What is a Fishbone Diagram?
A fishbone diagram (also referred to as the Ishikawa diagram, herringbone diagram, or cause-and-effect diagram) is a reference diagram used in manufacturing and production industries to analyze the existing problems in a process and find out the root cause. According to Karou Ishikawa, the pioneer behind quality control and one of the founding fathers of modern management, the fishbone diagram was designed as a diagrammatical layout to break down (in successive layers of detail) root causes that potentially contribute to a particular effect. In order words, a fishbone diagram is utilized for root cause analysis. But that aside, it also realizes many other benefits for an organization.
Fishbone diagrams are also used in manufacturing to plan product designs to a favorable end. An Ishikawa diagram can be primarily used in the design stage of a production or manufacturing process to minimize or avoid the existence of errors or problems. Mazda Motors famously utilized a fishbone diagram in the manufacturing of the Miata (MX5) sports car. A fishbone diagram is also a powerful control tool that can reduce variations in production and business processes, reducing the number of defects or failures.
First, why is it called a fishbone diagram? This causal diagram used in businesses draws its name from how it is created. The structure of the diagram resembles the skeleton of a fish. We’ll explain its structure clearly to help you with a clear picturization of an Ishikawa diagram.
- The head of the fish is represented by the main issue (problem or defect), which is indicated on a background (usually white).
- An horizontal line is drawn to meet the main issue (problem or defect), representing the fish’s backbone.
- Then, a series of branches (lines) stems out of the horizontal line on both sides, mimicking the ribs of the fish. They point out possible major causes.
- Then, sub-branches stem out to denote root causes.
A fishbone diagram is also primarily used under a brainstorming atmosphere in meetings and the like. Hence, it allows for an endless indication of as many possible causes of a problem. All you have to do is keep stemming out more branches. Fishbone diagram is one of the seven essential tools of Quality Control and is majorly used in the DMAIC analysis phase of Six Sigma.
In this article, we’ll discuss the following:
1. The 6 Ms of fishbone diagram
2. How to create a fishbone diagram
3. Advantages and disadvantages of a fishbone diagram with some tips for a progressive fishbone diagram
The 6 Ms Of A Fishbone Diagram
When making and using an Ishikawa diagram, it’s essential to understand the factors that lead to significant problems in production, manufacturing, and business. A method is usually followed through in a business or production process from start to finish to ensure a successful procedure. However, if there is variation at one point in the process, the expected outcome can no longer be met. This situation is what leads to major problems like process or product failure, defects, errors, etc.
To mitigate variations in manufacturing processes, Karou Ishikawa came up with the 6 Ms- all Ms representing a major influence on variations and success in processes. The 6 Ms are majorly known as the contributing factors in the manufacturing world. They are:
How To Create A Fishbone Diagram
A fishbone diagram is a very simplified process used in industries, companies, enterprises, and firms, so creating one and using it successfully is something anyone can do. It is a cause-and-effect analysis, so the agenda of the diagram is obvious- to find the causes and effects of a major problem or issue. To successfully create and use an Ishikawa diagram, you must get specialized software, a whiteboard, a flip chart, and some marking pens. Then, follow this particular step-by-step process that will help you achieve the layout of the diagram:
STEP 1: Identify the main issue
First of all, come together with your team members and conclude the major problem (effect) your process, business, or organization is going through. The main problem will act as the anchor of the fishbone diagram analysis; in other words, it’s the reason for the analysis and the problem that will be analyzed to find its root cause./p>
After agreeing on a major problem, indicate it on the right corner of the whiteboard inside a black box, triangle, or circle, indicating the heading and the head of the fishbone diagram. The main problem is what all team members will direct their attention to, so make it as bold as possible. Then, draw a thick horizontal line that connects to the main issue, acting as the backbone of the fishbone diagram.
