sensorless homing random wrong direction

moth4017

@droftarts
"Homing issue"= going randomly to the incorrect side

S1 current 200mA issue homing
S1 current 400mA issue homing
S1 current 500mA homing ok ( have my doubts on this value being ok)
S1 current 600mA issue homing

S5 current 200mA issue homing
S5 current 400mA homing ok ( have my doubts on this value being ok)
S5 current 500mA issue homing

S10 current 200mA issue homing
S10 current 400mA homing ok ( have my doubts on this value being ok)
S10 current 500mA issue homing

S15 current 200mA issue homing
S15 current 400mA homing ok ( have my doubts on this value being ok)
S15 current 500mA issue homing

s20 current 200mA issue homing
s20 current 400mA homing ok ( have my doubts on this value being ok)
s20 current 500mA issue homing
s20 current 600mA issue homing

s30 current 200mA issue homing
s30 current 400mA homing ok
s30 current 500mA issue homing
s30 current 1000mA homing ok

spent most of the Day testing values above, i still have the issue that the "emergency stop " button seems to toggle the homing direction, also tried changing Jerk to see if that would make any difference (800 and 400)

@dc42
another observation if i Home X and it goes in the correct direction , then the stepper motors time out, (M84 X Y S20) and i home X again it also goes in the wrong direction.

dc42

@moth4017 I can think of are three possible reasons why the motor may go in the wrong direction:

The driver is signalling a stall at the start of the G1 H1 X-350 homing move, so it skips that and proceeds directly to the G1 X150 move. This is the most likely explanation.
If the motor currrent is set very low and the motor is under load, it may move in the wrong direction.
If only one motor phase is connected then the motor will either vibrate or move in a random direction.

From your homex.g file:

@moth4017 said in sensorless homing random wrong direction:

M906 X600 Y600 ; Lower motor current

We recommend that you use M906 only in config.g. When you need to reduce motor current temporarily, use M913 instead to set a percentage of the current set by M906. Also, don't reduce the motor current until you want to do the stall homing. StealthChop calibration should be done at normal motor current.

G1 H1 X-0.2 F3000                               ; move a  little  for cal of sensorless homing / not stalled
G1 H1 Y-0.2 F3000    							; move a  little  for cal of sensorless homing / not stalled
M400											; make sure everything has stopped before we make changes

That's not a valid stealthChop tuning sequence. Use something like this instead (at normal motor current):

M17 X Y  ; enable X and Y motor drivers
G1 P140  ; pause to allow the drivers to characterise the motor

You can then reduce motor current (using M913) and do the stall homing move. 30% motor current is usually good.

However, there is the possibility that the motor may already be signalling a stall. So I recommend that after homing an axis, you back off a few mm and repeat the homing move. For example:

M913 X30  ; use X30 Y30 if the machine is CoreXY
G91
G1 H1 X-350                                     ; Home X-Axis
G1 H2 X10  ; back off a little (on a CoreXY machine use X10 Y10)
G1 H1 X-350                                     ; Home X-Axis again
M913 X100 ; restore motor current (use X100 Y100 is the machine is CoreXY)

HTH David

moth4017

@dc42
im still getting the wrong direct alternating after pressing the
"emergency stop" button.
new homex.g

; homex.g
echo "start"
M569 P0.0										; Check status in console
M569 P0.1										; Check status in console
G91                                             ; relative positioning
M569 P0.0 S1 D3 V10                             ; set to stelth chop
M569 P0.1 S1 D3 V10								; set to stelth chop
M915 P0.0:0.1 S20 F0 R1 H200                    ; Configure Z-Axis Stall Detection

echo "stall detection setup"
M17 X										; Check status in console
M17 Y										; Check status in console
G1 P140
G1 H1 X-0.2 F3000                               ; move a  little  for cal of sensorless homing / not stalled
G1 H1 Y-0.2 F3000    							; move a  little  for cal of sensorless homing / not stalle							

echo "lower motor current"
M913 X50 Y50									; Lower motor current %
G4 P150											; wait 150ms
M574 X1 Y2 S4									; Configure Z-Axis stall detection homing
M569 P0.0										; Check status in console
M569 P0.1										; Check status in console
		
echo "home x"
G1 H1 X-350 F6000								; Home Z-Axis actuators independently
M569 P0.0										; Check status in console
M569 P0.1										; Check status in console
G90 											; absolute positioning
G1 X150 F6000									; move to center of bed

;revert back 
echo "after revert back"
M913 X100  Y100                               	; Reset motor current %
M569 P0.0 S1 D2                                 ; reset motors back to spread cycle,
M569 P0.1 S1 D2									; reset motors back to spread cycle,
M569 P0.0										; Check status in console
M569 P0.1										; Check status in console

dc42

@moth4017 you haven't done the double homing move that I recommended. Assuming your machine is CoreXY, try this.

