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Reply To: | TechNet E-Mail Forum. |
Date: | Thu, 16 Jul 1998 09:04:28 +0100 |
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Abdullah,
Assuming that by defect you mean a product characteristic not
meeting spec, that by process indicator you mean a product
characteristic meeting spec but showing some undesirable feature
that would lead you to adjust the process, and that both are
attributes, I would do the following:
For process control:-
Chart both defects and process indicators on the same attribute
chart. Special causes can cause a change in the incidence of
process indicators as well as defects.
For process capability:-
For attributes, process capability is represented by the average
level of defects after the process has been brought into control. I
would just use defects here. Including process indicators would
effectively be changing (tightening) the spec.
Have you done a process analysis to identify critical process
parameters? You will benefit if you control them.
Try and get hold of:
IPC-PC-90 General Requirements for Implementation of Statistical
Process Control
and
Understanding Statistical Process Control
Wheeler, Donald J and Chambers, David S
SPC Press Inc
ISBN 0-201-54405-9
Just my tuppence worth.
Rick Price
[log in to unmask]
On 15 Jul 98 at 16:19, KRIMLYA AT AEC wrote:
>Date: Wed, 15 Jul 1998 16:19:23 +0300
>From: KRIMLYA AT AEC <[log in to unmask]>
>Subject: SPC
>Dear Tech Net:
>
>We are an electronics company located in the middle east and a member of
>IPC, we are implementing SPC and are having problems with Process
>Indicators, our questions are:
>
> 1- Should process indicators be placed into the same control chart as
>defects or should they be placed into a separate control chart.
> 2- Should process indicators be included in capability studies, should
>they be in the same capability study as the defects or should there be a
>separate capability study for process indicators.
>
>
>Best Regards
>
>Abdullah Al Krimly
>Industrial Engineer
>AEC SPC coordinator
>Advanced Electronic co. Ltd.
>P.O Box 11623
>K.S.A.
>e_mail: [log in to unmask]
>
>
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