STEP 2: Brainstorm categories of major factors
The next step in creating a fishbone diagram is to engage in a brainstorming session with your team members to figure out possible major factors and causes of the main issue. Ordinarily, organizations would look at generic factors like equipment, systems, resources, etc. In a manufacturing firm, the major possible factors often fall under the 6 Ms we highlighted earlier: manpower, method, material, mother nature (environment), machine, and measurements.
After coming up with the categories of major factors, draw a slant line that resembles a rib connecting to the backbone of the fishbone diagram. Draw the ribs (lines) on both sides of the backbone and use them to indicate the major factors.
Analyze possible immediate causes
In this next step, the brainstorming session will become more intense. You and your team members will try to analyze each factor contributing to the main issue and identify all possible causes. For instance, you are looking at “manpower” as a significant factor. Ask questions like; how is manpower contributing to the rise in the major issue? What is missing in the human labor needed to facilitate a process? Is it inadequate staff to compensate for a massive workload? Are staff not fully trained to handle equipment and machines seamlessly?
Asking questions will help you figure out more detailed causes relating to the existence of the major problem at hand. Once you have outlined a list of possible and likely causes, draw smaller branches stemming out from the ribs you used to indicate the major factors. Then indicate the identified possible causes on the smaller branches. Using the 5 Whys technique would be very helpful in this phase to help identify more possible causes.
Analyze the diagram
Following all the steps, you should have already completed your fishbone diagram. The next thing to do is analyze further using various techniques and tools like 5 Whys, GAP Analysis, Pareto Chart, Gemba Walk, etc. While analyzing the diagram further, you’ll be able to come up with more possible causes, if any, and finally, arrive at a root cause.
The layout of an Ishikawa diagram helps you with a broader analysis since you have gone through the trouble of outlining any and every possible cause relating to the problem statement. Further analysis will provide you with the information you’ll need to make better decisions and judgments concerning the development of a process or the termination of an existing problem.
What Are The Disadvantages & Advantages Of An Ishikawa Diagram?
The Ishikawa diagram is undoubtedly a beneficial technique in many use cases. Whether you’re trying to utilize it to develop a product to its final stage, identify problems with a process, or streamline the manufacturing process, a fishbone diagram will help you expand your analysis to a certain depth. While the problem-solving technique comes with various advantages regarding its purpose and method, it also has some disadvantages that quality managers, business owners, and manufacturers should be aware of. These are the pros and cons of the Ishikawa diagram.
Advantages
- One of the most prominent uses of the fishbone diagram is the ability to help find out causes and effects that relate to a problem statement in any industry, business, or organization.
- It is a tool that helps build up and facilitate brainstorming sessions in an organization. It does not only present a brainstorming process but also provides a problem-solving atmosphere if consistently used, whereby employees are workers will get used to thinking outside the box.
- The analysis phase of a fishbone diagram that emphasizes asking why things happen in a process or organization helps to drill down to more root causes.
- Helps in better decision-making and strategic planning in an organization for the improvement of a project, process, or system.
- It also helps with the prioritization of root causes in a simplified layout so that managers and employees can identify and focus on more underlying root causes.
Disadvantages
- Because a fishbone diagram allows for intensive brainstorming, it’s likely that project teams will spend so much time coming up with both relevant and irrelevant potential causes, which can result in confusion or misplacement of priorities.
- When using a fishbone diagram to analyze or solve complex issues, the diagram’s layout might look messy due to multiple sophisticated variables and factors that might need more details. Because of this possibility, a fishbone diagram is better utilized for simple problems.
- A fishbone diagram can be a perfect lure for managers to look into and fix every cause they encounter. A diagram that lets you outline numerous possible causes of a major issue will leave you with inadequate resources to handle them. More importantly, a team might be led to look into less important potential causes of a problem while leaving the more pressing causes.
- Based on opinions, an Ishikawa diagram needs testing to determine if the results will be successful. It’s possible for an organization to use a fishbone diagram and not get any remedial solutions, only potential and possible causes of a problem.
Notwithstanding the cons that a fishbone diagram presents, this problem-analysis tool can be used to achieve progressive results as long as you keep the following tips in mind:
