Problem with z-probe offset



  • I am running into trouble with my z-probe offset. I have my config.g as follows:

    ; Printer Settings
    
    M669 K4 P376 D376 A-137:110 B0:172 C-1:0:0 X0 Y0 W2 E-180:180 ; Printer class SCARA, proximal/distal length, proximal min/max angle in relation to x-axis, distal min/max angle in relation to proximal arm, crosstalk factor (depends on mechanical setup)
    M584 X0 Y1 Z2 W3 E4
    M208 X-752:752 Y-752:752 Z0:1270 W-360:360	; Set min/max positions for each axis
    M201 X400 Y400 Z200 E600			; Accelerations (mm/s^2)
    M203 X6000 Y6000 Z400 E3600			; Maximum speeds (mm/min)
    M566 X300 Y300 Z20 E400				; Maximum instant speed changes mm/minute
    
    ;Motor Settings
    
    M569 P0 S1					; Drive 0 goes forwards
    M569 P1 S0					; Drive 1 goes backwards
    M569 P2 S1					; Drive 2 goes forwards
    M569 P3 S0					; Drive 3 goes backwards
    M569 P4 S1					; Drive 4 goes forwards
    M350 X16 Y16 Z16 E16:16 W16 I1			; Set 16x microstepping with interpolation
    M92 X262.2222 Y262.2222 Z800 E700 W65.55555		; Set axis steps/degree, steps/mm
    M906 X1000 Y1000 Z1000 E400 W500 I60		; Set motor currents (mA) and increase idle current to 60%
    
    ;Endstops
    
    M574 X1 S1 P"!xstop"   ; X min active low endstop switch
    M574 Y1 S1 P"!ystop"   ; Y min active low endstop switch
    M574 Z1 S2             ; configure Z-probe endstop for low end on Z
    
    ;Z-Probe
    
    M574 Z0 P"nil" ; no Z endstop switch, free up Z endstop input
    M558 P1 C"zprobe.in" H18 F200 R.5 T3600 # Z-Probe connected to Z-endstop input
    G31 P500 Z2.41
    
    ;Mesh Bed Compensation
    
    M557 X150:600 Y-450:450 S50 ; probe from X=10 to 190, Y=10 to 190mm with a mesh spacing of 20mm
    
    ;Tool Definition
    
    M308 S1 P"e0temp" Y"thermistor" T110000 B4095 H127
    M950 H1 C"e0heat" T1
    M950 F0 C"fan0" 
    M563 P0 S"Hotend" D0 H1 F0
    M140 H0
    G10 P0 X0 Y0 Z0                                ; set tool 0 axis offsets
    G10 P0 R0 S0                                   ; set initial tool 0 active and standby temperatures to 0C
    

    When I run the G30 command to home the z-axis, it does so but instead of using the 2.41mm as I found while manually calibrating it. It sets the z-height to be 18.70, meaning it's using a z-probe offset of .7mm instead of the 2.41 as I've set. This is in RRF 3.2 so I don't know if there are any differences/something wrong.



  • It seems there was another post regarding link text which has to do with using an IR sensor and a defined offset. @dc42 I don't know if this has been changed or not, but I will look in my RRF source to see what is wrong.



  • Hi,

    What board are you using?

    To confirm you are using firmware 3.2.0?

    Frederick



  • DuetWifi 1.04 @fcwilt



  • @koaldesigns said in Problem with z-probe offset:

    DuetWifi 1.04 @fcwilt

    Wow.

    Have you considered updating?

    We are up to 3.2.2.

    I don't know anything about 1.04 so I might think something is wrong when it isn't

    At least investigate updating to 2.05.1 - which likely has syntax more like 1.04.

    Frederick



  • I think we understood eachother wrong. I have a DuetWifi 1.04 but I'm using firmware version RRF 3.2.1. haha @fcwilt



  • Currently the z-probe works and activates, it's just that the defined z offset in the G31 command isn't being used and instead defaults to .7mm. I have looked in the RRF source files and can't see as to why it is defaulting to the .7mm



  • @koaldesigns said in Problem with z-probe offset:

    This is invalid - delete it - or comment it out: M574 Z1 S2 ; configure Z-probe endstop for low end on Z

    This serves no purpose - do that same as above: M574 Z0 P"nil" ; no Z endstop switch, free up Z endstop input

    You have no X and Y offset values in this: G31 P500 Z2.41

    To be safe add them: G31 P500 Xnnn Ynnn Z2.41 where nnnn are the actual values for your printer.

    I have never encountered any situation where the Z offset value is simply ignored.

    Why do you think it is being ignored?

    Frederick



  • @fcwilt I have modified my config.g to what you suggested:

    ;Endstops
    
    M574 X1 S1 P"!xstop"   ; X min active low endstop switch
    M574 Y1 S1 P"!ystop"   ; Y min active low endstop switch
    M574 Z1 S0             ; configure Z-probe endstop for low end on Z
    
    ;Z-Probe
    
    M558 P1 C"zprobe.in" H18 F200 R.5 T3600 # Z-Probe connected to Z-endstop input
    G31 P500 X1 Y1 Z2.41
    M557 X150:600 Y-450:450 S50 ; probe from X=10 to 190, Y=10 to 190mm with a mesh spacing of 20mm
    

    I have tested this and the offset is still .7mm even though it is defined as 2.41mm. I have changed the dive height (H) and after homing it is always the dive height (H) +0.7mm instead of H + 2.41mm so the trigger height is definitely being ignored.



