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Extruding too much filament before printing?  

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paul.a13
(@paul-a13)
Eminent Member
Extruding too much filament before printing?

Hey, I just got my replacement hot end today and have installed it and started printing (my Mk3 arrived at the start of last week but after a few days I had some issues, got careless, and damaged the hot end). I've run through the pre-flight test and Z-Axis calibration. All good. I calibrated the extruder, found out it was under-extruding just a little, so adjusted the steps per mm accordingly.

However, I have a problem. When I start a print, and the nozzle preheats, I end up with excess filament coiling out. When it goes to find the 9 calibration points I often get the "Debris on nozzle" error and have to reset and clean it. This happens most of the time at the moment. If I raise the Z-axis up and just hit 'Preheat', I get an endless string of filament oozing out. I talked to Prusa support, but they said this was normal. It definitely is not. Even when I get past the calibration stage, the excess filament around the nozzle means the first layer usually fails by getting caught on it.

Any suggestions? Is my temp too high (Prusa PLA, using default settings of 215 first layer, 210 afterwards)? Could my extruder be too loose?

Postato : 13/07/2018 8:14 am
Martin Wolfe
(@martin-wolfe)
Reputable Member
Re: Extruding too much filament before printing?

See my no ooze mesh bed levelling thread.

Here is my current form of the printer start G-Code
M115 U3.2.1 ; tell printer latest fw version
M201 X1000 Y1000 Z1000 E9000 ; sets maximum accelerations, mm/sec^2
M203 X200 Y200 Z12 E120 ; sets maximum feedrates, mm/sec
M204 S1250 T1250 ; sets acceleration (S) and retract acceleration (T)
M205 X8 Y8 Z0.4 E1.5 ; sets the jerk limits, mm/sec
M205 S0 T0 ; sets the minimum extruding and travel feed rate, mm/sec
M83 ; extruder relative mode

M104 S160 ; set extruder temp
M140 S[first_layer_bed_temperature] ; set bed temp
M190 S[first_layer_bed_temperature] ; wait for bed temp
M109 S160 ; wait for extruder temp
G28 W ; home all without mesh bed level
G80 ; mesh bed leveling
G1 Z35.0 ; Move up before heating to temp
G1 Y-3.0 F1000.0 ; go outside print area
M104 S[first_layer_temperature] ; set extruder temp
M109 S[first_layer_temperature] ; wait for extruder temp
G1 Z{first_layer_height + z_offset} ; Lower to print first layer

G92 E0.0
G1 X60.0 E9.0 F1000.0 ; intro line
G1 X100.0 E12.5 F1000.0 ; intro line
G92 E0.0
M221 S{if layer_height==0.05}100{else}95{endif}

Regards,
Martin

Martin Wolfe

Postato : 13/07/2018 9:14 am
paul.a13
(@paul-a13)
Eminent Member
Topic starter answered:
Re: Extruding too much filament before printing?

Thanks for the response Martin. One quick question though - should your code replace the existing code in Slic3r, or should it be added alongside it? I'm assuming it should replace it, but I want to be sure.

EDIT: Yes, it has to replace the original G-code. It has resolved that problem. Now to solve the rest of the problems!

Postato : 13/07/2018 10:51 am
Martin Wolfe
(@martin-wolfe)
Reputable Member
Re: Extruding too much filament before printing?

Glad I could be of help.

Regards,
Martin

Martin Wolfe

Postato : 13/07/2018 2:14 pm
Nessuno0505
(@nessuno0505)
Trusted Member
Re: Extruding too much filament before printing?

I have the same problem (see my post) but I can't understand how you solved it. What is the original g-code? You deal with slic3r, but I have that excess of filament coiling out even if I print sd card preloaded models, even without connecting the printer to the PC. Can you tell me what to do exactly, please?

Edit: ok, I've understood the changes you did in slic3r: you keep the extruder temp at 160 while you do preliminary 9 points, then you heat it to target temperature after those steps, in order to minimize coiling. But if I modify my g-code in slic3r, then how I write it on the printer firmware? And is it valid for all the presets, or just for pla prints? Is not 160 too low for a PETG or ABS loaded filament? Do that types of plastic not coil?

Postato : 17/10/2018 9:05 pm
wcndave
(@wcndave)
Trusted Member
Re: Extruding too much filament before printing?

I have just discovered and understood this too. Although it feels like the pre-print routine is a printer firmware setting, it's not.

The gcode has the "directions" for how to draw, but also the pre-draw, as different models will require different temps, or different acceleration/ speed, etc..

