Simple yet effective Brainstorming and most widely used tool in Projects and Organizations for analyzing Root Cause. When we try to fix a problem, we need to address the symptoms. This tool or technique is used for exploring the cause and effect relationship of a problem.
The core idea is asking ‘Why’ repeatedly as each response will bring new insight to ask next ‘Why’. There is no hard rule to ask exact 5 numbers of ‘whys’, it is possible that occasionally one need to ask more than 5 times ‘why’ to get to the Root cause and sometime it can be achieved in less than 5. The Idea is to keep digging until no further useful information can be extracted.
Example:
Machining center that requires cooling, but the coolant supply suddenly stopped.
- Why? - A quick examination exposed that a circuit breaker had tripped.
- Why did the circuit breaker trip?
- Because the pump had overloaded.
- Why did the pump overload?
- Because metal chips got into the pump.
- Why did metal chips get into the pump?
- Because a metal screen meant to keep them out was missing.
- Why was it missing?
- Because on incorrect preventative maintenance and the safety screen was left off.
- Why was preventative maintenance done incorrectly?
- Because of not doing proper training and documentation. That is the root cause
