I am building a laser cutter and I am using external stepper drivers to power stepper motors. I have a driver for an optional stepper motor for a rotary attachment. I would only disconnect or connect the optional motor when the machine is powered off. Can I power the external stepper driver without the stepper motor connected, as long as I don't connect/disconnect the motor while it is powered?

This is the driver I am using https://cohesion3d.com/shop/peripherals/external-stepper-driver-4-amp/


1 Answer 1


I see no reason for stress using any half or full-bridge Stepper drivers with no load.

If you have the unit powered off and move the stepper motors connected, it will create enough back EMF to get rectified by the body diodes and power up any micro cooling fans on the same supply. I've done that before but I'm not recommending it.


I also have a 3-axis stepper driver 1.1m square gantry with 3rd axis for the laser and have run it disconnected when I loaned my laser to a buddy ... hmm who still has it. But I used a 2A CNC shield on an UNO card but very fast optimized using Gcode Panel over on Windows.

If you burn too slow you may as well go single or 1/2 step. You need lots of laser power to burn anything more than wood fast. Like 100W. I only had 10W to burn 1/4 million pixels in softwood in 3 hrs.

You will need lots of power for cutting foam and a toxic fume extractor. A hot wire cutter might be cheaper and faster with 300W.

  • \$\begingroup\$ Cool! I should have said 'I've mostly built' a laser cutter. Just putting the finishing touches on it. It's 1600 x 1500 mm, 90W co2, with 4 axes. I'll be using it mostly for cutting and engraving wood and plastic. When you say \$\endgroup\$
    – jbalk
    Commented Apr 28, 2022 at 15:18
  • \$\begingroup\$ 'no strees using stepper driver with no load', you mean I can power the driver without a motor, correct? I think that's what you mean I just want to be clear. Also - thank you! \$\endgroup\$
    – jbalk
    Commented Apr 28, 2022 at 15:30
  • \$\begingroup\$ no stress means no problems \$\endgroup\$ Commented Apr 28, 2022 at 20:50

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