Crash into bed on Z home

  • For the life of me cannot solve an issue with my new IR sensor.
    Below are my setting, following these instructions,

    Sending G92 Z0 and then G30 S-1 works fine and it homes.

    M558 P1 X0 Y0 Z1 H5 F120 T6000
    G31 P500 X0 Y2.4 Z0.949 ; Set Z probe trigger value, offset and trigger height

    But when I then run the homez it always crashes into the bed.
    Here is my homez file:

    ; homez.g
    ; called to home the Z axis
    ; generated by RepRapFirmware Configuration Tool on Sat Oct 21 2017 21:17:08 GMT-0500 (Central Daylight Time)
    ; Lift Z relatively to current position
    G1 Z5 F6000
    ; Back to absolute positioning
    ; Go to first bed probe point and home the Z axis
    G1 X30 Y27.6 F6000
    ; Uncomment the following lines to lift Z after probing
    ;G1 Z5 F100

  • administrators

    If you send these commands manually:

    G1 X30 Y27.6 F6000

    does it work?

  • Nope the LED turns on on the sensor and it just continues to press towards the bed.

    Here is a copy of my config.g

    And here is the Duet version:

    Firmware Name:	RepRapFirmware for Duet WiFi
    Firmware Electronics:	Duet WiFi 1.0
    Firmware Version:	1.19.2 (2017-09-01)
    WiFi Server Version:	1.19.2
    Web Interface Version:	1.19

  • administrators

    Sounds like a configuration or wiring problem then. Duet Web Control displays the Z probe reading on the Control and Print Status pages. The reading should rise to about 535 when you hold a target close to the underside of the sensor so that the LED illuminates. Please check this. Also please post your config.g file.

  • I linked the config.g up above:

    I do get the correct readings but for some reason when it goes to actually probe it ignores the signal.

    I did the following:

    G92 Z0
    G30 S-1

    Then took the reading and used the value for the Z parameter in G31 command in config.g

  • Not sure if it makes a difference but I have a black heater bed with a 6mm glass plate on top, but as mentioned the G30 S-1 command worked fine.

  • administrators

    Just to be clear: are you saying that if you position the head about 5mm above the bed and run G30 S-1 then the probe stops when the LED comes on; but if you position the head 5mm above the same point and send G30 without the S-1 then it doesn't stop? Please check this.

  • So I just did a test because nothing was working again even with S-1.
    If I lay a piece of paper on the glass, then it probes every time no problem, it isn't probing to the exact same spot it's quite a bit above the paper but the probe stops every time without crashing.

    Which is weird because I see the numbers go 464 and then 538 with only the glass bed but it wont stop. Where as with the paper it does the same thing but it stops.

  • I wanted to piggyback onto this as i have the same issue. (DuetWIFI coreXY build with IR probe, X and Y endstops are on high ends of build plate i.e 300, 290)

    I was running 1.19 and was having connectivity issues to the webcontrol UI, but no issues with homing.

    I updated just the other day to 1.20, and when i ran homeall, x and y homed, then z crashed to the bed.

    So i recalibrated my z probe per the wordpress article, and the z probe was triggering as expected at the same value i had set before in G31. I tested G30 S-1, AND G30 both probed the bed and stopped before a crash.

    My thought is that in the release notes there was mention of adding S2 to the M574 section, but doing that just caused the x and y to crash, never getting to Z.

    Below is my config.g and homeall.g files, maybe someone can shed some light on this for me.


    ; Configuration file for testing Duet Ethernet and Wifi

    ; Communication and general
    M111 S0 ; Debug off
    M550 PHC300 ; Machine name and Netbios name (can be anything you like)
    M551 Pcheats5 ; Machine password (used for FTP)
    ;*** If you have more than one Duet on your network, they must all have different MAC addresses, so change the last digits
    M540 P0xBE:0xEF:0xDE:0xAD:0xFE:0xED ; MAC Address

    ;*** Networking - Enable for both WiFi and Ethernet boards.
    M552 S1 ; Turn network on

    ;*** Ethernet networking: Adjust the IP address and gateway in the following 2 lines to suit your network
    M552 P10.10.10.250 ; (0 = DHCP)
    M554 P10.10.10.1 ; Gateway
    M553 P255.255.255.0 ; Netmask

    M555 P2 ; Set output to look like Marlin
    G21 ; Work in millimetres
    G90 ; Send absolute coordinates...
    M83 ; ...but relative extruder moves

