Cutter pushing back on OpenScad DXF files due to "too many nodes"
Hey all,
First post here, so let me know if I broke the rules... This is SCAD
related in that im getting pushback with cutters when I use it.
Ive been using OpenSCAD for years to design all kinds of projects. Ive had
a lot of trouble finding companies to produce acceptable results when doing
small quantities.. they act like im asking for charity usually...
anyway I started using "SendCutSend.com" and the first few projects went
fine, but they are now really pushing back hard on the way that OpenSCAD
handles arcs and circles. The fact that they are very small lines making
the arc instead of a "Smooth arc", causes them to have trouble (in their
opinion) with processing time and accuracy.
Note: I do understand the impact of fa, fs, and fn and tried to adjust to
make it better, but they still push back.
The projects they have done for me in the past have been fine, but they are
pushing hard to use Fusion-360 or QCad as they handle arcs better.
Frankly I like OpenScad as the programmatic style works well with my design
process as the projects are highly mathematical in design.
So is this that big of an issue for a cutter? (they use Amada Fiber Lasers)
Help he understand how big of an issue this is, changing my design process
now Is a problem....
Thanks
Chris
--
Sent from: http://forum.openscad.org/
On 2/16/2021 3:27 PM, Chris Story wrote:
First post here, so let me know if I broke the rules...
Not at all.
anyway I started using "SendCutSend.com" and the first few projects
went fine, but they are now really pushing back hard on the way that
OpenSCAD handles arcs and circles. The fact that they are very small
lines making the arc instead of a "Smooth arc", causes them to have
trouble (in their opinion) with processing time and accuracy.
OpenSCAD's underlying processing really wants to turn everything into
line segments and triangles. Curves are not a thing down there. I
wouldn't expect that to change.
So is this that big of an issue for a cutter? (they use Amada Fiber
Lasers)
Help he understand how big of an issue this is, changing my design
process now Is a problem....
Don't know. On the one hand, 3D printers do just fine with numerous
small line segments, and they have similar mechanical properties. On
the other hand, maybe a laser cutter has more of an issue with the need
to maintain a constant speed.
"OpenSCAD's underlying processing really wants to turn everything into line
segments and triangles."
Yeah, points and the segments that connect them, define everything.
I can't imagine how OpenSCAD could make solids in the same manner that
vector graphics can define curves etc. But it would be very interesting if
it could do that, and it might be a big help in various fabrication
technologies (not just this one).
On Tue, Feb 16, 2021 at 10:15 PM Jordan Brown openscad@jordan.maileater.net
wrote:
On 2/16/2021 3:27 PM, Chris Story wrote:
First post here, so let me know if I broke the rules...
Not at all.
anyway I started using "SendCutSend.com" and the first few projects went
fine, but they are now really pushing back hard on the way that OpenSCAD
handles arcs and circles. The fact that they are very small lines making
the arc instead of a "Smooth arc", causes them to have trouble (in their
opinion) with processing time and accuracy.
OpenSCAD's underlying processing really wants to turn everything into line
segments and triangles. Curves are not a thing down there. I wouldn't
expect that to change.
So is this that big of an issue for a cutter? (they use Amada Fiber
Lasers)
Help he understand how big of an issue this is, changing my design process
now Is a problem....
Don't know. On the one hand, 3D printers do just fine with numerous small
line segments, and they have similar mechanical properties. On the other
hand, maybe a laser cutter has more of an issue with the need to maintain a
constant speed.
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
It would be nice if we had a tool, either external or built into openscad or external, that did something for OpenSCAD's 2D export formats like what Arc Welder does for gcode. https://github.com/FormerLurker/ArcWelderPlugin
On Feb 16, 2021, 19:46 -0800, Daniel Shriver tabbydan@gmail.com, wrote:
"OpenSCAD's underlying processing really wants to turn everything into line segments and triangles."
Yeah, points and the segments that connect them, define everything.
I can't imagine how OpenSCAD could make solids in the same manner that vector graphics can define curves etc. But it would be very interesting if it could do that, and it might be a big help in various fabrication technologies (not just this one).
On Tue, Feb 16, 2021 at 10:15 PM Jordan Brown openscad@jordan.maileater.net wrote:
On 2/16/2021 3:27 PM, Chris Story wrote:
First post here, so let me know if I broke the rules...
Not at all.
anyway I started using "SendCutSend.com" and the first few projects went fine, but they are now really pushing back hard on the way that OpenSCAD handles arcs and circles. The fact that they are very small lines making the arc instead of a "Smooth arc", causes them to have trouble (in their opinion) with processing time and accuracy.
OpenSCAD's underlying processing really wants to turn everything into line segments and triangles. Curves are not a thing down there. I wouldn't expect that to change.
So is this that big of an issue for a cutter? (they use Amada Fiber Lasers)
Help he understand how big of an issue this is, changing my design process now Is a problem....
Don't know. On the one hand, 3D printers do just fine with numerous small line segments, and they have similar mechanical properties. On the other hand, maybe a laser cutter has more of an issue with the need to maintain a constant speed.
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
As a test, I opened a file I have in OpenSCAD that creates a projection, then exported the result to a DXF file. When I opened the file in LightBurn, a laser cutting program, the "arcs" were short segments, as described and as expected.
