NGC file with GRBL software

[DHFC]

 
Hi, I'm new to Inkscape. Using it to produce .ngc file for use with grbl controller software. I have worked out how to take an image and convert it to a .ngc file, I just don't know how to stop the laser from burning the path to the start point and between contours.  I think it has something to do with the z axis but just can't work it out.  Can anyone help?

[brynn]

Welcome to Inkscape Community!

I moved your message into its own topic.  I don't know if we can help, but I'm always happy to learn new things. 

After a little research, I found info about GRBL (sounds like the driver behind CNC machines), but am having trouble finding info about the NGC file type/format.  You say you managed to convert an Inkscape drawing to NGC?  How did you do that?  It may have something to do with the problem, although I'm only guessing.

So this is a laser cutter, and it's burning a path to the start point.  My first question would be --  How does it know where the start point is?  And it's cutting between contours....  Can you explain what a contour is, in this context?  Do you mean it's cutting between the paths where you want it to cut?  Like if you had a regular pencil attached to the cutter, it should be lifting the pencil between drawing one path and drawing the next?

Can you show us the SVG file, if you saved one?  I don't think I'll be able to open an NGC file....but there needs to be some way to compare how faithfully the NGC file is representing the vector paths.

Although when you mention the z axis, it sounds more like....  Well, are you working on a 3D project?  Since Inkscape can only handle 2D graphics, you likely could not have created a 3d project with it.  So maybe you just need to disable the z axis?  Hhmm...unless you're making a 3d project using a series of 2d drawings (like a 3d printer might work....at least what I've seen on TV - I really have no idea how they work).

Sorry, I wish I could be more help.  But maybe my simple questions would lead you to find the answer.

[DHFC]

Hi Brynn,
   Thanks for getting back to me.  I will respond to your post below in paragaph order.

1. Thanks for your willingness to offer help.

2. GBRL is an application to drive the Desktop CNC machine.  I use a 500nm laser for engraving wood that I have turned on a lathe.

I followed a number of instructions from youtube  http://www.keerbot.com/generating-gcode-using-inkscape

I open inkscape,
Set the page size (material size)
import a JPG or PNG file
use trace bitmap to create the vectors
(i believe this creates the svg file)
use extensions - gcodetools - engraving
set the options and preferences and apply
this produces the NGC file
I then open the file in GBRL and begin the burn.

3.  As mentioned above. this is a desktop CNC machine.   It burns paper, leather and wood  Your example of the pencil is exactly what is happening. the pencil wont lift during the transition between paths.

4. I have attached two files:
The svg file created

DDK Logo.svg
(273.15 kB - downloaded 5241 times) and

the NGC file (converted to txt)
DDK Woodturning.txt
(29.52 kB - downloaded 834 times)

5. I am doing a 2d project. my understanding of the Z axis is that it represents the laser beam and the position of the focal point. ie lifting the focus from above the material to the burn depth.

Hope my response provides some more information.  looking forward to your further responses.

Thanks
David

[brynn]

The SVG file only has the JPG in it.  I was hoping to look at the paths you're sending to the machine.  There's a good chance they're fine, but at least it's a first step.  Did you save an SVG file after using Trace Bitmap?

[DHFC]

Sorry,
  Please find attached

[brynn]

Ok, here's one problem that I think you  have, although I'm not sure.  Do you realize that there are not 2 paths there, but 4?

This is not a direct result from Trace Bitmap.  I guess you might have taken the result from TB and did Stroke to Path?  Is this the result you wanted?

Maybe I don't understand either the laser cutting, or your plans. 

Out of curiosity, how narrow can a line etched in wood be, with the laser?  Do you get different lasers that etch or cut different widths?  Or is it 1 laser, and you have the ability to configure it with different variables?  For the cutting of this file, you'd have to have....well I guess it depends on the outer dimensions.

If this would be the sign on the outside of a business, I guess a line the width of a pencil would work.  That's something I imagine that it does.  But for a plaque inside the office, you'd need....a line maybe the width of the lead in the pencil (graphite these days, I guess)(telling my age, I guess) or less.  That would be amazing to me!

But I thought you'd want to etch out the middle of those paths (like the black parts in the JPG), rather than the path around it.

[DHFC]

I was a little surprised to see it run the path twice. 

My plans are to be able to take an image and be able to burn it onto various sized objects.  It, wooden drink coasters, Pens, knife handles, etc

The beam is a singel size and quite fine. 0.025mm  so produces a fine line in the material being cut.  I fine that the outlines are best as the full image takes way too long to produce. 

[brynn]

Ok, so you do want it to etch only the outline.  To do that, don't do the Stroke to Path step.

After you do Trace Bitmap, that's basically the path  you want, although you may need to tweak it a bit, here and there.  (Select the black object, add a stroke and remove the fill, to see just the path.  Object menu > Fill and Stroke, and also Help menu > Inkscape manual, with an internet connection, if it's not obvious how to use the dialog.) 

You can tweak it with the Node tool, if necessary.  Notice how you can drag the nodes around and that certain nodes have handles, which can be adjusted as well, to change the curve.  If you haven't tried that yet, here's a tutorial I wrote as an introduction to paths.  It's quite thorough and long, but covers almost everything.  http://forum.inkscapecommunity.com/index.php?action=articles;sa=view;article=7

I still don't have a clue about what the problem might be, at the moment.  I think you probably have paths that should work.  Maybe without the double paths, it will work better?

I've heard about one particular type of cutter/plotter that doesn't like a lot of nodes.  Fyi, I'm just learning about this way of using Inkscape, as I just took over as admin on the Inkscape for Cutting Design site, and there is a LOT to learn.  Some of them will only cut paths of a certain color or width.  Another requires the paths to be enclosed in a rectangle.  It doesn't cut the rectangle, but if it's not there, it won't cut.  There seems to be all kinds of little peculiarities for these machines and their software.

Anyway, let me know if there's any change, when you don't have the double paths.

Wow, so with a line being etched so thin, how do you accomplish a wider etch line?  Do you have to draw a series of paths that are incrementally larger/smaller?  Or can you just tell the program to make several passes at certain intervals?  Sorry, I'm just so fascinated by these toys -- I have a million questions.

Oh, I did notice something else in that file!  You have arrows pointing to the page border, indicating coordinates for 3 points.  On the y axis (0,100,0) and the origin (0,0,0).  But for the x axis, you have (100,0,-1.5).  I'm not sure what the purpose for indicating those points is.  Is the -1.5 the depth for the laser to cut?

If so, why is it only at that point?  Could that be the problem?

A couple more things I noticed, but they're probably nit-picking.  The document units are cm, but those coordinates are mm.  And also, whatever those points are, they don't seem to relate to the drawing, that I can see, at all.  They're probably just for reference, I guess.