When combining grbl firmware with lightburn, what should I change when using a 100W CO2 laser instead of a 40W one?
Assuming it’s a different tube in the same machine, all the mechanics remain identical and only the power changes. After you align the mirrors, the available power will be about twice as high, so reducing the layer power settings by about 50% or increasing the layer speeds by about 100% should be close.
Of course, running new Material Tests to confirm the settings would be a Good Idea.
In earlier discussions you described the machine as having a 100 W tube: is it now working with a 40 W tube?
Also be aware that not all mirrors are designed for 100Watt, but you have probably already replaced them, along with the new tube and matching power supply.
I only use a 100 watt CO2 laser. I want to know when to use the (console) in LightBurn. Is there a difference between 40 watts and 100 watts?
Yes, but Lightburn does not know that. @ednisley already said you have to make settings corrections for power and speed. If you are thinking Lightburn automatically compensates for the added power, the answer is definitely not.