3D Print Stops When Cooling Switched On

[milnei 0]

Hope someone can help with this.....

 

When I turn on cooling in Cura, my print stops after approximately 1 minute.  For example I have a print roughly 15cm by 6cm in ABS with a 15mm brim and it only does around 3 laps of the brim and the printer stops.  The printer just hangs and I cannot stop or pause the print.  The only way to get control is to turn the printer off and on again!  When I turn cooling off the print runs fine.

 

I also have a minimum layer time but that just gets ignored too.

 

My printer is an Anycubic i3 Mega, and I'm using the latest Cura version.

 

Cura print and printer profiles attached

 

Start G-code

G21 ;metric values

G90 ;absolute positioning

M82 ;set extruder to absolute mode

M107 ;start with the fan off

G28 X0 Y0 ;move X/Y to min endstops

G28 Z0 ;move Z to min endstops

;G29

G1 Z15.0 F600 ;move the platform down 15mm

G92 E0 ;zero the extruded length

G1 F200 E5 ;extrude 3mm of feed stock

G92 E0 ;zero the extruded length again

G1 F{speed_travel}

M117 Printing...

G5

 

End G-code

M104 S0 ; turn off extruder

M140 S0 ; turn off bed

M84 ; disable motors

M107

G91 ;relative positioning

G1 E-1 F300 ;retract the filament a bit before lifting the nozzle, to release some of the pressure

G1 Z+0.5 E-5 ;X-20 Y-20 F{speed_travel} ;move Z up a bit and retract filament even more

G28 X0 ;Y0 ;move X/Y to min endstops, so the head is out of the way

G1 Y180 F2000

M84 ;steppers off

G90

M300 P300 S4000

[GregValiant 1,245]

Post your gcode print file that is stopping.  (Did you notice if the hot end shut off?)

 

The start and end gcodes for the Anycubic printers are a bit odd.  I would change the startup gcode to this:

;      StartUp Gcode

G21 ;metric values

G90 ;absolute positioning

M82 ;absolute extrusion

M106 S0 ;cooling fan off

M140 S{material_bed_temperature_layer_0} ;Start to heat the bed

M104 S{material_print_temperature_layer_0} ;Start to heat the hot end

M190 S{material_bed_temperature_layer_0} ;Wait for the bed

M109 S{material_print_temperature_layer_0} ;Wait for the hot end

G28 ;Auto-Home X Y Z

;G29 ;No ABL

G1 Z15.0 F600 ;move the platform down 15mm

G92 E0 ;zero the extruded length

G1 F200 E5 ;extrude 3mm of feed stock

G92 E0 ;zero the extruded length again

M117 Printing...

;     End of StartUp Gcode

I would change the Ending Gcode to this:

;      Ending Gcode

G91 ;relative positioning

M83 ;relative extrusion

G1 E-1 F600 ;retract the filament a bit before lifting the nozzle, to release some of the pressure

G1 Z0.5 E-5 ;move Z up a bit and retract filament even more

G1 X5 Y5 F3000 ;Wipeout move

G1 Z5 F600 ;move the nozzle up from the print

G1 X0 Y{machine_depth} F6000 ;Move the nozzle to the left rear

M106 S0 ;Turn off the layer cooling fan

M104 S0 ; turn off extruder

M140 S0 ; turn off bed

M84  X Y E ;steppers off except Z

G90 ;absolute positioning

M82 ;absolute extrusion

M300 P300 S4000 ;Beep

;     End of Ending Gcode

 

I see in the definition file for you printer that the last line of the StartUp Gcode is indeed "G5".  MarlinFW lists that command as "Bezier Curve".  Since your printer has Marlin firmware I'm thinking that command doesn't belong in there.  You can always add it again if there is a problem with the above StartUp code.

[milnei 0]

Hi Greg.  I think I've discovered what my issue is.  The cooling fan is cooling the nozzle down too much, and that stops the print since the heater cannot get the nozzle back to 250°.  I did wonder why it had got further inside my enclosure before stopping instead of the making one lap and stopping now I've opened the enclosure door........

 

The reason I want cooling on is that I get awfully lumpy ABS prints when making a large surface area part and the nozzle ends up dragging across the surface and has caused layer shifts where the belts has jumped when the nozzle can't get past.

 

But now I'm thinking cooling won't help since the previous layers are already hard enough to make the nozzle bump along.

 

I've replaced my start and end gcode with yours and will try pulling back on the flow rate compensator to see if that helps with the lumpy top surface issues.....

[GregValiant 1,245]

Top surfaces (the skins) are the best visual indicators of flow accuracy.  I happen to have a microscope I picked up at a garage sale and it was really helpful when I was starting out.  A decent magnifying glass is an acceptable alternative.  When you can actually see gaps or ridges between the lines of extrusion then you know for sure if you are over or under extruding, and when it's just right.

That "G5" command that your printer definition file adds to the end of your startup gcode is very odd.  There have been a lot of posts here by AnyCubic users and I don't recall it being mentioned before.  

 

It's hard to believe that the layer cooling fan has that much effect on the hot end.  Maybe you need to do a PID Auto-Tune on the hot end.  You would need something like Pronterface/Printrun to send the command and view the results.  The command is M303.  Something like M303 C8 S250 would work.

Edited June 21, 2022 by GregValiant