Abd ul-Rahman Lomax wrote:
> At 04:08 PM 5/17/01 -0400, Richard Sumner wrote:
> >Alas, the aperture limit is not available if you choose rs274x.
> >Not all pcb houses can manage large "apertures". Advanced circuits is
> >limited to 1"x1", for example.
>
> Usually such large apertures are created by fills. Protel had a bright idea
> to save gerber file size by flashing fills with an aperture created just
> for the fill, instead of drawing it with a square aperture.
>
> There is a problem with this, besides the problem which is being discussed:
> When the fill is reimported, Protel treats it as a pad.
>
> Protel, instead of flashing fills, they should be drawn with a maximum size
> square aperture (I won't define maximum here). Protel does not draw with
> square apertures, as far as I know. This would allow recreation of the fill
> as a fill when importing Protel-generated gerber. A square fill would be
> drawn as a line with endpoints equal. (That works in gerber; it is
> equivalent to a flash). And it should be possible to set a maximum aperture
> size for RS-274X output.
>
> A workaround, if one wants to use RS-274X, which is recommended, would be
> to replace fills larger than the maximum aperture size with a set of fills
> of the maximum size, 1 inch square would be very convenient if one is
> working on an inch grid, otherwise I'd choose a fill of 2 mm square.
Yes, this is close to a solution, although it takes manual intervention and
iteration until the plot outputs OK from Protel. But, because some fills
might
be 10" x .150", a 1" square fill will not work. A .150" square fill would
work,
though. You would have to search the entire aperture list for large
apertures,
delete them, and then add a few apertures that would satisfy the board house's
software and Protel's need for apertures that would fit within the fills that
are
actually present on the board. I often put long, narrow fills around the edge
of
the power and ground planes to keep the planes from extending to the edge of
the board. Some of these are inches in X and .1" in Y, the others are inches
in
Y and .1" in X. A single .1" square aperture would be able to fill both of
these
shapes with 2 lines of RS-274D (or X) code by going to one end and then
drawing to the other end.
Jon
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