What is the root cause analysis?

What is Root Cause Analysis?

Root Cause Analysis is an in-depth technique for identifying the most relevant, controllable and significant cause of a problem. If we take action on that cause then the problem will not repeat again due to that cause.

Root cause analysis

3 Requirements of the Root Cause:

Root cause,requirement for root cause
  • Root cause must be relevant to the problem. If it is not relevant to the problem then it is not the root cause.
  • It must be controllable. If the root cause is not controllable then it is not the root cause.
  • It must be significant.

What are the 5 Whys of Root Cause Analysis?

Five whys were invented by Sakichi Toyoda in 1920.

The first part is related to the process that made the defective part.

Then why did it occur?

The second one must address the detection system that was not able to detect the defective part.

Why did the outflow happen?

Why did not detected in our factory?

Why did the part go to the customer?

5 Whys are not always necessary to reach the root cause of the problem. It may take less or more than 5 whys to get to the root cause. It could be 4 whys or 6 whys. It will depend upon the complexity of the problem.

Stop asking why if your common sense says you have reached the controllable step of a process, relevant document, policy or a concerned person ( operator or supervisor)

As this tool is purely observation-driven, just keep asking next why till you feel that the root cause has now come evident.

Useful Tools for determining Root cause analysis:

Practical Examples of Root Cause Analysis :

Case Study 1 :

Problem: Flat Tyre

Why 1Why 2Why 3Why 4Why 5Root Cause
Nails on the garage floorNails cartoon split openCartoon got wetRain through a hole in the garage roofRoof tiles are missingThe roof is not a part of the daily checklist

Case Study 2:

Problem: The machine stopped

Why 1Why 2Why 3Why 4Why 5Root Cause
The overload circuit trippedThe pump was seizedMetal chips damaged the shaftChips entered the lubrication systemNo filter on the inlet pipeSump design is not OK

Case Study 3:

Problem: Rod Length undersize on Bandsaw cutting

Why 1Why 2Why 3Why 4Why 5Root cause
Rod movement lessLimit switch plunger not movingPlunger jammedChips got into the plungerNo cover on plunger and limit switchMachine design not OK

Case Study 4:

Problem: Blowhole in Aluminium casting

Why 1Why 2Why 3Why 4Why 5Root Cause
Casting filling is not OKMolten metal does not reach the effective areaCasting ends before filling areaCasting design as per modelDesign not adequateGate opening not adequate

Case Study 5:

Problem: Punching out

Why 1Why 2Why 3Why 4Why 5Root Cause
Part shiftedLocator gauge shiftedLocator looseBolt looseHardened bolt not usedNo checkpoint in design

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