Problem with PETG
Hi everyone!
I need some help or otherwise my printer will learn how to fly (out the window)... 🤯Â
So the problem I am suffering is that there seems to be some kind of "deposit" being build up over time at the extruder area (don't know how to describe it in a more precise way) that is being released at random points - random in time and in space - finally ruining the whole print because the extruder gets caught directly and goes into error mode when it hits that blob/string or the surface gets messed up:
3mf file: Tools Stand v1-1.3mf
- Printer: Prusa MK4s - upgraded from MK3s and there I had the same problem already
- Filament: PETG generally, I tried both Prusament and FormFutura HDGlass, same or very similar outcome - Prusament seems to be slightly thicker/viscous when heated, that's the only difference I can observe
- The bigger the print area, the bigger the problem generally
- Problem appears at random places, sometimes halfway through the very first layer
- I tried playing with temperatures (both extruder and bed) to no avail
- I do have 35% humidity in my office, so that should not have a major influence (please correct if I am wrong here)
- Small objects (e.g. Benchy) look good, maybe not 100% perfect, but nothing that can't be fixed somehow
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Any ideas on how to solve this are much appreciated!
Cheers... Pablo
RE: Problem with PETG
I had the same problem on my Mk3S+ until I realized my nozzle was not seated properly. Filament was oozing out above the heater block and collecting on the block until gravity finally dragged the burnt glob onto my print. I can't speak for the Mk 4 since it is a different set up but it took a while for me to realize it wasn't the machine but my own error that had caused the issue on my Mk3S+. Your bad prints are identical to mine. Hope you find the issue.Â
RE: Problem with PETG
See my GitHub and printables.com for some 3d stuff that you may like.
RE: Problem with PETG
Thanks guys, will have a closer look at it these days. The description indeed makes sense.Â
RE: Problem with PETG
A couple of things. PETG is sticky, and anything but black seems extra sticky. So there's some limit to how good of a result you'll achieve with anything but black. On some prints that encompass almost the entire bed I sometimes have had to pause the print and brush the nozzle off the buildup gets to much, again only with white.
First make sure it's dry, wet filament will be worse because it will ooze worse than PETG already does. Dry it in a filament dryer, and print from a drybox if possible.Â
More importantly your nozzle looks too close. When the first layer starts printing press and hold the control knob. The live Z will come up and start raising the nozzle until it's not gathering filament from the previous row. Maybe start with raising .025 and see how it looks. If it continues to gather on the nozzle raise it more. I'm guessing probably around . 04 will do it based on my experience. White is the worst, and I normally only have to do this on prints with very large areas on the print bed.Â
RE: Problem with PETG
Live Z adjustment might work, but the 3rd and subsequent layers will have the same problem. Â This looks more like over-extrusion where there is too much material for the space available so it pushes up and ends up being picked up by the nozzle.
Instead, try setting the Printing Flow (in Prusa Connect on the Control tab, or via the tuning menu on the LCD) lower - I've found that as my printer has aged this year, I'm setting the flow back down to 90% to avoid the build up. Â I'm thinking my brass nozzle is wearing and has a larger hole, but can't prove that.
Prusa MK4 since Jan 2024, Printables: @MikeB_1505898
RE: Problem with PETG
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Live Z adjustment might work, but the 3rd and subsequent layers will have the same problem.Â
I've not experienced this, usually after the first layer I'm good. There's still some buildup on the nozzle at the end of the print, but that's going to happen with PETG.
I've never adjusted the flow rate. 1.5 years old and over 1500 hours. I print almost exclusively PETG. I can't see the need to adjust this unless you've got filament with the diameter way oversized, or that fluctuates a bunch, or a hardware problem like a bad nozzle.Â
Good luck to the OP.
RE: Problem with PETG
I fought the same problem with my MK4 printers. I then upgraded my Mk3s to MK4s and the problem got worse. I would get lots of build up on the nozzle and get large blobs in my prints. I would also get a bad top layer with ripples. I finally figured out this was from over extrusion. I found an article about the extrusion multiplier setting in prusa slicer. This fixed my problem!! Basically the extrusion multiplier controls the flow rate of a given filament. I set my extrusion multiplier to .9 and my prints are so much nicer. I never get any blobs, no layer shift (due to nozzle crashes), and I get a perfect top layer! My MK4s printers finally actually print nicer than my old MK3 printers.
 The extrusion multiplier controls the flow rate of the extruder. So to check this, create a small box in prusaslicer and print it in Vase mode. Vase mode will make the open top box print with just one perimeter. This allows you to measure the thickness of the extrusion. The goal is .45 mm. So if your one perimeter measures more, you need to set the extrusion multiplier below one. A extrusion multiplier setting of 1 should produce a single perimeter thickness of .45 mm.
RE:
I've not experienced this, usually after the first layer I'm good. There's still some buildup on the nozzle at the end of the print, but that's going to happen with PETG.
Yeah, this is the clue whether it's Z offset, or over-extrusion.
I'm now officially confused - after months of adjusting flow because I was seeing buildup on the first layer, my last print (Prusament Orange PETG) didn't need it. So my worn nozzle theory is in doubt...
Prusa MK4 since Jan 2024, Printables: @MikeB_1505898
RE:
So the only thing I was able to check so far is the possible buildup at the heater block (leaking) - all clean as it can be but the odd black leftover (I need to clean) right at the nozzle.
RE: Problem with PETG
That's not too bad and should clean up easily with a wire brush.
The nozzle is all in one, so your not going to get leaking like on the V6 style nozzles at the heater block.
Did you read thru my previous comment? I gave you something to try.Â
RE:
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That's not too bad and should clean up easily with a wire brush.
The nozzle is all in one, so your not going to get leaking like on the V6 style nozzles at the heater block.
Did you read thru my previous comment? I gave you something to try.Â
It was really clean this morning, but it's now printing (6hrs and going...) and the same thing happening again. I have to check every 30mins or so.
I did not try your proposal yet as I want to try every single tweak and verify. If I try everything at once, I might not find out what was the root cause. So first change was the flow rate (now 0.98) as I did not have too much time this morning. Slightly better now, though not solved. Not sure the improvement is down to the thorough cleaning or the flow rate change.
Still have enough to print and try and will report back.