Using 0.9 deg LDO motors in StealthChop mode on a Delta

ignacmc

Hello to all

I recently upgraded my Predator delta from Duet 2 to Duet3 Mini5+. Even when I was satisfied with the Duet 2, I thought the Duet3 was a more modern design and I wanted to benefit from the silence of the TMC2209 steppers in StealthChop mode. At the same time I also changed from the original 1.8 deg Anycubic Motors (42HD4027-01-A) to 0.9 deg LDO Motors (42STH47-1684MAC).

In my config.g file I configured X, Y and Z motors in StealthChop mode:

M569 P0.0 S1 D3
M569 P0.1 S1 D3
M569 P0.2 S1 D3

In my first test print I knew from the beginning that something was wrong... Strange noises and vibrations and massive layer shifting made me abort the print after a few minutes.

Then I went back to SpreadCycle mode:

M569 P0.0 S1 D2
M569 P0.1 S1 D2
M569 P0.2 S1 D2

And the test print ended beautifully... but with the whines and motor noises I had supposed to have left behind after upgrading from the Duet 2.

I have tried to tune StealthChop M569 parameters the following way:(https://duet3d.dozuki.com/Wiki/Tuning_Stepper_Motor_Drivers#Section_stealthChop_tuning)

M569 P0.0 S1 D3 H50 V50
M569 P0.1 S1 D3 H50 V50
M569 P0.2 S1 D3 H50 V50
M915 P0.0 T50
M915 P0.1 T50
M915 P0.2 T50

But there is no noticeable improvement and the exaggerated layer shifting make printing impossible

There seems to be some problems with 0.9 deg LDO motors and Duet3 Mini 5:
https://forum.duet3d.com/topic/25442/rrf-v3-3-mini-5-wifi-major-problems-with-layer-shifting/38

Perhaps they don't play well with TMC2209?

Could you please suggest me a valid M569 configuration parameters for using these motors in StealthChop mode?
Have any of you been successful using another brand of 0.9 deg Motors in StealthChop mode on a Duet3 Mini5+? Could you please advise brand and model?

ibash

@ignacmc

The specific values depend on your machine, but the things to know are:

The H/V/T values set the speed at which stealthchop is enabled / disabled. When the printer is moving below the speed limit, stealthchop is enabled. The lower the number for H/V/T, the higher the speed limit for stealthchop (it's inverted).
I explained how that value is calculated here. But instead you can try setting the value with M569 ... and then send M569 P0 in the console with no parameters to see what the speed is set at.
The recommendation is typically to set a speed for stealthchop, and then limit the machine to not go over that speed. (So that it always stays in stealthchop).
You need a tuning step where you energize the steppers and pause. This needs to go before the first movement (so for me, this is in homex.g).

Here's my stealthchop config:

In my config.g:

; Trinamic Drive Tuning
; Tune tpwmthrs (V) so stealthchop runs at appropriate speeds
; and tune thigh (H) to avoid shifting into fullstep mode
; Tune stealthchop to 250mm/s, set coolstep to the same, and then limit the max speed to 120mm/s
; tpwmthrs = 12000000 / (<speed in mm/s> * 200 * 16)
; This keeps everything slow and quiet.

M569 P0 D3 V15 H15 ; Enable stealthchop on X
M569 P1 D3 V15 H15 ; Enable stealthchop on Y
M915 X Y T15       ; Coolstep only starts after stealthchop (effectively never)

; Limit speed / acceleration
M201 X1200 Y1200  ; Max Acceleration (mm/min)
M203 X7200 Y7200  ; Max Speed (mm/min)
M566 X600 Y600    ; Max "jerk" speed (mm/min)

Tuning at the top of my homex.g

G1 H2 X-0.005       ; 1 microstep movement to energize steppers
G4 P150             ; pause for 150ms to allow the driver to establish motor parameters
G1 H2 Z0.000625     ; 1 microstep movement to energize steppers
G4 P150             ; pause for 150ms to allow the driver to establish motor parameters

Again, your specific values for H/V/T depend on your machine. In my config I set it to 15, which corresponds to enabling stealthchop up to 250mm/s. But then I limit overall speed to 120mm/s because at higher speeds stealthchop will skip steps.

So, I'd recommend setting the number low (something like 10) so stealthchop is always enabled and then limiting the speed, acceleration, and jerk of your machine.

Last but not least, when troubleshooting it's useful to restart the machine between config changes (or use M999) sometimes setting config values can get a bit funky.

ignacmc

@ibash Wow! Thank you very much for your detailed explanation. It exceeds my expectations and I believe it sets me in the right direction to tune my delta. By the way and seeing that LDO 0.9 seems to not get along very well with TMC2209, I have ordered 3 OMC 17HM19-2004S1 for replacing them...I will report with my findings