Root Cause Analysis: Japan’s Problem Solving Secret
In 1930, Sakichi Toyoda, the father of the Toyota Motor Company developed a problem solving method called the “5 Whys”. In a nutshell, “5 Whys” is a kind of root cause analysis of any particular failure event. It was made popular after being used in the Toyota Production System (TPS) and is now used in many modern problem solving systems, such as Lean and Six Sigma. Maintenance issues are caused by a string of technical issues and process failures so the“5 Whys” method is often used to identify a cause and effect failure path.
5 Whys for Root Cause Analysis: In Practice
The root cause analysis technique is as follows: when you experience a problem, you start by asking, “Why did this occur?” You then repeat the process until a root cause becomes apparent. By asking “Why” repeatedly, you’re filtering out the symptoms and uncovering the heart of the problem.
For example: Your company missed a big product order when some equipment broke down. You need to figure out the root cause in order to fix the underlying issue. So, using the “5 Whys” method we start by asking why:
- Why did the equipment fail?: Because it overheated.
- Why did it overheat?: Because cooling fan failed.
- Why did the cooling fan fail?: Because regular servicing was missed.
- Why was its service missed?: Because we use a paper tracking system and it fell through the cracks.
- Why don’t we have an automated preventive maintenance system?: Because our maintenance guy is not great with computers.
If we just replaced the damaged fan, the issue would reoccur. The secret is to keep asking “Why” while the root cause still has a connection to the original problem. 5 whys is a good rule of thumb but it could take 6 or 7 iterations to get to the real root cause. The technique usually starts with a technical issue but eventually points to a process failure. Be careful not to turn in into the “5 Whos”.
To avoid going down the wrong ‘Why’ path, ask the following questions at each ‘Why’ node:
- Is there any visible or measurable evidence that each indicator could support the root cause determination?
- Could we ask another “why” and find a more plausible root cause?
- Could anything else produce this problem?
Root Cause Analysis: Taking it One Step Further
Be careful not to focus all attention on the lowest level root cause. If you do, you could leave your organization exposed to similar process breakdowns again. It’s usually a string of failures that contribute to the biggest issues so make an investment at each level in the ‘Why’ hierarchy.
In the above example, you could sign the maintenance guy up to a computer course; invest in a preventive maintenance program so service notifications are triggered automatically; configure servicing & replacement schedules as per manufacturers recommendations; even install a vibration sensor on the fan to predict a failure. Over time, continuous incremental investments and improvements like this compound, improving productivity of maintenance personnel and freeing up time previously lost fire-fighting breakdowns.
Benefits of Using The 5 Whys
The 5 Whys technique introduces the idea of systematic problem solving and is easy to complete without statistical analysis. It can be useful when tackling simple problems and offers a good starting point for complex issues. Its also prevents Band-Aid solutions where we tend to treat the symptoms rather than fix the real problems and prevent it from happening again. The 5 whys technique has its critics but it offers a simple problem solving technique that aids you in determining long term corrective actions.