Strange noise in X Axis of CNC

leendert

I am using a Duet 3 6HC with NEMA23 steppers (2315HS300AW from Ooznest https://ooznest.co.uk/product/nema23-stepper-motors/) to power my custom CNC with a Donek Drag Knife, powered by a 350W 24V power supply. The setup is using 8mm pitch leadscrews with delrin anti-backlash nut blocks.

Most movements are now working great and I can get speeds up to about 100mm/s, but I'm running into a few weird issues that I think might be related to the driver configuration. I've already reduced the speeds to 50mm/s, which seemed more suitable with a 24V power supply and these steppers.

Initially I had a lot of problems with noise and with getting the steppers up to speed at all, so I tried to tune the stepper configuration. I'm not expert at all, so I used this Excel sheet https://advanced3dprinting.com/2021/09/05/tuning-stepper-drivers/ for the TMC5160 configuration and ended up with M569 P0 B3 F3 Y00:02. With this configuration, the motors are usually pretty quiet, even at 100mm/s.

The current problems are:

Sometimes when moving the X-axis using the PanelDue +/- 100mm buttons, there will be an alert on the PanelDue about the B phase being disconnected. This doesn't happen during actual jobs. I have checked all the connectors and there are no visual issues, no burns and the crimps look good. I'm not sure if this is an actual problem.
When moving the Y-axis at a high speed and concurrently the X-axis at a much lower speed, one of the two Y-axis motors sometimes stops, causing the gantry to 'jam' sideways. I can get around this by only moving the X or Y axis at a time. There doesn't seem to be any physical 'blockage' of the lead screw in these cases, but one of the Y axis motors just stops. This often happened halfway through a movement of Y=-300mm, X=+50mm.
During some cuts, moving along the X axis will cause a very loud hum (video of the problem: https://vimeo.com/706101940). This only happens on X axis movements and seems to happen more around some spots on the X axis. It doesn't always happen, but when it does there is a noticeable vibration in the entire gantry.

Drive config:

M569 P0.0 S1                             ; X
M569 P0.1 S0                             ; Z
M569 P0.2 S1                             ; Y left
M569 P0.3 S1                             ; Y right
M584 X0.0 Y0.2:0.3 Z0.1                 ; set drive mapping
M350 X16 Y16 Z16 I1                  ; configure microstepping with interpolation
M92 X400.00 Y400.00 Z400.00  ; set steps per mm
M566 X900.00 Y900.00 Z900.00     ; set maximum instantaneous speed changes (mm/min)
M203 X3000.00 Y3000.00 Z3000.00 ; set maximum speeds (mm/min)
M201 X500.00 Y500.00 Z500.00     ; set accelerations (mm/s^2)
M906 X3000 Y3000 Z3000 I30         ; set motor currents (mA) and motor idle factor in per cent
M84 S30                                  ; Set idle timeout
M569 P0 B3 F3 Y00:02

Stepper motor specifications:

Motech motor co. LTD, Hybrid stepper motor MT-2315HS300AW-C, 2 coils
Rated voltage: 3.6 VDC/Phase
Resistance: 1.2 +-10% Ohm/Phase
Rated current: 3.0A/Phase
Step angle: 1.8 degrees
Inductance: 4.0 +-20% mH/Phase
Max starting PPS: 2500 PPS
Max slewing PPS: 5000 PPS

Does anyone know what might be the problem with my setup? Thanks in advance!

Phaedrux

@leendert said in Strange noise in X Axis of CNC:

Sometimes when moving the X-axis using the PanelDue +/- 100mm buttons, there will be an alert on the PanelDue about the B phase being disconnected. This doesn't happen during actual jobs. I have checked all the connectors and there are no visual issues, no burns and the crimps look good. I'm not sure if this is an actual problem.

This could be that the feed rate for the travel moves is too fast and it's generating more backemf than the supply voltage.

@leendert said in Strange noise in X Axis of CNC:

When moving the Y-axis at a high speed and concurrently the X-axis at a much lower speed, one of the two Y-axis motors sometimes stops, causing the gantry to 'jam' sideways. I can get around this by only moving the X or Y axis at a time. There doesn't seem to be any physical 'blockage' of the lead screw in these cases, but one of the Y axis motors just stops. This often happened halfway through a movement of Y=-300mm, X=+50mm.

During some cuts, moving along the X axis will cause a very loud hum (video of the problem: https://vimeo.com/706101940). This only happens on X axis movements and seems to happen more around some spots on the X axis. It doesn't always happen, but when it does there is a noticeable vibration in the entire gantry.

It all seems vibration related. What RPM are the lead screws rotating at?

leendert

@phaedrux
I think you're right about the backemf, using https://www.reprapfirmware.org/emf.html I see that even at 50mm/s, the backemf due to rotation is 22.7V and the backemf due to inductance is 23.6V. This is pretty close to the 24V of the power supply. Do you think a 32V power supply would be sufficient in that case?

The vibration in the X axis is happening at 50mm/s, which is 6.25 RPS or 375 RPM at the lead screw.

Phaedrux

You'd have to do the emf calculations to see what voltage you'd need.

As for the vibration, there may be a range where midband resonance is worse and speeds above or below may be better. It's harder with a lead screw driven system because you're dependant on the perfection of the leadscrew and how much deflection it has from gravity.

I'm not an expert in any of that, I only have a basic awareness that it might be happening. Hopefully someone with more experience in larger CNC machines will be able to chip in.

steve123

@leendert Your motor currents are all set to 3A so if three motors are running you could be sinking 9A from the power supply (12A if all four motors are running).

What gauge wire are you running from the PSU to the 6HCMB Vin? Your input voltage may be drooping if you are using a small wire.

leendert

I think the problem is solved

@steve123
I've connected the PSU to the Duet board with 2.5mm^2 solid core wires, I think that's 14 AWG.

You have a good point about the total amperage though, maybe my PSU isn't quite able to keep the voltage steady. I've set the M906 command to allow max 2A instead of 3A and so far it seems to work much better. I haven't heard the same noise anymore and the "B phase disconnected" error hasn't popped up anymore either.