DXF for cut and engrave
Yes but laser drivers don't offset the cut by half the kerf and they don't
accept a 3D model that represents a surface with engraving as trenches
equal to the kerf and so derive a tool path running down the centre. A CAM
tool to drive a mill accepts a model of the intended result, not a tool
path. Laser artwork is just the tool path in different colours not a model
of the desired end result. OpenSCAD can produce a perfectly good model of
the end result. It can't produce tool paths.
On Thu, 24 Oct 2019 at 11:50, Rogier Wolff R.E.Wolff@bitwizard.nl wrote:
On Thu, Oct 24, 2019 at 10:56:15AM +0100, nop head wrote:
The problem is a laser doesn't cut a line with zero thickness but people
pretend it does.
You can model any object a laser can produce in OpenSCAD. What is needed
is
a CAM stage for lasers that creates the tool path, just as 3D printing
and
milling. For some reason the CAM stage is ignored when laser cutting.
The CAM stage traditionally happens in the printer driver under
windows. A program, ANY program tells windows it wants to print
something. Then together with some confguration, the printer driver
translates e.g. the color of the line into different commands for the
laser (say: red: "all the way through at 100% laser power and 10%
speed, blue: "just a scorched line at 50% laser power and 100%
speed", green: "engraved in bitmap mode").
The problem is that with those things tightly coupled to the laser
device in question, and them being closed source, it is difficult to
optimize those things. For example, at my friends' the laser will
easily cut up a single "rounded box" outline into 4 lines and for
quarter-circles and do them in the woarst possible order you can
imagine.
Optimizing the toolpath is equivalent to the travelling salesman
problem and therefore NP complete. But that doesn't mean you can't do
a meaningful optimization. An easy optimization (that 3D printer
slicers should also do!) would be to always pick the closest
linesegment. In the rounded-box example that immediately leads to the
optimal solution. Then as a post processing step, investigate the
longest non-cutting moves and see if you can improve on them. Take a
segment between two long-moves and try to insert it in the path
somewhere to see if the total non-cutting path length can be reduced.
Sorry for my rant.
Roger.
On Thu, 24 Oct 2019 at 09:39, Troberg troberg.anders@gmail.com wrote:
OpenSCAD mailing list wrote
On Tue, Oct 22, 2019 at 11:10:03AM -0700, WillAdams via Discuss
wrote:
I have probably missed part of this discussion, but for me: I use
openscad to design a box for a project in 3D and then I lay the
pieces
flat and send the outline to be laser-cut.
OpenSCAD is heavily oriented towards 3D-printing, and, to some extent,
leaves us laser cutter guys out in the cold, or at least requiring us
to
make irritating workarounds.
For example, a line is useless in 3D-printing, but extremely useful in
laser
cutting (google "living hinge" for a good example).
I really hope that considerations for laser cuttings will enter into
the
plan for OpenSCAD, it would mean a lot to us. 3D-printing is just too
slow,
has too small work area and too limited in materials available to be
useful
for me.
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** R.E.Wolff@BitWizard.nl ** https://www.BitWizard.nl/ ** +31-15-2049110
**
** Delftechpark 11 2628 XJ Delft, The Netherlands. KVK: 27239233 **
The plan was simple, like my brother-in-law Phil. But unlike
Phil, this plan just might work.
OpenSCAD mailing list
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There is no reason why a proper CAM program can't convert a thin cut equal
to the kerf into a single line down the middle.
On Thu, 24 Oct 2019 at 14:02, Troberg troberg.anders@gmail.com wrote:
nophead wrote
The problem is a laser doesn't cut a line with zero thickness but people
pretend it does.
You can model any object a laser can produce in OpenSCAD. What is needed
is
a CAM stage for lasers that creates the tool path, just as 3D printing
and
milling. For some reason the CAM stage is ignored when laser cutting.
No, quite the contrary, we rely on it having some thickness, but we can't
model it with thickness, because that would make the laser cut twice.
