cutter control discussion

[SleeplessDad]

I have not seen any posts on this topic for a week or so.

I would like to help but I am terribly slow to get things done.

I am just wondering if we could hammer out what needs to be done so I
can add it to my "to-do list" volume 3

I could buy a cutter in July or August and I should be able to finish
reverse engineering the command protocol sometime in the fall.

I know there are different formats used to send information to the
cutters, would it be good to work on a more robust DXF export option
too? I don't know the first thing out GSD, does does someone want to
work on this ?

I am unfamiliar with Inkscape internals, if I provided the commands
could someone integrate this into Inkscape? Or do we even want to do
this? Is there a better way?

Thanks-Patrick

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[stuart-20]

Patrick wrote:
...<cut>...
> I could buy a cutter in July or August and I should be able to finish
> reverse engineering the command protocol sometime in the fall.

Are you talking about a Graphtec plotter like the Craft ROBO or any of
its derivations?

> I know there are different formats used to send information to the
> cutters, would it be good to work on a more robust DXF export option
> too? I don't know the first thing out GSD, does does someone want to
> work on this ?

I had thought inkscape read & saved DXF already.

Regarding GSD - there are people talking about this.  I think the
current efforts are outside of inkscape and involve translating to and
from GSD.  But I don't know if anyone has working code.

> http://wiki.inkscape.org/wiki/index.php/BlueprintCutterControl

On the other hand - I don't even bother w/GSD files.  I just pipe
inkscape's postscript output to a modified python script which does the
translation.  If that's a postscript to GSD translation, it is a fairly
simple process.  However, I understand it was mostly base on reverse
engineering.  That is, we know what to send the Graphtec cutters given a
post script command (like pen down or cut to here).  Or, in other words,
I don't think we have the slightest idea what's inside a GSD file.

> http://vidar.gimp.org/graphtecprint/

The down side to this is that the process is not integrated into
inkscape.  I have spent a lot of time explaining the installation
process only to have people give up when it finally occurs to them they
need to install python and glade and some other packages (oh, and the
above solution is really only for Linux).

> I am unfamiliar with Inkscape internals, if I provided the commands
> could someone integrate this into Inkscape? Or do we even want to do
> this? Is there a better way?
>
> Thanks-Patrick

I am trying to clear this up for my self as well.  If you want to be
wow'ed Ted posted a link to a graphic representation of some inkscape
inner workings:
> http://inkscape.modevia.com/doxygen/html/classInkscape_1_1Extension_1_1Print.php

I doubt the inkscape project wants to directly integrate a particular
cutter into it's code.  It's more likely a plug in approach might be
considered (to keep the two software components apart).

How are you getting the commands?  Are you sniffing the USB?  If you
are, I'd like to know about the commands associated with the optical
pick up.  I think that is a unique feature of these small cutters.  Or
can large cutters look for registration markings as well?

...thanks



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[SleeplessDad]

Hey Stuart

I think I worded that last email incorrectly. I am not presently
snooping commands yet, I don't own a cutter. I am not sure which one
will be the best to buy either but I figure I will just ask for
suggestions on which one will be best for Inkscape and then I will check
my wallet's opinion.

Inkscapes DXF export does not produce a fully featured DXF, I think most
CAD programs cannot open it, it is a minimalist DXF just for the
robocutter community.

Thanks for the links-Patrick

stuart wrote:

