Quality control is a process employed to ensure a certain level of quality in a product or service. It may include whatever actions a business deems necessary to provide for the control and verification of certain characteristics of a product or service. The basic goal of quality control is to ensure that the products, services, or processes provided meet specific requirements and are dependable, satisfactory, and fiscally sound.

Essentially, quality control involves the examination of a product, service, or process for certain minimum levels of quality. The goal of a quality control team is to identify products or services that do not meet a company’s specified standards of quality. If a problem is identified, the job of a quality control team or professional may involve stopping production temporarily. Depending on the particular service or product, as well as the type of problem identified, production or implementation may not cease entirely.

Usually, it is not the job of a quality control team or professional to correct quality issues. Typically, other individuals are involved in the process of discovering the cause of quality issues and fixing them. Once such problems are overcome, the product, service, or process continues production or implementation as usual.

Quality control can cover not just products, services, and processes, but also people. Employees are an important part of any company. If a company has employees that don’t have adequate skills or training, have trouble understanding directions, or are misinformed, quality may be severely diminished. When quality control is considered in terms of human beings, it concerns correctable issues. However, it should not be confused with human resource issues.

Often, quality control is confused with quality assurance. Though the two are very similar, there are some basic differences. Quality control is concerned with the product, while quality assurance is process–oriented.

Even with such a clear-cut difference defined, identifying the differences between the two can be hard. Basically, quality control involves evaluating a product, activity, process, or service. By contrast, quality assurance is designed to make sure processes are sufficient to meet objectives. Simply put, quality assurance ensures a product or service is manufactured, implemented, created, or produced in the right way; while quality control evaluates whether or not the end result is satisfactory.

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. These systems are often developed in conjunction with other business and engineering disciplines using a cross-functional approach.

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

Quality assurance

Quality assurance covers all activities from design, development, production, installation, servicing and documentation. Statistics shows, less than 5% of the world’s food is safe to consume. This introduced the rules: "fit for purpose" and "do it right the first time". It includes the regulation of the quality of raw materials, assemblies, products and components; services related to production; and management, production, and inspection processes.

[Edit] 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. 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. Failure testing or destructive testing is a valuable tool of earthquake engineering.

[Edit] 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 less than four 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.

 [Edit] 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, adequate 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.

 The approach to quality management given here is therefore not limited to the manufacturing theatre only but can be applied to any business activity:

     * Design work

    * Administrative services

    * Consulting

    * Banking

    * Insurance

    * Computer software

    * Retailing

    * Transportation

 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 behavior pattern, which supports the achievement of quality.

 This in turn is supported by quality management practices which can include a number of business systems and which are usually specific to the activities of the business unit concerned.

 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 control the major quality problems. This led to quality assurance or total quality control, which has come into being recently.

 [Edit] 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.

 The major problem which leads to a decrease in sales was that the specifications did not include the most important factor, “What the customer required”.

 The major characteristics, ignored during the search to improve manufacture and overall business performance were:

     * Reliability

    * Maintainability

    * Safety

 As the most important factor had been ignored, a few refinements had to be introduced:

    1. Marketing had to carry out their work properly and define the customer’s specifications.

   2. Specifications had to be defined to conform to these requirements.

   3. Conformance to specifications i.e. drawings, standards and other relevant documents, were introduced during manufacturing, planning and control.

   4. Management had to confirm all operators are equal to the work imposed on them and holidays, celebrations and disputes did not affect any of the quality levels.

   5. Inspections and tests were carried out, and all components and materials, bought in or otherwise, conformed to the specifications, and the measuring equipment was accurate, this is the responsibility of the QA/QC department.

   6. Any complaints received from the customers were satisfactorily dealt with in a timely manner.

   7. Feedback from the user/customer is used to review designs.

   8. Consistent data recording and assessment and documentation integrity.

   9. Product and/or process change management and notification.

 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.

 To conclude, the above forms the basis from which the philosophy of quality assurance has evolved, and the achievement of quality or the “fitness-for-purpose” is “Quality Awareness” throughout the company.