We do have a CAM stage. In my case, I use LightBurn, and it does create a
tool path. But, for example, a living hinge, requires lines of minimum
width
(ie the kerf of the laser, typically around 0.1 mm). The way OpenSCAD
works,
I would need to model them as very narrow rectangles, which causes the
laser
to cut twice (slow, cuts a wider line, leaves more charring and increase
the
tendency of the material to cach fire). Sure, LightBurn can remove
overlapping lines, but as it's a very narrow rectangle, they won't overlap,
they'll just be very close to each other.
--
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nophead wrote
The problem is a laser doesn't cut a line with zero thickness but people
pretend it does.
You can model any object a laser can produce in OpenSCAD. What is needed
is
a CAM stage for lasers that creates the tool path, just as 3D printing and
milling. For some reason the CAM stage is ignored when laser cutting.
No, quite the contrary, we rely on it having some thickness, but we can't
model it with thickness, because that would make the laser cut twice.
We do have a CAM stage. In my case, I use LightBurn, and it does create a
tool path. But, for example, a living hinge, requires lines of minimum width
(ie the kerf of the laser, typically around 0.1 mm). The way OpenSCAD works,
I would need to model them as very narrow rectangles, which causes the laser
to cut twice (slow, cuts a wider line, leaves more charring and increase the
tendency of the material to cach fire). Sure, LightBurn can remove
overlapping lines, but as it's a very narrow rectangle, they won't overlap,
they'll just be very close to each other.
--
Sent from: http://forum.openscad.org/
Except that OpenSCAD can perfectly model anything you actually produce on a
laser because it is a 3D object. There is nothing wrong with OpenSCAD. The
problem is laser CAM doesn't work the same way as milling CAM and 3D
printing CAM. It could though.
On Thu, 24 Oct 2019 at 14:13, Troberg troberg.anders@gmail.com wrote:
nophead wrote
Yes but laser drivers don't offset the cut by half the kerf and they
don't
accept a 3D model that represents a surface with engraving as trenches
equal to the kerf and so derive a tool path running down the centre. A
CAM
tool to drive a mill accepts a model of the intended result, not a tool
path. Laser artwork is just the tool path in different colours not a
model
of the desired end result. OpenSCAD can produce a perfectly good model of
the end result. It can't produce tool paths.
Actually, most laser software (LightBurn, RDWorks...) do offset by half the
kerf. Not only that, they do a lot of other stuff associated with a tool
path, such as which order to do things in (fastest, inside out, all at
once,
one object at the time...), burnthrough (remain still after igniting the
laser for a short while to get a clean burn through), slowing down in
corners (to avoid bounce), using less power in corners/starting/stopping to
avoid overburn, adapting to acceleration limitations of the cutter and so
on.
They don't start from a 3D model, though, for obvious reasons. Lasers don't
get 3D, they get X, Y, power, speed and that's all (slightly simplified).
So, If I want to, say, cut out a circle with an engraved X, I need to model
a circle, then two crossing lines. These needs to be in different layers in
2D.
OpenSCAD does 2D fairly good, so usually it works out, but there are two
missing primitives which would help a lot: line and point.
--
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On Thu, Oct 24, 2019 at 02:05:12PM +0100, nop head wrote:
There is no reason why a proper CAM program can't convert a thin cut
equal to the kerf into a single line down the middle.
That's a feature that you think that a proper CAM program SHOULD have,
or maybe you know of one that DOES have this.
Us mortals have to use the tools that are available now. I don't have
time to write everything myself. Other people don't have the time to
wait for the developers (of their CAM workflow) to include such a
feature.
Roger.
On Thu, 24 Oct 2019 at 14:02, Troberg troberg.anders@gmail.com wrote:
nophead wrote
The problem is a laser doesn't cut a line with zero thickness but people
pretend it does.
You can model any object a laser can produce in OpenSCAD. What is needed
is
a CAM stage for lasers that creates the tool path, just as 3D printing
and
milling. For some reason the CAM stage is ignored when laser cutting.