>
>
> Patrick wrote:
> ...<cut>...
>> I could buy a cutter in July or August and I should be able to finish
>> reverse engineering the command protocol sometime in the fall.
>
> Are you talking about a Graphtec plotter like the Craft ROBO or any of
> its derivations?
>
>> I know there are different formats used to send information to the
>> cutters, would it be good to work on a more robust DXF export option
>> too? I don't know the first thing out GSD, does does someone want to
>> work on this ?
>
> I had thought inkscape read & saved DXF already.
>
> Regarding GSD - there are people talking about this.  I think the
> current efforts are outside of inkscape and involve translating to and
> from GSD.  But I don't know if anyone has working code.
>
>> http://wiki.inkscape.org/wiki/index.php/BlueprintCutterControl
>
> On the other hand - I don't even bother w/GSD files.  I just pipe
> inkscape's postscript output to a modified python script which does
> the translation.  If that's a postscript to GSD translation, it is a
> fairly simple process.  However, I understand it was mostly base on
> reverse engineering.  That is, we know what to send the Graphtec
> cutters given a post script command (like pen down or cut to here).  
> Or, in other words, I don't think we have the slightest idea what's
> inside a GSD file.
>
>> http://vidar.gimp.org/graphtecprint/
>
> The down side to this is that the process is not integrated into
> inkscape.  I have spent a lot of time explaining the installation
> process only to have people give up when it finally occurs to them
> they need to install python and glade and some other packages (oh, and
> the above solution is really only for Linux).
>
>> I am unfamiliar with Inkscape internals, if I provided the commands
>> could someone integrate this into Inkscape? Or do we even want to do
>> this? Is there a better way?
>>
>> Thanks-Patrick
>
> I am trying to clear this up for my self as well.  If you want to be
> wow'ed Ted posted a link to a graphic representation of some inkscape
> inner workings:
>> http://inkscape.modevia.com/doxygen/html/classInkscape_1_1Extension_1_1Print.php 
>>
>
> I doubt the inkscape project wants to directly integrate a particular
> cutter into it's code.  It's more likely a plug in approach might be
> considered (to keep the two software components apart).
>
> How are you getting the commands?  Are you sniffing the USB?  If you
> are, I'd like to know about the commands associated with the optical
> pick up.  I think that is a unique feature of these small cutters.  Or
> can large cutters look for registration markings as well?
>
> ...thanks
>
>
>

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[Aaron Spike-2]

Patrick wrote:
> I have not seen any posts on this topic for a week or so.

I've been on vacation.

> I would like to help but I am terribly slow to get things done.

I think that is pretty common. But anything you do does help. So don't
worry about it and just do as much as you desire.

> I am just wondering if we could hammer out what needs to be done so I
> can add it to my "to-do list" volume 3
>
> I could buy a cutter in July or August and I should be able to finish
> reverse engineering the command protocol sometime in the fall.

This is really what needs to happen. Not that you need to buy one, but
these cutters need to get into the hands of technical people who are
open source minded and want to help. Right now there doesn't seem to be
much cross over between the cutter communities and the OSS community.

> I know there are different formats used to send information to the
> cutters, would it be good to work on a more robust DXF export option
> too? I don't know the first thing out GSD, does does someone want to
> work on this ?

We've made some simple improvements to DXF recently and more can be made
I'm sure. We just need to be more specific with what the problems are so
that we can find solutions. Thanks to everyone who has worked on it lately.

I started looking into GSD perhaps a year or more ago. I was able to
figure out some things, but my lack of need and infancy as a programmer
have hindered me. I'm not a GSD user and I have no need for it but I
would be happy to help anybody with interest learn more about the
format. I've published my code at:

http://code.google.com/p/cuft/

Aaron Spike

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[Aaron Spike-2]

Patrick wrote:
> Inkscapes DXF export does not produce a fully featured DXF, I think most
> CAD programs cannot open it,

We need bug reports filed in launchpad to support assertations like this
before they are useful. Anything else is just FUD.

> it is a minimalist DXF just for the
> robocutter community.

This is very true.

Aaron Spike


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[Aaron Spike-2]

stuart wrote:
> Regarding GSD - there are people talking about this.  I think the
> current efforts are outside of inkscape and involve translating to and
> from GSD.  But I don't know if anyone has working code.

There is no one working on GSD at the moment. If anyone wants to start
working on it, come talk to me. I have info you want. Some of it can be
found at:

http://code.google.com/p/cuft/

Aaron Spike

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[SleeplessDad]

Hi Aaron and fellow Inkscapers

Thanks for your cutter posts today Aaron. I have never been part of an
open source project and I would really like to help with this feature
and if I can manage it, improving the DXF output too.

