Tuning Homing for 0.9 Degree Motors  

RE: Tuning Homing for 0.9 Degree Motors

I should add that you can pretty quickly get multiple homing tests done with G28 [axis] C

like...

G28 Y C

That gets you 16 test samples

RE: Tuning Homing for 0.9 Degree Motors

Here are values from Moons 0.9 on X and threshold set to 4. 

Notice that motor resonance rears its ugly head around a feed rate of 2750

I would therefore set the x-homing feed rate at 2250. That above the low impact step = 12 values, but below the resonance. Can't really get above the resonance speed without making the impacts stupid fast.

G28 X C
M924 X4

M925 X1000
Recv: i= 0 step=12
Recv: i= 1 step=12
Recv: i= 2 step=12
Recv: i= 3 step=12
Recv: i= 4 step=12
Recv: i= 5 step=12
Recv: i= 6 step=12
Recv: i= 7 step=12
Recv: i= 8 step=12
Recv: i= 9 step=12
Recv: i=10 step=12
Recv: i=11 step=12
Recv: i=12 step=12
Recv: i=13 step=12
Recv: i=14 step=12
Recv: i=15 step=12

M925 X1250
Recv: i= 0 step=12
Recv: i= 1 step=12
Recv: i= 2 step=12
Recv: i= 3 step=12
Recv: i= 4 step=12
Recv: i= 5 step=12
Recv: i= 6 step=12
Recv: i= 7 step=12
Recv: i= 8 step=12
Recv: i= 9 step=12
Recv: i=10 step=12
Recv: i=11 step=12
Recv: i=12 step=12
Recv: i=13 step=12
Recv: i=14 step=12
Recv: i=15 step=12

M925 X1500
Recv: i= 0 step=12
Recv: i= 1 step=12
Recv: i= 2 step=12
Recv: i= 3 step=12
Recv: i= 4 step=12
Recv: i= 5 step=12
Recv: i= 6 step=12
Recv: i= 7 step=12
Recv: i= 8 step=12
Recv: i= 9 step=12
Recv: i=10 step=12
Recv: i=11 step=12
Recv: i=12 step=12
Recv: i=13 step=12
Recv: i=14 step=12
Recv: i=15 step=12

M925 X1750
Recv: i= 0 step=12
Recv: i= 1 step=12
Recv: i= 2 step=12
Recv: i= 3 step=12
Recv: i= 4 step=12
Recv: i= 5 step=12
Recv: i= 6 step=12
Recv: i= 7 step=12
Recv: i= 8 step=12
Recv: i= 9 step=12
Recv: i=10 step=12
Recv: i=11 step=12
Recv: i=12 step=12
Recv: i=13 step=12
Recv: i=14 step=12
Recv: i=15 step=12

M925 X2000
Recv: i= 0 step=43
Recv: i= 1 step=44
Recv: i= 2 step=44
Recv: i= 3 step=44
Recv: i= 4 step=44
Recv: i= 5 step=44
Recv: i= 6 step=44
Recv: i= 7 step=44
Recv: i= 8 step=44
Recv: i= 9 step=44
Recv: i=10 step=44
Recv: i=11 step=44
Recv: i=12 step=44
Recv: i=13 step=44
Recv: i=14 step=44
Recv: i=15 step=44

M925 X2250
Recv: i= 0 step=43
Recv: i= 1 step=44
Recv: i= 2 step=44
Recv: i= 3 step=44
Recv: i= 4 step=44
Recv: i= 5 step=44
Recv: i= 6 step=44
Recv: i= 7 step=44
Recv: i= 8 step=44
Recv: i= 9 step=44
Recv: i=10 step=44
Recv: i=11 step=44
Recv: i=12 step=44
Recv: i=13 step=44
Recv: i=14 step=44
Recv: i=15 step=44

M925 X2500
Recv: i= 0 step=43
Recv: i= 1 step=43
Recv: i= 2 step=43
Recv: i= 3 step=43
Recv: i= 4 step=43
Recv: i= 5 step=43
Recv: i= 6 step=43
Recv: i= 7 step=44
Recv: i= 8 step=44
Recv: i= 9 step=44
Recv: i=10 step=44
Recv: i=11 step=44
Recv: i=12 step=44
Recv: i=13 step=44
Recv: i=14 step=44
Recv: i=15 step=44

