Mail Archives: geda-user/2014/07/20/12:54:31
On Wed, 2014-07-16 at 10:36 -0700, Dave Curtis wrote:
> On 07/16/2014 02:56 AM, Peter C.J. Clifton wrote:
> > On 2014-07-15 05:41, Dave Curtis wrote:
> >> On 07/14/2014 09:09 PM, DJ Delorie wrote:
> >>>> "octagon" flag appears to do nothing on Pad[] directives. Is this
> >>>> correct?
> >>>
> >>> Correct.
> >>>
> >> Is that by plan? A friend and I are looking at "challenging footprint
> >> specs" (we're easily entertained..) and I've seen a couple where an
> >> interpolated octagon could be helpful.
> >
> > Thats a poly-curve.
> >
> > (As are ROUND pads, obround pads, square, .... (you get the idea).
>
> Well, but octagons are a RS-274X pad macro primitive, both flashed and
> stroked, so they are fair game for footprint pad construction.
I'd prefer to model things more generically in future, not by using
classes of template objects.
If we can always model a pad as a polygon / polycurve, it cuts out the
multiple choice code-paths where we must select ("Is it square-ended, is
it round-ended, (is it an octagon)"...)
> I guess I don't understand the logic of not allowing the octagon flag on
> Pad[]'s, since they are allowed on Pin[]'s. It seems to me that all the
> logic should be there to draw them -- wouldn't they be handled the same
> as a square aperture, even when the pad is parallel to the X/Y axes?
Square pads are already broken for rotation, no need to add octagons to
the list of broken geometric primitives as well!
> Bonus points for allowing "HOLES" to be non-round (poly-curve) too, to
> > support manufacturing slots ;)
> >
> > (And for footprints which use slots to pass wide tabs on a big power
> > connector, for example.)
>
> How are footprint slots communicated to the fab house? Outline layer
> paths are routed after fab, but slots would need to be routed
> pre-plating. Would another mechanical layer be added that contains slot
> routing information? And do you communicate slot outlines or a toolpath
> and tool diamater?
Its been a while since I was involved on a board which used them, but
IIRC, we manually pasted the relevant outline contours onto an unused
layer, which the fab used as a pre-plating process route-layer.
I think the communicated data was interpreted much as outlines usually
are.. they cut so the edge of the cutter follows along the centreline of
your layer geometry.
A more robust communication would just be the contour, with no width -
but gerber doesn't really do that. (I guess in theory, the outline trace
could be made with a 0-width aperture, but PCB doesn't natively support
this at the moment).
--
Peter Clifton <peter DOT clifton AT clifton-electronics DOT co DOT uk>
Clifton Electronics
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