Homing error and homing procedure



  • I seem to have a problem with my probing sequence…

    Everytime i home the printer i get an error message “G28, Homing failed” yet all axis appear as homed in DWC.

    What i do is probe X and Y then fasthome Z using the probe and do a G30 after. At the start of every print i run G29 because i switch bed surfaces.
    The printer is a custom cartesian I3 style using BlTouch.

    Also, I was wondering if there was a way to preheat bed, run G29 THEN AFTER preheat nozzle…
    The nozzle oozes while it's running the G29 and it leaves a trail on the surface.

    Here are my homing files and the pertinent sections from my config.g

    ; config.g
    
    M208 X-10 Y-15 Z0 S1                      ; Set axis minima
    M208 X310 Y280 Z270 S0                    ; Set axis maxima
    
    ; Endstops
    M574 X1 Y1 S0                             ; Set active low endstops
    M574 Z1 S2				  ; define z probe and home to min
    
    ; BlTouch config
    M307 H3 A-1 C-1 D-1			  ; disable 3rd heater
    M558 P5 H3 X0 Y0 Z1 H2 F200 T5000 	  ; set z probe mode 5
    G31 X0 Y15 Z1.68 P25   			  ; probe offset from nozzle
    M557 X24:276 Y24:276 S63         	  ; mesh grid zone and spacing
    
    ; homeall.g
    
    G91
    G1 Z3 F6000             ; lift Z relative to current position
    G28 XY
    G28 Z
    
    ; homex.g
    
    G91               ; relative positioning
    G1 S1 X-325 F2500 ; move quickly to Y axis endstop and stop there (first pass)
    G1 X5 F6000       ; go back a few mm
    G1 S1 X-325 F360  ; move slowly to Y axis endstop once more (second pass)
    G90               ; absolute positioning
    G1 X20 F2000
    
    ; homey.g
    
    G91               ; relative positioning
    G1 S1 Y-325 F2500 ; move quickly to Y axis endstop and stop there (first pass)
    G1 Y5 F6000       ; go back a few mm
    G1 S1 Y-325 F360  ; move slowly to Y axis endstop once more (second pass)
    G90               ; absolute positioning
    G1 Y20 F2000
    
    ; homez.g
    
    G29 S2
    G91               ; relative positioning
    M280 P3 S10 I1
    G1 S1 Z-325 F600  ; home Z with probe
    M280 P3 S90 I1
    G1 Z5 F1200
    G90               ; absolute positioning
    G30
    G1 Z5 F1200
    
    


  • What firmware version are you using?

    Your homeZ only needs the G30 portion to probe the bed. You could add an XY movement before that to probe the center of the bed.

    If you want to duplicate the fast home process using G30 you can do something like this

    [c]; homez.g
    ; called to home the Z axis
    ;

    ; BLTouch prep so we don't catch the probe pin on the edge of the bed
    ;
    M280 P3 S160 I1 ; Alarm Release and Push-Pin UP just in case it's in alarm and deployed
    G4 S1
    M402 ; Retract probe just in case it's down
    G4 S0.5

    ; Drop the bed for travel
    ;
    G91 ; Relative positioning
    G1 Z5 F200 S2 ; Lower bed 5mm to ensure it is below the switch trigger height

    ; Move probe into position
    ;
    G90 ; absolute positioning
    G1 X200 Y140 F4000 ; Move x and Y axis over to bed center so probe is on top of bed

    ; Set lower speeds for homing
    M566 Z5 ; Set maximum instantaneous speed changes (mm/min) (Jerk)
    M203 Z400 ; Set maximum speeds (mm/min)
    M201 Z100 ; Set maximum accelerations (mm/s^2)

    ; Probe the bed
    ;
    M558 A1 F350 ; Set single probing at faster feed rate
    G30 ; Do a single probe to home our Z axis
    M558 A10 F100 ; Set tripple probing at slower feed rate
    G30 ; Probe again to get a more accurate position

    ; Set normal speeds again
    M566 Z15 ; Set maximum instantaneous speed changes (mm/min) (Jerk)
    M203 Z500 ; Set maximum speeds (mm/min)
    M201 Z300 ; Set maximum accelerations (mm/s^2)

    ; Move X and Y back Home
    ;
    G1 X0 Y285[/c]

    Firmware 1.21 has a new probe type specifically for the BLTouch. P9. It will automatically deploy and retract the probe when appropriate. You only need the M280 P3 S90 I1 commands in the deployprobe.g and retractprobe.g files now.

