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Understanding the original Fishbone Diagram


Ishikawa diagram or the fishbone diagram.


One of the seven tools of QC, and often associated with as a tool for problem-solving by brain-storming.


Are you sure?

Are you sure that Ishikawa, the original inventor of the tool, used it in such a manner?

Ishikawa designed the tool to help design the quality management system. The diagram showed the link between the objective - factors - standards. And then used as a problem-solving tool.


Frequently, I ran into people who proudly presented the “fishbone” diagram. They have spent hours, if not days, in a meeting room brainstorming ideas. I always get into conflict with such people. The brainstorming was done, ignoring the actual condition of the factory. Nothing but collections of bias. Did they really understand what Ishikawa was saying? Did Ishikawa intend such a tool?


Kaoru Ishikawa was an academic who focused on Quality Control and Quality Management. His core message is “Build in quality by design and process control. Not by inspection.” He questioned the traditional inspection approach on quality. He criticizes traditional Japanese management of “Tunnel command” (Layers of managers repeating the exact words.), Spiritual management (Just slogans), and Force management (Just getting the numbers). 🤔 Sounds familiar outside of Japan, too. He is asking deep questions about the management 【管理】.


His thinking on quality management was the following.

  1. Define objective and target ⬅️ Direction (Housin) ⬅️ Information & Research

  2. Define the methods (Standards) to accomplish the objective

  3. Education & training

  4. Execute

  5. Check

  6. Action

  7. Check the results of the action

The “Fishbone” diagram was originally designed for step 2, not step 6.


It is essential to note the original Japanese name that Ishikawa gave. It is called 特性要因図.

特性 = Characteristic

要因 = Determiner, Factor

As a quality expert, he explains the importance of understanding the “Quality characteristics” that the customer needs. This diagram explains to accomplish specific quality characteristics what are the contributing factors. And then, he challenges the standards for each factor. He mentions Work standards, technology standards, design standards, job requirements, etc.

  1. Do we have a standard for each and every factor?

  2. Are the standards correct?

  3. Can we perform the way standards state?

  4. Are we following these standards?

  5. Are there any contradictions among the standards?

In other words, he was using this diagram to highlight the quality management system.


Here’s an episode of Ishikawa explaining how he came up with the “Fishbone diagram.”

“When I (Ishikawa) was teaching at the university in 1950, I had to distinguish the objective/target (Characteristics) and factors. This is why I can up with the diagram. In 1952, I introduced at Kawasaki Steel, which helped first with standardization and other things.”

Note here that he used this diagram first to standardize.


I found millions of problems with this diagram when I tried such a standardization method.

Very often, we find out that we don’t actually have a standard.

“An operator made a mistake.”

“Ok, where is the work standard?”

“We don’t have it, but the experienced one can do without it.”

“We should document the correct method. By the way, the defect was made by an experienced one.”

“…”

And then, as we investigated the problem, we found out that the operator was following an outdated standard set five years ago. But why was the operator miss informed? As we investigated, they changed the materials but did not inform the operator or the machine (later, we found problems with the machine). It was a classic example of what Ishikawa was trying to solve, understanding the link between the factors and standards. We should confirm that all other factors are aligned when you change one. Unless you know the relationships, you continue to do guessing, skipping many factors.


Today, you might not see such use of the “Fishbone diagram.” Why? Because the table version of the “Fishbone diagram” is similar to the Failure Mode and Effects Analysis (FMEA). But how often do you run into an FMEA which does not consider all factors? How often do you see an FMEA which misses the connections among the factors? There are some values to visualize in such a diagram.


I have not used the word “Brainstorming,” but I will post about that on a separate topic.


Reference; Kaoru Ishikawa “Introduction to Quality Control (Third edition)” 1989.

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