After printing, Nozzle parked in top of tall print melting it

Bambu Lab X1 Series
1

I had a print going overnight, and in the morning went to remove the print and found it was stuck to the print nozzle. I checked the video recording and found that the print had completed to its full height 249.9mm, the filament was cut and retracted, then the bed was raised a couple of mm and the nozzle was parked right on the print melting a 2.5mm notch in the top of the print. I use the included Bambu Lab X1 Carbon 0.4 nozzle printer profile.
I had printed 250mm tall prints before, but this is the first one that has a wall at the back middle of the print area. I did not expect to have an issue printing 249.9mm at least that is what Bambu slicer V 1.8.4.51 print preview shows as the height of my model.
I took a look at the G-code in the Bambu Lab X1 Carbon 0.4 nozzle printer profile and it looks like the printer did exactly what the Machine G-code told it to do, after “lower z motor current to reduce impact in case something in the bottom” it set the z height to 250, then is raised the z height to 248, then it moved the print head to X128 Y250 putting it right into the top of the print.
Looks like the X1 Carbon printer needs an update to its profile to not ram the nozzle into the print if the print includes the part of the build volume where the print head is parked or maybe don’t park the head inside the print volume.

2

At 249.9mm you should have been (just barely) OK, but before trying that print again, I think I’d adjust the printable height in the printer settings.

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image758Ă—248 11.4 KB

Save the change as a Preset Inside Project and save the 3mf so that the change will be automatic for that project without affecting your normal print profiles.

3

You will need to manually comment out the “G1 Z248” in the “Machine end G-code” as this isn’t controlled by the “Printable Height” parameter.

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5

Thank you for pointing this out and sorry you lost your part. I just looked at the end g-code and changed my end g-code to this. You can see the changes in the preview screen and show travel.

text edit had to delete first post to fix

;===== End G-code park off bed plate and disable 248 z drop
;===== 3DTech V1 ======================================  
;===== BBL date: 20230428 =============================
M400 ; wait for buffer to clear
G92 E0 ; zero the extruder
G1 E-0.8 F1800 ; retract
G1 Z{max_layer_z + 0.5} F900 ; lower z a little
G1 X65 Y245 F12000 ; move to safe pos 
G1 Y265 F3000

G1 X65 Y245 F12000 ; Y pull back 
G1 Y265 F3000
M140 S0 ; turn off bed
M106 S0 ; turn off fan
M106 P2 S0 ; turn off aux cooling fan
M106 P3 S0 ; turn off chamber cooling fan

G1 X100 F12000 ; wipe
; pull back filament to AMS
M620 S255
G1 X20 Y50 F12000
G1 Y-3
T255
G1 X65 F12000
G1 Y265
G1 X100 F12000 ; wipe
M621 S255
M104 S0 ; turn off hotend

M622.1 S1 ; for prev firmware, default turned on
M1002 judge_flag timelapse_record_flag
M622 J1
    M400 ; wait all motion done
    M991 S0 P-1 ;end smooth timelapse at safe pos
    M400 S3 ;wait for last picture to be taken
M623; end of "timelapse_record_flag"

M400 ; wait all motion done
M17 S
M17 Z0.4 ; lower z motor current to reduce impact if there is something in the bottom
{if (max_layer_z + 100.0) < 250}
    G1 Z{max_layer_z + 100.0} F600
    G1 Z{max_layer_z +98.0}
{else}
    G1 Z250 F600
;    G1 Z248 ; disable 248 z drop
{endif}
M400 P100
M17 R ; restore z current

G90
;G1 X128 Y250 F3600 ; park on bed plate disabled
G1 X54 F6000 ; Slow wipe and park in purge zone enabled

M220 S100  ; Reset feedrate magnitude
M201.2 K1.0 ; Reset acc magnitude
M73.2   R1.0 ;Reset left time magnitude
M1002 set_gcode_claim_speed_level : 0

M17 X0.8 Y0.8 Z0.5 ; lower motor current to 45% power
1 Like
6

If I find some time later on, I’m going to submit a Github bug report (or something), because the Wiki leads us to believe that editing g-code should not be necessary.

I followed the wiki instructions to set up a simple square vase 252 mm high with printable height setting of 255mm and Z hop when retract of 0.4mm (under 256mm total). The g-code did in fact still include the G1 Z248 command.

1 Like
7

Thank you 3DTech and lkraus, I will create a new printer profile for tall prints and comment out the park on build plate and z height change instructions. I wanted to let others know of this issue, maybe the default profile could be updated so that others don’t have the issue.
I was lucky that I was able to modify the connecting part to cover the melted bit so my 10 hours of print time and 500 g of filament did not go to waste.

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