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



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%.
* 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.
* 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.
* 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.

please don't take that personally, i just think it's not quite there --
at least yet.

to add constructively, i'd like to point out what's currently available
in the area of pcb gcode generaton as far as i am aware of it:

* visolate: a java gui tool that just recently got a command line
  interface (but still depends on having a graphics card, as
  calculations are done there). implements its own gerber loading,
  currently lacking polygon support. can generate both precise and
  voronoi toolpaths. no outline support, no drilling. most (only?)
  platform independent solution. development is rather quiet; maintained
  in second generation.
* pcb2gcode: command line tool that uses gerbv libraries and then uses
  pixel-wise flood-filling for toolpath generation. voronoi style
  patterns are a side effect of using an exagerated tool diameter
  (it is an open issue that this results in the paths being engraved two
  times, reducing the savings). supports drilling both with automatic
  tool changer and mill-drilling. outlines are supported (currently
  using polygons, there is ongoing consideration how to handle this
  best). platform dependent due to gerbv dependency. development is
  currently quite active; the project has an ancestry of similarly named
  tools written in different languages.
* brdtrace: the newest tool. does not touch gerber itself, but has
  helper scripts that use gerbv to generate images. quite optimized as
  far as i can tell. outlines are partially supported, mill-drilling is
  supported (also uses gerbv generated images). platform independent, as
  long as one finds a way to get pbm images from gerber w/o gerbv.

(i should state that i work with the visolate and pcb2gcode maintainers
to create debian packages of them, and am about to do so with brdtrace.
the things i am / we are using pcb and those tools for in the metalab
[1] can be seen at [2].)

this turned out to become a longer mail than i intended, and might be
interesting for -devel as well -- or are the relevant people on -users
anyway?

regards
chrysn

[1] http://metalab.at/
[2] http://geilomat.soup.io/

-- 
To use raw power is to make yourself infinitely vulnerable to greater powers.
  -- Bene Gesserit axiom

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