What is Root Cause Analysis (RCA)?
Definition:
Root cause analysis is a systematic evaluation that addresses the cause of failure rather than the symptom.
Example:
A failed CNC machine shuts down production, and the overheat alarm from the operator panel points to the axis five servo motor as the culprit.
After removing the servo from the machine, a seized bearing is uncovered, which is responsible for the unwanted and excessive heat. All sorts of contaminants are in the grease, and the seals were oriented in the wrong direction, preventing a proper seal.
By using root cause analysis, you not only eliminate the issue but save thousands in the process. Here are three more ways root cause analysis improves manufacturing operations (and makes life easier in the long run).
Benefits of Root Cause Analysis
1. More Productive
The actions taken today must mitigate future unplanned downtime. (Think long-term, not short-term). To boost productivity, operations and maintenance must minimize and control the time production lines are not operational.
Root cause analysis identifies process breakdowns in your systems, making it possible to determine a way to prevent them from happening in the future.
Solving the fundamental problem prevents damaging other parts of the machine when production resumes.
2. Cost-effective
The goal of every maintenance team is to optimize equipment availability at a minimal cost. Easier said than done. Practicing root cause analysis reduces the risk of burning through solutions that don’t solve anything. With a little extra time (and effort), you discover the root cause of the initial machine failure and reduce expenses on “solutions” that fail.
Manufacturers who implement root cause analysis eliminate unnecessary action and reduce the cost associated with excessive repairs and erroneous replacements compared to their non-believing root cause analysis counterparts.
Let’s look at the example from earlier again. At the beginning of the situation, if you decided to purchase a brand-new servo motor, it would cost roughly USD 6,500. Ouch! A repair would cost about USD 1,700, a 74% cost reduction compared to a new one—a good win.
But could we save even more if we continued our root cause analysis? Let’s find out.
If you continued to look and discovered the bearing issue, you would spend approximately USD 45 for each bearing you want to replace. Two per motor totals $90—a big win.
Remember, it wasn’t the bearing causing the issue, though. It was the seals. That’s right; the USD 12 ethylene propylene seals the size of the Washington quarter. The results?
98% less than the price of a new replacement and 94% less than a repair. That’s a minimum of $1,598 in savings—a fantastic win.
| Action Taken | Estimated Cost |
| New Servo Motor | $6,500 |
| Repair Servo Motor | $1,700 |
| Replace Bearings | $90 |
| Replace Seal | $12 |
3. Long-lasting
When maintenance activities and work performed focus only on treating symptoms, the benefits are often short-lived. Why? The cause still needs to be addressed. The issue(s) will happen again. With root cause analysis, the implemented fixes are permanent, and the process is improved.
These improvements are felt throughout the organization and help develop a working knowledge and understanding of causal relationships.
How to Implement Root cause Analysis
The 5 Whys
The 5 Whys
The five whys is a simple problem-solving exercise to explore the cause-and-effect relationships underlying a particular problem.
The concept is credited to Sakichi Toyoda, who is often called the father of the Toyota production system. Because of this, root cause analysis gets associated with Kaizen, a fundamental part of lean manufacturing.
The idea is to limit the number of “why” questions to five.
The good?
- Quickly get to the root of a problem
The bad?
- Asking the wrong questions
- Preconceived ideas
- Oversimplifying the situation
Some find the five whys to limiting to be helpful. Applications are complex, only sometimes simple. Small, apparently innocuous failures join to create the opportunity for a systemic accident.
Our advice ignores the pressure to limit the whys to five. Keep asking “why” until you are confident the root cause has been found and the “how” has been uncovered. In our example, the “why” ended up being the seals were oriented in the wrong direction—an easy fix. The “how” is the documented work instruction did not specify this information, and the maintenance technician was unaware of the damage this would cause. The solution? Specify in all work instructions the seal orientation and its importance. Lesson learned; let’s move on to the next.
