Z probe wrong direction unless I zero Z

fcwilt

From the documentation when using your Z probe for homing:

The S2 option of M574 is intended for use only when axes other than Z are using the Z probe for homing. The only printers known that do this using Duet electronics are the RepRapPro Ormerod, Huxley Duo, and Mendel Tricolour machines. When using the Z probe to home Z, M574 Z0 should be used.

nick9one1

Remove the H0 from your homing files. It's the default, so you don't need to specify it.

Done

M564 H0 ; allow jog without homing

It's best not to use this on a regular basis and could be hiding other issues. It's meant to save you from a crash.

I will do after this issue is resolved - at the moment I need to raise the bed at least 300mm to home successfully.

nick9one1

When you jog your Z axis normally after homing (after you remove the M564) does Z+ move the bed away from the nozzle and Z- towards the nozzle?

Yes, the jog buttons work as expected, and I get good prints.

G1 Z5 F6000 lowers the bed
G1 Z-5 F6000 raises the bed

When the bed is fully lowered at power on, I have to send this before a home;
G1 Z-500 F6000
G92 Z0

If I dont send G92 Z0 the printer seems to attempt a probe in the wrong direction (Z+ instead of Z-). I think this is because it thinks the bed is at Z-500 (my G1 Z-500 command).

If I attempt to home when the bed is fully lowered at power on, the bed raises about 1/2 way (Z-), then starts going to other way (Z+).
It seems to me like there is a timeout or travel limit safety.

nick9one1

@fcwilt

M574 now looks like this;

; Endstops
M564 H0					     ; allow jog without homing
M574 X1 S1 P"xstop"                          ;
M574 Y2 S1 P"ystop"                          ;
M574 Z1 S1 P"zstop"                          ;

not

; Endstops
M564 H0					       ; allow jog without homing
M574 X1 S1 P"xstop"                            ;
M574 Y2 S1 P"ystop"                            ;
M574 Z1 S2                                     ; configure Z-probe endstop for low end on Z

Unfortunately the behaviour is still the same

jay_s_uk

What fcwilt meant was remove the M574 line for the endstop, unless you still have one on Z maximum.

Your M558 included an I0, which is not supported as part of RRF3.

Your Z maximum is set as 350mm. How large is it as you seem to be issuing a -600mm move which would indicate your Z axis is larger than 350mm

droftarts

@nick9one1 this came up recently in another thread, where the M208 Z limit was much smaller then the actual Z movement. If the probe move has to move more than 1.1 times the M208 Z limit, probing is cancelled and it will try to move the bed back to Z0. So set you M208 Z limit to much closer to the actual size, eg Z600. You can always set up a fast Z home move, then slow Z home, if it’s painful to watch it home 600mm at slow speed!

Ian

nick9one1

@jay_s_uk said in Z probe wrong direction unless I zero Z:

What fcwilt meant was remove the M574 line for the endstop, unless you still have one on Z maximum.

Your M558 included an I0, which is not supported as part of RRF3.

Your Z maximum is set as 350mm. How large is it as you seem to be issuing a -600mm move which would indicate your Z axis is larger than 350mm

Thanks!

I will remove I0 frm M558

I guess Z max here is probably the cause of the bed getting to half way then reversing. I will change to Z650 (Z is 650)

M208 X305 Y332 Z350 S0                         ; set axis maxima

nick9one1

@droftarts said in Z probe wrong direction unless I zero Z:

@nick9one1 this came up recently in another thread, where the M208 Z limit was much smaller then the actual Z movement. If the probe move has to move more than 1.1 times the M208 Z limit, probing is cancelled and it will try to move the bed back to Z0. So set you M208 Z limit to much closer to the actual size, eg Z600. You can always set up a fast Z home move, then slow Z home, if it’s painful to watch it home 600mm at slow speed!

Ian

I like the idea of a faster Z home, so will try that.

I'm also using a mini IR Z probe which seems to have similar behaviour when Z gets close.

jay_s_uk

I use

M558 F250 				 										; Set the probing speed
G30					 											; Probe a single point
M558 F30 				 										; Set a slower probing speed
G30					 											; Probe a single point

In my Z homing file. That sets the first homing speed to just over 4mm/s and then 0.5mm/s. A similar change to your homing file would work for you.

