Root cause analysis using the 5 whys method

Equipment failure is not a single event—it is a process. The truth is maintenance issues are often caused by a string of technical issues and process failures. This is why the five whys method exists and is used to identify a cause-and-effect failure path as part of a larger root cause analysis (RCA).

What is Root Cause Analysis (RCA)?

Since the five whys analysis is only a segment of root cause analysis (RCA), it helps to first define what RCA typically entails and what it aims to achieve. Root cause analysis (RCA) is a systematic process for identifying the underlying causes of problems or incidents so that the most effective solutions can be identified and implemented. It is used to diagnose and address the primary or “root” causes of issues rather than merely addressing their symptoms.

The rationale behind RCA is that addressing the root causes of problems provides longer-term solutions and prevents the same problems from recurring. If only the symptoms of the problems are addressed, the underlying issues may remain uncorrected, and the problems can recur.

For every defect or equipment failure that occurs, there is an obvious, visible problem that lets you know a defect or failure has occurred. For example, you’ll know something is wrong with a piece of equipment if it’s producing material that isn’t to spec. But that’s not where the problem-solving begins and ends. There were likely many little things that contributed to the failure. If you want to prevent the problem from occurring again, you have to dig deeper and look at it from all sides.

Besides the five whys, there are other RCA analysis methods used in lean and Six Sigma manufacturing strategies. In a lean manufacturing setting, the eight causes of production waste are examined to see where problems are occurring and where improvements can be made. In Six Sigma, the “define, measure, analyze, improve, and control” (or DMAIC) method aims to use statistical analysis to implement process improvement wherever it’s needed.

Root cause analyses are typically carried out by a cross-functional team so the problem can truly be understood from as many viewpoints as possible.

What is the 5 Whys Analysis?

This brings us to the concept of the five whys. Since the root of a problem is usually multi-faceted and occurs somewhere beneath the obvious problem at hand, this method aims to ask, “why did this occur?” many times, in many different ways, until a root cause becomes apparent. By asking “why?” repeatedly, you’re filtering out the symptoms and uncovering the heart of the problem.

Take, for example, the scenario of your company missing a big product order when a piece of equipment broke down. You need to figure out the root cause to fix the underlying issue. Using the “five whys” method, we start by asking why:

1. Why did the equipment fail? Because it overheated.
2. Why did it overheat? Because the cooling fan failed.
3. Why did the cooling fan fail? Because regular servicing was missed.
4. Why was its service missed? Because we use a paper tracking system and it fell through the cracks.
5. Why don’t we have an automated preventive maintenance system? Because we have been resistant to adopting new technology.

This framework is a good rule of thumb, but it could take six or seven iterations to get to the real root cause. The technique usually starts with a technical issue but eventually points to a process failure. To avoid going down the wrong path, ask the following questions after each “why?”:

1. Is there any visible or measurable evidence that each indicator could support the root cause determination?
2. Could we ask another “why” and find a more plausible root cause?
3. Could anything else have produced this problem?

Download a 5 Whys root cause analysis template here

How to avoid the wrong “whys” in your analysis

Though a five whys exercise will expose a root cause, it’s important not to focus all attention on the lowest-level outcome of your analysis. Think of it this way: if you focus all your attention on fixing the lowest step on a broken ladder, you’ll still have a faulty ladder. Make an investment at each level of the “why” hierarchy, since there were likely smaller failures at every stage that stemmed from the root cause and require attention.

In the example of the faulty fan that we used above, you could invest in technical training for your maintenance team; invest in a preventive maintenance program so service notifications are triggered automatically; configure servicing and replacement schedules as per manufacturers recommendations; or even install a vibration sensor on the fan to predict a failure. Over time, continuous incremental investments and improvements will compound, improving the productivity of maintenance personnel and freeing up time that was previously lost to fire-fighting breakdowns.

Root cause analysis for maintenance

In the context of maintenance, the five whys framework offers a simple problem-solving technique for getting to the heart of an issue and determining long-term corrective actions that should be taken.

In fact, it’s a great place to start when attempting to move from a reactive to preventive maintenance strategy, because it introduces the idea of systematic problem solving without statistical analysis. It can be useful when tackling simple problems, but also offers a good starting point for complex issues. Most importantly, it keeps us focused on fixing real problems and preventing them from happening again rather than treating symptoms and allowing the cycle of breakdowns to continue.