In one of yesterday's posts, the topic of intelligence in part numbers
was mentioned. In the late 70's I went to work for a bio-med equipment
company owned by one of the largest medical consumables companies in the
world. We were the only experience they'd ever had with an electronics
equipment manufacturing company.
The part numbering system was one "invented" by the chief engineer based
on his religious affiliation (as Dave Barry would say "I am not making
this up"). It was a 12 digit number separated by dashes into groups of
four. The first four defined the category. 0799 and down was for
purchased components. If it was above 0800, it was for custom parts or
assemblies and there was a different set of rules defining the
assignment of the remaining 8 digits. The second set of four digits
was the modifier. 123 changed for each new part of assembly and the
dreaded 8th digit changed depending upon what you were dealing with.
"0" was the part, "1" was the mechanical drawing, "2" was schematic,
etc. You get the picture. The last four digits were the revision. The
second digit in that series would advance if the change was a "major"
change, and the last two advanced on a "minor" change. The rules
defining major and minor also changed depending on what the 8th digit
was.
The component (0799 and down) numbering contained significance. A
capacitor would be numbered based on voltage, rating, etc., but little
things like case sizes and styles were ignored. So, the floor never
knew whether they would receive axial or radial leaded parts and what
size they would be.
Now think what the poor person in receiving inspection went through
trying to identify and stock a part, then what the floor went through
trying to define their documentation and processes. Nightmare didn't
begin to describe it. The chief engineer continued to defend the system
even though the entire engineering department hated it. The system was
finally abandoned after the parent company installed new top management
and there was an absolute revolt from the manufacturing floor
management.
Has anyone else worked with a worse system?
Bob Croslin
Nielsen Media Research
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of TDK
Sent: Tuesday, October 11, 2005 8:30 AM
To: [log in to unmask]
Subject: Re: [TN] Assembly Documentation Question
You already have that matrix. It is call the BOM (Bill of Material) The
BOM lists ALL the documents ( & their REV's) which the PCB Assembly you
hold in your hand was built to. The PCB assembly will need to have the
PL Rev stamped, which it was built to ( so that ongoing repair &
maintenance people ) can pull up the BOM it was built to & work to that.
Even the test procedure rev will be listed. Each document should be
allowed to change on its own ( That is why we have Rev's, isn't it ??? )
Adding these sub-suffixes, is something my outfit also started doing &
its just another way to trip ourselves up on. I don't agree with it.
That is what the REV is for. REV A, B, C...... but not REV A1, REV B3...
What companies should do, as a starting exercise, is to develop a matrix
with all the possible changes listed ( we already know what that is ),
then go thru the paces.
In my way of thinking, the BOM is the ultimate controlling document (
the MATRIX ).
Regards
TDK
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Nutting
Sent: Friday, October 07, 2005 11:23 AM
To: [log in to unmask]
Subject: Re: [TN] Assembly Documentation Question
Michael,
My experience and preference is to have the BOM and assembly drawing
match in revision. If they don't match who is going to maintain a
matrix explaining what document goes with another document.
Does your BOM call out the revision of the assembly? If so wouldn't you
have to uprev the BOM to reflect the change in revision of the assembly
print?
We experimented with making "dash" prints where we started with a
"generic" design with a -X suffix and then for subtle changes made -1,
-2, etc. assemblies but all based upon the -X print. You wouldn't
believe the confusion this caused at outsource vendors and our
revisions. Imaging the problem when the assembly print and BOM revs do
not match.
I... Can... Not... Change! Must... Do... It... the...way... I...
Have... always... Done... It!
Wow that was close.
Phil
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Michael Kuczynski
Sent: Friday, October 07, 2005 12:19 PM
To: [log in to unmask]
Subject: [TN] Assembly Documentation Question
The company I work for is going thru some documentation change
discussions.
Below are the documents that are revisable. (The parts list contains all
the IC's, cap, res. etc. and documents.) The feedback I'm getting is the
the parts list and the assembly drawing should ALWAYS be the same
revision (becasue thats the way its always been).
Everywhere I've every worked, these are independent documents.
Here are my scenerio case: (All documentation released at Rev. A)
Scenerio (Rev: B): A part number change, of a 1K, 5% resistor to a 1K,
1% resistor.
In this case, the part list and schematic would change, but it has no
effect on the assembly (because no part number or value is on the
assembly drawing).
PL1234567-1 Rev: B Parts List
AW1234567 Rev: A Assy Dwg
DS1234567 Rev: A Drill Dwg
PC1234567 Rev: A Artwork
PA1234567 Rev: B Schematic
Scenerio (Rev: C): The length of the screw holding the stiffener bar is
changed from 3/8 in. to 1/2 in.
The change is to the parts list only, the assembly drawing stays the
same.
(no 3D view or side view)
PL1234567-1 Rev: C Parts List
AW1234567 Rev: A Assy Dwg
DS1234567 Rev: A Drill Dwg
PC1234567 Rev: A Artwork
PA1234567 Rev: B Schematic
The current discussion and question is;
-Can the parts list be independently revisible, from the assembly
drawing?
-What do most of the assembly houses usually like?
Thanks for any response to this question.
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