Phaedrux

@droftarts I thought it sounded familiar

nick9one1

All working as expected now thankyou.

I think the key change was setting the correct Z height

M208 X305 Y332 Z350 S0 ;

now;

M208 X305 Y332 Z950 S0 ;

Full Gcode;

950 ; Configuration file for Duet WiFi (firmware version 3)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.1.4 on Sat Sep 05 2020 23:57:30 GMT+0100 (British Summer Time)

; General preferences
M80					       	; Turns on the ATX power supply
G90                                            	; send absolute coordinates...
M83                                            	; ...but relative extruder moves
M550 P"BLV MGN Cube"                           	; set printer name
M669 K1                                        	; select CoreXY mode

; Network
M552 S1                                        	; enable network
M586 P0 S1                                     	; enable HTTP
M586 P1 S0                                     	; disable FTP
M586 P2 S0                                     	; disable Telnet

; Drives
M569 P0 S0                                     	; physical drive 0 goes backwards
M569 P1 S1                                     	; physical drive 1 goes forwards
M569 P2 S1                                     	; physical drive 2 goes forwards
M569 P3 S0                                     	; physical drive 3 goes backwards
M584 X0 Y1 Z2 E3                               	; set drive mapping
M350 X16 Y16 Z16 E16 I1                        	; configure microstepping with interpolation
M92 X200.00 Y200.00 Z800.00 E415.5             	; set steps per mm
M566 X600.00 Y600.00 Z24.00 E300.00            	; set maximum instantaneous speed changes (mm/min)
M203 X20000.00 Y20000.00 Z600.00 E2000.00      	; set maximum speeds (mm/min)
M201 X3000.00 Y3000.00 Z100.00 E5000.00        	; set accelerations (mm/s^2)
M906 X1500 Y1500 Z1500 E1100 I30               	; set motor currents (mA) and motor idle factor in per cent
M84 S30                                        	; Set idle timeout

; Pressure advance
; M572 D0 S0.05	

; Axis Limits
M208 X-23 Y0 Z0 S1                            	; set axis minima
M208 X305 Y332 Z950 S0                        	; set axis maxima

; Endstops
M564 H0					       	; allow jog without homing
M574 X1 S1 P"xstop"                            	;
M574 Y2 S1 P"ystop"                            	;
M574 Z1 S1 P"zstop"                            	; configure Z-probe endstop for low end on Z

; Z-Probe
M558 P1 H5 C"^zprobe.in" H5 F250 T9000 R0.5	; set Z probe type to switch and the dive height + speeds
G31 P500 X-2 Y-16.4 Z1.40                      	; set Z probe trigger value, offset and trigger height
M557 X10:292 Y5:300 P5                       	; define mesh grid

; Heaters
M308 S0 P"bedtemp" Y"thermistor"T100000 B3950 C0 R4700 A"Bed Temp"  	; configure sensor 0 as thermistor on pin bedtemp
M950 H0 C"bedheat" T0                          				; create bed heater output on bedheat and map it to sensor 0
M140 H0                                        				; map heated bed to heater 0
M143 H0 S100                                   				; set temperature limit for heater 0 to 100C
M307 H0 A466.3 C1262.5 D12.8 S1.00 V24.0 B0    				; Set PID for heated bed values
M308 S1 P"e0temp" Y"thermistor" T100000 B3950 C0 R4700 A"Hotend Temp"   ; configure sensor 1 as thermistor on pin e0temp
M950 H1 C"e0heat" T1                           				; create nozzle heater output on e0heat and map it to sensor 1
M143 H1 S260                              				; set temperature limit for heater 1
M307 H1 A340.0 C140.0 D5.5 S1.00 V24.0 B0     				; Set PID for hotend values

; Fans
M950 F0 C"fan0" Q500                           	; create fan 0 on pin fan0 and set its frequency
M106 P0 S0 H-1                                 	; set fan 0 value. Thermostatic control is turned off
M950 F1 C"fan1" Q500                           	; create fan 1 on pin fan1 and set its frequency
M106 P1 S1 H1 T45                              	; set fan 1 value. Thermostatic control is turned on

; Tools
M563 P0 D0 H1 F0                               	; 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