    ; Disable Fan 1 thermostatic mode
    M106 P1 H-1

    ; Axis and motor configuration
    M569 P0 S0 ; Drive 0 goes forwards
    M569 P1 S0 ; Drive 1 goes forwards
    M569 P2 S1 ; Drive 2 goes forwards
    M569 P3 S1 ; Drive 3 goes forwards
    M569 P4 S1 ; Drive 4 goes forwards
    M574 X2 Y2 Z0 S0 ; set endstop configuration (all endstops at high end, active high)
    ;*** The homed height is deliberately set too high in the following - you will adjust it during calibration
    M667 S1 ; switch to CoreXY mode
    M208 X0 Y0 Z0 S1 ; Set axis minima
    M208 X290 Y240 Z270 S0 ; Set axis maxima
    M666 X0 Y0 Z0 ; put your endstop adjustments here, or let auto calibration find them
    M350 X16 Y16 Z16 E16:16 I1 ; Set 16x microstepping with interpolation
    M92 X80 Y80 Z400 ; Set axis steps/mm
    M906 X500 Y500 Z500 E1120 I40 ; Set motor currents (mA) and increase idle current to 40%
    M201 X1500 Y1500 Z1000 E1000 ; Accelerations (mm/s^2)
    M203 X1000 Y1000 Z200 E3600 ; Maximum speeds (mm/min)
    M566 X1200 Y1200 Z1200 E1200 ; Maximum instant speed changes mm/minute

    ; Thermistors
    M305 P0 T100000 B3950 R4700 H30 L0 ; Put your own H and/or L values here to set the bed thermistor ADC correction
    M305 P1 T100000 B3974 R4700 H30 L0 ; Put your own H and/or L values here to set first nozzle thermistor ADC correction
    M305 P2 T100000 B3974 R4700 H30 L0 ; Put your own H and/or L values here to set 2nd nozzle thermistor ADC correction

    M570 S180 ; Hot end may be a little slow to heat up so allow it 180 seconds

    ; Adjustments for J-heads used as dummy heaters on test rig
    M307 H0 A250 C140 D5.5 B1
    M307 H1 A250 C140 D5.5 B0
    M307 H2 A250 C140 D5.5 B0

    M557 X0:250 Y0:225 S25 ;mesh grid probe pattern

    ; Fans
    M106 P1 S-1 ; disable thermostatic mode for fan 1

    ; Tool definitions
    M563 P0 D0 H1 ; Define tool 0
    G10 P0 S0 R0 ; Set tool 0 operating and standby temperatures
    ;*** If you have a single-nozzle build, comment the next 2 lines
    ;M563 P1 D1 H2 ; Define tool 1
    ;G10 P1 S0 R0 ; Set tool 1 operating and standby temperatures
    M92 E837:837 ; Set extruder steps per mm
    M143 H1 S290 ;set max hot end temp
    M307 H1 A576.4 C196.8 D6 B0 S1 ;Set PID values for hot end
    M143 H0 S125 ;set max bed temp
    M307 H0 A146.6 C693.4 D9 B0 S1 ;Set PID values for Bed Heater

    ; Z probe and compensation definition
    ;*** If you have a switch instead of an IR probe, change P1 to P4 in the following M558 command
    M558 P1 X0 Y0 Z1 ; Z probe is an IR probe and is used for homing Z axis
    G31 Z1.5 P500 ; Set the zprobe height and threshold (put your own values here)

    ;*** If you are using axis compensation, put the figures in the following command
    M556 S78 X0 Y0 Z0 ; Axis compensation here

    ;M208 S1 Z-1.95 ; set minimum Z

    T0 ; select first hot end


    G91 ; relative mode
    G1 S1 X340 Y340 F3000 ; course home X or Y
    G1 S1 X340 ; course home X
    G1 S1 Y340 ; course home Y
    G1 X-4 Y-4 F600 ; move away from the endstops
    G1 S1 X10 ; fine home X
    G1 S1 Y10 ; fine home Y
    ; Z homing section follows for IR Z probe
    G1 X-30 F3000 ; X offset to get z probe to bed
    G1 S1 Z-400 F500 ; course home Z
    G1 Z2 F500 ; move away from the Z Probe
    G1 S1 Z-4 F100 ; fine home Z
    G90 ;back to absolute mode
    G92 Z1.5 ;tell printer that it is at Z=1.5 (trigger height of z probe during homing)


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