Severe stringing issues  

RE: Severe stringing issues

Hi stubby,

I am new to 3D printing also, so I don't feel entitled enough to share any insights. But, this articles talks about settings the filament retraction up in case of stringing: https://help.prusa3d.com/en/article/stringing-and-oozing_1805

Though the article is not specifically for the Mini, maybe carefully playing around with the retraction settings might be worth a try.

If everything fails, I guess you could contact support. They are very helpful with any problems.

Regards,

Raik

RE: Severe stringing issues

increasing the retraction settings on the printer/filament made a world of difference for mine:

Printersettings - Retraction - Length Changed to 5mm
Printer settings - retraction - deretraction speed to 0mm
Printersettings - Retraction - retract on layer change ticked

theres also a few good string test prints out there that helped me dial it in with these, but the above really made it go from nasty stringy mess to something much better.

I do have to mention though certain filaments seemed much stringier than others.

RE: Severe stringing issues

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RE: Severe stringing issues

Posted by: @remington

I do have to mention though certain filaments seemed much stringier than others.

Yep. My newest Filament is Geetech White PLA (cheap stuff) which strings a lot compared to my Prusament Galaxy Black or Amazonbasic Neon Orange. Lowering Temperature to 200°C yielded big enough improvements though.

stubby is using Prusament, which I guess should work well with the mini without tuning the profile. At least it did for me and should be expected. Asking support like raik-2 suggested is probably a good idea.

RE: Severe stringing issues

@orkelprint

i couldnt even get the sample galaxy black to print correctly at all 😀

RE: Severe stringing issues

I found that reducing retraction down to 2mm solved an underextrusion issue I was having with Prusament Galaxy PLAs.

I tried virtually everything else (fiddling with hotend, PTFE tube, temperatures up and down) and was about to trash both spools. I got great prints from other brands, but could not make the good stuff work to save my life.

I suspect that with every retract at longer lengths, there was just the tiniest bit of buildup above the heatbreak - enough to mess up a print after a while, but not enough to cause an outright clog.

It worked for me.

RE: Severe stringing issues

@remington

 thanks for all the info from folks. i was curious if u have had any jamming since increasing the retraction?  also the picture showed 3 rows of prints was this progressive increases to the retraction with the last and best row being 5?? 

RE: Severe stringing issues

If I may hop onto this thread, I'm having the same problems as stubby. Been printing with the MINI for over a month now, got some very good first prints with simple models (featureless solids, such as the nut and bolt, and the sheep). But when I started printing designs with more features I noticed significant stringing.

First, I expected it was my filament. My 'Real' filament that had been lying on the shelf for over a year (in original packaging), so perhaps it was wet? Dried the filament in the oven, but that made no difference. Tried the provided samples of Prusament PLA (Lipstick?) Red and Galaxy Black, but these displayed stringing as well. Had a spool of Prusament ASA White that came in around this time, and this wasn't anything better. Some filaments stringed more than others, but they all stringed. My conclusion: the root cause is not in the filament.

Secondly, I disassembled and reassembled the extruder. Found some gunk on the extruder driven gear, originating from one of the Real filaments. Cleaned it. Increased the idler tension on top of that, a fair bit. Again, no difference. My conclusion: the root cause is not in the extruder.

Next, I had a good look at the hotend. I refitted the hotend in the heat sink (loosened the three bolts on the side, then pushed the extruder upwards while tightening them again) as I read that this could sometimes help. Cleaned the hotend through cold pulling. Also inspected the bowden tube and its connections; found nothing obvious wrong. My conclusion: the root cause is not in the hotend.

Finally, I naturally also played with printer settings.

• Increased retraction length up to >4 mm
• Set deretraction speed down to 0 mm/s
• Enabled retract on layer change 
• Tried printing with the print cooling fan disabled
• Tried printing at slightly higher/lower temperatures for the hotend (+/- 10 degrees)

Again, no difference. To illustrate, see this picture with the original print settings for Prusament PLA (left) and modified settings for retraction (right). I'd say that the result on the right is even slightly worse.

So, my endeavors haven't gotten me any further, and I'm all out of ideas. A friend of mine just picked up a MINI as well and he is more happy with his. Perhaps we should do a side by side comparison to get to the root of it all. In the meantime, I'm open to suggestions. I'll also search the web for other people their experiences. Maybe someone has found other ways to improve the print quality.

BTW stubby, have you managed to reduce stringing already?

RE: Severe stringing issues

Posted by: @stubby

@remington

 thanks for all the info from folks. i was curious if u have had any jamming since increasing the retraction?  also the picture showed 3 rows of prints was this progressive increases to the retraction with the last and best row being 5?? 

yep, that was top picture being stock pla settings 210/60 and 2 retraction i think it was, then moving up to 225/65 with 5 retraction in a few hops, the temp changes recuded the extruder clicking i was suffering and teh retraction got rid of the stringing.

