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When I'm auto-leveling my Anet A8 with Marlin firmware, the nozzle heats to 195°C during the leveling process, which leaves drops of filament. I checked the resulting G-code but makes no sense to me:

M107 M190 S55 ; set bed temperature and wait for it to be reached M117 Homing Axes G28 ; Home axis M117 Autoleveling G29 M117 Cleaning Nozzle ; Indicate nozzle clean in progress on LCD M109 S200 ; Uncomment to set your own temp run warmer to clean out nozzle M107 ; Turn layer fan off G21 ; Set to metric change to G20 if you want Imperial G90 ; Force coordinates to be absolute relative to the origin G0 X10 Y0 Z0.15 F9000 ; Move in 1mm from edge and up z 0.15mm G92 E0 ; Set extruder to 0 zero G1 Y190 E50 F500 ; Extrude 100mm filiment along Y axis 190mm long to prime and clean the nozzle G92 E0 ; Reset extruder to 0 zero end of cleaning run G1 E-3 F500 ; Retract filiment by 3 mm to reduce string effect G1 X3 Y190 Z15 F9000 ; Move over and rise to safe Z height G1 X3 Y0 Z15 F9000 ; Move back to front of bed at safe Z height to shear strings 

My printer heats the bed, then homes axes while setting the nozzle temperature to 195°C.

Then autolevels and finally M109 S200 does its job.

How can I prevent the nozzle from heating when there is no G-code for it (except the M109 S200)?

1 Answer 1

I am using CURA as my slicer, and it sets the bed and nozzle temp before printer start code is executed. You can easily check that by opening a file in a notepad and see, that there will be a few lines describing the job, nozzle and bed setting temperature and the user code that is inserted in printer properties screen.

To change that behavior - you need to open the file and move the M commands down after leveling is executed.

;FLAVOR:Marlin ;TIME:45 ;Filament used: 0.0187665m ;Layer height: 0.2 ;Generated with Cura_SteamEngine 3.3.1 M190 S60 M104 S200 M109 S200M82 ;absolute extrusion mode 

lines above are added by slicer so temperature is set before instritions from START G-Code section:

G21 ;metric values G90 ;absolute positioning M82 ;set extruder to absolute mode M107 ;start with the fan off G28; G92 E0 ;zero the extruded length G1 F20 E3 ;extrude 3mm of feed stock G92 E0 ;zero the extruded length again 

user start g-code screen