Homing vs. Printing height difference



  • I'm sure I'm missing something but... have zeroed Z and applied a trigger height for the difference between my z probe and nozzle. When I try to print, there is a +5.25mm difference between the nozzle and bed so doesn't print but spews in midair. I know it is me, but I can't seem to find the problem. Here are config.g and bed.g

    G90                                            ; send absolute coordinates...
    M83                                            ; ...but relative extruder moves
    M550 P"Q5"                                     ; set printer name
    
    ; Network
    M552 S1                                        ; enable network
    M586 P0 S1                                     ; enable HTTP
    M586 P1 S0                                     ; disable FTP
    M586 P2 S0                                     ; disable Telnet
    
    ; Drives
    M569 P0 S1                                     ; physical drive 0 goes forwards
    M569 P1 S1                                     ; physical drive 1 goes forwards
    M569 P2 S1                                     ; physical drive 2 goes forwards
    M569 P3 S0                                     ; physical drive 3 goes backwards
    
    ; Endstops
    M574 X2 S1 P"xstop"   ; X min active high endstop switch
    M574 Y2 S1 P"ystop"   ; Y min active high endstop switch
    M574 Z2 S1 P"zstop"   ; Z min active high endstop switch
    
    M665 R106.35 L215 B180.8 H224.5			   ;Set delta radius, diagonal rod length, printable radius and homed height
    M666 X-0.21 Y0.23 Z-0.02,					   ; put your endstop adjustments here
    M584 X0 Y1 Z4 E3                               ; set drive mapping
    M350 X16 Y16 Z16 E16 I1                        ; configure microstepping with interpolation
    M92 X79.40 Y79.40 Z80.0 E2650.00               ; set steps per mm
    M566 X1200.00 Y1200.00 Z1200.00 E600.00        ; set maximum instantaneous speed changes (mm/min)
    M203 X1800.00 Y1800.00 Z1800.00 E300.00     ; set maximum speeds (mm/min)
    M201 X1000.00 Y1000.00 Z1000.00 E40.00         ; set accelerations (mm/s^2)
    M906 X800 Y800 Z800 E600 I30                   ; set motor currents (mA) and motor idle factor in per cent
    M84 S30                                        ; Set idle timeout
    
    ; Axis Limits
    M208 Z0 S1                                     ; set minimum Z
    M208 Z215.4 S0                         	   ; set axis maxima
    
    ; Z-Probe
    M558 P5 C"e0stop" H5 F6000 T2000              ; set Z probe type to switch and the dive height + speeds
    G31 P500 X0 Y0 Z15.3							; set Z probe trigger value, offset and trigger height
    M557 R52 S20                                   ; define mesh grid
    
    ; Heaters
    M308 S0 P"bedtemp" Y"thermistor" T100000 B4138 ; 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
    M307 H0 B1 S1.00                               ; enable bang-bang mode for the bed heater and set PWM limit
    M140 H0                                        ; map heated bed to heater 0
    M143 H0 S100                                   ; set temperature limit for heater 0 to 100C
    M308 S1 P"e0temp" Y"thermistor" T100000 B4138  ; 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
    M307 H1 B0 S1.00                               ; disable bang-bang mode for heater  and set PWM limit
    
    
    ; Fans
    M950 F0 C"fan0" Q500                           ; create fan 0 on pin fan0 and set its frequency
    M106 P0 S1 H T45                               ; set fan 0 value. Thermostatic control is turned on
    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
    M950 F2 C"fan2" Q500                           ; create fan 2 on pin fan2 and set its frequency
    M106 P2 S1 H1 T45                              ; set fan 2 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
    
    M501
    
    ; Custom settings are not defined
    
    
    BED.G
    ; bed.g
    ; called to perform automatic delta calibration via G32
    
    M561 ; clear any bed transform, otherwise homing may be at the wrong height
    G28 ; home the printer
    
    ''' Probe the bed and do 6-factor auto calibration'''
    G30 P0 X-73.6 Y-42.5 Z-99999 ; X tower
    G30 P1 X0 Y-73.6 Z-99999 ; between X and Y towers
    G30 P2 X73.6 Y-42.5 Z-99999 ; Y tower
    G30 P3 X73.6 Y20 Z-99999 ; between Y and Z towers
    G30 P4 X0 Y67 Z-99999 ; Z tower
    G30 P5 X-73.6 Y20 Z-99999 ; between Z and X towers
    G30 P6 X-36.8 Y-21.25 Z-99999 ; half way to X tower
    G30 P7 X36.8 Y-21.25 Z-99999 ; half way to Y tower
    G30 P8 X0 Y42.5 Z-99999 ; half way to Z tower
    G30 P9 X0 Y0 Z-99999 S6 ; centre, and auto-calibrate 6 factors
    
    G1 X0 Y0 Z150 F8000 ; get the head out of the way of the bed
    
    ; If your Z probe has significantly different trigger heights depending on XY position, adjust the H parameters in the G30 commands accordingly. The value of each H parameter should be (trigger height at that XY position) - (trigger height at centre of bed)
    
    
    
    
    
    


  • Hi,

    On line 35 you have M208 Z215.4 S0 - according to the docs deltas don't use that form of the command.

