Subject: Re: REQ: Zero Defects /Bartol/Meron
Date: Fri, 18 Dec 1998 11:40:06 -0600
From: ISO Standards Discussion <[email protected]>
From: Emanuel Meron <[email protected]>
Subject: Re: REQ: Zero Defects /Bartol/Meron
>
> From: Dave Bartol <[email protected]>
>
> List Members:
>
> I have a question regarding ISO 9000 and the Zero Defects Philosophy
> of Crosby . . .
> For example, a part has the spec. of 11.000 +/- 0.005 inches. Anything
> within the specification is zero defect, but does the part at 11.005
> work as well as the part at 11.000? How about the part at 10.995
> inches?
This issue is addressed by Taguchi in his famous loss function which basically does away with the traditional concept of tolerance where all parts within specs are considered identical and "good", and those outside specs are equally "bad".
Using the concept of "loss" the nominal value is the target and every deviation from it entails a cost (loss). The farther away a part is from nominal the higher the loss, the smaller the deviation the lower the loss. This means that you have to strive for minimum variability around the nominal (target value), not just for being "in spec". The beauty of the theory is in that it provides you with a quantitative way to compare the benefits of variability (loss) reduction with the cost of achieving this reduction. There are many books on this subject, just look for Taguchi's loss function.
Emanuel Meron
Date: Fri, 18 Dec 1998 11:40:06 -0600
From: ISO Standards Discussion <[email protected]>
From: Emanuel Meron <[email protected]>
Subject: Re: REQ: Zero Defects /Bartol/Meron
>
> From: Dave Bartol <[email protected]>
>
> List Members:
>
> I have a question regarding ISO 9000 and the Zero Defects Philosophy
> of Crosby . . .
> For example, a part has the spec. of 11.000 +/- 0.005 inches. Anything
> within the specification is zero defect, but does the part at 11.005
> work as well as the part at 11.000? How about the part at 10.995
> inches?
This issue is addressed by Taguchi in his famous loss function which basically does away with the traditional concept of tolerance where all parts within specs are considered identical and "good", and those outside specs are equally "bad".
Using the concept of "loss" the nominal value is the target and every deviation from it entails a cost (loss). The farther away a part is from nominal the higher the loss, the smaller the deviation the lower the loss. This means that you have to strive for minimum variability around the nominal (target value), not just for being "in spec". The beauty of the theory is in that it provides you with a quantitative way to compare the benefits of variability (loss) reduction with the cost of achieving this reduction. There are many books on this subject, just look for Taguchi's loss function.
Emanuel Meron