Causes of Defects - Cause & Effect Diagrams

[Marc]

Date: Sat, 20 Feb 1999 14:44:15 -0500
From: RNav
Subject: Re: Causes of defects

In a message dated 2/16/99 12:35:33 AM, jgrout writes:

>I believe that organizational culture, complexity, and a host of other
>indirect causes lead to defects through their manifestation as either
>statistical variation or human error (both direct causes). What other
>direct causes of defects can you think of besides variation and human
>error.
>
>Your help or suggestions will be greatly appreciated
>
>John Grout

There are other good answers, but as a rule when doing Cause & Effect Diagrams, I use 6 groupings to start; Man, Machine, Method, Material, Measurement, & Environment.

Man - generally these are related to job qualification (was he trained for the works and certified to do so), aptitude, attitude, and then human error, a mis read on a gauge. One can argue different, I admit, but a definition must start somewhere.

Machine - This has to do with all aspects of the physical condition and capability of the machine, both design and current. The old adage applies, the right machine for the job.

Method - Are the job practices to do the work sound, repeatable.

Material - Are you getting materials up to the task, both in theory and practice. Iron products may have the same chemistry, but in working them the methods use to manufacture them can vary and result in materials unsuitable for a given process.

Measurement - This deals with the measurement system. Are they using tape measures when digital calipers would be the ideal? Are the measurement methods repeatable? I break this out to give it special attention since my experience has shown a lot of processing problems can be traced to faulty measurement systems. Could you group this into machine and methods, yes, but I think it is so important to deserve its own section.

Environment - This generally deals with the working environment, heat, light, cleanliness, etc. I work in wood these days and we are very sensitive to humidity changes within the plant. This is but one aspect of this.

All this aside, I do agree that this is of lessor importance than getting to root cause for an issue. On the flip side of the question, over time I have noticed that in "average" organizations, tremendous improvements can be attain for little capital by focusing on methods and measurements. I also realize that this part is unglamorous and takes a culture change to ensure sustainability.


Robert Drensek, CQE, CQA, CRE, CMI
Quality Engineer

[barb butrym]

I agree, I always use the 4 M and sometimes the ENV...have been for as many years as i can remember....works for me