Brad,
Just a thought,
I believe IPC docs do specify a formal Fab Dwg for complete documentation,
however whether
or not the IPC spec's defines needing one, unless one plans on providing a
very complete set of total electronic
files like IPC GenCAM or Valor to a fab house which also does provide the
ability to capture your
fab dwg intent within the file, I would say a fab house could make a board
for you if you scratched
out on a napkin what you needed, but I would not want to chance them wiping
their mouths with it
before fabing the board. If a company or designer needs to specify critical
dimensions or anything
else that may be required a certain way I would seriously suggest a proper
Fab Dwg be provided
or like using GenCAM or some other file structure to provide a complete
picture
of you rdesign intent to a fabricator regardless of what some spec may or
may not state.
Bob

Robert M. Wolfe, C.I.D.
[EMAIL PROTECTED]
----- Original Message -----
From: "Brad Velander" <[EMAIL PROTECTED]>
To: "'Protel EDA Forum'" <[EMAIL PROTECTED]>
Sent: Friday, May 17, 2002 12:08 PM
Subject: Re: [PEDA] Too many hole sizes


> Are there any IPC Certified designers who can confirm or deny the need for
a
> fab dwg?
> What is the current IPC comment on the issue, come on guys I know
> you're out there! Is the fab dwg not just part of the "complete"
fabrication
> information, what is the IPC training telling you guys to do about fab
dwgs
> these days? This is a test, are you a IPC man/woman or a mouse?
>
> Georg,
> here is the best example that I can give. Contrary to some very
> opinionated individuals, not all PCB inspectors have computers, nor CAD
> software, nor the training to operate CAD software, in a 'LOT' of PCB
> fabrication shops. Trust me, I have been in and out of many PCB shops in 3
> States and one Province for over 20 years. We aren't talking about the
> Merixs, Tycos or Praegitzers here, just normal small - med size fab shops.
> How does this inspector check drill sizes or locations? From manually
> reading the numeric information? Is the fabricator CAM shop supposed to
make
> a drill drawing for him? Do you trust the fab shop to generate this
drawing,
> if they make a mistake who's fault is it, you didn't supply the required
> information so they were forced to generate their own? They are not
perfect,
> neither are you but you didn't even have a chance to check/inspect their
> handiwork! What can they use for even their trained CAM operators to
confirm
> the correctness of the information which they are viewing on their
computer
> screens?
>
> When the PCB is received at your company's (or your assembly shop's)
> loading dock, who checks it for valid hole sizes, dimensions or other
> details? Is this a fully trained CAD operator, with system software to
deal
> with all forms of CAD data or a simple minimally trained inspector with
some
> pin gauges, calipers and the ability to read a technical drawing? If you
> don't supply them with a Fab dwg, do you get called to the loading dock to
> check the boards upon arrival because you are the only one in your company
> who can access and use the electronic data files?
>
> Here some other very good examples for you Georg. Where do your
> drill files locate themselves within you board outline? Where are any of
the
> holes with respect to the board outline? What are the dimensions of your
> board outline? Does everybody go into the CAM files again and again to
> generate their own measures of these items? Isn't that lost repetitive
> operations that could be done just once, checked, verified and
appropriately
> tolerance by the individuals who understand the design? What tolerances
> would be allowed by differing individuals who take their own absolute
> measures of the CAD data in the file? The CAD data is absolute isn't it?
Are
> the fabricated parts absolute without tolerance? I wish.
>
> Sincerely,
> Brad Velander.
>
> Lead PCB Designer
> Norsat International Inc.
> Microwave Products
> Tel   (604) 292-9089 (direct line)
> Fax  (604) 292-9010
> email: [EMAIL PROTECTED]
> http://www.norsat.com
>
> Visit us at Booth 2G2-09 at CommunicAsia 2002 in Singapore June 18-21.
>
>
>
> > -----Original Message-----
> > From: Georg Beckmann [mailto:[EMAIL PROTECTED]]
> > Sent: Thursday, May 16, 2002 10:17 PM
> > To: 'Protel EDA Forum'
> > Subject: Re: [PEDA] Too many hole sizes
> >
> >
> > I do not understand, what a drill drawing is good for. I only
> > use the drill
> > file and the
> > board shop read this to the drill machine.
> > Since I have a computer and CAD program, I'm happy
> > not to fill out a drill drawing sheet with any hole marked
> > with a secret
> > label and wether I or
> > the man in the board shop makes one or more mistakes when
> > programming the '
> > punchhole - tape for
> > the drill machine '.
> >
> > Georg
> >
>

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