No, quite the contrary, we rely on it having some thickness, but we can't
model it with thickness, because that would make the laser cut twice.
We do have a CAM stage. In my case, I use LightBurn, and it does create a
tool path. But, for example, a living hinge, requires lines of minimum
width
(ie the kerf of the laser, typically around 0.1 mm). The way OpenSCAD
works,
I would need to model them as very narrow rectangles, which causes the
laser
to cut twice (slow, cuts a wider line, leaves more charring and increase
the
tendency of the material to cach fire). Sure, LightBurn can remove
overlapping lines, but as it's a very narrow rectangle, they won't overlap,
they'll just be very close to each other.
--
Sent from: http://forum.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
--
** R.E.Wolff@BitWizard.nl ** https://www.BitWizard.nl/ ** +31-15-2049110 **
** Delftechpark 11 2628 XJ Delft, The Netherlands. KVK: 27239233 **
The plan was simple, like my brother-in-law Phil. But unlike
Phil, this plan just might work.
nophead wrote
Yes but laser drivers don't offset the cut by half the kerf and they don't
accept a 3D model that represents a surface with engraving as trenches
equal to the kerf and so derive a tool path running down the centre. A CAM
tool to drive a mill accepts a model of the intended result, not a tool
path. Laser artwork is just the tool path in different colours not a model
of the desired end result. OpenSCAD can produce a perfectly good model of
the end result. It can't produce tool paths.
Actually, most laser software (LightBurn, RDWorks...) do offset by half the
kerf. Not only that, they do a lot of other stuff associated with a tool
path, such as which order to do things in (fastest, inside out, all at once,
one object at the time...), burnthrough (remain still after igniting the
laser for a short while to get a clean burn through), slowing down in
corners (to avoid bounce), using less power in corners/starting/stopping to
avoid overburn, adapting to acceleration limitations of the cutter and so
on.
They don't start from a 3D model, though, for obvious reasons. Lasers don't
get 3D, they get X, Y, power, speed and that's all (slightly simplified).
So, If I want to, say, cut out a circle with an engraved X, I need to model
a circle, then two crossing lines. These needs to be in different layers in
2D.
OpenSCAD does 2D fairly good, so usually it works out, but there are two
missing primitives which would help a lot: line and point.
--
Sent from: http://forum.openscad.org/
No I don't know any CAM that does that except some slicers. I expect to
have to write it myself because the laser world has got this wrong.
On Thu, 24 Oct 2019 at 14:21, Rogier Wolff R.E.Wolff@bitwizard.nl wrote:
On Thu, Oct 24, 2019 at 02:05:12PM +0100, nop head wrote:
There is no reason why a proper CAM program can't convert a thin cut
equal to the kerf into a single line down the middle.
That's a feature that you think that a proper CAM program SHOULD have,
or maybe you know of one that DOES have this.
Us mortals have to use the tools that are available now. I don't have
time to write everything myself. Other people don't have the time to
wait for the developers (of their CAM workflow) to include such a
feature.
Roger.
On Thu, 24 Oct 2019 at 14:02, Troberg troberg.anders@gmail.com wrote:
nophead wrote
The problem is a laser doesn't cut a line with zero thickness but
people
pretend it does.
You can model any object a laser can produce in OpenSCAD. What is
needed
is
a CAM stage for lasers that creates the tool path, just as 3D
printing
and
milling. For some reason the CAM stage is ignored when laser cutting.
No, quite the contrary, we rely on it having some thickness, but we
can't
model it with thickness, because that would make the laser cut twice.
We do have a CAM stage. In my case, I use LightBurn, and it does
create a
tool path. But, for example, a living hinge, requires lines of minimum
width
(ie the kerf of the laser, typically around 0.1 mm). The way OpenSCAD
works,
I would need to model them as very narrow rectangles, which causes the
laser
to cut twice (slow, cuts a wider line, leaves more charring and
increase
the
tendency of the material to cach fire). Sure, LightBurn can remove
overlapping lines, but as it's a very narrow rectangle, they won't
overlap,
they'll just be very close to each other.
