Defect Diagnosis

Basic Business Cents

No product is perfect. No service is perfect. That is because the process that produces them is not perfect. Only about 20% of the time can people be blamed, the rest of the defects or poor services are system or process problems. Unfortunately, defects become routine, and people become callous and accept them until a competitor proves they have fewer defects, better products or services.

In order to reduce defects, people need to believe defects can be reduced, and they initiate action to discover and remove causes. The main cause is variation. If the same method prescribed is not followed, applied differently, or is incorrect, defects will occur. Experience and intuition can sometimes remove causes of variation but they can also cause increased variation. An example is, “I know from my experience or I think it is better or easier to do it my way.”

Another cause of variation is materials. A leader in the field of quality once said, “Any two things not the same are different.” He was implying that nothing is exactly identical. A chicken soup manufacturer has to adjust equipment when the supply of chickens changes from one grower to the next. Maybe they were fed differently, had larger growing area for more exercise, were of different age, etc. Clothing size varies from manufacturer to manufacturer. Food delivered to a restaurant varies in texture, taste, and age. Nothing is exactly the same.

A third cause of variation is machines. Condition, tool wear, age, manufacturer, temperature, and humidity are all causes of variation in the output of machines.

The worker cause of variation should also be investigated. They may be trying to do their best but do they have the same energy in the afternoon as the forenoon, is there a difference between shifts. Is there a difference in physical characteristics, have they slept well the night before, is there a difference in mental conditions, and are they receiving different directions from supervision.

Methods, materials, machines, and workers are all causes of variation in work processes that need to be reduced. Variation can never be eliminated; it can only be reduced!

The first action is to correctly diagnose the principal causes of variation. If the true causes are not properly identified, corrective action may be carried out on a minor cause and the major causes overlooked. An analysis of the “vital few versus trivial many” will provide direction to action where the best results are attained. Data should be collected on causes of defects and grouped in like types. In this way, a priority of where to focus attention will appear.

When the most important causes are identified, then data should be collected to prove they are the main problem. Then investigate remedies and try them out on an experimental basis. Collect data again to prove they have significantly reduced defects and, if so, standardize on the new process. If this proves not to be the main solution, then restart the process to detect the main cause of defects.

As stated earlier, defects will always occur, no process is perfect, variation always exists, and process improvement action needs to be sustained forever.