SOLVED: Homing already homed XY axis fails

[SupraGuy]

It also seems to me that even if this works, because you're moving at 45 degrees, you will get a motor stall when the print head hits EITHER X or Y limit, with no guarantee at all the you'll have hit the other. So if your print head were at X=150, Y=10, your print head would move back to X=140, Y=0, and the motor would stall, since it cannot move Y any further. If it now thinks that X=0, you're going to have a problem.

[toskium]

I deliberately positioned the head at X 150 and Y 30 and started homing. What happens is that Y hits the axis low end earlier but X continues moving to the low end and stops there and homing seems to finish as expected.

Do you think that this behavior is any different in a second homing pass?

[toskium]

@rs4race
Currently:
M208 X0 Y0 Z0 S1
M208 X300 Y300 Z410 S0

[dc42]

@toskium said in Homing already homed XY axis fails:

G1 S1 X-330 Y-330 F3600 ; move right/back 330mm, stopping at the endstop

Why are you moving both X and Y when you only want to home X?

See https://duet3d.dozuki.com/Wiki/ConfiguringRepRapFirmwareCoreXYPrinter#Section_Homing_files if you haven't already.

[toskium]

@dc42 TBH I thought I could take a shortcut since it first appeared to be working. I will change the homex and homey.g files so they only home their respective axis and try again. Maybe that is all it takes.

[dc42]

@dc42 said in Homing already homed XY axis fails:

G1 S1 X-330 Y-330 F3600 ; move right/back 330mm, stopping at the endstop

When you execute that on a CoreXY machine, it should move the print head until either the X or the Y axis reaches its endstop; then stop. On a Cartesian printer the move will continue until both X and Y have reached the endstops.

[toskium]

@dc42 I modified my homex.g and homey.g files so they only home their own axis. However nothing has changed in the outcome. For testing the homex.g looks like this:

;Sensorless Homing XY
M564 H0 		; allow movement of axis that have not been homed
M400 			; make sure everything has stopped before we make changes
M915 X Y S3 F0 R0 H400	; configure stall detection
M913 X40 Y40		; reduce motor current to 40% to prevent belts slipping
G91 			; use relative positioning
;G1 Z5 F6000 S2 		; lift Z relative to current position
G1 X30 F4600		; move away from home
G1 S1 X-330 F4600 	; move right/back 330mm, stopping at the endstop
G1 X6 	 		; move away from home
M400 			; make sure everything has stopped before we reset the motor currents
M913 X100 Y100		; motor currents back to 100%
G90 			; back to absolute positioning
G92 X0			; Set X and Y to 0
M574 X1 Y1 S1 		; define active low microswitches

What I observed is, that the G1 S1 X-330 F4600 is not executed at all. It only does G1 X30 F4600 and the G1 X6 afterwards.

In addition to that, if I do move X and Y at the same time, the first triggered endstop does not terminate the movement at all.

In case it helps, here is my config.g:

; Configuration file for Duet WiFi (firmware version 1.20 or newer)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool on Wed Jul 11 2018 18:31:06 GMT+0200 (W. Europe Daylight Time)

; General preferences
G90                              ; Send absolute coordinates...
M83                              ; ...but relative extruder moves
M555 P1                          ; Set firmware compatibility to look like RepRapFirmare

M667 S1                          ; Select CoreXY mode

; Network
M550 PHypercube Evolution 001    ; Set machine name
M552 S1                          ; Enable network
;*** Access point is configured manually via M587
M586 P0 S1                       ; Enable HTTP
M586 P1 S0                       ; Disable FTP
M586 P2 S0                       ; Disable Telnet

; Drives
M569 P0 S1                       ; Drive 0 goes forwards
M569 P1 S1                       ; Drive 1 goes forwards
M569 P2 S1                       ; Drive 2 goes forwards
M569 P3 S0                       ; Drive 3 goes forwards
M350 X16 Y16 Z16 E16 I1          ; Configure microstepping with interpolation
M92 X160 Y160 Z3200 E2649        ; Set steps per mm
M566 X900 Y900 Z12 E40           ; Set maximum instantaneous speed changes (mm/min)
M203 X12000 Y12000 Z600 E1800    ; Set maximum speeds (mm/min)
M201 X3000 Y3000 Z250 E120       ; Set accelerations (mm/s^2)
M906 X1600 Y1600 Z1600 E800 I30  ; Set motor currents (mA) and motor idle factor in per cent
M84 S30                          ; Set idle timeout

; Axis Limits
M208 X0 Y0 Z0 S1                 ; Set axis minima
M208 X300 Y300 Z410 S0           ; Set axis maxima

; Endstops
M574 X1 Y1 S3                    ; Set endstops controlled by motor load detection
M574 Z1 S2 			 ; Set endstops controlled by probe ( Z-endstop is Z-probe)

; Z-Probe
M558 P8 A3 I1 H3 R1 F480 T6000
G31 P100 X0 Y0 Z0.05                               ; Set Z probe trigger value, offset and trigger height

; Heaters
M307 H0 B0 S1.00                 ; Disable bang-bang mode for the bed heater and set PWM limit
M305 P0 T100000 B4138 C0 R4700  ; Default Values Set thermistor + ADC parameters for heater 0 (bed)
M143 H0 S150                     ; Set temperature limit for heater 0 to 150C (bed)
M305 P1 T100000 B4138 C0 R4700   ; Set thermistor + ADC parameters for heater 1 (hotend)
M143 H1 S350                     ; Set temperature limit for heater 1 to 350C (hotend)

; Fans
M106 P0 S0.3 I0 F500 H-1         ; Set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned off
M106 P1 S1 I0 F500 H1 T45        ; Set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned on
M106 P2 S1 I0 F500 H1 T45        ; Set fan 2 value, PWM signal inversion and frequency. Thermostatic control is turned on

; Tools
M563 P0 D0 H1                    ; Define tool 0
G10 P0 X0 Y0 Z0                  ; Set tool 0 axis offsets
G10 P0 R0 S0                     ; Set initial tool 0 active and standby temperatures to 0C

; Automatic saving after power loss is not enabled

; Custom settings
M557 X0:300 Y0:300 S30 ; probe from X=15 to 285, Y=15 to 285mm with a mesh spacing of 30mm

; Pressure Advance
M572 D0 S0.06

; Enable use of sys/config-override.g
M501

[toskium]

Update:

The repeated homing seems to work 99% now, I decreased the the current to the steppers from 1600mA to 1300mA in config.g. I am wondering if this might have been the reason behind the problem all the time.

The steppers I am using are the 0.9° high torque motors from E3D, in case you like to read the datasheet, it can be found here: https://e3d-online.dozuki.com/Item/High_torque_motor

What happens sometimes is that when the steppers get a bit temperature the stall threshold seems to be too low and it triggers early, however immediate homing again works fine, regardless the temperature.
Unfortunately it does not work reliable when I increase the stall threshold by 1.

[Phaedrux]

@toskium stall detection is a very tricky way to home the printer. Lots of variables and some of them change during operation. A simple switch is far more reliable.

[toskium]

@phaedrux It appears so, I was intrigued by the concept and less cables sounded like a nice bonus. But it is rather difficult to set up compared to a switch. It looks like it is working for now, I will mark this as solved, so nobody will invest more time in this.