--
Sent from: http://forum.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
--
** R.E.Wolff@BitWizard.nl ** https://www.BitWizard.nl/ ** +31-15-2049110
**
** Delftechpark 11 2628 XJ Delft, The Netherlands. KVK: 27239233 **
The plan was simple, like my brother-in-law Phil. But unlike
Phil, this plan just might work.
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
On 2019-10-24 15:22, Troberg wrote:
They don't start from a 3D model, though, for obvious reasons. Lasers
don't
get 3D, they get X, Y, power, speed and that's all (slightly
simplified).
So, If I want to, say, cut out a circle with an engraved X, I need to
model
a circle, then two crossing lines. These needs to be in different
layers in
2D.
When you do 3D printing, the 3D model is sliced (you could call that the
CAM part) and reduced to G-code which is essentially the same as "X, Y,
power, speed" with some additions for extrusion parameters. So what you
need is a kind of slicer software specialised for laser cutting.
OpenSCAD does 2D fairly good, so usually it works out, but there are
two
missing primitives which would help a lot: line and point.
Constructive Solid Modelling cannot use points and lines in the main
process. But points and lines could be the result of postprocessing in
some cases.
What is the typical file format you feed your laser cutter? Plain DXF?
Carsten Arnholm
On 24.10.19 15:22, Troberg wrote:
OpenSCAD does 2D fairly good, so usually it works out,
but there are two missing primitives which would help
a lot: line and point.
That question does come up now and again, but nobody
really took the plunge to design something that fits
into OpenSCAD.
It's not as simple as just adding line() as that
would break some of the current assumptions. However
I believe having a state with unclosed polygons is
not a problem in general as for example this happens
inside of text() too.
Just to highlight what I mean, here's some dummy code
that could model something resembling the letter L
p = [
[36,-5],[12,-5],[12,-48)],[6,-48],[6, 0],[36, 0]
];
polygon() {
point(p[0]);
for (a = [1:len(p)])
line(p[a - 1], p[a]);
}
Now that looks not very impressive as this would
work with just polygon(p) too, but text() also uses
quadratic and cubic splines. At that point it gets
much more interesting I think.
In the example above, the polygon() would also mean
that at this point the polygon is closed and could
be extruded to 3D. Without that guaranty it would be
still exportable to DXF or SVG.
ciao,
Torsten.
I like to generate my engravings in the PostScript graphic language, which allows full algorithmic numerical control of the lines, and understands fonts well.
Acrobat or Mac OS convert the file to PDF, which most laser cutters can be driven by.
--
David Gustavson
dbg@SCIzzL.com
On Thu, Oct 24, 2019, at 6:05 AM, nop head wrote:
There is no reason why a proper CAM program can't convert a thin cut equal to the kerf into a single line down the middle.
On Thu, 24 Oct 2019 at 14:02, Troberg troberg.anders@gmail.com wrote:
nophead wrote
The problem is a laser doesn't cut a line with zero thickness but people
pretend it does.
You can model any object a laser can produce in OpenSCAD. What is needed
is
a CAM stage for lasers that creates the tool path, just as 3D printing and
milling. For some reason the CAM stage is ignored when laser cutting.
No, quite the contrary, we rely on it having some thickness, but we can't
model it with thickness, because that would make the laser cut twice.
We do have a CAM stage. In my case, I use LightBurn, and it does create a
tool path. But, for example, a living hinge, requires lines of minimum width
(ie the kerf of the laser, typically around 0.1 mm). The way OpenSCAD works,
I would need to model them as very narrow rectangles, which causes the laser
to cut twice (slow, cuts a wider line, leaves more charring and increase the
tendency of the material to cach fire). Sure, LightBurn can remove
overlapping lines, but as it's a very narrow rectangle, they won't overlap,
they'll just be very close to each other.
--
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