I went to submit a bug regarding the fact that Autocad cannot open the
DXF. However there is already a bug that is similar:
https://bugs.launchpad.net/inkscape/+bug/197765

Can anyone suggest a Vinyl Cutter that would be good as the first to add
support for? I was hoping to spend under $500. Once I know which one
would be good I will likely search for a used one. Perhaps someone on
the Inkscape user list would like to sell me one of their old ones or if
not there are several online auctions.

If no one has a preference I will likely just buy a small one as that's
all I need(I am planning on using it to make stencils for Airbrushing)

ThX-Patrick


Aaron Spike wrote:

> Patrick wrote:
>> Inkscapes DXF export does not produce a fully featured DXF, I think
>> most CAD programs cannot open it,
>
> We need bug reports filed in launchpad to support assertations like
> this before they are useful. Anything else is just FUD.
>
>> it is a minimalist DXF just for the robocutter community.
>
> This is very true.
>
> Aaron Spike
>
>

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[Andy Fitzsimon]

Guys,
I'm actually looking into buying a vynil / sticker cutter right now.
knowing whats most supported and whats in need of testing will help
with my decision.

Finding where to buy the actual things in south east asia is quite
hard also.  seems both the US and UK are the only places to buy.
Andy

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[stuart-20]

Andy Fitzsimon wrote:
> Guys,
> I'm actually looking into buying a vynil / sticker cutter right now.
> knowing whats most supported and whats in need of testing will help
> with my decision.
>
> Finding where to buy the actual things in south east asia is quite
> hard also.  seems both the US and UK are the only places to buy.
> Andy

Note: Looking for low end less then $500 cutter, read on...  other wise
skip.

I'm only familiar with the old (blue) wishblade and the like.  These
represent the bottom of the Graphtec line and are usually less then $500
(more like $300).  They are for craft work and are mainly used for
cutting paper. They have a small format and can only cut to the width of
a standard sheet of notebook paper (about 7 1/2 inches).  Their blades
are not articulated (i.e. they rotate freely but are not controlled by a
motor).  So sharp turns will nick the media.

Wishblade's are marketed by Xyron in the US.  This company has a
terrible reputation for late product introduction. Add to that, Xyron is
not a technically savvy company.  They are "scarppers" and shipped me
static sensitive supplies in plastic bags that were certainly not plated
with nickel. Wishblade's PC based software does not allow for importing
DXF files.  It only works with GSD files.

In the rest of the world (perhaps in your part as well) I think Graphtec
markets something called a Robo CRAFT.  This is essentially the same
cutter however the software allows for importing DXF files.

Xyron markets a newer version of the wishblade that is pink.  I don't
know what the differences are.  The first people who buy it will be
scrappers.  No offense, but they are not likely to be able to comment on
technical aspects (i.e. does the plotter under stand anything beyond pen
up/down and move to here).

 From this list and my experience, inkscape can produce DXF files that
the Robo CRAFT PC based software can import and send to a Robo CRAFT
plotter.  Note, the Robo CRAFT PC based software will not talk to a
wishblade - probably by design (i.e. cripple ware). Also, it has been
mentioned in this list that inkscape's DXF format isn't (completely??)
compatible with other software.

I think the blue wishblade software support from Xyron is dwindling
(i.e. no path forward to Vista AFAIK).  If you get this type of cutter I
would use inkscape on a Linux platform with a modified version of
graphtecprint.  You can get graphtecprint here along with the
instructions to modify it to work with both a wishblade and Robo CRAFT
cutter (the down loadable version only works with a Robo CRAFT):
http://vidar.gimp.org/graphtecprint/.

...hope this helps.

P.S. Hey, there's a good comment here regarding these cutters.  They
recommend (I assume because vinyl cutting is thin) you go with the next
version up of graphtec cutters or a Roland:

http://www.specialty-graphics.com/index.asp?PageAction=VIEWPROD&ProdID=259



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[Alvin Penner]

Attached is a summary of what I have seen so far (from a purely software point of view) with respect to the use of Inkscape .dxf files in desktop cutting :

- the 'Desktop Cutting' export option supports two basic types of object : lines and cubic Bezier splines.

