E3d nozzle and blobs on the nozzle.
Hey guys. On some filament the e3d v6 nozzles builds up blobs which then fall off and cause missing steps. Ive turned down the extrusionfactor to the point where the lines dont meet anymore which should be sicnificant underextrusion. But still the problem remains. Havent got that on AbS but most on petg and pet. How do you deal with that?
PETG is the most “prone to get stuck on the nozzle” filament I know about. If you lowered extrusion like you said, it’s probably the nozzle itself (damaged, rough edges, etc) or the hotend/nozzle is not mounted absolutely vertical and picks up filament in a certain direction.
I get that a lot with PETG as well on my E3D v6. I don’t have any missing steps though, just burned bits of plastic that get embedded in the prints.
And I forgot to mention that a much slower retract is better for PETG. But you got no stringing, so that should be fine.
A fan on the bed helps - but don’t cool too much or you won’t have good layer adhesions
It’s one of the two things that I don’t like about PET. The redeposits are usually an ugly color too since they got cooked. The other thing I don’t like is that it doesn’t want to extrude as fast as either PLA or ABS.
PETG is a different beast than ABS. It is a more stringy plastic. I’d suggest adjusting your temperature settings.
With a 0.6 nozzle the problem gets less, at 0.8 it vanishes.
for me, high jerk and acceleration seetings and a fan blowing slightly at the nozzle helped alot with PETG stringing .
how high are we talking here?
I’m using Marlin, my X/Y jerk is 45mm and my Acceleration 4000. I also have a very high retract speed (3mm retract at about 200mm/sec speed ). The PETG is quite fluid when hot, so you don’t want to have your hotend pause on one spot longer than necessary. The high retract speed and jerk setting make the hotend move away bfore much of the PETG can ooze.
@Volker_Klaffehn yeah higher jerk is allways good besides from ringingartifacts. 45 is very high jerk. At 45 my printer wont keep its steps i believe
@VolksTrieb I think the most influence has the high retraction speed, because while retracting the hotend just sits on it’s last spot, letting the PETG ooze to a blob, and when it finally moves, it drags a string out of that blob, and, at least with PETG for me, those strings are cought by the nozzle and build those nasty blobs on the nozzle itself. Another helping setting, which is only present in Simplify3d afaik, is the coasting distance, where the extruder stops short before the end of the currently printed line.
so - i was plagued with this problem for the first few months printing petg.
for me it’s completely solved now (i print petg at ~7:1 of any other material i print). i’ll go into details below, but before i do - there is a solution i did not try that one of the forum members suggested, it was coating the nozzle with some type of oil (i forget the name of the material, not canola oil of course), but i did some research and that stuff emits toxic fumes at 250C or higher so i did not try it.
i tried a lot of different stuff. each time i tried something new i did a new print to see exactly what affects those buggers and how much. so i will list the factors i found by their effects from the greatest to lowest.
*note - this is my very subjective experience with my machine, but i have since helped a lot of people in my vicinity print in petg and reduce this problem to a minimum, and have so re-verified those findings…
first layer height and grip - if first layer adhesion is not perfect and adequate for all the print surface, some parts will then stick to the nozzle. sometimes so little that it is not visible without carefully looking. but that causes some more plastic to stick to it and more and more and then you get the “buggers”.
i had to test a lot of layer heights and bed materials to get it just right, but ever since i did it has cut the “buggers” by ~60-70% (around 2/3 i’d say).
i have tried a lot of things but what works best for me is just 1 thin layer of modpodge directly on my aluminum bed. modpodge is mostly made of some sort of pva based glue mixed with acrylic / acrylic glue and varnish. so it works wonders for adhesion.
i’ve printed pla, abs (i don’t print abs anymore) and nylon on it and they all worked great. petg specifically at 70C bed temperature with great adhesion and no warping or pulling even in very long and narrow prints with 100% infill.
i have a PEI sheet that i ordered a while ago, just have not had the chance to use it because modpodge has worked out so well that i haven’t had the need to replace it (occasional touch-ups).
i’m not mentioning that the bed has to be extremely level (not firmware-auto-level, just mechanically leveled and secured) because i’m assuming that’s something you’ve already got…
retraction - some people have already mentioned it, but you have to retract slower (i retract at 60mm/s for petg), and most importantly retract often! depending on the slicer you use (i use slic3r) there’s a setting to only retract when crossing perimeters which greatly reduces retracting. i turned it off and combined with slower retracts it cut the problem by ~20-25% (these numbers are not very scientific i know - but once you’ve seen so many “buggers” in so many prints, you kind of know how much you’ve reduced them).
3.cleaning the nozzle before a print. i’m adding a cleaning area to my printer now, so the nozzle can be automatically wiped before a print, but what i do until that is finished, is before a print starts, while the hotend is raised and warming up - when it gets to about 160-170C i’ll give it a good wipe around with a paper towel. that makes sure there’s no residual plastic from other prints so you are starting with a “clean slate”. if there is some residue, it will attract other residue which will turn into a fully fledged “bugger” in no time 
with these factors my problem has been reduced to no buggers at all. i’ve not had to check on any of my petg prints in about 6 months now.
hope this helps…
@Tom_Keidar What’s your minimum distance before retraction setting? So the slicer won’t go crazy and just retract wildly on short threads you can set a minimum distance it travels before performing another retraction, the default seems to vary from slicer to slicer.
@Volker_Klaffehn The new Cura v2.x has an experimental coasting option which I’ve never tried also skeinforge has dwindle if you feel like waiting an hour for your file to slice 
@VolksTrieb Here’s the article I used to try and tune my printer a bit better https://www.matterhackers.com/articles/retraction-just-say-no-to-oozing though I never completely eliminated the little boogers and strings but they’re manageable now and at least have never caused any missed steps. My jerk is only 20 and my acceleration is 2000 which seems low compared with a lot of others out there. I still get weird little burned bits in my prints sometimes but at least no missed steps so while ugly the parts are still usable.
It helps to make sure you aren’t over extruding. E3D style tip is very fat around the orifice and tends to plow up any excess from adjacent beads. I use Micro-Swiss plated nozzles for E3D and it reduces the nozzle blobbing a lot for me. I think it’s a combination of plating and nozzle geometry, slimmer margin around the orifice. Whatever PETG the tip does pick up tends to fall off as very fine hairs that are easy to brush off.