What is the Difference between Quality Assurance and Quality Control?

Quality Control is not Quality Assurance, in spite of the fact that many people uses these terms interchangeably. In summary:

Quality Control is used to identify defects, usually after the event and often when it is too late. It’s a reactive activity undertaken on product.

Quality Assurance uses techniques which are designed to ensure the process is correct and therefore help guarantee a correct and repeatable product which is produced in an efficient way. This in turn reduces lead time, minimises waste, reduces cost and should hopefully delight the customer. It also lends itself to simple and effective process control and monitoring, which can be undertaken quickly and efficiently by operators, and has the added advantage of empowering people and making their work more meaningful & satisfying. Quality Assurance is a proactive activity which is undertaken on the process (not product) and enables the fast identification of variation which can lead to out of specification product.

Quality Control uses statistical techniques to try and identify defects from a relatively small and random sample. It’s open to error and the risk shipping poor quality parts. On the other hand, Quality Assurance uses statistical analysis to monitor and control the process and to identify when the process is operating outside its usual and expected parameters. It’s there to highlight change and the need for process corrections with the aim of preventing future out of specification products.

Quality Assurance is a management tool which forms part of a Quality Management System. It is there to ensure the process and product are consistent and production is efficient. Simple mechanisms like Poka Yoke, a mistake-proofing tool, are built into the production tooling & process. It enabling every operation to be checked and verified before moving on to the next operation. Whereas Quality Control uses inspection tools and equipment, such as callipers and test rigs to measure against a customer’s specification and inspection criteria, rather than verifying each part. Quality Control is based on risk and random checks. In today’s world it’s a high-risk policy that manufacturers use at their peril.

Quality Assurance uses verification processes whereas Quality Control is a validation exercise.

Quality Assurance uses historical data to review and identify possible quality improvements which in turn lead to increased efficiency and profitability. It’s all about saving time, reducing waste and increasing profit while at the same time helping to delight the customer.

Quality Control is less about improvement and more about hoping you can prevent faulty parts reaching the customer. The surprising thing is that we tend to expect and accept that manufacturers will make and attempt to ship parts that weren’t ordered, faulty parts which we don’t want. We even expect to pay for such parts in the form of scrap rates.

Quality Assurance starts at the beginning of the design and development process whereas Quality Control is used after the product is made. Quality Assurance influences the design and production process and should help reduce waste and cost. Quality Control has no meaningful place in design and development and can increase products cost through allowing poor production efficiency, waste and a greater number of customer complaints.

By Charles Firbank, Director of Operations, CMD

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