Speed control +10% and -10% when actively burning

While you are burning, the move tab turns into a speed and power controller to adjust your burn on the fly. my question is, if i hit the -10% speed button, is there a way to tell how fast my laser is running after pressing? I know I know “do the math” and that is easy if i only need to adjust once. But say I need to adjust down, then adjust back up. (first adjustment 100-10%=90) (second adjustment 90+10%=99) OR does lightburn always adjust from the original value of 100 so you’ll be able to return to your original speed?

I hope this wasn’t too confusing. Please let me know if I need to clarify more.

This latter choice was always my understanding. It increments/decrements from the original figure, not of the current value. So as you say, going up by 10% and then followed by reduction of 10% should leave you at the original value.

I’ll caveat that I may have this wrong but I’m sure someone can correct me.

I haven’t used this but I have to ask, if you move it 10% does the display stay at 10%?

Logic would say it should be whatever the speed the layer is set, not the modified. If it were resultant it wouldn’t be 10%, it would have to move to 0 so you’d have 10% of the resultant…

I.E. 10% of 100 is 10, but 10% of 90 is 9, not the same…

Like to do this on my Ruida… :crying_cat_face:


There is no display to show the currently speed (that I’m aware of) and I’m not moving it to 10% of the original speed, I’m removing 10% of the original speed. 10% of 100 is 10, so 100-10=90. My laser is now moving at 90 speed. If I try to add that 10% back on (10% of 90 is 9) would the result be 99? Or am I supposed to be adding 10% of the original speed which was 100?

If it worked on the ‘adjusted’ speed, you could easily move it somewhere you couldn’t recover.

As in your example, you could never get back to 100%.


All LightBurn does is send feed and spindle override commands to GRBL. GRBL gives no feedback as to what the current values are, or whether the command was accepted or ignored. The numbers are cumulative until you hit the limit (10% / 200%), so clicking the +10% button 5 times will mean you’re now running at 150% the original value.

GRBL docs: grbl/commands.md at master · gnea/grbl · GitHub

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Perfect. Now at least I can figure out the speed when I change it on the fly.

Thank you!

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