The so-called 5-why analysis, also known as "5 questions", that is, a question point to five consecutive "why" from the question, is a constant ask "why" come to the root cause of the problem of quality management; A method of analyzing the possible causes of the occurrence of a problem phenomenon; an analytical method based on all the facts to find the root cause; it is a further causal analysis method to find the most influential factors.
Although it is necessary to find the root cause, and sometimes may be as long as 3 times, and sometimes may be 10 times as much as the old saying: to break the casserole Asked in the end. Here are a few examples to explain the specific usage and precautions:
Example 1 (Ohno-5-Why analysis):
On one occasion, Mr. Ohno I saw the machine on the production line is always stopped, although many times but still did not improve, they asked the front of the staff.
(1-Why) Q: "Why does the machine stop?" A: "The fuse is broken because the load is over."
(2-Why) Q: "Why is it overload?" A: "Because the bearing is not lubricated enough."
(3-Why) Q: "Why is lubrication not enough?" A: "Because the lubrication pump can not breathe oil."
(4-Why) Q: "Why do not you smoke?" Answer: "Because the pump shaft is worn and loosened."
(5-Why) asked: "Why wear it?" A: "Because there is no installation of filters, mixed with iron and other impurities."
After five consecutive times, ask "why" to find the real cause of the problem (the oil inside into the impurities) and the real solution (in the pump shaft to install the filter). By the phenomenon of pushing its essence, so find a permanent solution to the problem, this is 5-Why.
Example 2 (Washington-Jefferson Memorial 5-Why Analysis):
In the 1980s, the US government found that the Jefferson Memorial in Washington was seriously damaged by acid rain, and asked the home counselor to investigate. The following is a dialogue between the consultants and the building manager:
Q: Why is the Jefferson Memorial affected by acid rain more serious than other buildings?
A: Because cleaners often use a cleaning agent for full cleaning.
Q: Why should we always clean?
A: Because there are many birds in this shit.
Q: Why is there a lot of birds in this shit?
A: Because here is very suitable for insect breeding, these insects are birds of the meal.
Q: Why is it very suitable for insect breeding here?
A: Because the people inside the perennial curtains closed, less than the sun, the balcony and the windowsill on the dust to form a suitable insect breeding environment.
The curtains of Jefferson Memorial are so easy to solve.
But the 5-Why analysis does not seem as simple as the surface, the questioner not only asked five "why", but also need to accurately grasp the core of the problem, put forward the right question. For example: for the first answer - more than the load, the fuse is broken, if asked "why not choose a better fuse?", Then the problem becomes a problem on the purchase and use of parts; for the case of a The second answer - the bearing lubrication is not enough, if asked "why only part of the bearing lubrication is not enough?", Then the problem has evolved into the bearing part of the design and maintenance problems; or ask "why use lubricating oil to lubricate ? "Then the problem has become a re-definition of the lubrication method.
"The most common reason for the failure of a business is not because of the wrong answer to the right question, but because of the correct answer to the wrong question." I've seen too many businesses once, "says McKinsey's legend. Make a seemingly best but is based on the wrong assumptions on the decision, the results little bit to put themselves into a dead end ... ... McKinsey to help customers from the fate of the fate of the need to identify the problem ... ... ". It is the only way to avoid improvement and decision-making.
In addition, 5-Why analysis also need to be able to accurately grasp the other side of the answer is a real reason, otherwise it is easy to be wrong to answer each other astray. For example: the second question of case one - why is it overloaded? If the answer is "too much because of excessive tires, lack of capacity of the machine", then it evolved into a reduction in the number of workers or to increase the capacity of the machine The third question - why is not enough lubrication, if the answer is "because the quality of the oil is flawed, very viscous", then evolved into the requirements of the oil supplier to improve the quality of the problem. The fifth question - why is it worn ?, I believe that many field engineers will tell you smartly that "this is a normal wear and tear, completely within the scope of acceptance." Then the problem may be Game Over.
So before the 5-Why analysis, we must be in the field, hands-on, really to discover the reality of things presented, and based on the inherent technical theory to explore the state of the event, the development of norms and standards. Can see any improvement are inseparable from the site of relying on the improvement from the scene is bound to go astray.