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A Focus on Quality

A Focus on Quality – The 5-Why and Ishikawa Cause and Effect Research Methods

Nothing happens without a reason – effects are always the result of a cause. Unfortunately, detecting causes is not always easy, as effects are usually the result of a complex and often convoluted series of causes.

Experience shows that the immediate cause of a problem itself is generally the result of a variety of further causes, and each of these result from additional causes. Hence, you need to often dig very deep until you can uncover the actual root cause of a problem. Regardless of what field of business you operate in, the detection of causes and the correct designation of influence factors are the most important steps for effectively preventing negative effects.

Two techniques that are used within quality management to uncover the root cause of a problem are the 5-Why method and Ishikawa diagrams. The 5-Why method, developed by Toyota, uses a simple yet effective question asking technique in order to find root causes. Repeatedly asking the question of “Why?” peels away individual causes bit by bit and eventually exposes the root cause of a problem.

The 5-Why Method

An example: the production tolerance parameters of a product are not met.

  • Why? (1) The machine is not functioning correctly.
  • Why? (2) A required maintenance job was not done.
  • Why? (3) The maintenance job was not included in the maintenance plan.
  • Why? (4) The maintenance plan is out of date.
  • Why? (5) The maintenance plan is not checked on a regular basis.

Hence, the action that needs to be taken in order to prevent a failure of the machine is to regularly check that the maintenance plan is up-to-date. The 5-Why method allows you to keep questioning the problem until the root cause is uncovered.

The Ishikawa Diagram

The Ishikawa diagram works in a similar manner. It allows the user to consolidate all possible problem causes and interdependencies in a clearly structured fishbone diagram. The influencing variables are subdivided into primary and secondary causes which all point towards the main problem or potential for improvement. The individual arrows each stand for a contributing factor to a cause or improvement.

For the sake of a better overview, the primary causes are summarized in a selection of categories. These can, for example, consist of 6 Ms (Machine, Method, Material, Man Power, Measurement and Milieu) or 8 Ms (including Management and Maintenance). Any type or number of primary causes can be applied. These are then addressed step by step, thereby allowing valuable information to come to the fore. The analysis of the various influence factors via the Ishikawa diagram often reveals connections that no one would have thought of initially.

With its modules REM.Net and FMEA.Net, CAQ.Net® software offers you comprehensive support for tracking down the root causes of problems and uncovering idle potential for improvement. Apart from Ishikawa and 5-Why, CAQ.Net® also contains a variety of other powerful cause and effect research methods like fault tree analysis (FTA) or cause and effect matrix. Use the most refined research tools that today’s quality management has to offer and efficiently shed light on the hidden causes of problems.


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