K40 rotary locking up

I have a stock main board in k40 and I would like to run a rotary. I have a rotary unit that I like, the problem is that when it tries to spin with anything on the wheels the motor locks up and wont spin. If the unit is empty it will spin with no problem. Due to cost I was hoping to keep the stock main board. I was wondering if I can use a external driver to provide more power to the motor. The motor is a Nema 17. Thoughts please and thank you

I have a stock K40, and a self build rotary using a NEMA 17 but do not have this issue.

Does the stepper sound like its running smoothly when not under load?

Can you supply some pictures of the stepper, and wiring into the control board?

Have you used the rotary on anything else?

you likely have a higher power stepper motor in your rotary than the driver can support. K40 motors are ~0.8A on X and 1.2A on Y so you want a rather low power NEMA 17 motor. And the K40 motors are 400 steps/rotation( 0.9 deg) vs standard 3DP motors which are 200 steps/rev(1.8deg).

You might also monitor the controller’s DC supply. The stock LPS output is marginal even without a rotary.

Thank you, yes without a load it runs and sounds smooth. Is there anything I can add to increase power the motor. I was thinking something like a TB6600 driver.

This suggests to me the problem is not the controller’s stepper drive.
Can you put a DVM on the 5V and 24V supply to see if it droops when the rotary is under load?
What are you loading it with?

Also - my steppers are rated 12v, yours has 19v on it.

That may also be something to consider apart from the other troubleshooting tips posted.

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Yes I will. Im sorry Im out of town and will check the voltage when I get back, and will look for a 12 volt motor to test. Thank you guys for helping me with is.

Do you have a model number I can use to search for a 12v motor or do you know the current rating on your motors. Thank you

Here is a link :
[Rotary stepper](STEPPERONLINE Nema 17 Bipolar 0.9deg 11Ncm 1.2A 42x21mm 4-lead for CNC Milling Engraving Machine https://amzn.eu/d/5gH3ICS)

is the 1.2A on this motor consistent or lower than what motor is on the Y axis/driver it is replacing?


The X axis uses R360 (0.36 Ω) sense resistors, and Y axis R470 (0.47 Ω). That drives the X axis motor at 0.33A per phase, and the Y axis motor 0.44A per phase.

My X motor is supposedly 0.6A/phase and the Y one 1A/phase.

My rotary also uses a 1A/phase motor and it works fine, but I don’t use an M2 Nano anymore and the stepper driver is set to 1A peak.

Has anyone ever tried replacing those resistors? Theoretically, it should work, but you may need to glue on some heat sinks and maybe use a separate 24V supply since the “2A” 24V rail from K40 PSUs is already at its limit.