Carbide Motion Spindle Speed Control

I’ve upgraded my Shapeokos to run 1.5kw spindles. Got the VFD all wired up and it’s cutting beautifully.

The new spindle control within CM is also fantastic, I love having it spin up and down based on the job. So far though, regardless of the RPM’s I set for a toolpath, the voltage output is 0v or 5v - no gradient. Has anyone else run into this? It means I have to run everything at 24,000rpms (the spindle max), unless I want to switch back to manual control.

Side note, if you’re still on the fence about getting a water cooled spindle, at 24,000rpms I’m slotting through 6061 at 135in/min and .020 DOC all day long. :smiley:

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Probably need to adjust the spindle RPM range in Grbl.

Think SO3 default is 5000, so anything above is gonna max out the PWM pin, showing that 5v.


What Dan said, you need to set $30=24000 and then GRBL will generate a PWM that averages to a voltage proportional to the programmed RPM value.

Unrelated note: it’s also good practice to have a spindle warmup g-code file that you can run at the beginning of a session in the shop, that has the spindle ramping up from 0 to 24000 slowly over a few minutes, to get the spindle/bearing/grease up to nominal temperature. Not mandatory, but (probably) useful to optimize spindle life and accuracy and easy enough to do.


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