Inspection Methods to Fulfill Quality Requirements
by Ron Kurtus (revised 27 May 2008)
Whenever work is done or a product or part is made—whether it is a piece of hardware manufactured on the assembly line, a memo typed by a secretary, or code developed by software programmers—it should be inspected to see that it fulfills the requirements and specifications.
This is certainly a wise business practice. Some companies accept a certain failure rate, while others try to correct the problems they see from their inspection. Inspecting and then correcting will save a company money.
Questions you may have include:
- What is wrong with standard inspection methods?
- How is failure information gathered?
- How can workers inspect for quality?
This lesson will answer those questions.
Sorting out failures
The most common type of inspection that has been done for years on the assembly lines involves sorting the defective items from the acceptable product. This method is sometimes referred to as "creating quality by inspection" and is not considered an effective quality management approach.
Production line inspection
For example, at the end of a production line the inspector gives final approval whether or not parts are good. The rejects are put into scrap or are re-worked. This assures only quality material reaches the next stage, but it does not address the cause of the failed parts nor does it correct that problem.
Office work inspection
In another situation, office workers may complete reports only to have their manager reject many of them as unacceptable. Those reports must be re-done until acceptable. Again, the reason for the failures is not addressed, and the rejection rate remains constant.
Not a good approach
In both cases, sorting out failures can be a wasteful and expensive method to get quality goods.
Another thing it does is to accept a certain level of failure. That acceptance subtly creates an atmosphere of accepting failure in all work that is done by the company.
Gathering failure information
A more effective method to inspect consists of gathering information and using data gained from inspection to control the process and prevent future defects. Statistical Process Control (SPC) is a type of this type of inspection.
Inspections at intermediate stages
Since work-in-process undergoes many operating steps as it is moved through a manufacturing facility, inspections are often conducted at intermediate stages in the process. The inspections give statistical information necessary to determine the cause of the quality problem, so that it can be prevented in the future. SPC does not aggressively seek to eliminate defects and in some cases changes may be implemented too slowly to be fully effective.
White collar examples
One example in the office is that the boss may inspect a report at various stages, making corrections. He may then see that perhaps there was a communication problem in stating the requirements that may be rectified.
In the office, the engineering manager may monitor the designs of his engineers, making corrections along the way. The engineers learn from his changes and the final design is relatively free of errors.
This method of making inspections at intermediate stages is certainly better than waiting until the product in completed to inspect for acceptance or rejection.
Inspection by workers
One other inspection method is to have workers inspect the item from the prior operation before proceeding. In this way quality feedback can be given on a much timelier basis. Each operation performs both production and quality inspection.
By monitoring where most problems occur in a production line, a quality manager can pinpoint causeswhether it is a drunk worker or a defective piece of equipment.
In an office environment, there is no individual monitoring the quality of the work, as there often is in a factory. Perhaps there should be. Typically, when a piece of work gets passed from one person to another, informal corrections are told to the previous worker.
Sorting out failures is a common form of inspection, but it does not address the problems. Statistical measurements of where failures occur is a way to find out causes. Workers can inspect parts before starting and notify previous persons in the process of problems in quality. Inspection and correcting reasons for failure is important in reducing wasteful expenses in a company.
Set a tone for quality in your organization
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Inspection Methods to Fulfill Quality Requirements