacceptable batches. By extending the inspection phase and making inspection organizations more efficient, it provides inspectors with control tools such as sampling and control charts, even where 100 per cent inspection is not practicable. Standard statistical techniques allow the producer to sample and test a certain proportion of the products for quality to achieve the desired level of confidence in the quality of the entire batch or production run.
Postwar
In the period following World War II, many countries' manufacturing capabilities that had been destroyed during the war were rebuilt. General Douglas MacArthur oversaw the re-building of Japan. During this time, General MacArthur involved[citation needed] two key individuals in the development of modern quality concepts: W. Edwards Deming and Joseph 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.
Although there were many individuals trying to lead United States industries towards a more comprehensive approach to quality, the U.S. continued to apply the Quality Control (QC) concepts of inspection and sampling to remove defective product from production lines, essentially ignoring advances in QA for decades[citation needed].
Steps for a typical quality assurance process
There are many forms of QA processes, of varying scope and depth. The application of a particular process is often customized to the production process.
A typical process may include:
* test of previous articles
* plan to improve
* design to include improvements and requirements
* manufacture with improvements
* review new item and improvements
* test of the new item
Failure testing
Valuable processes to perform on a whole consumer product is failure testing or stress testing.[citation needed] In mechanical terms this is 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 are used to drive engineering and manufacturing process improvements. Often quite simple changes can dramatically improve product service, such as changing to mold-resistant paint or adding lock-washer placement to the training for new assembly personnel.
Statistical control
Many organizations use statistical process control to bring the organization to Six Sigma levels of quality,[citation needed] in other words, so that the likelihood of an unexpected failure is confined to six standard deviations on the normal distribution. This probability is less than four one-millionths. Items controlled often include clerical tasks such as order-entry as well as conventional manufacturing tasks.[citation needed]
Traditional statistical process controls in manufacturing operations usually proceed by randomly sampling and testing a fraction of the output. Variances in critical tolerances are continuously tracked and where necessary corrected before bad parts are produced.
Total quality management
The quality of products is dependent upon that of the participating constituents,[1] some of which are sustainable and effectively controlled while others are not. The process(es) which are managed with QA pertain to Total Quality Management.
If the specification does not reflect the true quality requirements, the product's quality cannot be guaranteed. For instance, the parameters for a pressure vessel should cover not only the material and dimensions but operating, environmental, safety, reliability and maintainability requirements.
During the Middle Ages, guilds adopted responsibility for quality control of their members, setting and maintaining certain standards for guild membership[citation needed].
Royal governments purchasing material were interested in quality control as customers. For this reason, King John of England appointed William Wrotham to report about the construction and repair of ships[citation needed]. Centuries later, Samuel Pepys, Secretary to the British Admiralty, appointed multiple such overseers[citation needed].
Prior to the extensive division of labor and mechanization resulting from the Industrial Revolution, it was possible for workers to control the quality of their own products. The Industrial Revolution led to a system in which large groups of people performing a similar type of work were grouped together under the supervision of a foreman who was appointed to control the quality of work manufactured.
Wartime production
At the time of the First World War, manufacturing processes typically became more complex with larger numbers of workers being supervised. This period saw the widespread introduction of mass production and piecework, which created problems as workmen could now earn more money by the production of extra products, which in turn occasionally led to poor quality workmanship being passed on to the assembly lines. To counter bad workmanship, full time inspectors were introduced into the to identify, quarantine and ideally correct product quality failures. Quality control by inspection in the 1920s and 1930s led to the growth of quality inspection functions[citation needed], separately organised from production and large enough to be headed by superintendents.
The systematic approach to quality started in industrial manufacture during the 1930s[citation needed], mostly in the USA[citation needed], when some attention was given to the cost of scrap and rework. With the impact of mass production required during the Second World War made it necessary[citation needed] to introduce an improved form of quality control known as Statistical Quality Control, or SQC. Some of the initial work for SQC is credited to Walter A. Shewhart of Bell Labs, starting with his famous one-page memorandum of 1924[citation needed].
SQC includes the concept that every production piece cannot be fully inspected into acceptable and nonacceptable batches. By extending the inspection phase and making inspection organizations more efficient, it provides inspectors with control tools such as sampling and control charts, even where 100 per cent inspection is not practicable. Standard statistical techniques allow the producer to sample and test a certain proportion of the products for quality to achieve the desired level of confidence in the quality of the entire batch or production run.
Postwar
In the period following World War II, many countries' manufacturing capabilities that had been destroyed during the war were rebuilt. General Douglas MacArthur oversaw the re-building of Japan. During this time, General MacArthur involved[citation needed] two key individuals in the development of modern quality concepts: W. Edwards Deming and Joseph 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.
Although there were many individuals trying to lead United States industries towards a more comprehensive approach to quality, the U.S. continued to apply the Quality Control (QC) concepts of inspection and sampling to remove defective product from production lines, essentially ignoring advances in QA for decades[citation needed].
Steps for a typical quality assurance process
There are many forms of QA processes, of varying scope and depth. The application of a particular process is often customized to the production process.
A typical process may include:
* test of previous articles
* plan to improve
* design to include improvements and requirements
* manufacture with improvements
* review new item and improvements
* test of the new item
Failure testing
Valuable processes to perform on a whole consumer product is failure testing or stress testing.[citation needed] In mechanical terms this is 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 are used to drive engineering and manufacturing process improvements. Often quite simple changes can dramatically improve product service, such as changing to mold-resistant paint or adding lock-washer placement to the training for new assembly personnel.
Statistical control
Many organizations use statistical process control to bring the organization to Six Sigma levels of quality,[citation needed] in other words, so that the likelihood of an unexpected failure is confined to six standard deviations on the normal distribution. This probability is less than four one-millionths. Items controlled often include clerical tasks such as order-entry as well as conventional manufacturing tasks.[citation needed]
Traditional statistical process controls in manufacturing operations usually proceed by randomly sampling and testing a fraction of the output. Variances in critical tolerances are continuously tracked and where necessary corrected before bad parts are produced.
Total quality management
The quality of products is dependent upon that of the participating constituents,[1] some of which are sustainable and effectively controlled while others are not. The process(es) which are managed with QA pertain to Total Quality Management.
If the specification does not reflect the true quality requirements, the product's quality cannot be guaranteed. For instance, the parameters for a pressure vessel should cover not only the material and dimensions but operating, environmental, safety, reliability and maintainability requirements.
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