Position Tolerance Exceeded

ash100

Whenever homing the axes of this large custom designed printer, the axes says "Warning: Driver 72.0 warning: position tolerance exceeded". I assume this is because the motors are moving fast when they suddenly stop at a limit switch. How do I fix this warning? Is there a way to fix it without compromising the speed?

I am using a mainboard 6HC connected to M23CL motors, which then have lead screws/pulleys to actuate a gantry.

config.g

; Configuration file for RepRapFirmware on Duet 3 Main Board 6HC
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.5.10 on Sun Jan 19 2025 10:10:54 GMT-0800 (Pacific Standard Time)

; General
G90 ; absolute coordinates
M83 ; relative extruder moves
M550 P"5axis" ; set hostname
G4 S2

;Drivers
M569 P70.0 S0 R1; driver 0.0 goes forwards (X axis)
M569.1 P70.0 T3 R100 I0
M569 P70.0 D4

;M569 P71.0 S1 D2 ; driver 0.1 goes forwards (Y axis)
M569 P71.0 S0 R1
M569.1 P71.0 T3 R100 I0
M569 P71.0 D4

;M569 P72.0 S1 D2 ; driver 0.2 goes forwards (Z axis)
M569 P72.0 S0 R1
M569.1 P72.0 T3 R100 I0
M569 P72.0 D4

;M569 P73.0 S1 D2 ; driver 0.4 goes forwards (U axis)
M569 P73.0 S0 R1
M569.1 P73.0 T3 R100 I0
M569 P73.0 D4

;M569 P74.0 S1 D2 ; driver 0.5 goes forwards (V axis)
M569 P74.0 S0 R1
M569.1 P74.0 T3 R100 I0
M569 P74.0 D4


; Axes
M584 X70.0 Y71.0 Z72.0 U73.0 V74.0 E75.0 ; set axis mapping
M350 X16 Y16 Z16 U16 V16 I1 ; configure microstepping with interpolation
M92 X640 Y640 Z1969.230 U800 V27.350 ; configure steps per mm
M906 X1500 Y1500 Z1500 U1500 V1500 ; set axis driver currents
M208 X0:1000 Y0:820 Z0:210 U-20:100 V-999:999 ; set minimum and maximum axis limits
M566 X500 Y500 Z500 U500 V1000 ; set maximum instantaneous speed changes (mm/min)
M203 X1500 Y1500 Z500 U500 V2000 ; set maximum speeds (mm/min)
M201 X500 Y500 Z500 U500 V1000 ; set accelerations (mm/s^2)

; Kinematics
;M669 K8 ; configure CoreXYUV kinematics

; Endstops
M574 X1 P"!io3.in" S1 ; configure X axis endstop
M574 Y1 P"!io0.in" S1 ; configure Y axis endstop
M574 Z2 P"!io7.in" S1 ; configure Z axis endstop
M574 U0 ; configure U axis endstop
M574 V0 ; configure V axis endstop

G92 V0 ; set V axis to zero upon startup
G92 U0 ; set V axis to zero upon startup

; Extruder
M350 E16 I1 ; configure microstepping with interpolation
M906 E900  ; set extruder driver currents
M92 E2682   ; configure steps per mm
M566 E120   ; set maximum instantaneous speed changes (mm/min)
M203 E3600  ; set maximum speeds (mm/min)  
M201 E250   ; set accelerations (mm/s^2)

;Nozzle Temperature
M308 S1 P"75.temp1" Y"thermistor" A"Nozzle" T100000 B4267 C7.06e-8 ; configure sensor #1
M950 H1 C"75.out0" T1 ; create heater #1 hotend heater
M143 H1 P0 S275 A0
M143 H1 P1 S285 A2
M307 H1 R4.663 K0.549:0.000 D1.95 E1.35 S1.00 B0


; Scanning Z Probe
M558 P11 C"75.i2c.ldc1612" F36000 T36000
M308 A"SZP coil" S10 Y"thermistor" P"75.temp2" ; thermistor on coil
G31 Z2 X302 Y245
; M558.2 K0 S13 R142607
M557 X292:312 Y235:255 P10

homex.g

; homex.g
; called to home the X axis
;
; generated by RepRapFirmware Configuration Tool v3.5.10 on Sun Jan 19 2025 10:11:00 GMT-0800 (Pacific Standard Time)

; increase Z
G90; ABSOLUTE positioning
G1 H2 Z200 ; move z axis to 5mm from top
G90 ; absolute positioning

; home X
G91 ; relative positioning
var maxTravel = move.axes[0].max - move.axes[0].min + 5 ; calculate how far X can travel plus 5mm
G1 H1 X{-var.maxTravel} F5000 ; coarse home in the -X direction
G1 X5 F6000 ; move back 5mm
G1 H1 X{-var.maxTravel} F300 ; fine home in the -X direction
G90 ; absolute positioning

dc42

@ash100 the reason we haven't seen this before is that or recommendation us to home in open loop mode. You can do this by using M569 with D parameter to switch to open loop mode at the start if each homing file, and back to closed loop mode at the end.

Homing in closed loop mode may be possible with the right mechanics. The reason you get the position error is probably because after the homing switch is triggered, there is a latency of a few milliseconds before the command to stop the motor is received. If you can arrange your homing switch to trigger a small distance (2mm may be enough) before the physical stop is reached, so that the motor can overshoot the homing position slightly without hitting a hard stop, that may avoid the error. If it doesn't then I will need to amend the firmware to ignore position errors immediately after the motor is commanded to stop during homing.