There are some settings in LightBurn that you might want to tweak in order to get the best out of both. This article describes how to configure LightBurn to get optimum results. The connection device you choose in new device is not critical. You can choose Gerbil or Grbl-M3 (uses just easy Gcode). Even the other profiles seem to work well. Note: pictures of LightBurn interface are old and might differ in the more up to date versions.
Set the Grid settings to mm/min
For some reason, setting the grid settings from mm/s to mm/min gives a better performance. So you can experiment with these settings. I speculate that this provides less overhead when converting coordinates into steps but not sure.
Speed and DPI hints
There is a relationship between engraving speed and DPI and the associated PWM frequency. The higher the engraving speed, the higher you need to set the PWM frequency via the Mini Gerbil settings command ‘$28’ (Grbl uses the $ sign as a token for configuration settings). It is set to default 5 which translates to 1.5kHz.
Power range (max power S parameter)
The S parameter is the max power that the laser produces. S=1000 means that when a user issues a G-code command for example G1 X100 Y100 F1000 S100 -> the S parameter here says 1/10 of the power (1/10th of 18mA is 1.8mA). This parameter must match the S parameter within the Mini Gerbil although you can change it to a custom value to suit your needs (make up for aging or worn tubes). In MG the S parameter is $30. E.g. $30=1000
When the out put of your laser is too weak because of age then you can tweak it to a lower value e.g. $30=500.
Auto homing on start up
Auto homing is great to ensure that the zero position is always the same. This is important for repeat jobs that uses a jig or when you want to optimise the use of the plywood.
However when you install the Mini on the first time, you might want to disable this to debug the machine because if the laser does not auto home it throws an alarm and you cannot move the axis unless you unlock the machine via the command $X. Just use the console and type $X <enter>. Then you can check the movement of the axis via the Move tab and arrows and test the direction (e.g. common error is Y axis moves opposite direction of the home. Turn the connector 180 degrees is the most simple solution)
Test Fire button
The Test fire button on the K40 does not work anymore because the Mini now controls the LO (laser on or enable) signal on the Laser power supply. Issuing a M4 S100 (turn laser on with strength 100) won’t work becasue of Grbl’s safety feature of switching of the laser when the axis are stationary.
However you can use those commands in CNC mode, just issue a $32=0 and the machine is in CNC mode. M4 S100 turns now the laser on. The macro below is a simple trick to switch on the laser for a few seconds and turn it off. You can make a macro by left click on the macro button. The P parameter is the dwell factor in milliseconds. So adjust to your needs.
Curious about those $ settings we talk about? Have a read here …