“5 Whys” in finding the root cause of the problem

TOYOTA TRADITIONS

Taiichi Ohno Taiichi Ohno, Former Executive Vice President of Toyota Motor Corporation

“Ask ‘why’ five times about every matter.”

We come across problems in all sorts of situations in life, but according to Taiichi Ohno, pioneer of the Toyota Production System in the 1950s, “Having no problems is the biggest problem of all.”  Ohno saw a problem not as a negative, but in fact as “a kaizen opportunity in disguise.”  Whenever one cropped up, he used to encourage his staff to explore problems first-hand until their root causes were found. “Observe the production floor without preconceptions,” he would advise.  “Ask ‘why’ five times about every matter.”

He used the example of a welding robot stopping in the middle of its operation to demonstrate the usefulness of his method, finally arriving at the root cause of the problem through persistent enquiry:

1. “Why did the robot stop?”
The circuit has overloaded, causing a fuse to blow.
2. “Why is the circuit overloaded?”
There was insufficient lubrication on the bearings, so they locked up.
3. “Why was there insufficient lubrication on the bearings?”
The oil pump on the robot is not circulating sufficient oil.
4. “Why is the pump not circulating sufficient oil?”
The pump intake is clogged with metal shavings.
5. “Why is the intake clogged with metal shavings?”
Because there is no filter on the pump.

 
  Toyota engineers working tirelessly to meet emission regulation standards in 1975  
 

Toyota engineers working tirelessly to meet
emission regulation standards in 1975

Toyota takes pride in the quality of both its products and its processes, and the ability to solve problems effectively has always been necessary to ensure this quality.  Even if initially timeconsuming, identifying the root cause of a problem is important because it allows us to take appropriate countermeasures to prevent recurrence in the long-term.  “The root cause of any problem is the key to a lasting solution,” Ohno used to say.  He constantly emphasized the importance of genchi genbutsu, or ‘going to the source,’ and clarifying the problem with one’s own eyes. “‘Data’ is of course important in manufacturing,” he often remarked, “but I place greatest emphasis on ‘facts.’”

These days, the global auto market is in a continual state of flux.  For Toyota to be able to respond to market change, it is essential that each associate is aware of problems and works to improve operations at every possible opportunity.  Whenever a problem arises, whether it be in the factory or on the sales floor, we should follow Ohno’s advice: go directly to the source and keep asking, “Why?” By never becoming complacent and always seeking to innovate, Toyota will be ready to overcome any challenges it may face in the future.

 

 
  Toyota employees ask  
 

Toyota employees ask “why” (five times of course) about issues relating to the BX truck

 
  Getting over problems: a Toyota employee gets down to kaizen during production of the gas turbine engine in 1988  
 

Getting over problems: a Toyota employee gets down to kaizen during production of the gas turbine engine in 1988

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