Problem Solving Techniques: Root Cause Analysis (RCA)

Have you ever encounter customer who loudly complains about the lack of real root cause presented in your 8D's?This can be very frustrating and often times resulted in a low moral in the problem solving team. It is a given fact that heart of any problem solving tool is the identification or determining the real root cause of the problem presented. However, it is not always treated with appropriate thought process. And in most cases, the root cause is often not the real system root cause. Without the real root cause, there are no meaningful corrective and preventive actions. It is therefore important for any team to be equip with the RCA methodology when presented with a problem.

Root Cause Analysis (RCA) is a methodology to ensure a thought process is followed when a problem is analyzed. RCA is a template that makes sure all important areas are considered. It is not a replacement for any existing problem solving tools (such as 8D) but rather an enhancement to make sure any problem solving method will identify all of the causes creating a problem.

There are several basic components of a good RCA. Analysis is done in three separate levels. First level is to analyze the root cause at process level. Traditionally, this root cause is often accepted as the real root cause. Second level is "Why problem was not detected earlier". The purpose of this analysis is to find the root cause why the detection or inspection system failed to detect the problem. Third level is the "conditions leading to the problem development" to find the system root cause which lead to the process root cause in first level. Finding the process root cause would fix the process. Finding the system root cause will fix many similar processes which might have similar problem.

For each of the levels, the following actions must be provided: Containment action, a short term actions to keep the defects from reaching the customers. Containment does not fix the problem and in most cases the most expensive part (sorting, blockage, product recall, temporary production stoppage, etc). Corrective action is done to fix the problem and is need to be verified for effectiveness. Recurrence prevention is the corrective action at the system level to fix all similar problems. This action is needed to ensure the same or similar problem will not happen again.

The most common method used in determining the real root cause is the 5-Why analysis. Research shows after about 5 times of asking "why" we usually arrive at the root cause, thus the term 5-Why analysis. The analysis begins with a box stating the problem. Second box answers the question "why the box above happened?" It identifies the cause of the box above. The next box is again answers to the same question "why the box above happened?"  Repeat until you cannot answer the "Why ?" anymore . This is often followed by series of simulations and trials to re-produced the problem and confirmed the real root cause based on the 5-Why analysis. Then, the real root cause of the problem is determined and appropriate action can be done.