On the bottom of my prints, there’s an area of underextrusion and I can’t figure out what’s causing it.
I first noticed it when I switched back to a textured PEI bed while trying to print ASA. It’s on 20x20mm squares, and it’s on the test print for setting up pressure advance… But only on the left-most object.
It’s the same even if I add 2 lines of skirt or not. (In addition to my KAMP Voron purge.)
It happens everywhere on the bed that I’ve tested. It happens to PLA, but it harder to see. For ASA, it’s very obvious. For PLA, it’s almost as smooth as the rest of the surface, but it’s there if you know what you’re looking for.
I’ve only been printing PLA for quite a while now, so I don’t know when this started.
I’ve got an LDO Voron 2.4 with Tap, KAMP, Revo hot end. I’ve calibrated pressure advanced and changed the value, and I’ve tried different z offsets with the textured bed, which doesn’t change it. (But does change how good the rest of the bottom surface looks.)
Anyone got any ideas?
It looks like it is happening in the same spot on your bed, and it looks almost like the filament is not extruded near the bed in that area.
It’s is possible for you to have a cool spot in that area? It sounds silly, but do you have a dent in that area?
Does this happen if you move the print away from where the defect is happening? Try moving it in your slicer.
If it still happens in the same spot on your print, try rotating it in your slicer and see if it appears in the same spot.
It’s happening in multiple spots on the bed. I’ve tried about 6 or 7 now, and 2 different sheets. (PEO for PLA, PEI for ASA).
Rotating the square 45 degrees puts a pattern on the corner instead. It’s always to the left. (To the right, when flipped upside down so I can see it.)
All seems to indicate something related to pressure advance, whereby the printer thinks it needs to extrude less because of some pressure buildup but it underestimates how much is really needed. Does it happen if you print slowly? E.g max 15 mm/s or less.
At 15mm/s, it looks like the underextrusion is about half the size.
Interesting, that would confirm the pressure advance as the likely culprit (speed and acceleration are taken into account in the algo). Maybe your slicer has a bug related to this? If changing the value wildly does not improve or worsen it, then it might not be calculating what it’s supposed to. Can you try another slicer?
I used an older Cura that I already had installed (instead of Orca 2 that I’ve been using) and the underextrusion pattern is different, but still there.
I turned pressure advance to 0 in both Orca and Klipper, and saw no difference. :(
If you’re slowing down significantly and seeing an improvement, I wonder if it’s an adhesion issue vs an extrusion issue. It is very weird that it’s so localized though. I almost wonder if the nozzle might be influencing things somehow. Is it clean? Get it up to temp and give it a wipe with a folded over paper towel.
I’ve cleaned the bed and not applied 3DLAC, and it hasn’t helped.
That’s disappointing. I’m sorry to say, but I’m out of ideas. Maybe try the Voron design forums since they have more active users?
Yeah, it’s pretty weird. I appreciate the help, though!
I’ll probably post over there soon. I’m a little burnt out by it at the moment.
I completely understand that. I’m fighting my own battles with getting a consistently perfect first layer. I’ve been fiddling away for a while now and for whatever reason my last print had extrusion stop about 2/3 way through. Heated the nozzle up this morning, told klipper to extrude, and it extruder perfectly happily. No console errors from the print and klipper thinks it completed successfully.
When I’ve had something like that (or just underextrusion randomly part way through a print) I’ve decided it was a clog and did a “cold pull” on the filament to fix it and it seemed to work. It can be insidious because it sometimes clog and sometimes doesn’t.
Though, I’ve also had people suggest it was “heat creep” where the heat gets too far upwards and melts the filament too early.
What are your bed temps for PLA and ASA? Does it still happen if you preheat the bed? If you rotate the print, does the rough spot follow the rotation?
ASA 105
PLA 60
I’ve tried with multiple different objects and all of them occur in the same place. If I turn a square 45 degrees, it’s now on a corner instead.
I think your bed is warping slightly as it heats up, which is normal. Set your bed temp to 105 for half an hour before starting your print and see if it still happens. If you have a V0 or other manually levelled printer, get the bed to 105 before levelling.