    On line 39 you have the trigger height as Z15.3 - is that accurate?

    If it is try changing the H parameter in line 38 to H20 just as a test.

    Frederick



  • OK. Corrected those issues. I tried them with those commands to see if it would help. I now get a "Z probe not triggered during " a G32 command. I'll check my wiring I guess though it was working before I installed the Duet. Hmmmm



  • Wiring triggers properly at the board. Maybe increase the trigger height even more? I'll try that...



  • @1d1 said in Homing vs. Printing height difference:

    Wiring triggers properly at the board. Maybe increase the trigger height even more? I'll try that...

    Is that 15.3 value correct?

    That value is supposed to be the Z position when the probe triggers.

    Frederick



  • @fcwilt I'm guessing it's a delta (probably an anycubic one) in which case that z probe offset is about right



  • @fcwilt That is what the indicated Z height is when the probe triggers. When I then check the distance to the bed, it requires an additional -4.9mm for the nozzle to reach printing height. Yeah, the distance the printer attempts to print is likely 4.9mm above the bed. This where I'm confused, exactly.



  • That is, -4.9 from Z0



  • @1d1 said in Homing vs. Printing height difference:

    @fcwilt That is what the indicated Z height is when the probe triggers. When I then check the distance to the bed, it requires an additional -4.9mm for the nozzle to reach printing height. Yeah, the distance the printer attempts to print is likely 4.9mm above the bed. This where I'm confused, exactly.

    The indicated height is simply the value you entered into the G31 command. It is "telling" the firmware that the nozzle is 15.3 mm above the bed when the probe triggers.

    If it is actually 15.3 + 4.9 use that value instead.

    Frederick



  • When I do that (for the 10th time) I get a probe not triggered response when running a G32. I know the probe triggers when pushed because the LED on the board goes off. If I increase that trigger value, it still doesn't work because the probe remains too high. If I decrease the trigger height value to 15.22 I get a calibrated mean deviation response after G32. All Good. I then enter an M500 to save it. And when I go to print, The extruder prints in midair about 4.9mm above the bed.



  • How did you measure the trigger height?



  • I take the indicated difference from the point at which the probe triggers, remove the probe, and then lower the extruder until the nozzle touches the bed. The total distance is appx. 20mm (15.3 + 4.9). When using that value, the probe doesn't trigger when G32 is used. If I lower the trigger height value to 15.4, the probe triggers. Then I get a mean deviation report, hit M500, and go to print... 4.9 mm above the bed... again. Pretty frustrated here.



  • @1d1

    If you home the printer and then move to Z=0 where does the nozzle end up, height wise?

    Frederick



  • 4.53mm above the bed





  • @1d1 said in Homing vs. Printing height difference:

    4.53mm above the bed

    Do you have a line like this in your config-override.g file?

    M665 R106.35 L215 B180.8 H224.5 ;Set delta radius, diagonal rod length, printable radius and homed height

    If you do change the H parameter to H229.4

    If not change that line in your config.g file.

    Then re-boot, home and move to Z=0 and see what happens.

    Frederick



  • @jay_s_uk Many times.



  • @fcwilt I'll try that. Though I have already in the past, maybe we're closer to the solution...



  • Well you're doing to z probe offset the wrong way.

    Heat the bed
    Heat the nozzle
    Take the nozzle down until it's touching the bed (using paper to determine when they're touching)
    G92 Z0
    G1 Z30 (to move the nozzle away from the bed)
    Fit the probe
    G30 S-1

    And the offset will be spat out



  • @jay_s_uk

    That is certainly one way but it is not the only way.

    Frederick



  • OK. Adding 5mm to my overall homing height didn't alter results, but I left it that way and did the G92 Z0 process again and we have ignition. A number was spat, changes were splatted and results regurgitated. PETG flows properly once again. Thank you both (all?) for your help.



  • @1d1 said in Homing vs. Printing height difference:

    OK. Adding 5mm to my overall homing height didn't alter results, but I left it that way and did the G92 Z0 process again and we have ignition. A number was spat, changes were splatted and results regurgitated. PETG flows properly once again. Thank you both (all?) for your help.

    Adding the 5, reboot, home and still Z=0 came out at 4.9? Very odd.

    Well, anyway, don't leave us in suspense - what number was "spat"?

    Frederick



  • @fcwilt thats what it says to do on the wiki



  • @jay_s_uk said in Homing vs. Printing height difference:

    @fcwilt thats what it says to do on the wiki

    I understand and it is a perfectly fine solution.

    Frederick



  • Sorry - had to step away. The homing height in M558 is locked at 229.4 and the number spat is 19.43. Still needs a teensy bit of fine tuning, but the grand picture includes printing again.


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