Mail Archives: geda-user/2014/06/27/07:06:43
On Thu, Jun 26, 2014 at 05:18:28PM +0100, Peter Clifton wrote:
> On Sat, 2014-06-21 at 12:27 -0400, DJ Delorie wrote:
> > > I "think" if gerber supports them, then getting arbitrary axis
> > > directions will still be awkward / impossible without approximation.
> >
> > Gerber doesn't support them. At least, not reliably across fabs. We
> > approximate them with line segments.
>
> Speaking of Gerber - at some point, we should re-validate our output
> choices against current UCAMCO recommended practice.
Indeed.
>
> I would suggest that we re-enable arc features in gerbers at some point,
> and see if we identify any fabs which still have issues. (They ought to
> fix their end, not be a reason to reduce the fidelity of our output).
>
>
> I know we do polygons "wrong", with stitching of pieces without holes. I
> vaguely recall that we used to do it the "right" way, but changed for
> sake of compatibility with bad fabs.
And this actually caised me issues, I had to keep an old version
of pcb while I finished a project.
>
>
> UCAMCO have recently issued a white-paper stipulating the "proper" way
> is to alternate positive and negative layers, I can see how this would
> help CAM software to process things nicely, and as a benefit - it would
> speed our output quite a bit for complex boards.
I completely agree.
>
> Similarly - do we stick to their recommended best practices of ONLY
> creating pads using a single flash of a single aperture?
No. In the Gerber files I produce, the only items which are flashed
are vias (and perhaps square pads).
> The white-paper
> citing this recommendation explains that this structure is used to allow
> the CAM tool to extract pad locations more reliably, and that ATE flying
> probe testers will use this extracted data to identify probe points.
>
Agreed.
Gabriel
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