Laser GCode Control

I have just hooked up the J-Tech Photonics Laser to my CNC and am wondering about what actually turns the laser on and off. Is it the G0 command turns it on and the G1 turns it off for fast moves?

Nathan, try to get this software PicSender V2.5.9 - . This software is design to work with the x-controller.

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Thanks Alain, I really just need to cut foamcore, will this software do that as well?

Nathan2, well your best bet is to look on the tutorial of the software, I am sure you should get the response that you are looking for.

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For normal setups M3 turns the laser on and M5 turns the laser off.

With the appropriate wiring and G-code you can vary the intensity of the laser beam using the S word.

With an rpm range of 0 - 255, 0 = laser off, 255 = laser full on, 128 would be half power.


M3 S128 turn laser on with 50 percent power
M5 turn laser off


Your best bet is to contact John Champlain of Pic Sender JohnChamplain, I am sure you will a good support from John regarding Pic Sender and G-code. Basically Pic Sender send the G-Code command to the X-controller which in turn feeds your laser system with the command.

Thanks guys. I did download PicEngraver and PicSender, however they both seemed to only import raster images. I’m not sure how accurate that would be. I ended up using Inkscape (V .91 - important as at writing) and the J-Tech Inkscape Extension to export the GCode, then UGS.

Just as a not to Larry’s post, the x-controller off the shelf is M3 S12000 for full power, and you also have to enable the PWM output… I think the command was $30

Actually, the X-controller as delivered by Inventables is running grbl 1.0c which has the rpm min/max set by $31/$30.

As long as you set the S word to a value that is equal to or greater than the value in $30 then you will have full power.

M3 is the spindle on G-code command and M5 is the G-code spindle off command.

If $30=1, then M3 S1 would turn the spindle on full power.

An S word with the value 0 (zero) will also turn the spindle off.

M3 S0 would have the result of no spindle turning. (M3 would enable the spindle, the S0 would specify 0 RPM)

No worries. My point more was that you have to set the max PWM as it seems to be set to 0 or 1 from the factory. So M03 S1000 which is the suggestion in the instructions to focus the laser, turns it on flat out instead of at ~10%.

Do you happen to know if the 3.8W laser fron J-Tech has a duty cycle recommendation? As in, cut for 15 minutes, give it a rest for 5 or something?

Those instructions were written for the JTech 0.9g version of grbl where the max rpm was set using a compile time option in grbl.

But, you have it figured out.

No, I don’t know if there is a duty cycle limitation. I haven’t heard anyone mention one, but I would check with JTech if you want to be sure.