Hi!
I replaced the original brushed 150W motor of my mini lathe with a BLDC 750W one. I managed to replace all electronics inside the lathe so speed controller works normally, reverse, and even I managed to make it all work in CNC using MACH3. M3, M4 and M5 works normally and speed control also, with an encoder.

I’m using MACH 3, a Gecko G540 and an Ethernet Smoothstepper. The Gecko, the Smoothstepper, the brushless motor controller and the spindle encoder have their grounds shared. I just didn’t share the ground with the PC, as it’s not using anymore the parallel port. Although I don’t know if the smoothstepper network plug shares it’s ground with the PC.


When I’m executing a GCODE program, everything works normally from start to end.

But when I want to turn something manually in Mach3, if I turn on the motor manually, and I use the keyboard’s arrows to jog, the movement of any axis is “choppy”, “jerky”. The axis doesn’t move smoothly. If I turn the motor off, then the both axis can be jogged normally with no jerky movements.

And another strange situation is: if I’m jogging using the arrow keys, with the motor on, and I touch the lathe’s bed, then the axis stop moving (I’m keeping any arrow key pressed - so still jogging). As long as I keep touching the bed, I can’t jog. If I take my finger from the bed, then i can jog again.

It didn’t happen when I used the old motor and no smoothstepper.

Any ideas on how to fix these effects? Could the motor create an EMI interference only when doing manual stuff? All CNC GCODE works normally…

Regards, Rodrigo