[OpenSCAD] Creating DXF file with round shapes

Rogier Wolff R.E.Wolff at BitWizard.nl
Wed Jun 29 12:12:38 EDT 2016


On Wed, Jun 29, 2016 at 08:56:20AM -0400, doug moen wrote:
> OpenSCAD represents 2D shapes as polygons. That's just the way it works. So
> circles are represented by regular polygons.
> 
> If you write

>    projection() cylinder(h=12, r=80, $fn=100);

> then you have direct control over the number of line segments used to
> approximate the circle (in this case, 100). You can pick a $fn value that's
> high enough so that the circle looks good in laser cutter output.

I'm not sure that this is the problem Eric is having. 

When there are SEPARATE line-pieces, the lasercutter will first cut
from say -1,0 to -0.99, 0.1 and then start cutting from +1,0 to
+0.99,0.1 and keep on alternating between the sides of the circle. 

I always import the dxf into coreldraw and then run a macro called
"nodeclean2". This will fixup all the separate line-segments into
multiple segments of one object, so that the objects can be lasered in
one go without any moves inbetween. It also "closes" the object so
that "vectorsort = on" works. (if that's off or not working, the laser
may first decide to cut out your gear, and then later cut the hole in
the middle. But by then the gear has fallen out of the blank, so that
it's moved and out-of-focus...)

	Roger. 

> 
> More information here:
> https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Other_Language_Features#.24fa.2C_.24fs_and_.24fn
> 
> 
> On 29 June 2016 at 07:49, Eric Buijs <ebuijs at mac.com> wrote:
> 
> > Hello,
> >
> > I use OpenSCAD to export dxf files that I need for laser cutting. When I
> > create circles a dxf file with multiple line segments per circle is
> > generated by OpenSCAD. This causes problems on the laser cutter that
> > "perceives" this a multiple independent lines.
> >
> > As an example: projection() cylinder(h=12, r=80); generates 30 line
> > segments.
> >
> > Is there a way around this within OpenSCAD or is it just the way that
> > OpenSCAD generates dxf files?
> >
> > I use OpenSCAD version 2015.03-3 on OSX (10.10).
> >
> >
> >
> > --
> > View this message in context:
> > http://forum.openscad.org/Creating-DXF-file-with-round-shapes-tp17833.html
> > Sent from the OpenSCAD mailing list archive at Nabble.com.
> >
> > _______________________________________________
> > OpenSCAD mailing list
> > Discuss at lists.openscad.org
> > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
> >
> >
> >

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