@phaedrux said in Duet Wifi - G29 causes extremely rapid Z movement and head crash:

Are you running a G30 before doing G29?

Bingo. That fixed it.
Thanks for the help. Got a new heightmap generated and printing away.

@veti said in Duet Wifi - G29 causes extremely rapid Z movement and head crash:

@lowracer said in Duet Wifi - G29 causes extremely rapid Z movement and head crash:

G1 S1 Z250 F7000 ; move Z towards the switch until it triggers

you move your bed up by 250mm? why

Thanks for the response.

Original Ultimaker 2+ (UM2+) behavior (no BLTouch) has the bed "zero" to the bottom of the case before printing and after print is completed. Moving it 250 sends down it to where it will trip the Z endstop at the bottom of the cage.

;G30 ; home Z by probing the bed

you disabled your probing of the bed. so no wonder the probe is not deploying.

The problem described in the original post occurs when issuing a G29 command from the web interface. I was not aware these homing scripts get called by the G29 command.

I commented out that G30 because I do not want "homing" behavior to include probing the bed. I have that done in the startup script in the GCODE of the file being printed, e.g.:

G28 XY ;Home XY
M561 ; Clear any bed transform that might be in place
G1 X104.5 Y130 ; Move Probe to middle of bed
G30 ; Do a single probe
G29 S1; load heightmap
G1 Z20.0 F6000 ; Move Z to 20

Flashed firmware up to 2.03RC1, G29 still exhibits the same behavior. Here are the homing files as requested:

; homex.g
; called to home the X axis
;
; generated by RepRapFirmware Configuration Tool on Fri Mar 15 2019 21:53:32 GMT-0700 (Pacific Daylight Time)
G91 ; relative positioning
;G1 Z5 F6000 S2 ; lift Z relative to current position
G1 S1 X-228 F9200 ; move quickly to X axis endstop and stop there (first pass)
G1 X5 F6000 ; go back a few mm
G1 S1 X-228 F360 ; move slowly to X axis endstop once more (second pass)
;G1 Z-5 F6000 S2 ; lower Z again
G90 ; absolute positioning

; homey.g
; called to home the Y axis
;
; generated by RepRapFirmware Configuration Tool on Fri Mar 15 2019 21:53:29 GMT-0700 (Pacific Daylight Time)
G91 ; relative positioning
;G1 Z5 F6000 S2 ; lift Z relative to current position
G1 S1 Y228 F9200 ; move quickly to Y axis endstop and stop there (first pass)
G1 Y-5 F6000 ; go back a few mm
G1 S1 Y228 F360 ; move slowly to Y axis endstop once more (second pass)
;G1 Z-5 F6000 S2 ; lower Z again
G90 ; absolute positioning

;homez.g
G91 ; relative mode
G1 S1 Z210 F7000 ; move Z towards the switch until it triggers
;G1 S2 Z-5 F100 ; move Z back 5mm
;G1 S1 Z10 F100 ; move Z slowly towards the switch until it triggers
G90 ; back to absolute mode

; homeall.g
; called to home all axes

;home Z to max extent (bottom of enclosure) first
G91 ; relative mode

G1 S1 Z250 F7000 ; move Z towards the switch until it triggers
;G1 S2 Z-5 F100 ; move Z back 5mm
;G1 S1 Z10 F100 ; move Z slowly towards the switch until it triggers

G1 S1 X-228 Y228 F9000 ; move quickly to X and Y axis endstops and stop there (first pass) (was F1800)
G1 X5 Y-5 F7200 ; go back a few mm
G1 S1 X-228 Y228 F360 ; move slowly to X and Y axis endstops once more (second pass)
G90 ; absolute positioning
G1 X110 Y110 F7200 ; go to first probe point (approx center of bed)

;G30 ; home Z by probing the bed

; Uncomment the following lines to lift Z after probing
;G91 ; relative positioning
;G1 S2 Z5 F100 ; lift Z relative to current position
;G90 ; absolute positioning

Here's a dropbox link to the video of the G29 operation in action (7.78MB .mp4):

https://www.dropbox.com/s/u8qfz1u7khgt8f5/G29 UM2%2B Duet Wifi.mp4?dl=0

Reflashing firmware did not fix the problem, unfortunately.

I'm suspecting something scrozzled the firmware. Will try re-flashing new firmware tonight to see if that fixes it.

Those linked tests work, M401 & M402 behave as expected, G30 properly extends the probe, raises the bed slowly and detects the bed with the probe, then stops.

To clarify, this printer is working and has been working very well to make prints, always using BLTouch probe before printing. It's just that the G29 is behaving oddly. And it hasn't always been this way because I'm using G29 S1 in the startup GCODE of each print to load up a heightmap generated from a previous G29 some time ago.

Thanks for the tips. I re-tried the G29 with the speed and probing settings suggested. Now it goes slowly enough that I can see more detail of what is happening.

During the slow rising of the bed, the BLTouch lights up red and is not extending its metal probe as it usually does at the beginning of a print.

Also, simultaneously with the Z axis motion, the Y axis is moving ever so slowly to the left.

Here is config.g: https://pastebin.com/p3RDx132

I'm running an Ultimaker 2+ upgraded to Duet Wifi and BLtouch Classic. G29 soon after install of the Duet board worked correctly and generated a heightmap which I've been using for some months now. Generated lots of good prints with no issues.

Recently, I decided to generate a new heightmap, but upon sending G29, this causes the bed to rise at a lightning fast pace until it impacts the hotend, at which point I feel compelled to do an Emergency Stop.

Any ideas what could be going on?

M115 reports: FIRMWARE_NAME: RepRapFirmware for Duet 2 WiFi/Ethernet FIRMWARE_VERSION: 2.02(RTOS) ELECTRONICS: Duet WiFi 1.02 or later FIRMWARE_DATE: 2018-12-24b1