Hello, Have a PETG printing issue that refuses to go away. Smaller items print fine, and on larger items the first layer is near perfect, but additional layers exhibit a grainy, incomplete coverage. As a result the part looks terrible and is fragile. I've attached a picture with the problem illustrated. How it started: Initially large parts printed fine. Then the problem started seemingly randomly, with the first layer still coming out fine or almost fine, but subsequent layers exhibiting the grainy coverage that seems to get worse throughout the print. I thought it was due to a faulty thermocouple, but after changing multiple of those and the hotend itself the problem persists. What I've tried: Changing thermocouple and hotend Changing speeds (slowing down considerably, even though it printed fairly fast before just fine). Changing temps (tried about the whole range for PETG, no improvement). Changing nozzle height for first layer (in case it was clogging due to being too close, no improvement) Changing filament (tried a different manufacturer in fact, right now I have eSun, before had MatterHackers brand) Simply extruding with the extrude command right after stopping the print when noticing the grainy pattern (seems to extrude fine, so apparently not clogged) What I haven't tried: Changing plastics (I have a new nozzle on the way and will test it with ABS to see if problem persists, don't want to cross-contaminate this one) Yet another hotend, which I will try with the PETG if it arrives and works fine with ABS Any thoughts? https://reprap.org/forum/read.php?262,733439,733439#msg-733439 Fri, 11 Sep 2026 00:17:05 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?262,733439,734122#msg-734122 https://reprap.org/forum/read.php?262,733439,734122#msg-734122
Edit: missed your edit :) Yeah, I can't print petg at 60 either, 30 is about my limit with typical nozzle sizes and layer heights.]]> JamesK Printing Fri, 30 Dec 2016 10:13:34 -0500 https://reprap.org/forum/read.php?262,733439,733966#msg-733966 https://reprap.org/forum/read.php?262,733439,733966#msg-733966
Extruder is unlikely as an issue, I did look for lost steps, etc. (simple Wade extruder). Also I agree that filament grinding usually leads to complete jams.

Currently testing on higher speeds to see if the issue goes away completely, but it's looking positive right now. I'll report back the results once I'm done with the latest print. For now, thanks to everyone for the thoughtful input.

Edit: prints fine at slow speed, but higher speed results in bad patches as in the original pictures. Considering I can at least get a decent print out now, I think I can call this more or less solved. Solution was to use low speed and turn the nozzle fan on.

Perhaps this filament just doesn't print at 60mm/s.]]> anvoice Printing Thu, 29 Dec 2016 19:36:21 -0500 https://reprap.org/forum/read.php?262,733439,733846#msg-733846 https://reprap.org/forum/read.php?262,733439,733846#msg-733846
a) The motor stalls - depending on type you'll see the gear jump backwards and hear the clicking noise (what sort of extruder are you using?)
b) The teeth slip on the filament, typically grinding some of the filament away into shavings that build up between the teeth and around the extruder housing.
c) Some part of the extruder drive chain slips on its axle.

edit: I just thought of a d) - filament buckles between drive gear and throat and makes an unholy mess inside the extruder. That one's real obvious too :)

a) is normally obvious, so I'm guessing you would have noticed that. b) usually goes straight to no extrusion at all, with a semi-circle chewed out of the filament, so doesn't seem likely with the symptoms you describe. On the other hand c) fits the bill pretty well, a gear slipping on the drive shaft will typically catch for a while on each rotation, and often seems to get worse as the print progresses (not sure why - heat?). You could disassemble the extruder and look for witness marks from a slipping set screw, or you could add alignment marks across the ends of the axles onto the gear so you can see if it slips.]]> JamesK Printing Thu, 29 Dec 2016 12:41:10 -0500 https://reprap.org/forum/read.php?262,733439,733804#msg-733804 https://reprap.org/forum/read.php?262,733439,733804#msg-733804 I believe the slow print speed is just a workaround to fully melt the energy hungry PETG.]]> o_lampe Printing Thu, 29 Dec 2016 10:37:18 -0500 https://reprap.org/forum/read.php?262,733439,733664#msg-733664 https://reprap.org/forum/read.php?262,733439,733664#msg-733664 20mm/s worked better: more of the surface was evenly covered. Attached is an example of the good region. Unfortunately there is also a poorly covered region (attached also) on the same print, again with the thin, drippy lines. The bad news is that I've run into the lower limit of how slow I'm willing to print this.

