Travel speed for engraving images

I am trying to engrave images but the laser will not maintain a constant speed while changing the laser power. It slows down for dark areas and speeds up for light areas while changing laser power. Is this normal or do I have something set wrong. Everything other feature works great.

Running GRBL version 1.1e or earlier (still haven’t figured out how to get the laser to fire with version 1.1e as M4 fires a high signal vs. M3 low signal and my laser power supply will not accept a high signal)

I think you will have to upgrade to GRBL 1.1g to be able to properly take advantage of the laser mode you’ve enabled with $32=1. I’m running Lightburn on an Arduino Uno and all the features seem to be working perfectly. If you are using an Arduino product like Uno or Nano, use Arduino IDE to upgrade. If not, you’ve got some research to do… Check out the Github page regarding GRBL Laser mode as well.

I would like to update the UNO to Version 1.1g but I can’t seem to get the laser to fire running the M4 spindle direction code. M3 fires a low signal to spindle on and M4 fires a high signal. I have a K40 laser and the power supply has a k- and k+ pin but for some reason the k+ pin doesn’t want to work. I have to use the spindle on signal as using PWM to the laser only does not work(laser will fire constantly). My idea is to wire in a solid state relay to change the signal from a high signal to a low signal and be able to use the M4 code but I was hoping I could skip that. Not looking that way unless anyone has an idea for a solution.

The travel speed is constant with raster engraving objects which is why I am a bit confused on it slowing down during grayscale.

The ‘K’ pins on that power supply are for “key”, as in, the test fire button. The PWM signal for laser should be connected to either ‘In’ or ‘L’. ‘In’ also requires an on/off signal to the ‘L’ pin, whereas using the ‘L’ pin by itself works well for systems where the ‘In’ pin is connected to power through a pot to control the maximum output. This is how the C3D board is wired, for example.