M925 X2750
Recv: i= 0 step=11
Recv: i= 1 step=11
Recv: i= 2 step=11
Recv: i= 3 step=11
Recv: i= 4 step=11
Recv: i= 5 step=11
Recv: i= 6 step=12
Recv: i= 7 step=12
Recv: i= 8 step=12
Recv: i= 9 step=12
Recv: i=10 step=12
Recv: i=11 step=12
Recv: i=12 step=12
Recv: i=13 step=43
Recv: i=14 step=44
Recv: i=15 step=44

M925 X3000
Recv: i= 0 step=11
Recv: i= 1 step=12
Recv: i= 2 step=27
Recv: i= 3 step=27
Recv: i= 4 step=27
Recv: i= 5 step=27
Recv: i= 6 step=28
Recv: i= 7 step=28
Recv: i= 8 step=59
Recv: i= 9 step=59
Recv: i=10 step=59
Recv: i=11 step=59
Recv: i=12 step=59
Recv: i=13 step=59
Recv: i=14 step=60
Recv: i=15 step=60

RE: Tuning Homing for 0.9 Degree Motors

Are you using an o-scope to know when resonance and emf is becoming significant?

RE: Tuning Homing for 0.9 Degree Motors

No. I am only using the variance in steps value.

Mainly trying to help people who have trouble getting tuned and not much help if we require tools that only a few of use have.

You definitely can measure the steps variance increase when the Stallguard system starts to falter.

On x, if the the test sequence ends with a blurrrt motor noise, the belt is probably a little too loose.

RE: Tuning Homing for 0.9 Degree Motors

Here is another test set. This time with Moon's 0.9 on X. SGThreshold = 4. I take measurements varying homing rate by 100.

What I see is that from 1800 to 2200 feed rate SG is getting unstable step positions for home. This motor I would set up with a homing rate of 2300 to 2400. 

====

Moons on X axis
M924 X4
G28 X C <-- this is the command that gets the data. The M925 Xnnn labels how feed rate was set before G28 X C

M925 X1500
Recv: i= 0 step=28
Recv: i= 1 step=28
Recv: i= 2 step=28
Recv: i= 3 step=28
Recv: i= 4 step=28
Recv: i= 5 step=28
Recv: i= 6 step=28
Recv: i= 7 step=28
Recv: i= 8 step=59
Recv: i= 9 step=60
Recv: i=10 step=60
Recv: i=11 step=60
Recv: i=12 step=60
Recv: i=13 step=60
Recv: i=14 step=60
Recv: i=15 step=60

M925 X1700
Recv: i= 0 step=59
Recv: i= 1 step=59
Recv: i= 2 step=60
Recv: i= 3 step=60
Recv: i= 4 step=60
Recv: i= 5 step=60
Recv: i= 6 step=60
Recv: i= 7 step=60
Recv: i= 8 step=60
Recv: i= 9 step=60
Recv: i=10 step=60
Recv: i=11 step=60
Recv: i=12 step=60
Recv: i=13 step=60
Recv: i=14 step=60
Recv: i=15 step=60

M925 X1800
Recv: i= 0 step=44
Recv: i= 1 step=44
Recv: i= 2 step=44
Recv: i= 3 step=44
Recv: i= 4 step=44
Recv: i= 5 step=44
Recv: i= 6 step=44
Recv: i= 7 step=44
Recv: i= 8 step=44
Recv: i= 9 step=60
Recv: i=10 step=60
Recv: i=11 step=60
Recv: i=12 step=60
Recv: i=13 step=60
Recv: i=14 step=60
Recv: i=15 step=60

M925 X1900
Recv: i= 0 step=28
Recv: i= 1 step=43
Recv: i= 2 step=44
Recv: i= 3 step=44
Recv: i= 4 step=44
Recv: i= 5 step=44
Recv: i= 6 step=44
Recv: i= 7 step=44
Recv: i= 8 step=44
Recv: i= 9 step=44
Recv: i=10 step=44
Recv: i=11 step=44
Recv: i=12 step=44
Recv: i=13 step=44
Recv: i=14 step=44
Recv: i=15 step=44

