J Tech laser pause

OK new to all this and need help. I have a Shapeoko running a JTech laser. I use lightburn for laser software and Aspire for cutting. I was trying to make the JTech chess board. Problem I have is when I save the Gcode and run it on carbide motion, and start the laser activities the laser pauses before it starts moving. I have seen other blogs stating the pause is due to spindle wind up or spin up (not sure how to say that) before it allows the machine to move.

Hi @Skipy,

Welcome to the community!
Did you enable laser mode ($32=1)?
Also, you don’t need to use Carbide Motion, Lightburn is actually a G-code sender and if you use it for creating your laser design you might as well use it for lasering the piece too.

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Hi Julien,
Thanks for the warm greeting. How do you enable laser mode in carbide motion?

It’s not something at Carbide Motion level, it’s a parameter in the GRBL controller itself at the machine side.

You can change that parameter from Carbide Motion though: go to the MDI tab, type $32=1 and hit send

To revert back to CNC mode (important!) type $32=0 and send

Thank you I will try that and see if it helps.

In addition to what Julien mentioned you may want to have a look at this if you haven’t already, lots of good info, especially the macro setups. You can set the $32 values with in them and send them along with other configurations as needed.

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Thanks Ed, I went through the set up when I installed LightBurn. I switch the macro’s they had me set up for Use laser and Use CNC but when I put it back to CNC and used carbide motion it still stalled the laser on movement start-up. I will try burning the chess board again using the $32=1 and then revert that back when finished burning. There is a lot more to this than I originally thought. Buy a CNC they said get a laser it will be fun they said. ugh! LOL I feel I will be on this site often.

Just out of curiosity, could you do this from within the g-code file, by adding the relevant enable/disable code at each start/end of the toolpath?

I’ve not done anything with lasers, but never say never!

Last time I checked it was not possible to insert “$xx=yy” type commands in G-code files to modify GRBL params, not with the G-code senders I use anyway (CM and CNCjs). I guess this would be both a blessing and a curse (imagine having to track configuration errors in the Gcode file in addition to the toolpath mistakes…)

I hesitated for a long while before getting one, mostly because I was not comfortable with the eye-safety aspects. With adequate (safety) caution, a laser opens up a lot of opportunities. If I were to use a laser to cut things, I would get a powerful CO2 one, but for engraving/etching surfaces the low-power models that can be attached to the router mount are perfect (for me)

I have always used Lightburn to drive the laser…it works great. If you’re using it to do your designs anyway, why not use it to do the burning? Lightburn makes it really easy to create and execute custom GRBL macros. My UseCNC and UseLaser macros (in Lightburn) have all the necessary parameter changes to go between CNC and Laser settings. I’ve made it part of my start up and shut down procedures to run the appropriate macro (UseLaser when I start up and UseCNC before I shut down) whenever I use Lightburn in the shop.


It’s my understanding that one can send settings using a text file, but that it’s not good practice — potential issues:

  • repeatably writing to EEPROM and wearing it out
  • timing — I don’t believe that writing the setting sends back an acknowledgement, so it’s possible to send commands which get lost

@chamnit could speak to this.

AVR eeprom is rated to about 10,000 write cycles, if I remember right. So you could theoretically write to it 10 times a day for three years. Obviously it’s ok to do intermittently but not for sustained cycles as part of a constant work flow.

Grbl provides a ‘ok’ response like any other command when writing a setting. So it can be streamed via txt file. It just locks out writing a setting if it is not in an idle state.

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The place to add codes like “$32=1” is in a post-processor. I don’t know how generally available that is, but Vectric software makes it available for editing. We have a post-processor for the router and a different one for the laser. These are used by the design software to create the grbl files.

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