Quality control (QC) is a process by which entities review the quality of all factors involved inproduction.ISO 9000 defines quality control as "a part ofquality management focused on fulfilling quality requirements".[1]
This approach places emphasis on three aspects (enshrined in standards such as ISO 9001):[2][3]
Inspection is a major component of quality control, where physical product is examined visually (or the end results of a service are analyzed). Product inspectors will be provided with lists and descriptions of unacceptableproduct defects such ascracks or surfaceblemishes for example.[3]
Earlystone tools such asanvils had no holes and were not designed asinterchangeable parts.Mass production established processes for the creation of parts and system with identical dimensions and design, but these processes are not uniform and hence some customers were unsatisfied with the result. Quality control separates the act oftestingproducts to uncover defects from the decision to allow or deny product release, which may be determined by fiscal constraints.[6] For contract work, particularly work awarded by government agencies, quality control issues are among the top reasons for not renewing a contract.[7]
The simplest form of quality control was a sketch of the desired item. If the item did not match the sketch, the item was rejected, in a simpleGo/no go procedure. However, manufacturers soon found it was difficult and costly to make parts be exactly like their depiction; hence around 1840 tolerance limits were introduced, wherein a design would function if its parts were measured to be within the limits. Quality was thus precisely defined using devices such asplug gauges andring gauges. However, this did not address the problem of defective items; recycling or disposing of thewaste adds to the cost of production, as does trying to reduce the defect rate. Various methods have been proposed to prioritize quality control issues and determine whether to leave them unaddressed or usequality assurance techniques to improve and stabilize production.[6]
There is a tendency for individual consultants and organizations to name their own unique approaches to quality control—a few of these have ended up in widespread use:
| Terminology | Approximate year of first use | Description |
|---|---|---|
| Statistical quality control (SQC) | 1930s | The application of statistical methods (specificallycontrol charts andacceptance sampling) to quality control[8]: 556 |
| Total quality control (TQC) | 1956 | Popularized byArmand V. Feigenbaum in aHarvard Business Review article[9] and book of the same name;[10] stresses involvement of departments in addition to production (e.g., accounting, design, finance, human resources, marketing, purchasing, sales) |
| Statistical process control (SPC) | 1960s | The use ofcontrol charts to monitor an individual industrial process and feed back performance to the operators responsible for that process; inspired bycontrol systems |
| Company-wide quality control (CWQC) | 1968 | Japanese-style total quality control.[11] |
| Total quality management (TQM) | 1985 | Quality movement originating in theUnited States Department of Defense that uses (in part) the techniques of statistical quality control to drive continuous organizational improvement[12] |
| Six Sigma (6σ) | 1986 | Statistical quality control applied to business strategy;[13] originated byMotorola |
| Lean Six Sigma (L6σ) | 2001 | Six Sigma applied with the principles oflean manufacturing and/orlean enterprise; originated by Wheatet al.[14] |
Inproject management, quality control requires the project manager and/or the project team to inspect the accomplished work to ensure its alignment with the project scope.[15] In practice, projects typically have a dedicated quality control team which focuses on this area.[16]
Metrology, the science of measurement, plays a fundamental role in quality control across manufacturing industries. It ensures that tools, machines, and parts are precisely calibrated and measured throughout the production cycle. Without accurate metrology, quality control would lack the precision needed to detect and prevent defects.
In industrial contexts, quality control depends on accurate and consistent measurements to ensure that each product meets the intended specifications. A deviation in measurement can result in flawed products, increased waste, and reduced customer satisfaction. Metrology supports quality control by providing standardized methods and calibrated tools for inspection, calibration, and testing.
Both disciplines aim to guarantee the reliability and repeatability of production processes. Metrology achieves this through regular calibration routines, inspection protocols, and support for new product development. This shared focus on precision helps drive continuous improvement, ensuring that systems and outputs comply with rigorous quality standards.
The termtotal quality management, orTQM, has been commonly used to denote the system of managing for total quality. (The term TQM was actually developed within the Department of Defense. It has since been renamed Total Quality Leadership, since leadership outranks management in military thought.)
When practiced as a management system, Six Sigma is a high performance system for executing business strategy.
This article incorporatespublic domain material fromFederal Standard 1037C.General Services Administration. Archived fromthe original on 22 January 2022. (in support ofMIL-STD-188).
