While working as a Process Engineer at a major company in Cincinnati, I helped
implement a manual SPC program. Our volume was low and slow enough to allow
visual inspection of about every 20th board, or image in a panel, under a scope.
As a result of this process, we were able to reduce over a period of about a
year, our defect level from 3% defects per opportunity to .2%. The operators at
each process inspected their own product, charted their defects and
corresponding chart points, using a small computer formula we provided to them,
and really took possession of the process. It was very successful. It even
resulted in a series of multilayer boards being totally redesigned for
solderability when the subject program manager was walking by the wave solder
machine and noticed that another program's cards were running at a visibly lower
defect rate than his, and asked me why. I explained to him and his design group,
and the redesign was a result.
I do not know how to do this on a fast-paced line. Obviously there is not time
to inspect the way we did, but it certainly can work if it is able to be
implemented, and is introduced correctly.
Terry Basye
---------------------- Forwarded by Terry W. Basye/Lex/Lexmark on 11/17/98 11:31
AM ---------------------------
Mary Smoot
11/17/98 11:15 AM
To: Terry W. Basye/Lex/Lexmark@Lexmark
cc:
Subject: Re: [TN] SPC
---------------------- Forwarded by Mary Smoot/Lex/Lexmark on 11/17/98 11:15 AM
---------------------------
[log in to unmask] on 11/16/98 09:41:26 PM
Please respond to [log in to unmask]; Please respond to
[log in to unmask]
To: [log in to unmask]
cc: (bcc: Mary Smoot/Lex/Lexmark)
Subject: Re: [TN] SPC
Al,
I agree with your logic in not wanting to put up a chart just to please
Management. However, management has apparenlty recognized that SPC can provide
valuable information. I recommend evaluating your process and your quality
records. Determine what is of most concern to you that you feel needs to remain
as consistant a possible. Look at it initially from a process stand point and
not measuring what come off the line. Before you can obtain any useful data from
" after the fact" measurements you must first detemine what elements of the
process is most likely to contribute to any negative results you are currenlty
obtaining. Once you have identified the most important process elements ( ie:
temps, speeds, solder condition/purity, ionic levels, etc...) you can chart and
monitor those elements to insure they are maintained as consistant as possible.
Once you have determined the process is stable, then start monitoring the
results. Remember , you already have data on what your currenlty getting. A
chart monitoring a process result that is intially and continously out of
control really does nothing but tell you what you already know. Control Charts
can only be used as an effective tool once you have the process in control and
now can use the information on the chart to react to out of control indicators..
Just my two cents.
Ed Cosper
Director Quality Assurance and Engineering
Graphic Electronics Inc,
Tulsa, OK
----------
From: Alan Kreplick
Sent: Monday, November 16, 1998 6:16 AM
To: [log in to unmask]
Subject: [TN] SPC
Hello Technetters:
What are you doing to meet management's desire for SPC on the PWA Process - both
thru-hole and smt.
I'm using the Wave Solder Optimizer at wave and counting the number of misses at
auto-insert (p-t-h), although this does not seem to be value-added.
Any success stories out there. I don't want to put a chart up just to please
management.
Thanks in advance,
Al Kreplick
Sr. Mfg. Eng.
Teradyne, Inc.
Boston, MA 02111
617-422-3726
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