1. What is a Fishbone Diagram?
Also known as a fishbone diagram, the name Ishikawa is derived from the Japanese academic Kaoru Ishikawa, who popularised its use in the Japanese industry in the 1960s. It is a visual tool that helps you organise and display the possible causes of a specific problem or effect. It looks like a fish skeleton, with the head representing the problem or effect, and the bones representing the main categories and subcategories of causes. The main categories are usually based on the 6M framework: Man (people), Machine (equipment), Material (input), Method (process), Measurement (data), and Milieu (environment). However, you can customise the categories according to your specific situation and industry.
2. How to create a Fishbone Diagram?
To create a Fishbone Diagram, you need to begin by defining the problem or effect in a box at the right end of the diagram. Draw a horizontal line from the box to the left, forming the spine of the fish. Next, identify the main categories of causes and write them along the spine, using diagonal lines to form ribs. To generate ideas for possible causes within each category, use tools such as 5 Whys, Surveys, or Checklists. Finally, analyse the diagram and prioritise the most likely or significant causes that need further investigation or improvement.
3. How to use a Fishbone Diagram in Six Sigma?
Fishbone Diagrams can be used during the various stages of Six Sigma DMAIC methodology. For example, in the Define phase, a Fishbone Diagram can help clarify the problem statement and project scope by illustrating the relationship between the problem and its causes. During the Measure phase, it can assist in collecting data and measuring the current performance of the process by identifying key variables and metrics that affect the problem. Analysing this data using a Fishbone Diagram can help to identify root causes of the problem by testing hypotheses and verifying assumptions. During Improve, it can generate and evaluate solutions for the problem by focusing on causes that have the most impact and feasibility. Finally, it can be used to monitor and sustain improvements in Control by establishing standards and procedures to prevent the recurrence of the problem.
Types of Ishikawa Diagrams
At its core, Ishikawa diagrams are the same. However, different types rely on various categories that may spur different innovative or strategic thinking. Here are the more common types of Ishikawa diagrams.
The 6 M’s Ishikawa Diagram
Each of the “bones” or “ribs” in a classic Ishikawa diagram represents an issue relevant to quality control, and may be described by the six “M”s, where failures or potential failures can be identified and rectified. These are:
- Manpower – The training, skill, and attitude of the employees or workers
- Machines – Maintenance of machines, whether upgrades to better technology is needed
- Materials – Are raw materials and inputs properly labelled, stored, and of high quality? Have they been ordered in the right size and quantity?
- Measurement – Are the methods of measurement and control correct and accurate? Do they need to be adjusted?
- Mother Nature – Often uncontrollable environmental factors like fire or bad weather, but specific safety measures can be undertaken, as well as insurance purchased for damage or disaster
- Method – Does the production process have the most efficient number of steps? Are there bottlenecks? Is it overly complex and error-prone?
The 3 M’s Ishikawa Diagram
A simple variation to the 6 M’s Ishikawa diagram is the 3 M’s diagram. In this variation, only “man”, “machine”, and “materials” are used. This is more commonly seen in manufacturing processes that experience less interaction with Mother Nature or those that do not require constant measurement or refinement.
The 8 P’s Ishikawa Diagram
Similar to the classic 6P diagram, a variation of organisations’ information is organised into eight different categories listed below.
- Procedures – What are the set of instructions in place to complete a task or activity?
- Policies – What internal rules dictate how things are done, and are they being followed accordingly?
- Place – Where are events occurring, are there better locations the events could occur, and what are the implications of events happening at these places?
- Product – What is being produced, why is it being made, and what else could be produced?
- People – Who is involved in the process, and who is being incorrectly omitted from it?
- Processes – What are the steps of a process, and are they being followed accordingly?
- Price – What are the financial inputs of the process, and what are the economic outputs of the process?
- Promotion – How are goods introduced to the market, and what strategies are used to convey the benefits of the product?
The 4 S’s Ishikawa Diagram
The 4S Ishikawa diagram has fewer components, as it categorises elements into only four categories. This diagram is more suited for the service industry as it omits categories that would be more helpful when contemplating a product or manufacturing process.
- Suppliers – Who do we rely on for goods, and what do we need from these third parties?
- Systems – What overarching processes are in place, and how can they be improved or modified to serve customers better?
- Surroundings – What physical experience does a customer have when they engage with our business, and what circumstances near our business impact the way we operate?
- Skills – What talents do we have, what talents do we need, and what do customers demand from us that we must be good at?
4. What are the benefits of using a Fishbone Diagram in Six Sigma?
Using a Fishbone Diagram in Six Sigma can bring several benefits, such as visualising and structuring the problem and its causes in a logical way. It also encourages team and stakeholder engagement in the problem-solving process through brainstorming and collaboration. Furthermore, it helps to identify and prioritise the most critical and actionable causes that need improvement, while eliminating irrelevant or trivial factors. Finally, it can help to communicate and document the problem and its causes clearly and effectively by creating a common language and understanding.
5. What are the challenges of using a Fishbone Diagram in Six Sigma?
Using a Fishbone Diagram in Six Sigma can also present some challenges, such as being time-consuming and complex to create and update. This is particularly true if the problem has many causes and subcauses. Additionally, the diagram can be subjective and biased, depending on the knowledge and experience of the people who create and use it. It can also be incomplete or inaccurate if the data and information used to make it are unreliable or invalid. Furthermore, the diagram may be misleading or oversimplified if the causal relationships are not verified or tested with data and analysis.
