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Preheat oozing, and wispy stringing  

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ChinookCrafts
(@chinookcrafts)
New Member
Preheat oozing, and wispy stringing

I am uncertain if the two issues are connected, but I figured I would mention them both. 

My mk3s+ (preassembled) is printing phenomenally, but I have experiencing two issues from the start. The first is an oozing of filament during PLA preheat, usually around 2" or so (215 degrees). This isn't a problem, but I do have to repeat the preheat step between every job or else it oozes during the 9 point calibration and gunks up the nozzle. 

The second issue is very thin cotton candy like wispy stringing between any parts that are separated by a small gap. It's quite excessive and occurs between multiple points on a single print, and between a single job with multiple prints. 

It may be worth mentioning that I also get tiny, tiny raised flicks on the top surface of irregular prints whenever the printer is done a layer. It may be a result of the same oozing problem though, as when a job is finished it does continue to ooze another inch or so over the next minute. 

Any insight would be welcome!

Posted : 09/06/2022 4:15 am
jsw
 jsw
(@jsw)
Famed Member
RE: Preheat oozing, and wispy stringing

Irregular prints and stringing are often due to damp filament.

The first thing I would do is dry the filament to be sure.

Posted : 09/06/2022 6:02 am
ChinookCrafts
(@chinookcrafts)
New Member
Topic starter answered:
RE: Preheat oozing, and wispy stringing

It's all factory. Brand new, upwards of ten or so stock rolls over the last 8 months.

Checking again this morning, I do get a tiny blob after the initial prime strip and wipe before it moves onto the skirt, so the oozing does seem to be consistent during the whole print, and is manifesting in the stringing due to the fast movement. 

Are there any settings that deal with ooze primarily? Perhaps it's attempting to relieve pressure? Flow rate, retraction? I am still new to this. 

Posted : 09/06/2022 3:15 pm
mpothmann
(@mpothmann)
Eminent Member
RE:

You can adjust the startcode in order to heat to let’s say 170c before 9 point calibration to prevent oozing and afterwards heating to print temperature 215 for pla.

for stringing, oozing, blob and so on… this sounds like overextrusion. Try calibrating flow.…. And dry the filament. 

This post was modified 4 months ago by mpothmann
Posted : 09/06/2022 7:02 pm
ChinookCrafts
(@chinookcrafts)
New Member
Topic starter answered:
RE: Preheat oozing, and wispy stringing

I will look into remedies for over-extrusion, but changing the pre-heat start code wouldn't accomplish much. The oozing occurs during the pre-heat process no matter when it occurs. At least if I use the preheat function before the job I can remove the oozing in a controlled way, rather than trying to snag the debris before it does the priming and skirt. 

Are there any recommended guides for adjusting Flow and/or Overextrusion?

Posted by: @mpothmann

You can adjust the startcode in order to heat to let’s say 170c before 9 point calibration to prevent oozing and afterwards heating to print temperature 215 for pla.

for stringing, oozing, blob and so on… this sounds like overextrusion. Try calibrating flow.…. And dry the filament. 

 

Posted : 09/06/2022 7:19 pm
hawai
(@hawai)
Reputable Member
RE: Preheat oozing, and wispy stringing

Do not easily dismiss the idea of tinkering with the start code. @bobstro, and I'm sure a few others wrote a modified startup routine that works quite well and addresses a few potential issues. I didn't bother to look for the original source atm but here is what I have in my modified startup code (thanks again @bobstro!):

 

; Last updated 20191117

M300 S40 P10 ; chirp

M862.3 P "[printer_model]" ; printer model check

M862.1 P[nozzle_diameter] ; nozzle diameter check

M115 U3.7.2 ; tell printer latest fw version

M117 Initializing; Set coordinate modes

G90 ; use absolute coordinates

M83 ; extruder relative mode

; Reset speed and extrusion rates

M200 D0 ; disable volumetric e

M220 S100 ; reset speed

M221 S{if layer_height >= 0.32}90{else}100{endif} ; compensate for thick layer heights

; Set initial warmup temps

M117 Nozzle preheat

M104 S160 ; set extruder no-ooze temp

M140 S{max(first_layer_bed_temperature[0],75)} ; set bed PINDA warmup temp

; Nozzle warmup before home to avoid driving hardened ooze into PEI surface

M109 S160 ; wait for extruder no-ooze warmup temp before mesh bed leveling, cool hot PINDA