- it may sometimes be necessary to use the menu option 'Path | Object to Path', to convert rectangles, or ellipses, or text, before exporting to .dxf.

- the exported .dxf file complies with the Autodesk dxf spec to the extent that it can be viewed using Autodesk software such as Volo View Express 2.01 and DWG TrueView R17 (2008).

- the exported .dxf file can be both edited and viewed using QCad from RibbonSoft.

- the desktop cutting software program Winplot V6.8 from Summa has been tested on .dxf files. It will load .dxf files, but it does not render the spline correctly : a cubic Bezier spline consisting of four points will be rendered as a combination of a circular arc based on the first three points, and a straight-line segment based on the last two points. The developers at Winplot have been made aware of this issue, but it is not likely that it will be addressed, see https://bugs.launchpad.net/inkscape/+bug/192923/comments/36 . Luckily, in this case there is a workaround, namely use 'Postscript via Cairo' export, which can be read properly by Winplot, see https://bugs.launchpad.net/inkscape/+bug/168411/comments/17 .

- the desktop cutting software program ROBO Master-Pro Version 4.3 from Graphtec has been tested on .dxf files. It can read .dxf files, and as far as I can tell, it is also rendering them correctly on the screen. However, any attempt to edit a spline that originated from a .dxf file will immediately lead to a software crash. Also, even if this file is saved as a native .GSD format file, and then reloaded as a .GSD file, it will still crash when attempting to edit the spline : which suggests that this is not specifically a .dxf issue, but a more general problem. Also, the ROBO Master software supports the creation and editing of a spline starting from scratch, but the mathematical form of the spline they generate does not appear to be compatible with the cubic Bezier spline that Inkscape uses. I am attaching a .GSD file with both types of spline present. The cubic Bezier spline is not editable (you'll be sorry if you try), but the native ROBO spline is editable. However, no matter how hard I try, I cannot make the two curves superimpose on each other, and I believe they are mathematically incompatible. I have emailed ROBO Master concerning this issue, and will await their response.

- I should not speculate, but I suspect that this mathematical incompatibility may be the source of some of the mechanical stuttering that has been reported. In any event, it would be a relatively simple matter to produce a reasonable approximation of one spline curve to another, based on matching slopes and curvatures at vertices, but before this is done we need a mathematical description of the shape of the curve that ROBO Master uses.

Alvin Penner
demo.GSD

[Aaron Spike-2]

Alvin Penner wrote:
> Attached is a summary of what I have seen so far (from a purely software
> point of view) with respect to the use of Inkscape .dxf files in desktop
> cutting :

Excellent summary! Everyone please read this twice. :-)

> - the 'Desktop Cutting' export option supports two basic types of object :
> lines and cubic Bezier splines.
>
> - it may sometimes be necessary to use the menu option 'Path | Object to
> Path', to convert rectangles, or ellipses, or text, before exporting to
> .dxf.

I think some motivated hacker should investigate adding an option for
output extensions so that they can optionally convert objects and text
to paths. This will solve all these problems in one place for all sorts
of output extensions.

> - the exported .dxf file complies with the Autodesk dxf spec to the extent
> that it can be viewed using Autodesk software such as Volo View Express 2.01
> and DWG TrueView R17 (2008).
>
> - the exported .dxf file can be both edited and viewed using QCad from
> RibbonSoft.

Again, if someone is aware of software that will not open our simple
DXFs please file a bug report on launchpad with all relevant example
files and error messages.

