A customer complaint and a question
A customer reports a batch of housings with a sealing face out of flatness. Their first question is not “how many are bad?” but “how do you make sure this doesn’t happen?” The answer cannot be “we check carefully”. The customer wants to see a system: which characteristics are controlled, how, how often, by whom, what happens when a check fails, and evidence that all of it was actually done.
That system is quality assurance.
Assurance and control
ISO 9000:2015 describes quality assurance as the part of quality management focused on providing confidence that quality requirements will be fulfilled. Quality control is the part focused on fulfilling them, for example by inspection and testing.
The difference is one of direction. Quality control looks at the product and asks “is this right?” Quality assurance looks at the way of working and asks “will this keep coming out right, and can we show it?” Inspection is one of the tools of quality assurance, but it is not the whole of it.
The cycle
Quality assurance is usually described as a cycle, based on Plan-Do-Check-Act, which ISO 9001:2015 uses as the basis of its process approach.
- Plan: define the requirements, assess the risks, decide which characteristics to control and how. Tools such as FMEA and control plans belong here.
- Do: carry out the work according to instructions, with trained people and suitable equipment.
- Check: measure the result and compare it with the requirement. Statistical methods such as statistical process control show whether the process stays where it should.
- Act: correct deviations, find root causes, and feed what you learn back into planning.
In the middle of the cycle sits the evidence: the records that show each step was carried out. ISO 9001 calls these documented information.
Worked example: one characteristic through the cycle
Take the flatness of the sealing face, with a requirement of 0.05 mm.
- Plan. The process FMEA identifies clamping distortion as a cause of poor flatness. The control plan specifies a check of five parts per shift on a flatness gauge, with a reaction plan to stop and sort if a value exceeds 0.05.
- Do. The work instruction describes the clamping torque and the sequence. Operators are trained on it.
- Check. Values are recorded per shift and plotted. A slow increase over a week is visible before any part exceeds the limit.
- Improve. The cause turns out to be a worn clamp. Clamp inspection is added to preventive maintenance, and the FMEA is updated.
Every step leaves a record: the FMEA, the control plan, the measured values, the investigation and the change. The numbers are illustrative; the pattern is the point.
What makes it work in practice
- Requirements that are clear. A control is only as good as the requirement it checks.
- Controls where the risk is. Inspect what matters most, based on risk, rather than everything equally.
- Reliable measurements. A check with a poor gauge gives false confidence; see measurement system analysis.
- Records that are easy to keep and to find. Paper forms work, but they are slow to search and easy to lose. This is one of the main reasons companies move towards digital records.
Common misunderstandings
- “Quality assurance is the quality department’s job.” It depends on everyone who plans, does and checks the work.
- “More inspection means better quality.” Inspection finds defects; it does not prevent them. Prevention comes from stable, capable processes.
- “We are certified, so we are assured.” A certificate shows that a system exists and has been audited. It is the daily practice that delivers the confidence.
In short
Quality assurance is the answer to the question “how do you know?” It combines planned controls, disciplined work, checks and improvement, and keeps the evidence. Done well, it means a customer complaint can be answered with facts.
