External Stepper Config

Machine: DIY CO2 laser.

Board: LaserBoard
Firmware: _Smoothie

Problem/ Question: _Do I need to change any settings in config file of laserboard if I am using external stepper drivers? I am losing steps and I have tight belts, 4amp nema23 and stepper driver set to 3.5amps.



Hi Charlie,

Thanks for your patience while we reviewed this. I noticed that you have a custom build. That sounds like a fun project!

The external drivers themselves do not require a config change since our cabling strategy handles everything in the hardware, but the associated larger motors and mechanics of the machine would need all the physics values adjusted for them. Also, make sure all of the wires are connected properly.

It sounds like you have your current set properly on the DIP switches, if they are similar to the ones we carry. If they are different, please let us know what model.


Can you confirm what you have your microstepping set to? In the configuration file, our default values are set to work with 1/16 microstep.


You can change the microstepping to whatever you want on the external driver, as long as you account for it in steps per mm, max speed, and acceleration values, but we highly recommend sticking with the default and working from there to start with.

These values will also depend on what type of belts you have installed, what pitch they are, and how many teeth the pulleys have. Our settings are based off of the standard pitch MXL belts for the X and Y axes (typically 2.032 pitch, at 5.08mm/0.2" and 9.4mm/0.37″ respectively). Here is a useful calculator online to help you determine if you have your steps/mm set properly if you are using a different belt, such as GT2.

What size is your work area? If you have a larger bed size than the standard 300 x 200 mm work area, you will also need to make some adjustments for these configurations as well. You can find more information in our Cohesion3D LaserBoard Larger Laser Machine Installation Guide.

If you continue to experience issues after reviewing and making the needed adjustments, please provide additional information and we will work from there.

Thanks for the response. I am using 1/16 micro steps. My work area is 1300mm x 900mm. When I am vector engraving I am losing the same amount of steps every time. My ending position is always a couple mm lower than the start point. The vector engraving obviously becomes distorted.

Do I have to change the amps in config if I’m using external? I’m reading that link about larger lasers and it says to adjust current. Is that only if I’m using the internal drivers? Thanks again.

So I did everything in that large co2 write up and it didn’t change. So I just tried loading GRBL onto the board and it fixed all my problems.

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