I've used these settings on PETG (with petg stock temps) and it printed out the string test flawlessly

the temp changes seemed to get rid of any jamming too

RE: Severe stringing issues

torx, i haven’t had time to play with it. everything i am printing now is not subject to the issue so i haven’t worked on solving it.  right now i am just cleaning the parts up if necessary but would love to have a definitive answer to this problem if there is one lol. i will update as i try different things please also respond if u find out anything which seems to solve problem. sounds like u tried remmingtons solution with little reduction in stringing. i was hoping that might fix it. 

RE: Severe stringing issues

Sorry to hear you didn't find a solution yet, stubby. However, I did make an interesting discovery that and managed to get a much improved result. Perhaps it will help you too.

Since I was unable to find anything wrong with the MINI itself, I started second-guessing my initial conclusion regarding the filament. Filaments can attract moisture pretty quickly. I had stored my Prusament samples in ziplock bags and they were less than two months old. Surely, they couldn't accumulate a significant amount of moisture in so little time, right?

Well, I dried my Galaxy Black at 40 degrees C and under vacuum (< 10 mbar) for 2 hours. Redid the stringing test afterwards. In the pictures below, the left sample is before drying and the right sample is after drying. Both were printed using stock settings for the MINI with Prusament PLA. The difference is significant.

Next I'm going to is to see if results with the Real PLA filaments and the Prusament ASA filament can be improved in the same way. I did try to dry the Real filaments earlier, but only at 40 degrees C, without vacuum. That may not have yielded enough of an improvement. As for the Prusament ASA: it arrived very recently, however, I did notice the occasional *pop* during printing already on the first day I printed with it. Back then I wasn't sure what to think about this -- maybe it was due to the high hotend temperature? In hindsight though, the popping could also be due to moisture. So, maybe it was a bit wet already when it arrived? (But maybe it is also just a more difficult material to print -- ASA is new to me and the MINI is my first system with a Bowden, so I do not have a point of reference).

RE: Severe stringing issues

@torx

WOW, just WOW. I had been told that this could be happening. I would love to see the pla test though. I am using Hatchbox and now 3D fuel PLA. I got rid of most of my oozing but now with no lift z I think on a print I did this weekend the part deformed slightly and the nozzle hit it and broke the print. It was a thin part and am now rethinking the lift z setting.

RE: Severe stringing issues

torx what system did u use to dry the filament in that manner? 40C plus vacuum.  

RE: Severe stringing issues

@shags72 No problem, I'm not ready to draw conclusions based on a single test. When I have performed more tests, I'll report back.

@stubby I used a piece of lab equipment that I would not recommend buying -- it is not exactly affordable. If you're interested in drying stuff at home, an affordable option that comes to mind may be to use a second-hand vacuum desiccator + diaphragm pump. Caveats are that the desiccator may be difficult to get in a size large enough to hold a spool, and also that heating a desiccator is not recommended (unless you know what you're doing). However, I think that, ultimately, prevention is easier than drying. I've seen people use cheap plastic containers with silica gel in them to store their spools in. Depending on a few factors, this setup may even remove some moisture from the filament when given enough time.

RE: Severe stringing issues

@torx

Thank you sir. I am going to get as you said a cheap plastic container but at least with a gasket to seal it and I will order me up some desiccant.

You're probably right, prevention is better than dealing with the results.

RE: Severe stringing issues

Sorry for taking some time with my follow-up. I've finished drying the Real PLA filament (40 degrees C + vacuum) and Prusament ASA filaments (70 degrees C + vacuum) and redid the stringing test.

Left: prior to drying. Right: after drying.

My personal verdict: PLA (purple) improved a lot, but we're not there yet. I'm wondering if further improvement is possible by tuning the print settings. ASA (white) did not improve as much as I hoped, but I can still hear the occasional pop during printing, so it may still contain too much moisture. A bit strange IMO, considering the high temperature at which it was dried.

Love to hear what you guys and gals think.

RE: Severe stringing issues

i observed something strange when i printed the same object as above with all the same settings except that i printed it in .1 detail versus .05 i had virtually no stringing or blobs.  i thought maybe just luck but i printed a 3rd copy using .1 instead of .05 and no stringing. it would seem i get lot more stringing with finer detail setting. has anyone else observed this?

RE: Severe stringing issues

Stefan at CNC Kitchen found that heat was more effective at removing moisture than applying a vacuum.  He suggests weighing your spool before and during the drying process.  Once it asymptotes, you're done.

RE: Severe stringing issues

Posted by: @torx

Sorry for taking some time with my follow-up. I've finished drying the Real PLA filament (40 degrees C + vacuum) and Prusament ASA filaments (70 degrees C + vacuum) and redid the stringing test.

 

How much vacuum did you apply while heating it?  What's recommended?  Maybe Stefan didn't apply enough vacuum.