> - the desktop cutting software program Winplot V6.8 from Summa has been
> tested on .dxf files. It will load .dxf files, but it does not render the
> spline correctly : a cubic Bezier spline consisting of four points will be
> rendered as a combination of a circular arc based on the first three points,
> and a straight-line segment based on the last two points. The developers at
> Winplot have been made aware of this issue, but it is not likely that it
> will be addressed, see
> https://bugs.launchpad.net/inkscape/+bug/192923/comments/36 . Luckily, in
> this case there is a workaround, namely use 'Postscript via Cairo' export,
> which can be read properly by Winplot, see
> https://bugs.launchpad.net/inkscape/+bug/168411/comments/17 .

I do not believe DXF supports any sort of bezier curve, at least not the
mathematical model we are familiar with in Inkscape and most other
design oriented software. DXF supports NURB splines. Yes, the curves
created by our beloved cubic beziers are a subset of the curves that can
be represented by NURBs but many many more curves are possible in the
NURB world. Most importantly the on disk representation and the model of
interaction are different. (Someone with math-fu please correct me if
I've misspoke.)

Anyway for software that cannot interpret DXF SPLINE directives properly
we should offer an approximate polyline output. There is python code
around to do this polyline approximation (flatten.py), but it could be
improved.

> - the desktop cutting software program ROBO Master-Pro Version 4.3 from
> Graphtec has been tested on .dxf files. It can read .dxf files, and as far
> as I can tell, it is also rendering them correctly on the screen. However,
> any attempt to edit a spline that originated from a .dxf file will
> immediately lead to a software crash. Also, even if this file is saved as a
> native .GSD format file, and then reloaded as a .GSD file, it will still
> crash when attempting to edit the spline : which suggests that this is not
> specifically a .dxf issue, but a more general problem. Also, the ROBO Master
> software supports the creation and editing of a spline starting from
> scratch, but the mathematical form of the spline they generate does not
> appear to be compatible with the cubic Bezier spline that Inkscape uses. I
> am attaching a .GSD file with both types of spline present. The cubic Bezier
> spline is not editable (you'll be sorry if you try), but the native ROBO
> spline is editable. However, no matter how hard I try, I cannot make the two
> curves superimpose on each other, and I believe they are mathematically
> incompatible. I have emailed ROBO Master concerning this issue, and will
> await their response.
>
> - I should not speculate, but I suspect that this mathematical
> incompatibility may be the source of some of the mechanical stuttering that
> has been reported. In any event, it would be a relatively simple matter to
> produce a reasonable approximation of one spline curve to another, based on
> matching slopes and curvatures at vertices, but before this is done we need
> a mathematical description of the shape of the curve that ROBO Master uses.

As I said above, DXF and GSD use NURB splines; SVG uses polycurves
comprised of line segments, quadratic beziers, cubic beziers and
elliptical arcs. Some conversion is necessary. I believe conversion from
SVG paths to NURB splines can maintain the curve perfectly but from what
I can understand some approximation may be necessary coming back to SVG
from NURB.

The method of conversion I'm currently using in the DXF export is this.
Everything in svg is a line or a cubic bezier (cubic beziers can
represent all quadratic beziers and elliptical arcs are approximated by
a few cubic beziers). SVG cubic beziers are converted to a NURB
representation by the method described at the bottom of NURB Curves: A
Guide for the Uninitiated By Philip J. Schneider:
http://devworld.apple.com/dev/techsupport/develop/issue25/schneider.html

I have a hunch about the issue with DXF->RoboMaster->GSD. The splines in
our DXF are a subset of NURBs that prefectly represent cubic beziers. In
GSD files and DXF files it is possible to represent any and all NURB
curves. The RoboMaster drawing code can draw any NURB but the editing
code only understands the subset of NURB curves that their editing
interface can create.

That is actually one of the places I got stuck with my GSD exploration.
I don't understand NURB curves well enough to have a real solid handle
on the NURB representation inside of the GSD file. I can see it. And it
makes some sense to me, but not enough to so anything about it. I would
like to find a person with sufficient understanding of NURB math to:

1) examine the storage of NURBs in GSD files and explain it so that
mortals can implement reading and writing it.
2) examine the editing interface in RoboMaster and postulate what
special properties are possessed by the subset of NURBs it will create
and edit
3) Provide a method of approximating our cubic bezier NURB subsets with
RoboMaster NURB subsets.
4) Provide a method for round tripping NURBs to and from SVG

I think 2Geom can probably provide much help in this area but I haven't
found any one interested in working with it yet.

