Identifying a problem is just the beginning. Soon after, you’ll need to identify the cause. There are many ways to do this and the Fishbone Diagram is one of them. Simple as it may be, even the fishbone diagram has several different structures for different purposes. The key is to choose the one that best fits the problem you’re addressing.
What is a Fishbone Diagram?
The Fishbone Diagram is also known as the Cause and Effect Diagram, C&E Diagram, or the Ishikawa Diagram, named after its inventor Kauoru Ishikawa, organizational theorist and engineering Professor at The University of Tokyo. It is used to first brainstorm the potential causes of a problem, then narrow potential causes to find the root cause and move on to a solution.
It’s called a Fishbone Diagram, because it looks like a fish skeleton with the symptom, or effect of the cause, as the head and potential causes branching out from the spine. Each branch is a category.
For each category, brainstorm specific things that could be causing the effect, or symptom (i.e. how the problem is showing up on the manufacturing floor). Once you’ve added enough data to be helpful, dive into evaluating each one with a series of questions – Why’s. This helps you narrow the possibilities to a list of most likely causes and test from there. Eventually, you’ll come up with the root cause. Along the way, you may also discover other issues or causes for other effects.
Resources to build a Fishbone Diagram
There are the variations that can tailor the cause and effect diagram to your specific situation. ASQ also offers a Fishbone Diagram builder to make the setup process easier. Scroll to the bottom of that page to download the Excel template. Minitab and Visio are also good options. Canva, a free graphic design platform, will also help you make a Fishbone Diagram in exchange for your email address.
Existing types of Fishbone Diagrams
5M/1E (Standard Manufacturing) Fishbone Diagram
Most of the time, manufacturing teams will use these six categories in their Fishbone Diagrams: Machine, Methods, Measurements, Materials, Manpower, and Environment. It covers all the major aspects we come across in a manufacturing setting.
Here are a few more you may find helpful.
Simple Fishbone Diagram:
This version doesn’t have any predetermined categories, so it is the most flexible. Rather than starting with the method, materials, etc. the team starts by thinking of their own categories. It leaves everything open to be specific to the topic at hand. That means any team could use it for any reason.
The 4S Fishbone Diagram
This is often used in a service organization and include categories like systems, surroundings (like environment or mother nature in other versions), skills (people), suppliers. It could also be helpful in the internal services in a manufacturing plant, which can be especially helpful if your goal is to include the entire facility in using the Fishbone Diagram as a problem-solving tool.
8P Fishbone Diagram
As you might imagine based on other Lean Manufacturing tools, the 8P Fishbone Diagram got its name from its eight categories and they all begin with “P:” Price, processes, people, product, procedures, promotion, policies, physical location or place. This is also popular in administrative functions and the service industry.
Design of Experiments Fishbone
The Fishbone Diagram can also be a great tool to help in setting up a new experiment. Use these categories to gather and organize information about the factors you expect to see or have seen in an experiment: Controllable Factors, Uncontrollable Factors, Held-Constant Factors (i.e. factors that will be held constant so as to not change their influence on the experiment), and Blockable Nuisance Factors (i.e. factors that have some affect on the experiment, but are not the main focal point).
There are literally endless patterns you can use with a Fishbone Diagram. The goal is to choose the right one for your situation. Think about things like the level of customization needed for your situation or required for the pattern, the amount of time you have to complete the exercise, and how many different categories of causes there could be. Could they all fit into one of the established patterns or do you need to create something new?
Tips on leading a brainstorm:
One of the most critical parts of using the Fishbone Diagram is your team’s ability to brainstorm. To help you get that started on the right foot, here are a few tips you might find helpful.
- Give people multiple ways to contribute, such as sticky notes on a board or brainstorming in small groups first.
- Give people time to prepare before they arrive. Think of it as priming their minds.
- Stick the “no idea is a bad idea” mantra. All it takes is one idea getting shot down to discourage others from contributing an idea they aren’t 100% certain about.
- Invite the right people to the brainstorm and don’t be afraid to think outside of the regular team.