Some Z-offset error after bed replacement.



  • So, this is a followup of https://forum.duet3d.com/topic/8340/replaced-bed-now-have-some-geometry-issues
    But since it is a separate issue, i figured I would make a separate topic for it.

    Basically, after my re-build, if i tram my printer to Z0 i am still at about 0.2mm over the bed. A 0.15mm feeler blade slides freely under nozzle, but a 0.20 blade hits the nozzle ever so lightly. I can slide the 0.2 under the nozzle without feeling any noticable resistance. I'm running a Smart Effector on 2.02

    I really can not understand what (most likely silly) thing that I have missed this time. Seem almost like a probe offset thing, but if so I think I would have had similar issues with my previous bed?

    config.g
    ; Configuration file for Duet WiFi (firmware version 1.20 or newer)
    ; executed by the firmware on start-up
    ;
    ; generated by RepRapFirmware Configuration Tool on Sat Mar 10 2018 00:14:59 GMT+0100 (W. Europe Standard Time)

    ; General preferences
    G90 ; Send absolute coordinates...
    M83 ; ...but relative extruder moves
    M665 R179.489 L360.2 B150 H451 X0.746 Y0.761 Z0 ; Set delta radius, diagonal rod length, printable radius and homed height
    M666 X0.85 Y-0.81 Z-0.04 A0 B0 ; Put your endstop adjustments here, or let auto calibration find them

    ; Network
    M550 PFullMetalDelta ; Set machine name
    M552 S1 ; Enable network
    ;*** Access point is configured manually via M587
    M586 P0 S1 ; Enable HTTP
    M586 P1 S0 ; Disable FTP
    M586 P2 S0 ; Disable Telnet

    ; Drives
    M569 P0 S1 ; Drive 0 X goes forwards
    M569 P1 S1 ; Drive 1 Y goes forwards
    M569 P2 S1 ; Drive 2 Z goes forwards
    M569 P3 S0 ; Drive 3 E0 goes backwards, Zesty Nimble
    ;M569 P3 S1 ; Drive 3 E0 goes backwards, Titan Extruder

    M350 X16 Y16 Z16 E16 I1 ; Configure microstepping with interpolation
    M92 X200 Y200 Z200

    ;M92 E418.5 ; Set steps per mm (Titan)
    M92 E2855 ; Set steps per mm (Zesty)

    ;M566 X1200 Y1200 Z1200 E1200 ; Set maximum instantaneous speed changes (mm/min) Titan
    M566 X1200 Y1200 Z1200 E40 ; Set maximum instantaneous speed changes (mm/min) Zesty
    M203 X18000 Y18000 Z18000 E1200 ; Set maximum speeds (mm/min)
    ;M201 X1000 Y1000 Z1000 E1000 ; Set accelerations (mm/s^2) Titan
    M201 X1000 Y1000 Z1000 E120 ; Set accelerations (mm/s^2) Zesty
    M906 X1000 Y1000 Z1000 E500 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

    ; Endstops
    M574 X2 Y2 Z2 S1 ; Set active high endstops

    ; Z-Probe
    M558 P5 R0.4 F1000 H5 ; Smart Effector
    G31 P100 X0 Y0 Z-0.1
    M557 R148 S20 ; Define mesh grid

    ; Heaters
    ;M305 P0 T99670 B4471 C8.262085e-8 R4700 ; Set thermistor + ADC parameters for heater 0 Keenovo heater
    M305 P0 T100000 B3950 R4700 ; Set thermistor + ADC parameters for heater 0 Clever3d heater
    M143 H0 S120 ; Set temperature limit for heater 0 to 120C
    M305 P1 T100000 B4725 C7.060000e-8 R4700 ; Set thermistor + ADC parameters for heater 1
    M143 H1 S280 ; Set temperature limit for heater 1 to 280C

    ; Fans
    ;M106 P0 S0 I0 F10 H-1 ; Set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned off
    M106 P0 S0 I1 F100 H-1 L0.3 ; Set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned off
    M106 P1 S1 I0 F500 H1 T45 ; Set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned on
    ;M106 P2 S1 I0 F500 H1 T45 ; Set fan 2 value, PWM signal inversion and frequency. Thermostatic control is turned on
    M106 P2 I1 H100:101 T45:55 L0.3

    ; Tools
    M563 P0 D0 H1 ; 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

    M572 D0 S0.03 ; Pressure advance

    M912 P0 S-22 ; Temperature offset.

