Sensorless Z-homing don't work [tmc2130] [Marlin-bugfix-1.1.x - 16.06.2018]

[alakond]

Hi. I have 3 TMC2130 and I'm trying to make a sensorless home. Marlin settings in the attachment. Z-axis.zip

The problem is that the X and Y axes work correctly, and the Z axis does not stop when it stops in the nozzle.

In addition, M914 why is this (see Stallguard thrs 7 6 0):

Recv: M122
Recv:       X   Y   Z
Recv: Enabled       false   false   false
Recv: Set current   900 900 500
Recv: RMS current   887 887 489
Recv: MAX current   1251    1251    689
Recv: Run current   28/31   28/31   15/31
Recv: Hold current  14/31   14/31   7/31
Recv: CS actual     14/31   14/31   7/31
Recv: PWM scale     0   0   0
Recv: vsense        1=.18   1=.18   1=.18
Recv: stealthChop   true    true    true
Recv: msteps        16  16  16
Recv: tstep     1048575 1048575 1048575
Recv: pwm
Recv: threshold     98  98  329
Recv: [mm/s]        100.85  100.85  3.00
Recv: OT prewarn    false   false   false
Recv: OT prewarn has
Recv: been triggered    false   false   false
Recv: off time      5   5   5
Recv: blank time    24  24  24
Recv: hysteresis
Recv: -end      2   2   2
Recv: -start        3   3   3
Recv: Stallguard thrs   7   6   0
Recv: DRVSTATUS X   Y   Z
Recv: stallguard
Recv: sg_result     0   0   0
Recv: fsactive
Recv: stst      X   X   X
Recv: olb
Recv: ola
Recv: s2gb
Recv: s2ga
Recv: otpw
Recv: ot
Recv: Driver registers: X = 0x80:0E:00:00
Recv:   Y = 0x80:0E:00:00
Recv:   Z = 0x80:07:00:00

or:

Recv: echo:Sensorless homing threshold:
Recv: echo:  M914 X7 Y6

The firmware states:

#define SENSORLESS_HOMING // TMC2130 only
   #if ENABLED (SENSORLESS_HOMING)
     #define X_HOMING_SENSITIVITY 8
     #define Y_HOMING_SENSITIVITY 7
     #define Z_HOMING_SENSITIVITY 8
   #endif

[teemuatlut]

You're using a probe to home Z axis, this also disables sensorless homing on Z.

Also the option should ONLY be used with delta printers or machines where Z is driven with belts. A typical cartesian with lead screws has way too much torque on Z to reliably detect motor load and accurately trigger an endstop pulse.

[tobyak]

Would sensor less homing work on a core XY, given its unique motion system.

[pgScorpio]

@teemuatlut Sensorless Z homing on machines where Z is driven with lead screws can work fine, but you need to tune the motor current and homing speed correctly....

See chapter 2 of https://www.trinamic.com/fileadmin/assets/Support/Appnotes/AN002-stallGuard2.pdf

(Systems with two motors on one driver however can be a pain in the ass, no matter if belt or lead screw driven.)

[alakond]

Hi all. Thnx all for the help. I'll make "a pain in the ass" with a piezo Z-sensor.

[thinkyhead]

Would sensor less homing work on a core XY, given its unique motion system.

Yes.

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