Filament Extruding During Preheat
 
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kevin.c5
(@kevin-c5)
New Member
Filament Extruding During Preheat

I have a issue with filament coming out of the nozzle well before even the calibration starts. This can cause major issues if any remains are not removed before the actual print starts.

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Posted : 27/02/2017 4:45 am
johnny.g
(@johnny-g)
Active Member
Re: Filament Extruding During Preheat

mine too... but if I do a quick skirt.. no problems

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Posted : 27/02/2017 4:53 am
kevin.c5
(@kevin-c5)
New Member
Topic starter answered:
Re: Filament Extruding During Preheat

The problem is sometimes it curls back on itself while doing the calibration before a print.

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Posted : 27/02/2017 5:11 am
cristian.s
(@cristian-s)
Trusted Member
Re: Filament Extruding During Preheat

I have this problem as well.
It also adds blobs of material on the bed during calibration.

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Posted : 27/02/2017 8:01 am
mavu
 mavu
(@mavu)
Estimable Member
Re: Filament Extruding During Preheat

Every printer I know does this, its because the plastic melts and then gravity raises its ugly head, and it oozes out.

you could maybe reduce the effect if you do a retract in the end-gcode of you prints, but I'm not sure thats a smart idea.

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Posted : 27/02/2017 8:43 am
JeffJordan
(@jeffjordan)
Moderator
Re: Filament Extruding During Preheat

➡ that's a quite normal behaviour, usually i "park" the extruder before every print at a decent height so that i can remove the filament with the tweezers when it starts printing.
💡 and yes, sometimes (during the 9 point calibration before each print) the nozzle leaves some remainders at the printing surface... which i immediately remove with the tweezers, at least in the areas that are used for the started print.

❗ if you've got hygroscopic filament (like nylon) and it has collected some moisture, the effect is even more nasty 👿 .
the "boiling" moisture inside the filament really increases the oozing out of the nozzle of the filament.
if it's really moist, you'll even hear some crackeling noise out of the hotend (like fried fish fingers in a hot pan 😕 ).
💡 so dry your hygroscopic filament in the oven before printing !

➡ to avoid that filament which oozes out of the nozzle curls back and sticks to the nozzle, you can use so called "silicon socks". these "socks" cover the whole heater block and leave only a little hole for the tip of the nozzle. so if something curls back, it will touch the silicone instead of the brass nozzle and won't stick at it.... at least that's the idea behind the concept.

dem inscheniör is' nix zu schwör......
Posted : 27/02/2017 9:03 am
patrick.s13
(@patrick-s13)
Eminent Member
Re: Filament Extruding During Preheat

I added 40mm retract to my ending gcode. This helps greatly ! You just have to remember to add that 40mm extrude to whatever your current purge / extrude value is in your start gcode.

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Posted : 27/02/2017 12:27 pm
JeffJordan
(@jeffjordan)
Moderator
Re: Filament Extruding During Preheat

I added 40mm retract to my ending gcode. This helps greatly ! You just have to remember to add that 40mm extrude to whatever your current purge / extrude value is in your start gcode.

so in fact you unload the filament after each print.

dem inscheniör is' nix zu schwör......
Posted : 27/02/2017 12:35 pm
PJR
 PJR
(@pjr)
Moderator
Re: Filament Extruding During Preheat

Simplest method to prevent oozing on calibration - adjust the start GCode:

G21 ; set units to millimeters
G90 ; use absolute coordinates
M83 ; use relative distances for extrusion
M140 S<BED> ; Heat the bed
M104 S170 ; Heat Extruder
M190 S<BED> ; Heat the bed and wait
M109 S170 ; Heat extruder and wait
G28 W ; Home all Without calibration
M104 S<TEMP> ; Set extruder temperature to print temp
G80 ; 9-point calibration
M109 S<TEMP> ; Heat extruder to print temp and wait
G92 E0.0 ; Zero extruder
...

NOTE: the replacement codes <BED> and <TEMP> are used in KISS - you will have to replace those with whatever your slicer uses.

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…...
Posted : 27/02/2017 12:48 pm
Knickohr
(@knickohr)
Moderator
Re: Filament Extruding During Preheat

OK, this is the default start gcode from slic3r :
M115 U3.0.9 ; tell printer latest fw version
M83 ; extruder relative mode
M104 S[first_layer_temperature] ; set extruder temp
M140 S[first_layer_bed_temperature] ; set bed temp
M190 S[first_layer_bed_temperature] ; wait for bed temp
M109 S[first_layer_temperature] ; wait for extruder temp
G28 W ; home all without mesh bed level
G80 ; mesh bed leveling
G1 Y-3.0 F1000.0 ; go outside pritn area
G1 X60.0 E9.0 F1000.0 ; intro line
G1 X100.0 E12.5 F1000.0 ; intro line

I have to change it to :
M115 U3.0.9 ; tell printer latest fw version
G21 ; set units to millimeters
G90 ; use absolute coordinates
M83 ; extruder relative mode
M104 S170 ; Heat Extruder
M140 S[first_layer_bed_temperature] ; set bed temp
M190 S[first_layer_bed_temperature] ; wait for bed temp
M109 S170 ; Heat extruder and wait
G28 W ; Home all Without calibration
M104 S[first_layer_temperature] ; set extruder temp
G80 ; 9-point calibration
M109 S[first_layer_temperature] ; wait for extruder temp
G92 E0.0 ; Zero extruder[
G1 Y-3.0 F1000.0 ; go outside pritn area
G1 X60.0 E9.0 F1000.0 ; intro line
G1 X100.0 E12.5 F1000.0 ; intro line

Is this correct ?
But is this a bit better ? The last M104 moved after the G80
M115 U3.0.9 ; tell printer latest fw version
G21 ; set units to millimeters
G90 ; use absolute coordinates
M83 ; extruder relative mode
M104 S170 ; Heat Extruder
M140 S[first_layer_bed_temperature] ; set bed temp
M190 S[first_layer_bed_temperature] ; wait for bed temp
M109 S170 ; Heat extruder and wait
G28 W ; Home all Without calibration
G80 ; 9-point calibration
M104 S[first_layer_temperature] ; set extruder temp
M109 S[first_layer_temperature] ; wait for extruder temp
G92 E0.0 ; Zero extruder
G1 Y-3.0 F1000.0 ; go outside pritn area
G1 X60.0 E9.0 F1000.0 ; intro line
G1 X100.0 E12.5 F1000.0 ; intro line

Thomas

Posted : 27/02/2017 3:23 pm
PJR
 PJR
(@pjr)
Moderator
Re: Filament Extruding During Preheat

Thomas

I have my GCode as it is for a reason...

Tht extruder can start to heat during the 9-point calibration; starting the calibration at 170 and increasing to 185 (or thereabouts) does not allow the filament to ooze and saves a few seconds heating time.

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…...
Posted : 27/02/2017 3:54 pm
Knickohr
(@knickohr)
Moderator
Re: Filament Extruding During Preheat

Ahhh, OK.

Thanks Peter.

Thomas

Posted : 27/02/2017 7:35 pm
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