Certainly, speaking for our shop it is both appropriate and appreciated, as
is anything related to good design. I myself have done board design and
library managment, and you are correct, to do these jobs well is certainly
time consuming initially. I have found that if you have to deal with a
board through its entire life span of manufacturing and design changes, you
(or someone else in your organization) will appreciate this extra time you
took in the beginning.
CAM aside the number of tool changes has an impact of the length of time
required to drill a panel, the more tools, the longer the drill cycle, the
more the board costs to manufacture.
Please remember that the primary job of a CAM operator is to produce the
tools required for the fab shop to manufacture your board. Although we do
our best, our primary function is not to run DRC checks and clean up your
CAD data to ensure that it is manufacturable.
As far as isolating hits with a tighter tolerance, It is probably not
required to isolate the holes within the drill file, but on the fab drawing
for inspection/acceptance criteria as you have mentioned, it is probably a
good idea to continue.
These are all great questions, and it is my feeling that a designer who
thinks of them is a just that, a Designer. There are lots of people out
there sitting in from to CAD stations plopping out board layouts, but they
certainly leave a lot to be desired.
If you were looking for someone who would back you up and save you lots of
time, I am sorry but I am not the one. Keep up the good work and please do
not stop thinking about us (manufacturers).
John Parsons
Pre-Production Engineering
Circuit Graphics Ltd.
----------
> From: Jeff Seeger <simon.ipc.org!bort.mv.net!rapidcad!jseeger>
> To: [log in to unmask]
> Subject: FAB: Drill size proliferation
> Date: Monday, July 29, 1996 1:33 PM
>
>
>
> Hello, Technet!
>
> A question for the fabrication planning/engineering/CAM folks:
>
> Over the years we've all seen the proliferation of drill sizes
> as products become more complex. To this day, we in design have
> attempted to optimize the number of drill sizes. I am wondering
> if this step is still appropriate or appreciated?
>
> There are cases where Library management would become noticably
> simpler, and our throughput could improve, if we could be blind
> (sorry) to the quantity of drill sizes. The step of reconciling
> drills on a complex PWB can take appreciable time, with the assoc-
> iated thermal relief/anti-pad/drc steps added in.
>
> Similarly, what's preferable when one has a tight-tolerance (ie press-
> fit) hole size, with other componentry using the same size. We
> normally isolate these cases as seperate callouts, for limiting
> potential acceptance problems. Is there a quantity threshold
> to this question?
>
> I have heard this level of concern called "redundant", as the fab-
> rication setup will combine as needed to suit each individual case.
> Is this automated in CAM equipment, and therefore the effective
> home for this task?
>
> What's the design world giving you these days? Is this one of the
> areas where "minimalist design" shaves a corner that the end-user
> doesn't see? (are we being too anal for our own efficiency?)
>
> TIA, hope I'm not opening too large a can for my apetite!
>
> Best Regards,
>
> Jeff Seeger Applied CAD Knowledge Inc
> Chief Technical Officer Tyngsboro, MA 01879
> [log in to unmask] 508 649 9800
>
>
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