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May 2002

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From:
John Parsons <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 1 May 2002 10:51:43 -0700
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Phil,

While I am leaning to rule in your favour I can see how the misunderstanding
occurred.  Clearly there has been a misinterpretation on the part of the CAM
operator of the fab drawing as to what you required.  I would have to agree
with your fabricator that the "best" way would have been to dimension the
location of the rectangular cutouts and include a note specifying the
required maximum radius.  Your method of dimensioning also requires much
(well, not that much) more work by the CAM operator to create the outline as
it is not directly dimensioned.

This is not to say that your existing drawing is wrong, just that it does
require  a little more thought on the part of the CAM operator that my
suggested alternative.  What the CAM operator probably thought you wanted,
which we do see on occasion, is the ability to put a square cornered device
into the cutout so by putting center of the hole at the corner of the
rectangle you achieve this (I assume that this is what you received).  In
your defence, putting the center marks inboard of the rectangular outline
should have tipped them off but clearly it did not.

From your perspective, you may always do your drawings this way and it is
perfectly clear but for the board shop who sees a whole bunch of different
techniques used to explain a given requirement this sort of error can, and
clearly does happen from time to time.

Hopefully the board shop will come good by reworking the product and the
whole experience will serve as a learning tool for both parties.
Sorry for the rambling :o)

Good Luck
John Parsons
Pre-Production Engineering Manager
Enigma Interconnect - Vancouver

> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Phil Nutting
> Sent: May 1, 2002 9:56 AM
> To: [log in to unmask]
> Subject: [TN] Hole routing in PCBs
>
>
> Hi all,
>
> I wanted to tap into your collective knowledge (opinions).  We
> have a small circuit board that is supposed to have a rectangular
> cutout to accept ferrite cores.  My board house used an 0.093
> diameter cutter with the argument that it cut through the "corner
> holes" specified on the print.  He says that I need to add a
> radius spec to my board drawing.  My board designer (and I) have
> reviewed this board and think that it is clear what should be
> done [we need the 0.043 (0.0215 radius corners) holes for clearance].
>
> I have asked Steve Gregory to post a JPEG file of the board. It
> can be found at;
>
> http://www.stevezeva.homestead.com/ and click on "Routing", or
>
> http://www.stevezeva.homestead.com/files/Routing.jpg
>
> How do you think this should be specified/machined?
>
> Thanks in advance.  Thanks Steve for posting the file.
>
> Phil Nutting
>
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