Please help troubleshoot PETG blobs ruining my prints!!!
I am trying to print using Overture black PETG but blobs are ruining my prints!
Here's my info:
Prusa MK3S Kit - stock setup
Overture reel says: Nozzle temp: 230 - 250, Bed temp: 80-90
Trying to print this: https://www.thingiverse.com/thing:3572399
Sliced using Prusaslicer (.30 mm Draft, Prusament PETG filament profile; no adjustments, No supports, 15% infill, No brim.)
History: So far I have had some real nice prints using the Silver Prusament PLA and they just keep getting better the more I dial in the settings. I already printed the covers for this current project using the Overture PETG and they are beautiful.
See photos of successful prints, ruined prints and extruder blobs here:
https://photos.app.goo.gl/GLYfkiRiJatJK8sD8
The problem: The extruder sometimes curls the filament. Sometimes it curls back around on the nozzle and as the print progresses it gets bigger and bigger. Then it will eventually fall off the nozzle onto the print and harden. The nozzle can run into this hard blob sometimes! I always clear off any filament that is hanging off the extruder before the print starts but sometimes it creates a curling filament just before starting the print and I can't grab it because the extruder is so close to the print surface.
What I have tried:
Cleaning the bed between every print with 90% isopropyl alcohol
Heating up the nozzle to 240 and cleaning off the leftover PETG with a brass brush
Making sure to align the bondtech gear with the filament
Adjusting the idler gear tension. I find conflicting info on the web about how tight loose it should be. Currently the screw head sits flush with the surface of the extruder body and there are about 3 threads protruding through the idler door nut.
3 cold pulls: None of them had any visible debris but I wouldn't expect much since the printer is a week old. The first two didn't have very defined nozzle shapes but the 3rd one seemed ok.
Recalibrated X, Y, Z
Used Jeff Gordon's Live Z adjustment to dial in the Z height for PLA. Do I need to also do that for PLA and then switch the Z height when switching filament types?
Thank you in advance for reading this and any advice you may offer.
Todd
RE: Please help troubleshoot PETG blobs ruining my prints!!!
A silicone sock can help reduce filament sticking to the heater block. A coated nozzle (available from E3D, P3-D and others) can help reduce filament sticking to the nozzle.
and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan
RE: Please help troubleshoot PETG blobs ruining my prints!!!
I have seen this curling problem with PETG when the moister content is too high. The water in the filament makes tiny bobbles when heated and makes the curls on the extruded filament.
I solved the problem by drying the filament form time to time, when noticing the bobble problem. As I print a lot of PETG all my nozzles is nickel plated with low friction coating from MicroSwiss - they make nozzles for E3D all metal extruder.
If you plan to primary print in PETG, a plated nozzle or a silicone sock (covering the nozzle) is a must - PETG is very sticky and hard to clean off the nozzle.
Have a look at my models on Printables.com 😉
RE: Please help troubleshoot PETG blobs ruining my prints!!!
@area51
Thanks for this advice. I will look into it and see what can be done.
RE: Please help troubleshoot PETG blobs ruining my prints!!!
I tried using a Silicone sock. The first one I tried was the E3D Pro sock. The hole was so small that only the tip of the nozzle poked through. I think maybe the sock was dragging in the filament sometimes. So I switched to the standard E3D sock and that seems to have stopped the blob problems and doesn't drag in the filament any more. Thanks for the advice everyone!
RE: Please help troubleshoot PETG blobs ruining my prints!!!
You can use some thin wire to hold the sock in place. They do start to say, bit with the wire "retainer" in place, I usually get a couple of months out of each one. Just avoid the thermistor and heat cartridge wires.
and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan
RE: Please help troubleshoot PETG blobs ruining my prints!!!
You can use some thin wire to hold the sock in place. They do start to say, bit with the wire "retainer" in place, I usually get a couple of months out of each one. Just avoid the thermistor and heat cartridge wires.
Yep - I actually took two of the twist ties taken off something or another when building my MK3S kit, stripped off the plastic (since it would melt) and used the aluminum wire inside for precisely this purpose, keeping a genuine e3d pro sock up and snug on the heatblock. Has been working great for a few hundred hours of print time so far.
RE: Please help troubleshoot PETG blobs ruining my prints!!!
Looks like everyone else beat me to it.
Nickel plated copper nozzle and silicone sock.
Also modified startup G-Code to improve the initial purge to clean the nozzle better, but this will only work with a nickel plated nozzle, PETG positively welds itself to the brass nozzle as anyone whom has tried to remove the last bits when cold knows.
I wouldn't bother with the sock with the little hole in in unless printing with 0.25 mm or smaller, just the normal sock which leaves the nozzle exposed.
And of course filament drying, even leaving PETG out in the open (UK Winter) for 24 Hrs can start to affect it.
When you load the filament with the nozzle in the air, it should come straight out, not curl up, smooth no zits, pops or any blemishes in the extruded filament. If you can achieve this, you should end up with a nice clean successful print.
Oh and for trouble free nozzle changing, get some cleaning filament / floss, purge the old PETG out with this, then put some PLA in, once this is loaded, turn the heat off, and carry out a cold pull at 80 Deg. You will now have a spotless nozzle etc inside so no danger of getting filament stuck between the heatbreak and nozzle when replacing it.
Normal people believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet.
RE: Please help troubleshoot PETG blobs ruining my prints!!! - Filament Tolerance ±0.05mm is the problem
I recently had issues printing with Black Overture 3d PETG filament as well. This filament has +250% larger diameter tolerance than previous PETG from another supplier that worked very well on my Prusa i3 MK3s:
Poor Printing - Overture 3d PETG filament tolerance: 1.75mm ±0.05mm
Good Printing - Sain Smart PRo-3 Series PETG tolerance: 1.75mm ±0.02mm
In my experience, I had intermittent print bed adhesion issues (could be caused by undersized filament) and stringing issues (could be caused by oversized filament):
- Excessive Small Diameter 75 – 0.05 = 1.70 mm
When the slicer software calculates based on exactly 1.75mm filament, but only 1.70mm on the spool, the result will be under-extrusion. If this happens during the first layer of printing, it results in Low print bed adhesion – exactly as I experienced with Overture 3d filament. - Excessive Over-Tolerance 75 + 0.05 = 1.80 mm
When the slicer software calculates based on exactly 1.75mm filament, but has 1.80mm on the spool, an “Over-Extrusion” occurs whereby the filament expands laterally under the nozzle, to the degree that it pools around the nozzle and sticks to the nozzle. This over extrusion condition leads to stringing – exactly as I experienced with Overture 3d filament.
So I believe that the root cause of this problem is Low Manufacturing Tolerance from Overture 3d (±0.05mm), and the corrective action is to replace it with PETG filament that is made with higher manufacturing tolerances (±0.02mm) such as Sain Smart Pro-3 series.