Duet 2 -> Duet 3 Mini - Stepper tuning

MartinNYHC

@jay_s_uk said in Duet 3 mini5+ and Ender 3 Pro: "grinding" motors?:

Add D3 V40 for the X Y and Z motor M569 commands

Just replaced a Duet 2 Wifi with a Duet 3 Mini and stepper sounded terrible. Then I've found a post where someone recommended to add 'D3 V40' to X, Y, and Z. Did so and stepper are soooo quiet But is V40 really a good choice?

Stepper are 14HS17-0504S (1.8deg, 0.5A, 23Ncm)

Typical value are from 100 (high speed) to 4000 (low speed).

Thanks, Martin

jay_s_uk

@martinnyhc

the D3 part is setting the drivers in stealthchop (which they are by default but it doesn't hurt to add it). The V40 part sets the changeover speed. This can be seen in the M569 command
heres an output of mine

m569 p0
Drive 0 runs in reverse, active low enable, timing fast, mode stealthChop, ccr 0x00053, toff 3, tblank 0, thigh 0 (inf mm/sec), tpwmthrs 40 (234.4 mm/sec), pwmScaleSum 84, pwmScaleAuto 0, pwmOfsAuto 159, pwmGradAuto 14, pos 40

This is the important section tpwmthrs 40 (234.4 mm/sec) it shows that at 40, the changeover from stealthchop to spreadcycle will be at 234.4mm/s.
Stealthchop runs quieter with lower torque and spreadcycle runs louder with more torque. You may find that faster moves have a higher chance of skipped steps etc in stealthchop.
Some people also report bangs and/or skipped steps on the changeover between stealthchop and spreadcycle.
I don't print particularly fast on my machine and don't have an issues with the higher changeover speed. You might have different results with your printer.

MartinNYHC

@jay_s_uk Thanks, got it.

I just found out that setting this for Z is not a good idea. Had some terrible layer shifts.

jay_s_uk

@martinnyhc
Yea, again Z is a special use case. As most of the time it does very littlle, stealthchop probably doesn't need to be set.
Make sure you don't set it on an extruder and you may even want to consider enforcing spreadcycle with D2 rather than D3

MartinNYHC

@jay_s_uk said in Duet 2 -> Duet 3 Mini - Stepper tuning:

you may even want to consider enforcing spreadcycle with D2 rather than D3

May I ask you for another lesson?

jay_s_uk

@martinnyhc ask away

MartinNYHC

@jay_s_uk I don't have any experiences with Stealthchop or Spreadcycle.

You wrote

you may even want to consider enforcing spreadcycle with D2 rather than D3

which I unfortunately don't really understand (not yet)

jay_s_uk

@martinnyhc
ah, ok.

this is a good page for an overview between modes https://www.trinamic.com/technology/motor-control-technology/chopper-modes/

For the D2 you would add it to the M569 e.g.
M569 P3 S0 D2 rather than D3 V40

droftarts

@jay_s_uk I've got my Mini 5+ set to stealthchop extruder and Z axis (2 motors), haven't noticed any problems yet, but may be because I don't have particularly aggressive jerk and acceleration settings. Any particular reason not to set them to stealthchop, if your motor settings can cope?

@MartinNYHC I set D3 V0 for all axes, effectively turning off spreadcycle. If you've set V40, it's probably a very high speed for changeover (which would be potentially catastrophic), and you may never get to that speed while printing. The alternative is to use a low speed changeover, so the motor is quiet at standstill, but uses spreadcycle (with it's extra torque) when it's moving. If you aim for a changeover speed that is lower than your M566 instantaneous speed, you won't notice the changeover.

Ian

jay_s_uk

@droftarts I run my Z axis in stealthchop no bother.
The comment around E is the drop in torque between stealthchop and spreadcycle. Why potentially lose torque where you really need it if you're running that slow that the noise wouldn't be an issue anyway

droftarts

@jay_s_uk I've got an Orbiter extruder with a small LDO stepper and 30:1 planetary gearing, and while I haven't had any obvious skipping in stealthchop, I thought that it was quite noisy in spreadcycle. However, that was a while ago when we were troubleshooting, so I should probably go back to it and try it out.

Ian

gloomyandy

Having an extruder (or any driver) in spreadcycle mode all of the time may also mean that they are "hissy" when not moving, so maybe using stealthchop with a very low speed switchover is better.

Oh and don't forget that if you are using sensorless homing then the driver must be in stealthchop mode during the homing process, you can set it to other modes once homed.

I run all my drivers in stealthchop all of the time, but I don't tend to use particularly high speeds.