    ; Automatic saving after power loss is not enabled

    ; Custom settings are configured
    M501

    ;Load mesh calibration
    G29 S1

    config-override.g
    ; This is a system-generated file - do not edit
    ; Delta parameters
    M665 L360.200 R179.529 H453.948 B150.0 X0.135 Y-0.070 Z0.000
    M666 X-0.496 Y0.126 Z0.370 A0.00 B0.00
    ; Heater model parameters
    M307 H0 A241.5 C325.9 D1.5 S1.00 V12.1 B0
    M307 H1 A263.0 C111.3 D6.3 S1.00 V12.1 B0
    M307 H2 A340.0 C140.0 D5.5 S1.00 V0.0 B0
    M307 H3 A340.0 C140.0 D5.5 S1.00 V0.0 B0
    M307 H4 A340.0 C140.0 D5.5 S1.00 V0.0 B0
    M307 H5 A340.0 C140.0 D5.5 S1.00 V0.0 B0
    M307 H6 A340.0 C140.0 D5.5 S1.00 V0.0 B0
    M307 H7 A340.0 C140.0 D5.5 S1.00 V0.0 B0



  • Did you remeasure your z probe trigger height again after replacing the bed?



  • @phaedrux said in Some Z-offset error after bed replacement.:

    Did you remeasure your z probe trigger height again after replacing the bed?

    Well, thats part of the issue, even with M564 S0 i am not able to drive Z past 0.

    (Following https://duet3d.dozuki.com/Wiki/Test_and_calibrate_the_Z_probe)



  • @phaedrux said in Some Z-offset error after bed replacement.:

    Did you remeasure your z probe trigger height again after replacing the bed?

    Aha!

    This bit me!
    https://github.com/chrishamm/DuetWebControl/issues/99

    So, now i could disable limits with S564 S0

    I get pretty consistant trigger heights now of -0.176mm (varies between -0.174 and -0.177 when running approx 25 tests)

    Then i read

    Once you are satisfied with your trigger height result (should be between 0 and 1mm, depending on your printer), open your config.g file (this can be found in your DuetWebControl), find the G31 command and enter your trigger height as a negative value in the Z parameter (ex. G31 X0 Y0 Z-.43).

    Since i get a negative trigger height, does that mean that I should enter a positive value there?

    And also... When running G30 S-1 it says "Probe the bed" so i assume that i should have removed my paper?



  • The smart effector is a nozzle contact type probe, so it would be expected to get a negative trigger height, since it has to push into the bed slightly in order to trigger. So your G31 Z value would be negative.

    If you are using a nozzle-contact Z probe, the trigger height will be slightly negative. For any other type of Z probe where the probe triggers before the nozzle contacts the bed, it will be positive.

    You've just found one reason I dislike using paper to get the nozzle close to the bed. When you use paper you need to know how thick the paper is, and how hard did the nozzle press into it? How much friction is enough or too much?

    I find it far more accurate to just shine a light behind the printer and watch while lowering the nozzle. You can easily see the gap disappear when it touches.

    In contrast, it's quite easy to see the difference between 0.05mm by eye. Even with such a small gap the daylight between the nozzle and bed is obvious.



  • @phaedrux said in Some Z-offset error after bed replacement.:

    The smart effector is a nozzle contact type probe, so it would be expected to get a negative trigger height, since it has to push into the bed slightly in order to trigger. So your G31 Z value would be negative.

    If you are using a nozzle-contact Z probe, the trigger height will be slightly negative. For any other type of Z probe where the probe triggers before the nozzle contacts the bed, it will be positive.

    You've just found one reason I dislike using paper to get the nozzle close to the bed. When you use paper you need to know how thick the paper is, and how hard did the nozzle press into it? How much friction is enough or too much?

    I find it far more accurate to just shine a light behind the printer and watch while lowering the nozzle. You can easily see the gap disappear when it touches.

    In contrast, it's quite easy to see the difference between 0.05mm by eye. Even with such a small gap the daylight between the nozzle and bed is obvious.

    Well, I have a set of feeler gauges.

    But regardless of that... GOt any hints on how i should proceed in my case? 🙂



  • @janjoh What issue are you still having? It sounded like you were able to get a proper z probe trigger height measurement.



  • @phaedrux said in Some Z-offset error after bed replacement.:

    @janjoh What issue are you still having? It sounded like you were able to get a proper z probe trigger height measurement.

    Well, as i said. The guide says to enter the offset as a negative value, and that the hegith is usually 0 to 1mm . But i am getting a negative value on my readings. Does that mean i should put in a POSITIVE trigger value in my G31?

    Because if i enter -0.176 in G31, and reset my machine, I end up back where the head will be at about 0.2mm over the bed when the machine reads Z0

    Edit: Crap.. Starting to regret the "New" WebControl. Mesh compensation didnt disable propery. I think I've got it now.. lesseeeee


 

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