It's fairly clear it's an extrusion issue, but not sure what's causing it. I'll try the new hotend once it arrives (couple of weeks at worst), but for now I'm out of ideas. Still gladly taking suggestions.]]> anvoice Printing Wed, 28 Dec 2016 22:02:49 -0500 https://reprap.org/forum/read.php?262,733439,733661#msg-733661 https://reprap.org/forum/read.php?262,733439,733661#msg-733661
It's not the fan. I notice the second layer starts ok (a couple of good solid lines) then goes to thin, drippy lines that don't completely fill the model, even with fan off.

I'm trying out the speed suggestion right now: slowed it down to 20mm/s. Would be a shame if that's it since it printed fine before at 60mm/s for infill (same settings, same filament), and all prints would now take 3x the time.]]> anvoice Printing Wed, 28 Dec 2016 20:33:45 -0500 https://reprap.org/forum/read.php?262,733439,733556#msg-733556 https://reprap.org/forum/read.php?262,733439,733556#msg-733556 PDBeal Printing Wed, 28 Dec 2016 12:08:01 -0500 https://reprap.org/forum/read.php?262,733439,733520#msg-733520 https://reprap.org/forum/read.php?262,733439,733520#msg-733520 Srek Printing Wed, 28 Dec 2016 09:28:30 -0500 https://reprap.org/forum/read.php?262,733439,733511#msg-733511 https://reprap.org/forum/read.php?262,733439,733511#msg-733511
I'm actually thinking of turning the fan off altogether and trying to print like that since it's the first layer that prints perfectly (no fan), will report back on how that goes tomorrow along with pointing the fan at the part.

If you don't mind me asking, why was your extruder not working consistently? Stepper motor issue, slipping, poor heating, something else? Sounds like that could conceivably be a problem for me.]]> anvoice Printing Wed, 28 Dec 2016 08:59:23 -0500 https://reprap.org/forum/read.php?262,733439,733501#msg-733501 https://reprap.org/forum/read.php?262,733439,733501#msg-733501 I had similar bad results with to high speeds and with an extruder that did not work continously.]]> Srek Printing Wed, 28 Dec 2016 07:56:53 -0500 https://reprap.org/forum/read.php?262,733439,733439#msg-733439 https://reprap.org/forum/read.php?262,733439,733439#msg-733439 Have a PETG printing issue that refuses to go away. Smaller items print fine, and on larger items the first layer is near perfect, but additional layers exhibit a grainy, incomplete coverage. As a result the part looks terrible and is fragile. I've attached a picture with the problem illustrated.

How it started:
Initially large parts printed fine. Then the problem started seemingly randomly, with the first layer still coming out fine or almost fine, but subsequent layers exhibiting the grainy coverage that seems to get worse throughout the print. I thought it was due to a faulty thermocouple, but after changing multiple of those and the hotend itself the problem persists.

What I've tried:
Changing thermocouple and hotend
Changing speeds (slowing down considerably, even though it printed fairly fast before just fine).
Changing temps (tried about the whole range for PETG, no improvement).
Changing nozzle height for first layer (in case it was clogging due to being too close, no improvement)
Changing filament (tried a different manufacturer in fact, right now I have eSun, before had MatterHackers brand)
Simply extruding with the extrude command right after stopping the print when noticing the grainy pattern (seems to extrude fine, so apparently not clogged)

What I haven't tried:
Changing plastics (I have a new nozzle on the way and will test it with ABS to see if problem persists, don't want to cross-contaminate this one)
Yet another hotend, which I will try with the PETG if it arrives and works fine with ABS

Any thoughts?]]> anvoice Printing Wed, 28 Dec 2016 04:26:44 -0500