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Wednesday, February 18, 2015

You Can’t Inspect in Quality

Unfortunately, there are not enough organizations that understand quality. Quality is not additive or final. It must go beyond the product or service. We cannot add it at the end of the line or inspect it into the product. At best that is only a false sense of security. If we want a quality product it must be made with quality processes by quality minded people.

Inspection can be useful to gather data on the process. Using that data to see if a process has gone out of control and a special cause needs to be investigated is useful. Using that data to evaluate the success, or failure, of an attempt to improve (via the PDSA cycle) is useful.

Many traditional companies use a final inspection department to 100% check the product just before it is shipped to make sure that any errors that occurred in-process are caught before the product is shipped.

Inspecting to pull out the failed items from the production before a customer sees them is a path to failure. When companies do this, they are trying to inspect quality into the product.  However, 100% inspection has been shown to be only about 80% to 85% effective. If the process is this bad, the process needs to be improved.

"Inspection does not improve the quality, nor guarantee quality. Inspection is too late. The quality, good or bad, is already in the product. As Harold F. Dodge said, “You can not inspect quality into a product." — W. Edwards Deming, Out of Crisis, Page 29

In some organizations, we might as well give the quality folks a uniform, a badge and a gun. They act like they are the Quality Police. Progressive companies realize you cannot inspect quality into a product.  By the time product is inspected, its level of quality has already been established. The primary means of ensuring a quality product is delivered is not by waiting until the product is assembled to test it. Great companies build quality in from the start and maintain that quality throughout the manufacturing process. To improve quality, you have to improve the process that produced it.

Generally the most effective way to achieve quality is to avoid having defects in the first place. It is much less costly to prevent a problem from ever happening than it is to find and correct the problem after it has occurred. Focusing on prevention activities whose purpose is to reduce the number of defects is better. Companies employ many techniques to prevent defects for example statistical process control, quality engineering, training, and a variety of tools from the Lean and Six Sigma tool kit.

Start with the idea of preventing defects, not waiting until they are identified and correcting them. Many companies have an active Zero Defects policy where defect prevention is paramount and quality inspection is almost just a verification of what they already know – that the product is defect free. If we can start with quality and maintain that quality throughout the process we will have a quality product.

Quality is about prevention—you cannot "inspect" quality into a product. It has to happen before the inspection process.

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1 comment:

  1. Hi Tim

    Business that use final inspection to catch defects, generally drive up their rework and scrap costs. If you stop and fix an issue as soon as it comes up, at worst you lose one unit of production or you have one unit that needs some extra work. But if you choose to ignore it you can scrap or rework hundreds if not thousands of units. It is still common in some companies that they keep running despite an issue arising. One such company routinely has to fix several hundred units, because they ignore issues until after production is done for the day or even at times the week, while one of their competitors will stop a line to fix an issue right away. It may surprise some people, but one company is always struggling and their quality focussed competitor is healthy and growing steadily.