Two key principles characterise QA: "fit for purpose" (the product should be suitable for the intended purpose) and "right first time" (mistakes should be eliminated). QA includes regulation of the quality of raw materials, assemblies, products and components; services related to production; and management, production and inspection processes.
It is important to realize also that quality is determined by the intended users, clients or customers, not by society in general: it is not the same as 'expensive' or 'high quality'. Even lowly bottom-of-the-range goods can be considered quality items if they meet a market need.
Early civil engineering projects needed to be built from specifications, for example the four sides of the base of the Great Pyramid of Giza were required to be perpendicular to within 3.5 arcseconds.
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. Centuries later, Samuel Pepys, Secretary to the British Admiralty, appointed multiple such overseers.
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. Working conditions then were arguably more conducive to professional pride.
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.
To counter bad workmanship, full time inspectors were introduced into the factory 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, separately organised 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 appropriate form of quality control which can be identified 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.
SQC came about with the realization that quality cannot be fully inspected into an important batch of items. 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.
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 QC concepts of inspection and sampling to remove defective product from production lines, essentially ignoring advances in QA for decades.
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.
The major problem which leads to a decrease in sales was that the specifications did not include the most important factor, “What the specifications have to state in order to satisfy the customer requirements?”.
The major characteristics, ignored during the search to improve manufacture and overall business performance were:
As the most important factor had been ignored, a few refinements had to be introduced:
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.
The CMMI (Capability Maturity Model Integration) model is widely used to implement Quality Assurance (PPQA) in an organization. The CMMI maturity levels can be divided in to 5 steps, which a company can achieve by performing specific activities within the organization.
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 four aspects :-
The quality of the outputs is at risk if any of these aspects is deficient in any way.
The approach to quality management given here is therefore not limited to the manufacturing theatre only but can be applied to any business or non-business activity:
It comprises a quality improvement process, which is generic in the sense it can be applied to any of these activities and it establishes a behaviour pattern, which supports the achievement of quality.
In manufacturing and construction activities, these business practices can be equated to the models for quality assurance defined by the International Standards contained in the ISO 9000 series and the specified Specifications for quality systems.
Still, in the system of Company Quality, the work being carried out was shop floor inspection which did not reveal the major quality problems. This led to quality assurance or total quality control, which has come into being recently.
It has become customary to use consultants and contractors when introducing new quality practices and methods, particularly where the relevant skills and expertise are not available within the organisation. In addition, when new initiatives and improvements are required to boost the current quality system, or perhaps improve upon current manufacturing systems, the use of temporary consultants becomes a viable solution when allocating valuable resources.
There are various types of consultants and contractors available in the market; most will have the skills needed to facilitate improvement activities such as Quality Management Systems (QMS) auditing and procedural documentation writing. More experienced consultants are likely to have knowledge of specialised quality improvement activities such as CMMI, Six Sigma, Measurement Systems Analysis (MSA), Failure Mode and Effects Analysis (FMEA), Advance Product Quality Planning (APQP).