The second issue where I got stuck with my exploration of GSD files is
that I don't really know how to program an object model for reading and
writing GSD files or any other sort of files. I assume there isn't much
magic involved and this is just my inexperience and lack of time
showing. I'd love to have some pointers and some help.

Aaron Spike


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[Aaron Spike-2]

Aaron Spike wrote:
> Alvin Penner wrote:
>> However, no matter how hard I try, I cannot make the two
>> curves superimpose on each other, and I believe they are mathematically
>> incompatible.

I should also point out that I believe a single NURB spline should be
able to represent any SVG Path. But we are currently using a single NURB
spline to represent each cubic bezier path segment. If you were using a
single NURB to represent each bezier segment in RoboMaster I bet it
would be much easier to make them match within a reasonable error.

Aaron Spike

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[Alvin Penner]

thanks for the kind comments, this is getting very interesting...
just one more parting shot concerning .GSD files.
  I hate to be a pessimist, but these are the most unusual "vector-based" files I have ever seen, which worries me a bit concerning how to support them. First of all they are binary, not readable, which is uncommon for a vector representation. Secondly, it is not even entirely clear that they are vector-based. I once did an experiment where I took a single spline with four points, modified just one end point just for fun, and then compared the two .GSD files. The two files were different in many different physical locations in the file, not just one point, which kind of suggests some kind of crunched raster image, not very encouraging if trying to reverse-engineer the format.

[Jon A. Cruz]

On Sat, 2008-06-14 at 15:22 -0700, Alvin Penner wrote:

> thanks for the kind comments, this is getting very interesting...
> just one more parting shot concerning .GSD files.
>   I hate to be a pessimist, but these are the most unusual "vector-based"
> files I have ever seen, which worries me a bit concerning how to support
> them. First of all they are binary, not readable, which is uncommon for a
> vector representation. Secondly, it is not even entirely clear that they are
> vector-based. I once did an experiment where I took a single spline with
> four points, modified just one end point just for fun, and then compared the
> two .GSD files. The two files were different in many different physical
> locations in the file, not just one point, which kind of suggests some kind
> of crunched raster image, not very encouraging if trying to reverse-engineer
> the format.
>

I wouldn't say that myself. In fact, most vector formats I've used have
been binary.

Just exactly *how* the files are changing is probably important.
Especially since GSD files are used for cutters, chances are very very
high that they are some "cut along this curve" approach, rather than a
"punch out all black dots" raster format.


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[Alvin Penner]

Jon A. Cruz wrote:

high that they are some "cut along this curve" approach, rather than a
"punch out all black dots" raster format.

yes, that sounds reasonable, so you mean like a multi-segmented polyline.
that probably would not be that hard to confirm, if one didn't mind getting one's hands dirty with some brute force dumping of raw data.

[Aaron Spike-2]

Alvin Penner wrote:
>
> Jon A. Cruz wrote:
>> high that they are some "cut along this curve" approach, rather than a
>> "punch out all black dots" raster format.
>>
> yes, that sounds reasonable, so you mean like a multi-segmented polyline.
> that probably would not be that hard to confirm, if one didn't mind getting
> one's hands dirty with some brute force dumping of raw data.
>

That's what my project Cuft was about. It dumps the binary data from GSD
files into human readable XML or TXT.

http://code.google.com/p/cuft/

If you dump a gsd file to a txt document you will see the various
comments I have smattered around for what I think the structures in the
file represent.

There are a few reasons that the file changes in more than one place.
NURBs are more complex moving an endpoint probably doesn't just move two
control points like it does with beziers. And each drawing object in GSD
stores a number of data items including the curve data and the bounding
box. Changing the curve usually changes the bounding box too.

Please check out Cuft. :-)

Aaron Spike

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