GCode, V-Carve, PicSender and Lasers, oh my

So I’ve been using V-Carve Desktop 9, along with the JTech GRBL No_Z (inch) post processor to control the X-Carve with the 2.8 watt laser and have been pretty impressed with the results, especially once I switched from the Offset fill to the Hatch at 0 degrees. Watching it reminds me of my days using AutoCAD and a CalComp plotter.

So as I’ve been playing with the laser, I’ve noticed that it seems like it doesn’t burn the first group of vectors in any job until it moves to another location. Usually this isn’t a problem as it does the outlines first and then the fill. However, tonight it for some reason it started with the fill first and the outline second, which left a letter have engraved. I tried to re-run the job, but it did the exact same thing.

So as I’m looking at the GCode file in PicSender, I noticed something odd, I don’t know if this is a glitch in the Post Processor or if it’s something that I’m doing so I thought I’d toss this out to the community.

Here’s the typical start to the GCode file for the laser:

M03 S0
G1F0.5 S12000
G1X1.1466Y0.7054F50.0 S12000

For those of you well versed in GCode for the laser, you might see the issue right away, for those who aren’t, here’s what’s happening.

We’ll skip down the “M03 S0” line, that is telling the laser to turn on with a power of 0, essentially setting it so low that it doesn’t produce a beam that could burn anything. The next line “M05”, actually turns the laser off. The next several lines that start with “G” are movement commands and the ones with the “S12000” are the ones that tell the laser how powerful to shine the beam. The only problem with that is that the “M05” command turned off the laser. So, depending on how many vectors are “linked” together for engraving it could be awhile until the laser is turned off, moves to a new location and receives an “M03” command to turn on.

If I put an “M03 S0” after the “G0” line everything engraves as it should. I would also imagine that removing the first “M05” would have the same effect as the laser power at this point is “0”.

My question: Has anyone else seen this? Am I doing/not doing something? Is it a bug?

Let me know.



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There was an error in the JTech Post Processor on the JTech web site. Try downloading the current version there and re-do your test.

The one that is currently on the web site does not have the M05 in it.


Thanks Larry, I’ll give that a try!!