Root Cause Analysis

1
Root Cause Analysis

• Training and Explanation

2
Purpose of EasyTools

• There are lots of Quality tools around that can
  help improving many situations of the daily
  quality life. The problem with many tools is that
  you need training and experience to use them
  effectively.
• EasyTools is a collection of easy to use and
  mostly self explaining tools that everybody can
  use.
• No need for weeks of training or years of
  experience.

Just use it!
3
Tools for Root Cause Analysis

• The root cause analysis is the central method
  when solving a problem. It can be done by
  different methods using different tools.
• Here we discuss an easy to use method using
• - the 5 why
• - the fishbone diagram
• - root cause verification

4
Team work

• Team work
• Never do a root cause analysis alone.
• Nothing against your intelligence and your
  experience but you dont know enough! People of
  your team will tell you details of the problem
  you cant imagine.
• Put the team together
• So you need to select the right people for your
  team. There is no general rule which departments
  shall be involved. Just think who knows most
  about the product and the process where the
  problem occurred.
• Just as an example assume a welding problem
  maybe the welder himself, a welder of another
  shift, the welding expert, a welding maintenance
  guy, and maybe a product engineer could be part
  of your team.

5
The 5 why

• The 5 why tool
• 5 why is a tool where you ask why did that
  happen and you get a cause for it. Now you ask
  for this cause why did that happen and you get
  a cause for the cause. Then you ask again why
  did that happen and so on.
• Why to ask 5 times? Why not 4 times or 6 times?
• Some people found out that with 5 whys you dig
  deep enough. For me it is simple a synonym for
  Dig as deep as you can, until there is no
  sensible answer to your why question.
• Is 5 why enough for a root cause analysis? No, it
  is not!
• The root causes are like the roots of a tree
  from the trunk it goes maybe into 4 roots each
  root goes into another 5 roots etc. On the 5th
  level you may have thousands of roots.
• So we need to combine the 5 why with a second
  tool.

6
The fishbone diagram (Ishikawa diagram)
Problem

• The fishbone diagram helps to find causes by
  putting them into categories
• Man, Machine, Measurement, Material, Method,
  Environment.
• Some people replace Environment by Mother
  Nature just to make it begin with another M. I
  think this is stupid because of the completely
  different meanings of the terms.

7
Man

• Man
• Here we check if the problem could have been
  caused by people related issues such as
• Lack of training or education
• Poor employee involvement
• Previously identified issues which were not
  eliminated
• Bad or missing supervision
• You may find other sub-categories make your own
  list!

8
Machine

• Machine
• Here we check if the problem could have been
  caused by machine or equipment related issues
  such as
• Incorrect tool setting
• Poor maintenance or design
• Poor equipment or tool placement
• Defective equipment or tool
• You may find other sub-categories make your own
  list!

9
Measurement

• Measurement
• Here we check if the problem could have been
  caused by measurement related issues such as
• Poor process capability
• Bad or missing gages
• Poka Yokes switched off
• You may find other sub-categories make your own
  list!

10
Material

• Material
• Here we check if the problem could have been
  caused by material related issues such as
• Defective material or supplier parts
• Wrong material or parts
• Lack of material or parts
• You may find other sub-categories make your own
  list!

11
Method

• Method
• Here we check if the problem could have been
  caused by the applied method or standard such as
• No or poor work instructions
• Work instructions are not followed
• Practices are not the same as written procedures
• Poor communication
• You may find other sub-categories make your own
  list!

12
Environment

• Environment
• Here we check if the problem could have been
  caused by the workplace environment such as
• Orderly workplace, 5S
• Bad ergonomics of work place
• Lights, workplace environment
• Physical demands of the task
• You may find other sub-categories make your own
  list!

13
Combine fishbone diagram and 5 why

• How to combine the fishbone diagram with the 5
  why
• Very easy!
• For each identified cause apply the 5 why.
• Example Assume we had found a bad weld. We go
  for example to machine in the fishbone diagram
• The robot didnt weld correct why?
• The weld tip was dirty why?
• Preventive maintenance was not done as planned
  Why?
• The maintenance guy had to do some other
  emergency work -
• Attention we are not at the end! We can now
  follow different trees
• Maintenance why was the preventive maintenance
  not done after the emergency work was completed?
  etc.
• Robot why did the control unit not indicate a
  welding problem? etc.
• Etc.
• This example is far away from being completed. We
  have to consider all other trees of the fishbone
  diagram!

14
Possible root causes, probable root causes, true
root causes

• What is a possible root cause?
• When you have asked your whys you may come to a
  cause that could be a root cause. But at the
  moment you dont know. So you identify this as a
  possible root cause.
• Dont start to say I dont believe that this is
  a root cause we remove it from the list. Your
  opinion is not verified so you must not remove
  it from the list until the verification is done.
• What is a probable root cause?
• All possible root causes that need further
  investigations are named probable root causes.
• What is a true root cause?
• The investigation proofs whether the probable
  root cause is a true root cause or not a root
  cause.

15
Root cause verification - list

• We use a simple Excel sheet to document the root
  cause verification.
• No. A number to identify a possible root cause
• Possible root cause the possible root cause as
  written statement
• Location Optional if the problem could be caused
  by a supplier,
• indicate it here
• Root cause Y N P Here you assess if the possible
  root cause is a true root
• cause (Y), not a root cause (N), or a probable
  root cause (P)
• which needs further investigation
• Reason the reason for your Y N P decision
• The next 3 columns show a mixture of verification
  activities and prevention activities.
• Date Responsible Date and responsibility for the
  action to be done
• Preventative measures a) actions to verify a
  probable root cause (P) into a true root
• cause (Y) or not a root cause (N)
• b) Preventive actions to eliminate the true root
  cause
• Root cause Y N indicate a true root cause (Y) or
  not a root cause (N)

16
Root cause verification - flow
Possible root cause from fishbone diagram
Assessment
Evidence
Evidence
Probable root cause (P)
Investigation
Evidence
Evidence
Not a root cause (N)
True root cause (Y)
Prevention
17
Root cause analysis (RCA) example and template

• RCA Example
• The example shows Management in the fishbone
  diagram instead of Measurement.
• The example shows time in the analysis sheet
  instead of Date and Responsible.
• But it gives a good example how to proceed.
• RCA template