Therefore this code is put into your slicer, and is included with every gcode, which is what you put on the SD card and print.

However, just using the old code someone's posted here is probably not as good as modifying your own existing code.

I'm going to comment on that on the other thread.

Postato : 25/11/2018 1:43 pm
Martin Wolfe
(@martin-wolfe)
Reputable Member
Re: Extruding too much filament before printing?

@david.m86 I agree with you the code I pasted needs changing. Prusa themselves have updated part printer start G-Code since I made my last post and as a result I incorporated their changes. Also I have since changed to a volcano heater block and so my maximum feed rates are different.

My code should only be used for hints. It's main trick is to do a partial heating on the extruder before the mesh bed levelling. That is the critical part of the code. In the code I posted the partial extruder temperature is 160°C.

Regards,
Martin

Martin Wolfe

Postato : 26/11/2018 9:38 am
Andy
 Andy
(@andy-20)
New Member
RE: Extruding too much filament before printing?

@martin-w15

I am new to this where do you copy and paste the g code to in slicer? And do you need to do it every time or does slyer save the g- code 

Postato : 09/10/2020 5:13 pm
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(@)
Illustrious Member
RE: Extruding too much filament before printing?

Printer settings, in the custom gcode, startup. You change the code once, then save it as a new printer profile. Then after you select that profile, PSlicer generally remembers the printer you've selected.

 

And you need to have EXPERT selected.

Questo post è stato modificato 4 years fa da --
Postato : 09/10/2020 6:48 pm
Andy
 Andy
(@andy-20)
New Member
RE: Extruding too much filament before printing?

@tim-m30

You type all three pages of code into that section you talked about.  In the exact order you have it from top to bottom and that will hopefully solve my extruder from having filament come out while it is warming up? 

Postato : 10/10/2020 12:14 am
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(@)
Illustrious Member
RE: Extruding too much filament before printing?

@syqraz

No - the above is partial. Here's my complete startup gcode (copy paste works) -- BUT: this is for a Prusa MK3, not the MK3S.  There could be minor differences - but it should be okay. 

Known issues are:

1) your M115 line should match whatever you are using today.
2) my scribble purge may not work well for you
3) it slows down prints, sometimes a lot, but worth the extra time, IMHO
4) seasonal changes in room temperature affect the time it takes: I change the set point based on where I keep my house set.

M115 U3.7.1 ; tell printer latest fw version
G90 ; use absolute coordinates
M83 ; extruder relative mode

; cool down PINDA
M106 S255 ; turn on fan
M104 S0 ; turn off nozzle heat
M140 S0 ; turn off bed heat
M860 S35 ; wait until PINDA is less than 35C
M106 S0 ; turn off fan

; preheat nozzle to a low temp, get plastic mushy before driving into the bed with G28
M140 S[first_layer_bed_temperature] ; set bed temp
M109 S175 ; wait for extruder temp
M190 S[first_layer_bed_temperature] ; set & wait for bed temp
G28 W ; home all without mesh bed level

; soak PINDA then level
G0 X50 Y50 Z1 F3000; this is a good PINDA heating position
M860 S37.5 ; wait until PINDA is >= 35C in winter, 37.5C spring/fall, 40C summer
G80 N7 R5; mesh bed leveling

; heat to extrude temp
G0 X0 Y-3.0 Z10 F3000; this is a good nozzle heating position
M109 S[first_layer_temperature] ; set & wait extruder temp

; purge
G1 Y-3.0 Z0.20 F1000.0 ; go outside print area
G92 E0.0
G1 X1.0 Y-1.0 E0.5 F500.0 ; scribble 1
G1 X1.0 Y-3.0 E0.5 F500.0 ; scribble 1
G1 X2.0 Y-1.0 E0.5 F500.0 ; scribble 2
G1 X2.0 Y-3.0 E0.5 F500.0 ; scribble 2
G1 X3.0 Y-1.0 E0.5 F500.0 ; scribble 3
G1 X3.0 Y-3.0 E0.5 F500.0 ; scribble 3
G1 X60.0 E9.0 F1000.0 ; intro line
G1 X100.0 E12.0 F1200.0 ; intro line
G1 X97.0 F2000.0 ; wipe left
G1 X105.0 F3000.0 ; wipe right
G92 E0.0

M221 S{if layer_height<0.075}100{else}95{endif}

; end Printer Start gcode

Postato : 10/10/2020 3:45 am
Andy
 Andy
(@andy-20)
New Member
RE: Extruding too much filament before printing?

@tim-m30

Thanks 

Postato : 10/10/2020 5:22 am
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