Sensorless homing on two drives at the same time?

EducatingSavvas

Hiya - I'm trying to setup sensorless homing on a CNC machine to occur while homing a dual stepper motor driven y axis - which are either end of an x axis. I've got x, z and y working individually but if I split the drive mapping Y and V together it doesn't seem to work.

Here is my homing code. Is this even possible to do?

G21					; Set units to mm
M584 Y1 V4 P4				; separate Y axis for aligning them independently
M913 Y40 V40				; drop motor current for Y and V Axis
G91					; relative positioning
G1 H2 Y5 V5 F400			; go back
G4 P500					; dwell
G1 H1 Y-1000 V-1000 F300		; move quickly to Y nd V axis endstop
G1 H2 Y1 V1 F200			; go back a few mm
G90                   			; absolute positioning
G4 P1000				; dwell
M584 Y1:4 P3				; apply custom drive mapping
M500					; save

I may try a work around homing the combined Y and V first and separating the V to perform an individual homing cycle on that side.

Many thanks, Savvas

oliof

@educatingsavvas should be possible, you need to set M574 accordingly (S3 or S4 may be appropriate, bears testing).

Phaedrux

Yes you should combine the axis as one and then home with S3 to stop when one motor stalls, or S4 to stop each motor separately as it stalls.

https://duet3d.dozuki.com/Wiki/M574

EducatingSavvas

@oliof @phaedrux

Thanks for the reply guys - I've tried this...

; Endstops
M574 Z2 X1 Y1 S4		; Low endstop senessorless homing

and...

; Endstops
M574 Z2 X1 S3			; Low endstop senessorless homing
M574 Y1 V1 S4			; Low endstop senessorless homing

with the following homey.g

G21					; Set units to mm
M913 Y50 				; drop motor current for Y
G91					; relative positioning
G1 H2 Y3 F400				; go back
G4 P500					; dwell
G1 H1 Y-1000 F700			; move Y axis endstop and stop there
G1 H2 Y1 F200				; go back a few mm
G4 P500					; dwell
G90                   			; absolute positioning
M913 Y100				; return motor current to 100%
M500					; save current parameters

But it doesn't seem to be working still. Despite the V drive being mapped to Y when I home, V always crashed while the motor load is detected for Y. Could this be a bug?

Phaedrux

@educatingsavvas Normally in RRF3 the M574 commands must be on their own line. I'm not sure if that also applies to sensorless homing with S3/S4 but might want to split them out and check.

Have you gone through this?

https://duet3d.dozuki.com/Wiki/Stall_detection_and_sensorless_homing

EducatingSavvas

@phaedrux Thanks again for that pointers. I'm going to have to investigate this in the new year now. I'll try commenting out the M574 commands from the config file and placing individual lines into each homing file. It sounds like I should also include M915 in the config file but sensorless homing individual axis has worked without it.

The only other thing I can imagine may be causing an issue is I have the following line in my config file...

M584 X0 Y1:4 Z2 V4 P3;	Apply custom drive mapping, P3 hides V(Y2) axis. ***

and I should remove V4 from that as it's not needed. Thanks again, and hope you have a good xmas break. Savvas