    Your dive height in M558 seems a little low. It also appears you have two H values in the command. Try just H5.

    I don't know if any of that is the cause for your homing failed message, but I was experiencing that occasionally as well, but in my current config it doesn't happen anymore.

    [c]; ############################
    ; 3 - ENDSTOPS AND ZPROBE
    ; ############################

    M574 X1 Y2 S0 ; Set active-low switches, low end endstop for X, high end endstop for Y, add Z2 for Zmax
    M574 Z1 S2 ; Use zprobe and home to min
    M307 H3 A-1 C-1 D-1 ; Unbind heater 3 pins for probe use.
    M558 P9 X0 Y0 Z1 H5 F100 T4000 A10 R0.5 S0.008 ; P9 for BLTouch, dive height 5mm, probe at 100mm/s, travel 4000mm/s, up to 10 probes, pause 0.5s
    G31 X-42.5 Y-2.2 Z1.8 P25 ; probe offset from nozzle, p is trigger value, set low for bltouch, set Z=0 for testing
    ; (z height is 1.8006 after calibration March 29th)
    M557 X20:310 Y2:282 S14 ; Define mesh grid
    M376 H20 ; Taper off compensation over 20mm of height
    M375 ; Load heightmap.csv
    [/c]



  • @3D_low:

    …........................
    Also, I was wondering if there was a way to preheat bed, run G29 THEN AFTER preheat nozzle...
    The nozzle oozes while it's running the G29 and it leaves a trail on the surface.
    .......................

    Yes of course. If you want to pre-heat the bed every time you home Z, the simply put M190 Snn (where nn is the bed temperature) at the start of your homez file and at the beginning of the homez section of your homeall file. If you want to heat the nozzle, you can do that too by using M109 in the same manner. Generally, if you just want to soften the plastic, you can use a lower temperature of around 140 deg C (but experiment with it) which will soften it but prevent it from oozing.



  • @deckingman:

    @3D_low:

    …........................
    Also, I was wondering if there was a way to preheat bed, run G29 THEN AFTER preheat nozzle...
    The nozzle oozes while it's running the G29 and it leaves a trail on the surface.
    .......................

    Yes of course. If you want to pre-heat the bed every time you home Z, the simply put M190 Snn (where nn is the bed temperature) at the start of your homez file and at the beginning of the homez section of your homeall file. If you want to heat the nozzle, you can do that too by using M109 in the same manner. Generally, if you just want to soften the plastic, you can use a lower temperature of around 140 deg C (but experiment with it) which will soften it but prevent it from oozing.

    Perhaps I forgot to mention that this was only when printing parts. I’m using s3d but I could not find a way to alter the starting sequence. Do you know of a way? Perhaps scripting to replace some lines like I do with the retraction?



  • @Phaedrux:

    What firmware version are you using?

    Your homeZ only needs the G30 portion to probe the bed. You could add an XY movement before that to probe the center of the bed.

    Using 1.21RC2. I wasn't aware of the new probe type. Thanks for noticing the double H… i didn't even notice.

    I'll try making some modifications following your advice. The printer is working right now (actually it works like a charm it's just some little problems i wanna clean out)
    As soon as it finishes i'll try a new homing strategy



  • You may want to upgrade to the full release of 1.21 now that it's out.

    As for changing your startup script in simplify 3d, check this out https://forum.simplify3d.com/viewtopic.php?t=1959


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