  • @koaldesigns

    Odd.

    Please post your homeALL.g and homeZ.g files

    Frederick



  • I do not have a home.z files as it is impossible for my printer to only home the Z-axis as it is dependent on the other axis being homed. My homeall.g is as follows:

    G91							;Relative positioning
    M561					;Remove any mesh leveling
    G92 W0					;Set Z to 0 (temporary no z stop yet)
    
    G1 H2 Z30 F400
    G0 H1 Y-300 X-300 F800		;Move both distal and proximal to home positions
    G0 H2 X5 F200				;Slowly turn proximal away from home position
    G0 H1 X-10 F200				;Slowly home proximal
    G0 H2 Y5 F200				;Slowly turn distal away from home position
    G0 H1 Y-10 F200				;Slowly home distal
    
    G90							;Absolute positioning
    
    G0 H2 X-60 Y60 W0 F800			;Move arm to center of range
    G30
    

    @fcwilt



  • @koaldesigns

    I don't think you need the H2 parameters on the X and Y moves.

    Everything else looks fine.

    When you say it ends up at dive height + 0.7mm - is that as reported by the DWC or are you measuring it?

    Thanks.

    Frederick



  • I do need the H2 parameters because it's a SCARA machine. Everything has been tuned and works properly for what I need except the z offset. Also, I don't have to measure it because that's what the firmware says, and when I move to Z0, the hotend is always the same distance above the bed no matter the z-offset so it is being ignored. @fcwilt



  • @koaldesigns

    Have you executed a G31 from the console after booting to see what it reports?

    You don't by chance have another G31 somewhere this overriding the one in config.g?

    Frederick



  • The G31 command yielded this before and after homing:

    G31
    Z probe 0: current reading 487, threshold 500, trigger height 2.410, offsets X1.0 Y1.0
    

    but still reports 18.7mm z height after homing when it should be 20.41. @fcwilt



  • @koaldesigns said in Problem with z-probe offset:

    The G31 command yielded this before and after homing:

    G31
    Z probe 0: current reading 487, threshold 500, trigger height 2.410, offsets X1.0 Y1.0
    

    but still reports 18.7mm z height after homing when it should be 20.41. @fcwilt

    What kind of probe is it?

    That reading of 487 is awfully close to the threshold value.

    I noticed that in your homeALL.g file you used G92 W0 with the comment that there was no Z end stop yet.

    It got me to thinking. Does your printer have a axis named Z? If not how does G30 know to move on W.

    Curious.

    The only other thing I can think of is that 3.2 has a bug. I know for my printer with 3 Z steppers each with their own Z end stop switch there was a bug that prevented it from working correctly.

    Frederick



  • The W axis is a wrist joint and is irrelevant for this. I'm going to give it a break for tonight and see whats up tomorrow. It could be something to due with mesh bed leveling but I'm unsure. @fcwilt


  • Moderator

    Do you get any errors when sending M98 P"config.g"?



  • Sorry to hijack this thread but would just like to get something off my chest.
    Ive had problems with both my corexy printers regarding Z height and first layer issues since upgrading from RRF3.1.1. Both printers have SBC. They both now running on RRF3.2.2 and neither are capable of printing anything from scratch without my intervention. Each time I have to adjust babystepping to get the first layer height correct.
    Example: In config.g one printer has Z offset G31 X-30 Y-5 Z2.72 which was found by doing correct process to find Z height. On attempting to print, Z is too high. If I lower Z by 0.28 using on the fly babystepping the first layer is spot on. Before next print I change G31 in config.g to G31 X-30 Y-5 Z3.0 so as to equal the difference with babystep. On next print Z is too low and babystepping back up by 0.28 corrects this!!!!
    Just in case I'm doing something wrong I then change config to G31 X-30 Y-5 Z2.44 (minus 0.28). This time the print too low by 0.28!!!
    Both printers have similar issue and neither printer has any other G31 command in any other piece of gcode or macro.
    I have only one functional printer which is old faithful ender 3 pro which in my opinion prints every time because there's no Z probe present, everything is set up manually, no SBC attached and therefore much simpler.
    Ever since RRF3 firmware versions have been available I've had issues and still have issues with SBC not always connecting to DCS, when booted up, sometimes config.g not been processed so DWC shows no extruders, no heaters, no fans etc...
    It was months and months ago that i first reported an issue that any gcode command that I enter into the console in DWC has to be clicked on twice before DWC responds, I find that this issue is STILL present and has now even expanded to include the emergency stop icon on DWC. So at one point my head crashed into the bed because the emergency stop does not always work first time!!!
    Lastly, I fail to understand how on both printers with SBC attached i often encounter "network failed, no network connection" showing on SBC's DWC but im somehow happily connected to DWC via laptop!!
    I spent £1500 on my last printer but the best and most reliable prints come from my simple £250 Ender 3.
    Rant over, feel better now!


  • Moderator

    @chas2706 said in Problem with z-probe offset:

    Rant over, feel better now!

    Well that's something at least. 😉 Feel free to start a new thread if you want to work through any other issues.


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