Another PETG stringing post - but with new twists
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Another PETG stringing post - but with new twists  

New Member
Another PETG stringing post - but with new twists

I just wanted to give my input, just reiterating most of your conclusions on other posts but adding new questions.  This is all using PrusaSlicer and starting January 2022.  When I first assembled my MK3S+, I used the PLA the printer came with, and I did DOZENS of different configuration prints until I get the perfect first layer.  My initial prints came out absolutely perfect (3 rolls of PLA and PETG).  After my first few PLA prints, I switched to brand new out of the vacuum sealed bag, orange Prusament PETG, used the default Prusa settings and my prints were pretty damn amazing.  No stringing to speak of, just tiny little dabs here and there that I could pretty much wipe off with little effort.  This was in January when my the climate where I live is pretty dry.  Every day or 2 I would print some items and my prints would come out perfect.  A few weeks ago, I used that SAME Prusament PETG from earlier in the year because I wanted this part to be orange, and I got nasty crazy stringing, all over the place, even though the filament was stored in a dry cabinet, it was still exposed to my Illinois humidity.  Obviously, the filament had been out of it's vacuum sealed back for 6 months now, so I dried the filament for 5 hours (65C - 150F), and the stringing was a LITTLE better, but not solved.  I tried drying the filament for 10 hours (65C - 150F) this time and it's still pretty stringy with maybe a slight improvement.

At first I was thinking my initial prints were just so nice because I was using brand new Prusament filament, that was perfectly dry, but you'd think 4 hours and then 10 hours in a dehydrator at 65c would sufficiently dry the filament.  My next step was to try brand new out of the sealed bag PETG.  I didn't have a new Prusament PETG, but I had Hatchbox, which gave me the same result as the Prusament PETG when my printer was newly built.  I got the same stringing that I got with the "old" but dry Prusament PETG.  I noticed that the default temperature for Prusament and "generic" PETG is not the same, so I tried using the default settings and I tried choosing the Prusament default setting.  Still the same problem with little improvement and nowhere NEAR the prints when new.

So now, I'm thinking that maybe some of the stringing problem is simply just wear in the nozzle, or maybe something else?  I haven't messed with retraction length or Z lift yet simply because it USED to be just fine.  I'm worried that changing those setting is just chasing a different problem, like the extruder nozzle just needing replaced?  Is there any other adjustable item or part other than an worn extruder nozzle on the printer that could cause the stringing that wasn't present before?  Could an out of spec extruder be the BIGGEST issue causing stringing, or could it be that my filament is simply unable to stay dry in my humid climate, even when it's straight out of the bag?

Am I wrong to think I'm "chasing the problem" with retraction length or are the settings changes just part of the process to extend the time-to-replace life of the extruder?  I know I gave a lot of questions that probably can't be answered, but I'm just frustrated with the sudden change in performance of my printer.  I would much rather replace the extruder if there's a good chance that is causing my problem.

Posted : 13/07/2022 1:46 pm
Reputable Member
RE: Another PETG stringing post - but with new twists

I doubt that you have worn out your nozzle in 6 month printing, unless you printed abrasive filaments (like glow in the dark PLA).

My bet would still be on moisture, even sealed filament can be moist "out of the bag" and even freshly dried filament can absorb moisture quickly depending on environmental conditions. Also: what did you dry the filament in? Modern ovens are often designed to keep the moisture in during operation...

Consider building or buying a filament dryer and printing out of a dry box with a lot desiccant.

Not messing with retraction and z lift is definitely a wise decision. 

If at first you don't succeed, skydiving is not for you.

Posted : 13/07/2022 3:14 pm
New Member
Topic starter answered:
RE: Another PETG stringing post - but with new twists

Thanks for the reply.  I've been drying the filament in a rack style food dehydrator.  It can hold 4 rolls at once, but I only do one roll at a time.  After the first 4 hours of drying didn't seem to fix anything, I accidentally left my timer at 10 hours for the next batch of drying.  Still didn't fix anything. 

I have a few pounds of desiccant, so maybe I'll try putting the filament in a desiccant box after drying.  The humidity here is 60%-90% much of June and July, so maybe the filament wicks up moisture immediately after drying.  I'm really curious if the filament could be absorbing moisture/humidity as it comes out of the extruder.  That doesn't seem possible, but I have no clue.


I don't like messing with settings that previously worked, other than changes for quick prototype fitment prints.

Posted : 13/07/2022 3:25 pm
Famed Member
RE: Another PETG stringing post - but with new twists

I'm with @robin. Almost certainly not the nozzle. I have PrintDry Pro dryers which do a nice job. Most Prusament PETG prints fine after drying but Neon Green i have to print straight of the dry box. 

Posted : 13/07/2022 6:30 pm