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Fishbone / Ishikawa diagram

KZK Solutions /kzoli62/
Published by Z. Kovács in Quality · 15 September 2021
Tags: QA8D
What is a Fishbone chart?

The Herringbone Diagram, also known as the “Causal Diagram” or Ishikawa Diagram (named after its creator, Kaoru Ishikawa, a Japanese quality control expert (1968)). The teams use a herringbone diagram to illustrate all possible causes of the problem and predict the consequences with an impact analysis.

The Isikava diagram is most often used in product design and quality error prevention to identify all potential factors that may be responsible for the final impact. Each factor that causes or triggers imperfections is the source of another variation.

Advantage of Fishbone Diagram 4

1. Focus on one cause rather than symptoms

Using the Fishbone Diagram helps teams really get to the root of the problem, rather than simply describing the situation and ignoring the secondary causes of the root cause.

2. All possible causes become visible in an instant

The Fishbone Diagram displays several reasons, in a logical order, visually. All stakeholders can explore and understand how these fit together holistically.

3. Create an idea for brainstorming

Many teams use the Fishbone chart as a starting point for a structured brainstorming session to generate a large number of possible ideas about what could be the trigger.

4. Concentrate everyone around the root cause

Instead of identifying the causes of the problem on their own, the Fishbone Diagram allows the team to focus on working together, analyzing and prioritizing different options until they get to the root cause.

How to make a Fishbone Diagram in 3 steps

1. Define a description of the problem

Create a statement that explains exactly what the problem is and how and when it occurs. This should be added to the right side of the chart as the “head” of the fish. Before delving into the causes, make sure your team agrees with the definition of the problem.

2. Define the categories of causes

What are the broad categories or areas of possible causes? For example, if you’re trying to diagnose a problem with your software product, you might want to look at users, software, or marketing. In the case of a physical product, it may include people, methods, materials, machines, or the environment. Try to keep the number of categories below ten.

Many companies, especially in the automotive industry, use 6 M (Man, Method, Machine, Material, Measurement, Milieu) as a starting point.

The causes are usually grouped into the following main groups so that these differences can be identified:
  • Man: Anyone involved in a given process
  • Methods: how the process takes place and what regulations apply to it, such as business policies, procedures, internal regulations and legal requirements
  • Machine: any device needed to perform the task (eg computers, tools, etc.)
  • Materials: all raw materials, semi-finished and finished products that are needed to produce the final product
  • Measurements: all data that comes from a process and is suitable for evaluating the quality of the process
  • Environment (Milieu): the conditions under which the process operates (eg location, time, temperature, culture, etc.)

3. List the reasons

Once you have your category, you need to list the specific reasons for each category. These fish become “strands” that can be used as a basis for diagnosing the root cause of the problem. Some groups use the Fishbone Chart 5 Why-all together to systematically dig deeper and explore new possible causes.

Although I have already written about the 5 Why, but next time we will look at this topic, now from a quality assurance point of view, considering the completion of the 8Ds.

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