Root Cause Analysis

The fundamental goal of business process improvement is to reach the root cause of a problem.

Lean kaizen or lean management is the pursuit of continuous process improvement by root cause analysis and waste elimination.

Shigeo Shingo states in his book, A Study of the Toyota Production System "...only those aspects of process that transform material or improve quality... add value to a product. Inspection, delay, transport and other operations within processing (set up, auxiliary and margin allowance operations) only increase cost and should be eliminated. Processing itself and essential operations should be examined carefully for possible improvements." Root cause analysis is a highly effective process improvement tool. Koji Suzuki, Process Improvement Japan

Five Times WHY

It is said that asking "why" is an effective process improvement tool to find a real cause. This concept can be applied not only for technical and/or quality issues but also for every area of business.

According to my understanding, there are several principles when we repeat WHY five times.

1. The next WHY should be (a) cause(s) of the previous one.

2. Reasonable and elaborate analysis, hopefully a scientific approach is necessary to proceed to the next step. In other words, groundless imagination is not acceptable and persuasiveness is required.

The following are typically unfavorable examples that I have heard:

Example 1

Problem: The length of a product is shorter than its speck by 5mm.

WHY 1: The product has warpage

WHY 2: Inadequate molding condition (no evidence)

WHY 3: A new person operated a machine.

WHY 4: Lack of people.

WHY 5: HR department did not hire new people as requested.

Countermeasure: The length should be adjusted!

Example 2

Problem: Too much inventory of cardboard boxes.

WHY 1: Ordered too much.

WHY 2: Offered cheaper price by big volume.

WHY 3: Production Control department did not give proper information.

WHY 4: Did not contact Production Control department.

WHY 5: No people were in the office when tried to contact.

Countermeasure: Use the boxes for other products (no actual plan).

You may think these examples are too absurd to be taken seriously, but we often make mistakes similar to these.

Make root cause analysis part of your lean management meetings.

Root Cause Analysis by Fishbone Diagram, Process Improvement Japan

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