Cutter pushing back on OpenScad DXF files due to "too many nodes"

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Cutter pushing back on OpenScad DXF files due to "too many nodes"

nbkhwjm
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


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Re: Cutter pushing back on OpenScad DXF files due to "too many nodes"

JordanBrown
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.


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Re: Cutter pushing back on OpenScad DXF files due to "too many nodes"

DanS
"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 <[hidden email]> 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.

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Re: Cutter pushing back on OpenScad DXF files due to "too many nodes"

Whosawhatsis
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 <[hidden email]>, 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 <[hidden email]> 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.

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Re: Cutter pushing back on OpenScad DXF files due to "too many nodes"

OpenSCAD mailing list-2
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 <[hidden email]> 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/ArcWelderPlugin
On Feb 16, 2021, 19:46 -0800, Daniel Shriver <[hidden email]>, 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 <[hidden email]> 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.

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Re: Cutter pushing back on OpenScad DXF files due to "too many nodes"

caggius
In reply to this post by nbkhwjm


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

  

On 16 Feb 2021, at 23:27, Chris Story <[hidden email]> wrote:

Amada Fiber Lasers


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Re: Cutter pushing back on OpenScad DXF files due to "too many nodes"

mondo
In reply to this post by OpenSCAD mailing list-2
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


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Re: Cutter pushing back on OpenScad DXF files due to "too many nodes"

nbkhwjm
In reply to this post by OpenSCAD mailing list-2
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?


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Re: Cutter pushing back on OpenScad DXF files due to "too many nodes"

nbkhwjm
In reply to this post by mondo
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...

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Re: Cutter pushing back on OpenScad DXF files due to "too many nodes"

mondo
In reply to this post by nbkhwjm

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.



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Re: Cutter pushing back on OpenScad DXF files due to "too many nodes"

mondo
In reply to this post by nbkhwjm


On 17/02/2021 12:51, nbkhwjm wrote:
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...

Thanks, I'll try that. Most of my cnc stuff is 2.5D, anyway. As dxf can be 3d, I thought that openscad would cater for that. What version/release of dxf does openscad export?

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Re: Cutter pushing back on OpenScad DXF files due to "too many nodes"

OpenSCAD mailing list-2
In reply to this post by nbkhwjm
You can set the level of optimization and observe any severe changes. If anything, I'd suggest that the optimization improves the accuracy by removing the jaggies, putting the lines on the circle instead of creating chords.

On Wednesday, February 17, 2021, 7:21:34 AM EST, nbkhwjm <[hidden email]> wrote:


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?


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3D to 2D

mondo
In reply to this post by mondo

Well, whatever version of dxf, my cam program can import it OK and generate the required G-codes. Now, since it is mostly 2,5D (simple pocketing/profiling on 3 axis mill) I basically need outlines and depths of cut, the illustration shows a simple part. Using intersections on a large cube, I can get the profiles, but is there a simple way to get them into 2d, and perhaps combine them as one dxf export?


On 17/02/2021 13:30, Ray West wrote:


On 17/02/2021 12:51, nbkhwjm wrote:
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...

Thanks, I'll try that. Most of my cnc stuff is 2.5D, anyway. As dxf can be 3d, I thought that openscad would cater for that. What version/release of dxf does openscad export?

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Re: 3D to 2D

nbkhwjm
if you drop the Z parameter on the translates, and change Cube to Square it will be 2D, im not sure how that works for you since you need depth of cut...  also when you render it, its distinctly different looking..  like the attached picture...



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Re: 3D to 2D

nophead
Use projection() to convert 3D to 2D.

On Wed, 17 Feb 2021 at 16:30, nbkhwjm <[hidden email]> wrote:
if you drop the Z parameter on the translates, and change Cube to Square it will be 2D, im not sure how that works for you since you need depth of cut...  also when you render it, its distinctly different looking..  like the attached picture...



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Re: Cutter pushing back on OpenScad DXF files due to "too many nodes"

Troberg
In reply to this post by OpenSCAD mailing list-2
OpenSCAD mailing list-2 wrote
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.
I second that. LightBurn is the gold standard for laser cutters, there really isn't anything even close to it. If you have spent the money on a fiber laser, the cost for LightBurn is neglible.

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Re: 3D to 2D

mondo
In reply to this post by nbkhwjm

Thanks for your help. I can get the similar change of colour on rendering, and a dxf file, if I draw in 2d. However, in the 3d example I quoted, I can 'slice it' by using squares, by translating the 3d object down, instead of increasing the square height, so to speak, However, if I render it, it ignores the 2d parts. If I remove the 3d part (comment out it's display line) then it will not render.

I've a simpler part below, that I can't get to export. How do I get a dxf file for the two 'discs' ?


module test(){
    cylinder(50,20,10);
}

test();

module bot(){
    intersection(){
         square(100,true);
        translate([0,0,-1])test();
    }
}
   
translate([50,50,0])bot();

module upper(){
    intersection(){
        square(100,true);
        translate([0,0,-40])test();
    }
}

translate([0,50,0])upper();


//Best wishes,

//Ray

On 17/02/2021 16:29, nbkhwjm wrote:
if you drop the Z parameter on the translates, and change Cube to Square it will be 2D, im not sure how that works for you since you need depth of cut...  also when you render it, its distinctly different looking..  like the attached picture...
 

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Re: Cutter pushing back on OpenScad DXF files due to "too many nodes"

lar3ry
In reply to this post by Troberg
Even for a low cost laser cutter, Lightburn is well worth the $40, but
only provided your control board is one that's compatible with it.

On Wed, 2021-02-17 at 11:12 -0700, Troberg wrote:

> > OpenSCAD mailing list-2 wrote
> > 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.
>  I second that. LightBurn is the gold standard for laser cutters,
> there really isn't anything even close to it. If you have spent the
> money on a fiber laser, the cost for LightBurn is neglible.
> Sent from the OpenSCAD mailing list archive at Nabble.com.
> _______________________________________________
> OpenSCAD mailing list
> [hidden email]
> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org


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