M925 X2000
Recv: i= 0 step=27
Recv: i= 1 step=28
Recv: i= 2 step=28
Recv: i= 3 step=28
Recv: i= 4 step=28
Recv: i= 5 step=28
Recv: i= 6 step=28
Recv: i= 7 step=28
Recv: i= 8 step=28
Recv: i= 9 step=28
Recv: i=10 step=28
Recv: i=11 step=28
Recv: i=12 step=28
Recv: i=13 step=44
Recv: i=14 step=60
Recv: i=15 step=60

M925 X2100
Recv: i= 0 step=12
Recv: i= 1 step=28
Recv: i= 2 step=28
Recv: i= 3 step=28
Recv: i= 4 step=28
Recv: i= 5 step=28
Recv: i= 6 step=28
Recv: i= 7 step=44
Recv: i= 8 step=44
Recv: i= 9 step=44
Recv: i=10 step=59
Recv: i=11 step=59
Recv: i=12 step=60
Recv: i=13 step=60
Recv: i=14 step=60
Recv: i=15 step=60

M925 X2200
Recv: i= 0 step=12
Recv: i= 1 step=12
Recv: i= 2 step=12
Recv: i= 3 step=12
Recv: i= 4 step=44
Recv: i= 5 step=44
Recv: i= 6 step=59
Recv: i= 7 step=59
Recv: i= 8 step=60
Recv: i= 9 step=60
Recv: i=10 step=60
Recv: i=11 step=60
Recv: i=12 step=60
Recv: i=13 step=60
Recv: i=14 step=60
Recv: i=15 step=60

M925 X2300
Recv: i= 0 step=59
Recv: i= 1 step=59
Recv: i= 2 step=60
Recv: i= 3 step=60
Recv: i= 4 step=60
Recv: i= 5 step=60
Recv: i= 6 step=60
Recv: i= 7 step=60
Recv: i= 8 step=60
Recv: i= 9 step=60
Recv: i=10 step=60
Recv: i=11 step=60
Recv: i=12 step=60
Recv: i=13 step=60
Recv: i=14 step=60
Recv: i=15 step=60

M925 X2400
Recv: i= 0 step=59
Recv: i= 1 step=59
Recv: i= 2 step=59
Recv: i= 3 step=59
Recv: i= 4 step=59
Recv: i= 5 step=59
Recv: i= 6 step=60
Recv: i= 7 step=60
Recv: i= 8 step=60
Recv: i= 9 step=60
Recv: i=10 step=60
Recv: i=11 step=60
Recv: i=12 step=60
Recv: i=13 step=60
Recv: i=14 step=60
Recv: i=15 step=60

M925 X2500
Recv: i= 0 step=59
Recv: i= 1 step=59
Recv: i= 2 step=59
Recv: i= 3 step=59
Recv: i= 4 step=59
Recv: i= 5 step=59
Recv: i= 6 step=59
Recv: i= 7 step=60
Recv: i= 8 step=60
Recv: i= 9 step=60
Recv: i=10 step=60
Recv: i=11 step=60
Recv: i=12 step=60
Recv: i=13 step=60
Recv: i=14 step=60
Recv: i=15 step=60

RE: Tuning Homing for 0.9 Degree Motors

Interesting. Do you know how this homing calibration plays into crash detection? So far I am getting reliable homes on 0.9 motors (using stock firmware values, no less), but false crash detects during a print :-/

RE: Tuning Homing for 0.9 Degree Motors

Crashes during print are detected using the TMC2130_SG_THRS_X, TMC2130_SG_THRS_Y, TMC2130_SG_THRS_Z, TMC2130_SG_THRS_E values. They are a separate set of threshold, distinct from the ones used during homing. How the 0.9's affect what values those will need, I have not investigated.

I'm always in stealth and simply don't use crash detection. From how I see SG behaving during homing, I'm surprised crash detection even works. You need a pretty big drag on the motor to trigger things. 

RE: Tuning Homing for 0.9 Degree Motors

I suspect they may just need a slight nudge up for 0.9s; all the crashes I was observing (I think) were right after fast travel moves so my suspicion is that the back-EMF from slowdown/stop is very close to the threshold for a crash. 

Y is naturally worse than X because it's got more mass. 

