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Subject:
From:
Inge Hernefjord <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Inge Hernefjord <[log in to unmask]>
Date:
Thu, 7 Jul 2016 17:05:00 +0200
Content-Type:
text/plain
Parts/Attachments:
text/plain (118 lines)
Well, I'm not much of the adviser I once was, so the question is if you
should read this.

-  You've already answered yourself when you ask for the level of a minor
deviation,which doesn't have a dentrimental effect on the process, and
ditto about a major deviation. Practical experience will give the level
individually for each process.

- In fact, the two parameters 'minor' and 'major' are not of interest in
programming point of  view, because the machines that sample and do the
data aquisition, they can accept such arguments as 'minor' and 'major' ,
because they want mathematic useful levels, e.g. so and so many
milliamperes or nn % or other expressions..So, I would skip the whole
question and give the processing computer values that counts.

- There is a area that has the most advanced processing of all, namely the
semiconductor processing. The sharpest brains arfe involved and there you
have the answers on practically everything you want to know..One reference
that I used to read is Dimitri Kececioglu and Feng-Bin Sun's wwork '
QUANTIFICATION and OPTIMIZATION OF BURN-iN TESTING. isbn 0-43-324211-0.
Editid and printed by Prentice Hall, Upper Saddle River, NJ 07458.
Examples on content

Chaper 4: Obsevations and the physical insight of the failure process
Chapter 5: Math  Models Describing the Failure Process during Burn-In and
the Parametres Estimation.

-  What more to say is that your question is more or less difficult to
quantify, because of the complexity of  the actual process.  If yoy ask for
a simple process, let's say the manufacturing of a general purpose, cheap
resistor with the tolerance of +/-  10 %, you have only one proceessto keep
an eye upon, the laser trimming. If the you use modern trimmers, the
outgoiing tolerance is probably much better for Sigma 1-3, while Sigma 6
represents only a few + 10% or  .10 % per each one million batch. That
means that a deviation from normal +/. 2 %  to new value l.et's say +/- 5 %
is not causing any problems.

Making a car, for instance, is so complex and holds so many parameters
(thousands) that you need aqusite data for hundreds of cars before you get
experience of what deviations are acceptable or not. So, take into
consideration the complexity of the process you are asking for.

My 2 p +/- 0.05 p

 /Inge

PS. Think your younger and  fresher (?) mate Dave got a lot to say.



On 30 May 2016 at 01:54, Yuan-chia Joyce Koo <[log in to unmask]> wrote:

> hopefully, it is not voting system.  otherwise, you get vote out to the
> lowest std.  (one system designer, with many part vendor, supplier,
> marketing guys, bean  counters, etc. the program mgr will get over powered
> sometimes... horrible).
>         jk
>
> On May 29, 2016, at 2:19 PM, Richard Kraszewski wrote:
>
> I would suggest  the use of a pFMEA or dFMEA  to assist in making that
>> decision.
>> Need to have all stakeholders involved in that exercise.
>> (yes I know this can be pain)
>>
>> Rich  Kraszewski
>> (920) 969-6075
>>
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
>> Sent: Thursday, May 26, 2016 10:00 AM
>> To: [log in to unmask]
>> Subject: [TN] How much change is change?
>>
>> Good morning all,
>>
>> One of the IPC groups that I am leading is presently wrestling with the
>> issue of minor vs. major change.  Generally along the lines that if you
>> have a baselined or qualified manufacturing process, how much can that
>> process change before it needs to be re-baselined or re-qualified?
>> Sometimes this is referred to as Level 1 vs. Level 2 change.
>>
>> So far, every quality documentation system that I have looked at, like
>> AS9100, ISO9000, etc., gets really fuzzy and uses vague terms when you
>> approach this issue.  Most of these documentation systems have change
>> better defined for products, but get extremely fuzzy and extremely vague
>> about manufacturing processes.
>>
>> This forum has a lot of very smart, very experienced people. How would
>> you differentiate a minor change, which would not impact form fit or
>> function, from a major change, which "could/would" impact form fit or
>> function?
>>
>> And I want all you lurkers to come out of the woodwork on this one.
>>
>> Doug Pauls
>> Principal Materials and Process Engineer Rockwell Collins
>>
>>
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