What are the differences between quality control and quality assurance?

Understanding what they do, how they work together

TPJ - THE TUBE & PIPE JOURNAL® JULY/AUGUST 2011

July 20, 2011

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The terms quality control and quality assurance are often used interchangeably, but they are not synonymous. Quality assurance is a big-picture program executed by company management; quality control is a small-picture initiative that takes place on the production floor. Understanding these programs, and their roles, is critical in making sure the respective staffs carry out their duties effectively.

What are the differences between quality control and quality assurance? - TheFabricator.com

If you were to ask several purchasing agents to name the three most important criteria for evaluating the goods they purchase, they probably would agree on a fair price, on-time delivery, and quality. If you ask which is the most valuable, in all likelihood the most common response would be quality. Quality isn’t simply a cost. It can be a powerful tool that contributes to the economic success of the business. Therefore, while a supply chain partner needs to control all three, quality can be the most significant.

Many manufacturers recognize that quality leads to a higher customer retention rate and helps to build competitive boundaries. However, the term quality by itself isn’t sufficient. Two aspects are quality control (QC) and quality assurance (QA). Understanding what these terms mean, and what they don’t mean, is a crucial first step in understanding how they work together.

Defining QC and QA

ISO 9000 definitions provide a solid starting point:

  • QC: The operational techniques and activities that are utilized to fulfill requirements for quality
  • QA: All those planned and systematic activities implemented to provide adequate confidence that the entity will fulfill requirements for quality

A QC manager typically is interested in product yield. He focuses on the products, inspecting them in search of flaws. QC is a production line function. The aim of QC is to offer the highest reasonable quality of product or service to the client, thereby meeting or even exceeding the client’s requirements.

A QC method is intended to:

  • Provide regular product inspection, thereby guaranteeing the output’s correctness, completeness, and integrity. It finds and addresses mistakes.
  • File and record all the QC procedures.

A QA manager is interested in process yield. He is proactive at investigating technologies and processes that prevent defects. QA is a staff function. The aim of QA is to apply a planned and systematic production process, establishing confidence that the process generates suitable products.

A QA program is based on these principles:

  • The product or service needs to be suitable and fit for the intended purpose.
  • The methods and processes should decrease errors and shortcomings the first time through the manufacturing process.

QC is product-oriented; it focuses on tests and inspections carried out at various production line checkpoints. QA is process-oriented; its concerns are process definitions, proper selection of tools, proper use of testing methods, and operator training. QC works at locating defects; QA works at preventing them. QC emphasizes testing of products to discover defects, and reporting the results to management. QA attempts to improve and stabilize production to minimize or prevent the conditions that trigger defects.

Typically, quality control involves problem identification, problem analysis, problem correction, and feedback. Quality assurance involves data collection, problem trend analysis, process identification, process analysis, and process improvement.

Simply put, QC finds flaws; QA looks for the root cause that led to the flaw and addresses it.

How Do They Work Together?

Suppose a QC manager suspects that some substandard products are being shipped to customers. The QC manager would like to have a system in place that monitors the manufacturing process and triggers alerts when a product’s characteristics fall outside predetermined control limits. After QC personnel segregate these parts from the lot, QA personnel analyze them further, look for the root cause of the variation, and implement changes to improve compliance.

After the system is implemented, QA personnel can address any future problem by reviewing historical data, looking for correlations, and making interpretations. This information is critical, because if the QA staff finds an event that is meaningful and repeatable, it can devise a procedure that prevents that event from recurring.

Together both team members contribute to the process and goal of maintaining quality standards for the company.

What Do They Accomplish?

Because product quality is proportional to liability and profitability, risk management is one of the main reasons for establishing a quality-oriented mindset among employees and companies. A manufacturer is at less risk of having to make costly compensation payments resulting from faulty products if a good quality system is in place to prevent such mistakes. Revenue is also at stake because noncompliance can damage a company’s reputation.



Pierre Huot


Xiris Automation Inc.
1016 Sutton Drive
C5
Burlington, ON Canada
Phone: 905-331-6660

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