; homex.g
echo "start" 
M569 P0.0					; Check status in console
M569 P0.1					; Check status in console 
G91                                             ; relative positioning   
M569 P0.0 S1 D3 V10                             ; set to stealth chop  
M569 P0.1 S1 D3 V10								; set to stealth chop  
M915 P0.0:0.1 S20 F0 R1 H200                    ; Configure Stall Detection   
echo "stall detection setup"
M17 X Y 
G1 P140 
echo "lower motor current"  
M913 X50 Y50									; Lower motor current %   
M574 X1 Y2 S4									; Configure Z-Axis stall detection homing     
M569 P0.0										; Check status in console    
M569 P0.1										; Check status in console  
echo "home x"  
G1 H1 X-350 F6000
G1 H2 X20 Y20     
G1 H1 X-350 F6000
M569 P0.0										; Check status in console        
M569 P0.1										; Check status in console     
G90 											; absolute positioning 
G1 X150 F6000									; move to center of bed

;revert back   
echo "after revert back"   
M913 X100  Y100                               	; Reset motor current %      
M569 P0.0 S1 D2                                 ; reset motors back to spread cycle,    
M569 P0.1 S1 D2									; reset motors back to spread cycle,   
M569 P0.0										; Check status in console     
M569 P0.1										; Check status in console

pro3d

@dc42

Regarding M906/913 - You recommend using 913 in the homing file. 913 is a function of 906 and 913 is not an exact number so it does not make sense to use 913 as it does not tell you what current is being used unless you pull out a calculator. Why is it bad practice to use 906 in the homing file when this is what sets the motor current and then you know what currents will work?

PS! I have the same machine as @moth and a fully working stallguard homing on all 5 axes (XYZUV) but I run a Duet wifi 2 with a Duex5 so different drivers. I have how ever experienced the same problems as @moth4017 before I started moving my printhead between homing X and Y. After I made the change of moving my printhead between homex an homey it has been working 100%

; homex.g
; called to home the X axis
M400                                                   ; make sure everything has stopped before we make changes
G91                                  ; relative positioning
M915 P0:1 S4 F0 R0                            ; Configure Stall Detection
M906 X750 Y750                                      ; Lower motor current
G1 F9000
G1 H1 X350                           ; Home Z-Axis independently
M400                                                   ; make sure everything has stopped before we make changes
M906 X1000 Y1000                                    ; Reset motor current
G90                                  ; absolute positioning
G1 F12000 X155

; homey.g
; called to home the Y axis
;
M400                                                   ; make sure everything has stopped before we make changes
G91                                  ; relative positioning
M915 P0:1 S4 F0 R0                            ; Configure Z-Axis Stall Detection
M906 X750 Y750                                      ; Lower motor current by 50%
G1 F9000
G1 H1 Y-350                           ; Home Z-Axis actuators independently
M400                                                   ; make sure everything has stopped before we make changes
M906 X1000 Y1000                                    ; Reset motor current
G90                                  ; absolute positioning
G1 Y160	; move to probe position midle bed (x155 y150)

; homeall.g
; called to home all axes
M400
M98 P/sys/homey.g  ;P define the parameter and is not part of the name
M98 P/sys/homex.g  ;P define the parameter and is not part of the name
M98 P/sys/homez.g  ;P define the parameter and is not part of the name

moth4017

@dc42

hi did try double homing worked on X axis but not so good on Y , the Y axis seems to move in the x direction
x home
G1 H1 X-350 F6000
G1 H2 X10 Y10
G1 H1 X-350 F6000

y home
G1 H1 Y350 F6000
G1 H2 X-10 Y-10
G1 H1 Y350 F6000

dc42

@moth4017 said in sensorless homing random wrong direction:

G1 H2 X-10 Y-10

That line in homey.g needs to be changed because as it stands it will back off in the -X direction. I think the correct combination to back off in the -Y direction is: G1 H2 X-10 Y10

moth4017

@dc42
did some tests tonight with the "double bump" on homing , sometimes there was only a single bump , i did see it go 10mm in the wrong direction though, so didnt do the "G1 H1 X-350 F6000" , is this now down to tuning the "S" parameter and current?

echo "home x"
G1 H1 X-350 F6000
G1 H2 X10 Y10
G1 H1 X-350 F6000

echo "Home Y"
G1 H1 Y350 F6000
G1 H2 X-10 Y10
G1 H1 Y350 F6000

moth4017

So , im still getting a random wrong direction now and then but ill put that down to tuning the "S" parameter and current.

if i switch the machine on and do a home X it always goes in the wrong direction can not remember it doing this in the previous version.

moth4017

solution and files here :- https://forum.duet3d.com/topic/28653/3-4-1-rc2-g30-turns-off-z-motors/14?_=1653704200634