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Re: gEDA-user: comments on gcode generation (was: Re: exporting single pcb layers)


Am 30.11.2010 um 16:29 schrieb chrysn:


On Mon, Nov 22, 2010 at 08:29:31AM +0100, Alberto Maccioni wrote:
in the process of cnc-milling a pcb with a custom shape using pcb2gcode 
[1], i created a polygon on a separate layer...

Have you ever tried the g-code exporter included in PCB?
I've never been able to make pcb2gcode work with minimally complex boards.
i just did so, and found out there are some reasons i'll -- at least for 
the time being -- will continue to use external tools:

* no voronoi mode: all the "other tools" (see below) support a mode
  where they fill the unused area of the board with the closest net.
  this cuts the machining time down to less than 50%.
Yes, this would be a very welcome addition. Is there a pure C library with this stuff available somewhere? Java or C++ isn't an option for inclusion with gEDA. 


* strange outline behavior: i'm not sure what the outline file is
  supposed to do, but for my testing example it cuts on the inside and
  the outside of the outline line, and additionally cuts in the drill
  holes. this might be a bug, depending on what it is supposed to do
  exactly.
Without code patches, lines on the outline layer are handled just like any other traces. This is improved with some of these patches:
http://sourceforge.net/tracker/? func=detail&aid=3100354&group_id=73743&atid=538813
You can apply them all without loosing anything. Outline milling is still limited to rectangular boards without holes, though.
* no mill drilling: if a milling head is used to cut out the board along 
  its outline, the same tool can be used to drill arbitrarily large
  holes by moving in circles. that might be what is intended with the
  holes in the outline layer, but they don't really fit size- and
  shape-wise.
Actually, this is on my today's work list. With some luck it'll appear in the above set of patches this week. 


* parameters: there are five tunable parameters in the gcode export,
  while there are roughly three times as many in pcb2gcode, most
  prominently the feed rates and speed settings. while of course the
number of parameters is not an indicator of completeness or quality, i 
  think it is roughly representative of the state of pcb's gcode
  support.
User definable feedrates went into the patchset just yesterday :-) The unpatched exporter is more directed towards Emacs-savy people, replacing the single F command near the top of the G-code isn't that difficult.
I had a look into brdtrace and, well, it's _very_ basic. Only one layer per run, no solder side flipping. Impressive for a weekend's worth of work, though. 






Markus

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Dipl. Ing. (FH) Markus Hitter
http://www.jump-ing.de/







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