Cause and effect diagram = fishbone in continuous improvement

What is the method and when is it used?

 

Cause and effect diagram, otherwise it is also called Ishikawa diagram, fish or fishbone. Sometimes you can also meet with the term – tree chart, because after turning about 90o it resembles, as the name suggests, just a tree.

 

The Ishikawa diagram is one of the most popular methods used to analyze the problem in the process of continuous improvement. It can be used when we want to identify all possible causes (input) of a given problem (output).

 

 

The fish bone diagram is used to analyze cause and effect relationships.

It leads to a comprehensive approach to all causes that result in a specific effect. In a transparent and orderly way, it also shows the links between the effect (result, result) and the related causes.

Based on the conducted analysis, the hierarchy of reasons for the occurrence of a specific phenomenon is determined, which is very important from the point of view of an effective solution to the observed problem.

 

What are the advantages of using a cause-and-effect diagram?

 

1. Presentation of all possible causes of a given problem or phenomenon in a figurative and graphic way.

This form of data presentation greatly facilitates their subsequent interpretation and analysis.

2. Identification of the most significant causes of the problem.

3. Concentration on the causes of the problem and not on the symptoms of non-compliance.

4. The use of knowledge and experience of people involved in the analysis – based on expert knowledge.

 

Structure and types of cause-and-effect diagram systems

 

Structure of the cause-and-effect diagram, source: own study

 

Types of Ishikawa diagram:

 

Most often you can meet three fish bone chart layouts. Visually, they do not differ from each other, they have the same structure. What is different is the approach to formulating the main categories of causes of the phenomenon / problem.

For this reason, we therefore distinguish the following systems:

objective – product structure

technological – structure of the production process

– participating factors – 5M

 

The most widespread approach, and thus the most commonly used, is the last variant, i.e. 5M.

 

And what does the 5M abbreviation mean?

 

Men (personnel, human factor so-called executing, i.e. having a direct impact on the course of the process, operation of the device, etc.)

Machine (equipment, equipment, tool that can affect the problem)

Material (ingredients, raw materials, substances, goods, etc.)

Method (processes, work techniques, methods of executing given processes and operations)

Management (human management factor, i.e. one that indirectly affects processes, device support, etc.)

 

By creating a cause-and-effect diagram, you can add additional categories, such as the surroundings, the environment or any of your own categories. It all depends on the problem being analyzed and the reasons for its creation, which will be indicated by the participants of the meeting.

 

How to conduct an analysis using a cause-and-effect diagram?

 

Step by step instruction

 

Step # 1 Draw the main axis of the graph and enter the analyzed problem at the end of the arrow.

 

 

Step # 2 Draw the side axes with the main categories of the cause of the problem or process steps and connect them to the main axis.

 

The following are examples of the main categories. Depending on the type of the analyzed issue, you can freely choose them.

 

 

Step # 3 Collect possibly all potential causes of the analyzed problem, phenomena and assign to appropriate categories.

 

Suggested reasons can be collected earlier, eg during brainstorming sessions, methods 6-3-5 or other. You can also collect ideas directly during the preparation of the fish bone diagram.

The cause should only be assigned only to one category.Sometimes it is possible to assign proposals to a larger number of main causes, but only in extremely complex problems – rather you have to beware of this. Otherwise, it may be difficult to properly interpret the final Ishikawa diagram.

Step # 4 Ask questions for each indicated cause of the problem: what? how? when? why? where?

By asking these questions to the given input information you will gradually reach the source cause.

 

 

What could cause power outages?

A: Melted wires.

Why are the wires melted down?

a: Due to too high temperature caused by the lack of coolant.

How did it happen that there is no coolant in the pipes?

a: The cooling water supply pipe is drained.

As you can see, asking questions, for each of the suggested reasons, makes it very easy to find a root cause. It does not remind you of the method 5 Why? Yes of course!

The cause and effect diagram combines at least three methods presented in earlier entries.

 

Step # 5 Analyze the root causes of the problem and take action to eliminate them.

 

The final stage of the analysis is, of course, the selection of all the causes and the selection of those that, in the opinion of experts, had the greatest impact on the problem.

All that remains is assigning tasks to people who will be responsible for their implementation and setting a deadline for when to do it.

After the implementation, it is worth conducting an audit of the effectiveness of the introduced actions, and if it turns out that the effect is permanent – prepare a description, the so-called Lesson learned to avoid similar problems in the future.

 

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