Ishikawa Diagram is a graphical tool used by the administrative sector for the management and quality control in various processes. In short, it helps to reflect on the causes and effects of a given problem and how to prevent it.
Also known as Cause and Effect Diagram, Fishbone Diagram or 6M Diagram, this scheme was originally proposed by the chemical engineer. Kaoru Ishikawa, in the year of 1943, and was perfected in the following years.
In its structure, problems are classified into six different types (6 Ms): method, raw material, labor, machinery, measurement and environment. This system makes it possible to hierarchically structure the potential causes of a given problem or also an opportunity for improvement, as well as its effects on the quality of products.
The Ishikawa Diagram is one of the most effective and most used tools in quality control and improvement actions in organizations, allowing you to group and visualize the various causes that are at the origin of any problem or result that intends to improve.
These diagrams are usually made by working groups and involve all agents of the process under analysis. After identifying which problem or effect to study, a list of possible causes is made and then a cause and effect diagram is drawn.
How to make an Ishikawa diagram?
Before starting to draw the diagram, the following steps must be completed:
- Determine the problem that will be analyzed in the diagram and the objective that you hope to achieve. However, abstract and vague words should be avoided;
- Gather information about the problem at hand;
- Assemble a group that can help with the creation of the diagram, and after presenting the necessary information, promote a session of brainstorming about the problem;
- Order all information succinctly, point out the main causes and eliminate unnecessary information;
- Draw the diagram taking into account the causes that must be in accordance with the 6 M's (machine, method, labor, raw material, environment, measurement).
An Ishikawa diagram should contain the following components:
- Header: Title, author(s), date.
- Effect: It must contain the quality indicator and the problem to be analyzed. The effect usually occupies the right side of the sheet.
- Central axis: Represented by a horizontal arrow, it points to the effect and is a horizontal line in the middle of the sheet.
- Category: indicates the most important groups of factors related to the effect. In this case the arrows depart from the central axis and are inclined.
- Cause: Potential cause, belonging to a category that can collaborate with the effect. The arrows are horizontal lines, which point to the category arrow.
- Sub-cause: Potential cause that can contribute to a specific cause. They are derivations of a cause.
See too Diagram and Venn diagram.