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Finding the Root Cause - Which technique is better?

Terry

Involved In Discussions
#1
Hello everyone,

I have a question and needs you to help me.

There are 22 pieces of part rust defects in PDI report last month, I want to establish a projct and organize a team to analysis the root cause with cross function dept. guys, but now I think up two kinds of ways to analysis it, I don't know which ways is better?

The first ways is that I directly input " part rust" into the result column of fish bone diagram, then we use brainstorming to get some possible causes or root causes.

The second ways is that we ask "5 why" to each rust defect to find root cause.

I am a new man for the use of quality tools.

I hope you can give me some good advice.

Thanks & regards!

Terry
 
T

tbsiva

#2
Both are good.... We cannot pinpoint and say that which analysis method is best suited to identify the root cause... Practically, I would suggest you to use fishbone diagram first so that you can identify all the 4M causes and hopefully you can solve your problem quickly..
 
Last edited by a moderator:
M

mzeeshanz

#3
I have a question and needs you to help me.

There are 22 pieces of part rust defects in PDI report last month, I want to establish a projct and organize a team to analysis the root cause with cross function dept. guys, but now I think up two kinds of ways to analysis it, I don't know which ways is better?

The first ways is that I directly input " part rust" into the result column of fish bone diagram, then we use brainstorming to get some possible causes or root causes.

The second ways is that we ask "5 why" to each rust defect to find root cause.

Terry
Dear Terry,

Not an expert but try to answer depending upon my limited knowledge. (Comments are welcome from experts).

IMO both tools have different way of analyzing a situation.

1- Fish bone diagram works in traditionally four dimensions/categories of thoughts (Man-Machine-Material-Method although some have included more categories to widen the scope/dimensions). IMO this tool suits you in condition where you have a problem with many/unlimited influencing factors/causes. In that situation you need to brainstorm with open boundaries of thoughts.

2- 5-Why Analysis works in usually single dimension/direction. It is used to dig out a situation by a series of interrelated questions. It means it goes to the finest detailed root cause of a particular problem. IMO this tool suits you in condition where you have a problem with limited/well-known/well-defined influencing factors/causes. In this situation it is usually enough to brainstorm or investigate with limited boundaries of thoughts.

IMHO, if your "part dust defect" may be caused by a combination of many seen and unseen causes with probable known contribution of factors under man-machine-material-method categories then obviously only fish bone diagram could help you instead of 5-why analysis.

If you have ample time for in-depth analysis, you may use both techniques in synergistic way. First identify the the most suspected causes though fish bone diagram and then apply 5-Why analysis on each individual cause. Doing this way you can not only confirm/justify each individual cause but may also identify some unseen/unrealized causes during inter-relevant questioning.

Hope it helps.

M. Zeeshan
 
#4
The first ways is that I directly input " part rust" into the result column of fish bone diagram, then we use brainstorming to get some possible causes or root causes.

The second ways is that we ask "5 why" to each rust defect to find root cause.
I don't know if I'm complicating or simplifying matters here, but I'll drop this suggestion as food for thought if nought else: I often combine all of the above by the use of a Mindmap. I don't have any examples at hand here and now, but if you have a look at the old thread How effective is 100% inspection? you will find a mindmap summary of the discussion in post 20. So much for the Mindmap format. Now imagine such a map on a whiteboard, starting in the middle, branching out to Man, Machine, Method, Material and Environment. From this setup, you and your group can keep branching outwards (5w & Brainstorm in one) towards possible root causes. This setup works well here.

/Claes
 
#5
Why bother? The root cause for rust is the chemical reaction of oxygen with iron to form ironoxide. Now hopefully you can find a solution which meets your needs short of going to the moon. Good luck.
 

Stijloor

Staff member
Super Moderator
#6
Why bother? The root cause for rust is the chemical reaction of oxygen with iron to form ironoxide. Now hopefully you can find a solution which meets your needs short of going to the moon. Good luck.
While corrosion is a natural chemical reaction, it can be eliminated by preventing the oxygen to react with the metal.
Paint or any other coating comes to mind. ;)

Stijloor.
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#8
Not being a fan of fishbone diagrams or root cause brainstorming, I would suggest an alternate approach.

I typically begin with some Problem definition questions (such as those utilized by the Kepner-Tregoe 'Is, Is Not' approach: starting from the very good point that the actual root cause of rust is a well known reaction, I might ask if the parts have some type of rust proofing that has been compromised. Does the customer require that these parts not exhibit rust by contract/drawing requriement? Is this a chronic problem or are these 22 parts with rust something that hasn't been seen before? Are these 22 parts all from one lot? what is a PDI report? were these defects found internally? or by the customer? how many customers?

asnwers to these questions can help direct us and will begin to provide clues as to the next steps...
 

Chennaiite

Never-say-die
Trusted
#9
Hello everyone,

I have a question and needs you to help me.

There are 22 pieces of part rust defects in PDI report last month, I want to establish a projct and organize a team to analysis the root cause with cross function dept. guys, but now I think up two kinds of ways to analysis it, I don't know which ways is better?

Terry
IMO, choice of Problem solving tools depends on the needs, I mean the nature and depth of analysis required
(Sometimes the Customer needs, of course :D)

:topic:
Had it been that one specific tool is regarded effective for all Problems, our ISO/TC 176 would have taken care to include it in 8.5.2 Corrective action ;)
 
T

TShepherd

#10
Morning everyone,

I believe that Terry has hit on the root cause of this issue.

I don't think that Rust is the problem but rather trying to decide which problem solving method/concept is best for your situation.

People become endeared to one method/concept or another based on their experience and success at using them as opposed to their actual effectiveness as a problem solving method/concept.

I would suggest that you select which method(s) / concept(s) that you are most familiar with and move forward.

Most of the methods/concepts mentioned here have value - the real challange is your ability to understand them and make them work for you.

As the issue of rust sounds like it may be a re-occuring issue - if you find your answer to be the same as in the past, either the cause was incorrectly identified or the implimentation of the corrective action was not completed or verified.

The second issue is that it is important that you learn these methods/concepts and determine for yourself which work best for you.

Good Luck,

Tom
 
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