Loud z axis motor irrespective of micro-stepping

j3d

I should also mention that I am running the printer on 24V.

According to the EMF calculator for 800mA, it says:

Approximate peak back EMF due to rotation per motor: 6.5 V at 200.0 mm/s
Approximate peak back EMF due to inductance per motor: 56.5 V at 200.0 mm/s
Step pulse frequency: 16.0 kHz at 200.0 mm/s
Speed at which torque starts to drop (low slip angle): n/a
Speed at which torque starts to drop (high slip angle): n/a

For 400mA:

Approximate peak back EMF due to rotation per motor: 6.5 V at 200.0 mm/s
Approximate peak back EMF due to inductance per motor: 28.3 V at 200.0 mm/s
Step pulse frequency: 16.0 kHz at 200.0 mm/s
Speed at which torque starts to drop (low slip angle): 106.7 mm/s @ 8.5 kHz
Speed at which torque starts to drop (high slip angle): 126.5 mm/s @ 10.1 kHz

The back EMF due to inductance is very high. Is this the cause?

Phaedrux

@j3d said in Loud z axis motor irrespective of micro-stepping:

Step angle: 1.8
Rated voltage: 13.2
Current: 0.4A/phase
Resistance: 33 ohms/phase
Inductance: 45 mH/phase
Holding torque: 2.4 kg/cm

I would say those motors aren't very suitable for a 3d printer. You should seek out motors with a lower inductance.

https://duet3d.dozuki.com/Wiki/Choosing_and_connecting_stepper_motors

o_lampe

@j3d
I'd also scream with a current 2 times of max. current.
Even 0.4A is too much, better go for 80% of max current or the steppers will get pretty hot.
Did you try to run the motors without the Bed (no load)?
Where does the noise come from, the leadscrews are OK?
Greased and run-in?

Also your test code has no speed limit. Try to add a

G1 F180

before G28 Z, which is half speed. Those leadscrews get really loud when driving too fast.

dc42

@j3d said in Loud z axis motor irrespective of micro-stepping:

The back EMF due to inductance is very high. Is this the cause?

Yes. If the motors are run at a current/speed combination that makes the peak back emf greater than the VIN supply voltage, then the drivers can't generate a smooth current waveform and the motors will be noisy.

gloomyandy

It may be worth trying to get them to run in stealthchop rather than spreadcycle, try adding V20 to your M569 for whichever motor you are using for Z.

j3d

@o_lampe
The lead screw is oiled, and it still makes the noise when the bed has been removed. The lead screw is straight.

Setting the motor current to 300mA made no difference.

I changed my test gcode to include your change. No difference.

I changed the max requested speed in the EMF calculator to what I actually set (60mm/s) and the results are better, however in practice, it's still quite loud.

Approximate peak back EMF due to rotation per motor: 3.9 V at 60.0 mm/s
Approximate peak back EMF due to inductance per motor: 6.4 V at 60.0 mm/s
Step pulse frequency: 4.8 kHz at 60.0 mm/s
Speed at which torque starts to drop (low slip angle): 121.6 mm/s @ 9.7 kHz
Speed at which torque starts to drop (high slip angle): 163.2 mm/s @ 13.1 kHz

@gloomyandy Unfortunately setting the driver to spread cycle didn't make a difference either.

I'll put in an order for another motor. Fingers crossed!

gloomyandy

@j3d What change did you actually make? My suggestion was to keep the driver in stealthchop mode, not to use spreadcycle. By default it will be switching to spreadycycle at a pretty low speed, spreadcycle can on some motors produce a noise like the one you are hearing.

j3d

Thanks @gloomyandy, I misunderstood. Changing it to:

M350 Z16 I1
M92 Z400
M906 Z300
M569 D3 P0.2 V20
G1 F60
G28 Z
G1 Z10 F60
G1 Z0 F60

made it silent. Thank you so much!

o_lampe

@j3d
Glad you found a solution.
The speed setting in G1 moves are in mm/min while the calculations of the EMF tool are in mm/sec
So your setting of F60 might be very slow.
I doubt the leadscrews will be silent at F3600, but you will find a max. speed you can live with.

devpeeps

@o_lampe OMG I switched from a duet 2 to a 3 mini 5+ and this was driving me mad. This setting makes the ffcp run so quiet i can't even tell it's moving. TY!