M300 S40 P10 ; chirp; Home

M117 HomingG28 W ; home all without mesh bed level

; Present bed for final cleaning <- I removed the g-code for that one, originally it did a full outward y-axis move, chirped and waited for a few seconds before continuing

G0 Z3; Raise nozzle before move

G0 X125 Y180 F10200; Move nozzle to PINDA warming position

G0 Z0.15 F10200; Lower nozzle to PINDA warming position

; Wait for PINDA warmup

M117 PINDA warmup

M860 S35 ; wait for PINDA temp to stabilize

M140 S[first_layer_bed_temperature] ; set target bed temp

G0 Z3; Raise nozzle before move

M300 S40 P10 ; chirp

; Mesh bed leveling

M117 Mesh bed leveling

G80 ; mesh bed leveling

M117 Saving results

G81 ; save mesh leveling results

; Final warmup routine

M117 Final warmup

G0 Z5; Raise nozzle to avoid denting bed while nozzle heats

M140 S[first_layer_bed_temperature] ; set bed final temp

M104 S[first_layer_temperature] ; set extruder final temp

M109 S[first_layer_temperature] ; wait for extruder final temp

M190 S[first_layer_bed_temperature] ; wait for bed final temp

M300 S40 P10 ; chirp

; Prime line routine

M117 Printing prime line

G0 Z0.15 ; Restore nozzle position - (thanks tim.m30)

M900 K0; Disable Linear Advance for prime line

G92 E0.0 ; reset extrusion distance

G1 Y-3.0 F1000.0 ; go outside print area

G1 E2 F1000 ; de-retract and push ooze

G1 X20.0 E6 F1000.0 ; fat 20mm intro line @ 0.30

G1 X60.0 E3.2 F1000.0 ; thin +40mm intro line @ 0.08

G1 X100.0 E6 F1000.0 ; fat +40mm intro line @ 0.15

G1 E-0.8 F3000; retract to avoid stringing

G1 X99.5 E0 F1000.0 ; -0.5mm wipe action to avoid string

G1 X110.0 E0 F1000.0 ; +10mm intro line @ 0.00

G1 E0.6 F1500; de-retract

G92 E0.0 ; reset extrusion distance

; Final print adjustments

M117 Preparing to print

M300 S40 P10 ; chirp

M117 Print in progress

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

 

By doing the mesh bed levelling at a non ooze temp this avoids spreading blobs and droplets over the bed. Works really well and I hadn't any mesh bed levelling blobs since then. I don't know if the SuperPINDA is as sensitive to temperature changes as the PINDA on the Mk3S but it definitely won't hurt to have the build plate heated to a uniform temp before the mesh bed levelling.

 

Regarding the stringing I'm with @jsw. Depending on the brand and within some brands even on the production batch there are some moderately poor quality filaments out there. If you have access to a dehydrator it won't hurt to give it a go. There is also the option of printing a temp tower to find the right printing temp for your specific filament. Sometimes a few degrees make a significant difference. Also look at the extrusion multiplier setting, reducing it by a few percent might also help as well as the retraction settings. There are unfortunately many knobs you can and might need to turn to get it right.

 

It seems that so far I have been an extremely lucky bastard and most of the prints go well enough for my expectations or needs so that I hadn't to go through all this.

 

hat

Hansjoerg

Posted : 09/06/2022 10:16 pm
ChinookCrafts
(@chinookcrafts)
New Member
Topic starter answered:
RE: Preheat oozing, and wispy stringing

So I have done many, many tests, and the main culprit seems to be a tiny bit of oozing at the end of every extrusion. When the nozzle does the z-lift, the filament strings and is dragged in the direction of the next extrusion. 

I print a lot of fantasy gaming terrain, so this is VERY problematic for things like cobblestone streets, where every single stone has a 'nick' on the top error. I am not getting smooth tops at all. I can see now these are all symptoms of the same problem.

Is there anything I am overlooking?

I've tried the retractions settings, and dropping the extrusion multiplier in case I am overextruding. Disabling wipe, and reducing the z-lift as much as I dare. 

Posted : 15/06/2022 5:33 am
JoanTabb
(@joantabb)
Moderator
RE: Preheat oozing, and wispy stringing

try dropping extrusion temperature a little and try setting retraction for PLA to 0.4mm

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Posted : 15/06/2022 7:23 am
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