www.stangerweb.de root cause analysis training and explanation 1

www.stangerweb.de

Root Cause Analysis

Training and Explanation

1

www.stangerweb.de

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.

2

Just use it!

www.stangerweb.de

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

3

www.stangerweb.de

Team work

Team workNever do a root cause analysis alone.Nothing against your intelligence and your experience; but you don’t know enough! People of your team will tell you details of the problem you can’t imagine.

Put the team togetherSo 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.

4

www.stangerweb.de

The 5 why

The 5 why tool5 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.

5

www.stangerweb.de

The fishbone diagram (Ishikawa diagram)

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.

6

Man Machine Measurement

Material Method Environment

Problem

www.stangerweb.de

Man

7

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!

www.stangerweb.de

Machine

8

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


www.stangerweb.de

Measurement

9

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


www.stangerweb.de

Material

10

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


www.stangerweb.de

Method

11

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


www.stangerweb.de

Environment

12

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


www.stangerweb.de

Combine fishbone diagram and 5 why

How to combine the fishbone diagram with the 5 whyVery 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 didn’t 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! 13

www.stangerweb.de

Possible root causes, probable root causes, true root causes

What is a possible root cause?When you have asked your why’s you may come to a cause that could be a root cause. But at the moment you don’t know. So you identify this as a possible root cause.

Don’t start to say “I don’t 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.

14

www.stangerweb.de

Root cause verification - list

We use a simple Excel sheet to document the root cause verification.

No. A number to identify a possible root causePossible root cause the possible root cause as written statementLocation Optional; if the problem could be caused by a supplier,

indicate it hereRoot 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 donePreventative 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)15

www.stangerweb.de

Root cause verification - flow

16

Possible root cause from fishbone diagram

Assessment

Probable root cause (P)

Investigation

Not a root cause (N)True root cause (Y)

Prevention

EvidenceEvidence

Evidence Evidence

www.stangerweb.de

Root cause analysis (RCA) – example and template

RCA ExampleThe 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

17

www.stangerweb.de root cause analysis training and explanation 1

Documents