LightBurn has an optimize feature with sliders for magnitude. When I pushed the slider even a small amount, the individual segments were turned into Bezier curves and the number of nodes was reduced from 549 overall to 62.
The program is not free, but one can purchase a GRBL version for US$40. It's one more post-processing step, but works fast and may provide a solution.
On Wednesday, February 17, 2021, 12:00:19 AM EST, Whosawhatsis <whosawhatsis@gmail.com> wrote:
It would be nice if we had a tool, either external or built into openscad or external, that did something for OpenSCAD's 2D export formats like what Arc Welder does for gcode. https://github.com/FormerLurker/ArcWelderPluginOn Feb 16, 2021, 19:46 -0800, Daniel Shriver tabbydan@gmail.com, wrote:
"OpenSCAD's underlying processing really wants to turn everything into line segments and triangles."
Yeah, points and the segments that connect them, define everything.I can't imagine how OpenSCAD could make solids in the same manner that vector graphics can define curves etc. But it would be very interesting if it could do that, and it might be a big help in various fabrication technologies (not just this one).
On Tue, Feb 16, 2021 at 10:15 PM Jordan Brown openscad@jordan.maileater.net wrote:
On 2/16/2021 3:27 PM, Chris Story wrote:
First post here, so let me know if I broke the rules...
Not at all.
anyway I started using "SendCutSend.com" and the first few projects went fine, but they are now really pushing back hard on the way that OpenSCAD handles arcs and circles. The fact that they are very small lines making the arc instead of a "Smooth arc", causes them to have trouble (in their opinion) with processing time and accuracy.
OpenSCAD's underlying processing really wants to turn everything into line segments and triangles. Curves are not a thing down there. I wouldn't expect that to change.
So is this that big of an issue for a cutter? (they use Amada Fiber Lasers)
Help he understand how big of an issue this is, changing my design process now Is a problem....
Don't know. On the one hand, 3D printers do just fine with numerous small line segments, and they have similar mechanical properties. On the other hand, maybe a laser cutter has more of an issue with the need to maintain a constant speed.
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
ArcWelder is a great looking tool - but as input it takes the output of the slicer, the gcode, not the STL file and post processes the gcode by looking for sequences of G0/G1 movements that approximate arcs and converting them to G2/G3 commands.
OpenScad produces STL files which are basically just a description of a large number if linked tile shapes. With no knowledge of how it was produced or what it represents. The slicer literally draws the 3D object in memory and then takes a series of slices through it with all the myriad of points hat produces.
CAD programs proprietary formats often contain descriptions of planes and curves. Laser manufacturers software can easily interpret the CADs curve descriptions into movement arcs. Speeding up the cutting process
There is very little difference between a laser cutter and a FDM printer mechanically they both have X-Y motors to position the head. Curves are quicker and smoother to generate. I wonder if the lasers are being switched on/off at the end of each segment at the d
So the real ne
I've only used dxf format as an interchange between a cad drawing
package and my simple cnc cam software - I only thought it was for 2D.
In openscad, If I try exporting a dxf file from a 3d object, it throws
an error message. I'm not sure of the advantage of using openscad to
produce 2d drawings. If the final object is a profile, then I would
expect a 2d drawing package, which is designed for that, dealing with
arcs as smooth curves, etc. to be better option. Virtually all machine
tools generate curves in small segments, interpolating from G2, G3.
Fwiw, wrt arc welder, it is only recently that Marlin, for example, has
been able to handle such codes, but, afai,k it has no effect in the z
direction, due to the fact that is dealing with horizontal slices, the
nature of fdm printing. The advantage of g2/ g3, is it gives much
shorter code files, and as the calculations are loaded into the drivers,
'stuttering' is reduced which can occur if the communication interface
can not keep up with the fast dispensation of tiny steps, slowing the
cutting/printing speed can overcome these transmission problems.
I would be interested to know how you get dxf files from openscad 3d
objects.
Best wishes,
Ray
I downloaded LightBurn and used the Optimize function as recommended.. the
number of nodes went from 6000+ to 260, then exported it as dxf. I sent a
sample to the cutter for evaluation.
I do worry about losing accuracy with any kind of "optimization" process
though... am I being paranoid?
--
Sent from: http://forum.openscad.org/
if I don't add a 3d Z parameter to any translates or use any 3d object then
it exports just fine.. Actually I think that OpenSCAD is quite good at
doing a 2D layout as I can programmatically layout multiple objects
mathematically quickly...
--
Sent from: http://forum.openscad.org/
On 17/02/2021 12:20, nbkhwjm wrote:
am I being paranoid?
Maybe... If it is of concern, do some tests. Not knowing about the
specific optimization you are using, but, if for example you have a hole
(given by subtracting a cylinder), if that is machined direct from the
openscad file, it will be smaller than the diameter, since the 'circle'
is composed of segments. If you have increased the diameter, to fit an
existing shaft, then any optimisation to convert the segments into a
circle, is likely to give a much sloppier fit. But, for laser cutting,
any precise holes may need to be machined as a separate operation, so a
slight alteration to diameters will most likely suffice.