Perhaps that's not even necessary though... I wonder if it might be sufficient to just drop the jerk value for 0.9 degree motors so there's less momentum involved in such a brake event.

RE: Tuning Homing for 0.9 Degree Motors

Sorry if I'm completely off track, but whilst trying to understand the firmware, I came across this in Marlin_main.cpp and tmc2130.cpp

and it refers to the number of fullsteps and babysteps during homing procedure.

uint8_t tmc2130_home_bsteps[2] = {48, 48};

uint8_t tmc2130_home_fsteps[2] = {48, 48};

Since the motor is now a 0.9 stepper, then should the 48 not be a 96?

Like I said, I'm learning, so dont shoot me down in flames if I have got this completely wrong.

RE: Tuning Homing for 0.9 Degree Motors

Sorry, took a bit before circling back around to this.

Thanks. I think you are correct. The effect would be to halve some of the setup moves done during homing.

Updated my branch to switch the constants from 48 to 96 depending on whether X or Y are set to be 0.9 degrees in configuration_Prusa.h

Homing hits sound a bit more vigorous after the fix.

PLEASE READ BELOW

This correction also changes the steps at which printer is at homing position. Your old home position may be outside of the new legal dimensions. The effect of that is x-axis test will immediately fail if the first thing you do is self-test, but your print head is still outside the expected legal positions. That can happen if your head is at home when you first switch to firmware with this fix.

Solution is easy and only needs to be done ONCE. You won't have to do this again after printer passes self-test and stores its new homing position.

Manually push the x-axis about an inch to right of home or do a calibration/home BEFORE executing calibration/self-test. That puts the head into a position that allows self-test to succeed.

Definitely do a self-test after installing firmware with this homing steps fix. The self-test lets printer store its new home position under the new step constants.

RE: Tuning Homing for 0.9 Degree Motors

Nope. More testing across printers ---> homing is less reliable if the steps are set to 96.

Reverting back to 48.

RE: Tuning Homing for 0.9 Degree Motors

The change in steps count from 48 to 96 was a bust. It might actually be pedantically correct, but makes a mess for self-test and doesn't improve homing. However, this got bunny scientists working on the old homing issue. They made a change that should make it easier to tune homing. 

In Marlin_main.cpp,

void homeaxis(int axis, uint8_t cnt) includes a check after each homing iteration testing the result against a lower count limit. If the measured position count is below 63, it errored out and we see the slow bed move.

Looking back through my measured test values for the count I found that 0.9 motors often cluster their homing values well below 63. My x-motors can cluster as low as 11 and the Y motor often is about 31. Unless belt tension and velocity were just right to get the result value above 63, homing fails. 

Latest firmware in my branch now sets a lower acceptance limit of 10 if a 0.9 degree motor has been defined on X or Y.

#ifdef X_AXIS_MOTOR_09 //Kuo adjust min acceptable homing count for 0.9 motors
  #define kHOMING_CNT_MIN 10 //0.9 motors often home at much lower count
#elif defined(Y_AXIS_MOTOR_09)
  #define kHOMING_CNT_MIN 10
#else
  #define kHOMING_CNT_MIN 63 //original was 63 for 1.8 motors
#endif //---Kuo

A corresponding change was made in Marlin_main.cpp to use the new constant.

RE: Tuning Homing for 0.9 Degree Motors

Kuo, you've defined kHOMING, but the define isn't used anywhere. The implementation is missing.

RE: Tuning Homing for 0.9 Degree Motors

Weird. Commit wasn't accepted apparently. Should be there now.

RE: Tuning Homing for 0.9 Degree Motors

Just finished replacing my PSU (Meanwell LRS-350-24, Now running at 26V, Printer reports 25.6v) and X & Y motors with OMC 17HM15-0904S  0.9 Deg steppers. Fitted heat sinks to rear and fronts of all stepper drivers and FET'S for Hot End and Heated Bed. Replaced EINSY case with revers case, Uprated the PSU wiring to Einsy board and extended stepper motor cables as they were too short.

Just about to download latest firmware from guy-2k, compile it and upload to printer. Tested all parts work with existing firmware for 1.8 Deg motors before hand (Move in correct direction and sensors all report back correctly), but of course X and Y only move half the distance.