Monday, June 6, 2011

Lean Tool: Fishbone Diagram. . . Add some fish to your diet!

A Fishbone Diagram is an extremely useful problem solving tool. After smoothing out your flow with the Spaghetti Diagram, it's time to use the Fishbone diagram to do some root cause analysis.

First reduce the carbs, then add some seafood to your Lean diet!

Having the Fishbone diagram in Powerpoint may actually be more helpful then the Spaghetti diagram, since it's more likely you'll be in a meeting room setting when filling out a fishbone with your group.

Also called the Ishikawa diagram or "cause and affect diagram," this Lean tool will assist you in your problem solving and brainstorming sessions. Using a structured approach, the fishbone diagram forces the group to focus on all aspects of the process.



The Powerpoint file pictured can be found at workflowdiagnostics.com under the heading "Fishbone."

The Fishbone Diagram takes a burning question and looks for all things that could possibly contribute to that issue. When trying to determine the root cause of a technical issue, the team needs to think of everything. The structure of a Fishbone Diagram standardizes your approach to ensure you consider all the possibilities.

And we all like standards!

The diagram is designed with the "Effect" located at the head of the fish, and each bone or branch containing a family of potential "Causes".

There are 6 main bones in the standard Fishbone diagram skeleton. Different terminologies are sometimes used, but they represent the common major influences in any process.

  1. Man - How can a person contribute to the effect (training, mistakes, non-standard work)?
  2. Method - How the design of the process can cause the effect (job design, process steps)?
  3. Machine - What equipment contributions are there (process settings, machine malfunctions, equipment variability)?
  4. Material - Any raw material influences (differences in lots, traceability)?
  5. Metrics - How are we measuring this (gauge r&r, capability)?
  6. Mother Nature - What environmental impacts are there (weather, air quality, heat)?
On each branch of the fishbone diagram, you begin to write all the specific potential causes that could influence your effect. For example, in the Machine branch, you might have several causes related to the equipment, such as machine breakdown, start-up, differences between machines.  

Depending on the process, you may have a lot of information on one branch and very little on another. It's ok. The purpose of the fishbone diagram is to guide your team, using a structured approach, not to make a pretty picture. 

After you've completed the fishbone diagram, you'll have a list of things to investigate. Just assign priorities to each and go after the big ones first. 


There's a good summary of how to fill out an Ishikawa diagram here: http://www.spcforexcel.com/creating-cause-and-effect-diagrams

I've added this to my list of Lean tools and resources.

What other names have you seen or used for labeling the branches in a Fishbone Diagram?

2 comments: