Okay, I'll jump in... The PCB fab house can do what ever it wants to make
the board.....YOUR FAB DRAWING allows your company to ACCEPT/REJECT it if it
does not meet your standards. Tolerances need to be specified for
inspection. The FAB Drawing is the control document that protects your
company. If you think of it that way you will not go wrong. 
So, making a board without a FAB drawing is do-able, but it leaves your
company no recourse to reject whatever they ship unless you have some
accept/reject criteria specified for the material they ship to you, IN
WRITING. That is usually defined in the Fab Drawing.

Bill Brooks 
PCB Design Engineer , C.I.D., C.I.I.
3030 Enterprise Court 
Vista, CA 92083 
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510 
mailto:[EMAIL PROTECTED] <http://www.dtwc.com/>

-----Original Message-----
From: Bob Wolfe [mailto:[EMAIL PROTECTED]]
Sent: Saturday, May 18, 2002 9:02 AM
To: Protel EDA Forum
Subject: Re: [PEDA] Too many hole sizes

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
of you rdesign intent to a fabricator regardless of what some spec may or
may not state.

Robert M. Wolfe, C.I.D.
----- 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
> 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"
> information, what is the IPC training telling you guys to do about fab
> 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
> a drill drawing for him? Do you trust the fab shop to generate this
> 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
> 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
> the correctness of the information which they are viewing on their
> 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
> with all forms of CAD data or a simple minimally trained inspector with
> 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
> 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
> 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?
> 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
> 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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