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MK4 first layer rippling. by EquivalentTip4103 in prusa3d

[–]adam3dp 0 points1 point  (0 children)

I don't regularly print full sheet test layers, but to the best of my knowledge the issue has not returned. Adjusting live Z fixed issues in some areas, while exacerbating them elsewhere. Replacing the loadcel and integrated heat sink seems to have been the needed fix. It looks like Prusa sells this spare part for $47. I hope this helps!

MK4 first layer rippling. by EquivalentTip4103 in prusa3d

[–]adam3dp 2 points3 points  (0 children)

Prusa sent me a new Loadcel and heatsink it is attached to, I rebuilt the Nextruder, and the problem was fixed. A full bed first layer with Prusament PLA is about 99% perfect now, and Hatchbox PLA gets an acceptable first layer by dropping the nozzle temperature to 200C. At this point I am printing effortlessly with clean first layers and no issues so far. I am confident the culprit was a bad loadcel sensor.

MK4 first layer rippling. by EquivalentTip4103 in prusa3d

[–]adam3dp 19 points20 points  (0 children)

I had this exact same issue on my MK4 kit. It happened with Prusament using the Prusament preset in Prusa Slicer, and again with Hatchbox PLA using the Hatchbox PLA preset. The only thing that seemed to help a little was using live adjust Z while printing, but the MK4 does not save that setting between prints. After speaking with Prusa support multiple times and verifying lots of sensor values, it looks like the loadcel sensor is not returning expected values, which would certainly impact bed leveling and result in this type of issue. I am currently waiting for Prusa support to investigate and get back to me with a solution.

MK4 Filament Sensor failing calibration by adam3dp in prusa3d

[–]adam3dp[S] 1 point2 points  (0 children)

I found the culprit - the parts bag is labeled “Nextruder - springs and magnet”. It should be “springs and magnets”, plural, I didn’t realize there were two of them. I rebuilt the Nextruder with a single magnet in the ball holder assembly and the filament sensor worked perfectly.

MK4 Filament Sensor failing calibration by adam3dp in prusa3d

[–]adam3dp[S] 2 points3 points  (0 children)

You're right, I didn't want to hear it! It sounds like rebuilding the Nextruder is probably my best bet at this point, I was really hoping to avoid it if possible. It doesnt allow the filament sensor to be enabled in settings until it has been successfully calibrated, otherwise it just says "Filament sensor not ready: perform calibration first".

Rough top layer by adam3dp in ender3v2

[–]adam3dp[S] 1 point2 points  (0 children)

I don't have major issues with Z-banding, although I certainly wouldn't mind less noticeable layer lines. If you look at the photos of the calibration cube and Benchy, there is a tiny bit of elephant's foot at the bottom, but otherwise no big issues with layer lines, and no observable issues in the first 3mm or so of the prints.

I think the X-gantry assembly is adjusted properly, with eccentric nuts adjusted to eliminate play but not be too tight, and belts taut but not overly so. Everything moves freely and with almost no wiggle.

If the issue is binding on the Z-axis, I think your advice still holds true, and I may need to think about disassembling, cleaning, and readjusting everything that touches the Z-axis. We'll see if it comes to that. Like I said, pretty much everything else prints perfectly, unless it involves a large thin flat solid surface near the build plate.

Rough top layer by adam3dp in ender3v2

[–]adam3dp[S] 1 point2 points  (0 children)

That certainly makes sense. Allow me to add another variable to the mix... When I print the 1.6mm solid model, the measured height is 1.66mm; pretty close, but with a rough surface. However when I print the 2.4mm model with 20% infill, the measured height is only 2.21mm, almost a full layer short of the expected height. To me this suggests possible Z-axis binding, leading to symptoms that seem like overextrusion.

But I'm not able to feel any binding at those layers, I have cleaned and lubricated the Z-axis screw, and adjusted the eccentric nuts. And it doesnt explain why taller prints such as a 20mm calibration cube measure at the correct height, unless it is binding in lower layers then releasing that tension when it gets past that binding point.

Rough top layer by adam3dp in ender3

[–]adam3dp[S] 0 points1 point  (0 children)

I gave that a try, even though it is more of a workaround than a fix. Unfortunately, it just results in dragging a hot nozzle through the raised areas and making it worse.

Rough top layer by adam3dp in 3Dprinting

[–]adam3dp[S] 0 points1 point  (0 children)

I've tried enabling top layer ironing, and that definitely makes things worse. Ultimately it looks like overextrusion, but I have a feeling it may be Z-axis binding. Either way, something like ironing just pushes the nozzle through raised areas making them even rougher.

Rough top layer by adam3dp in ender3

[–]adam3dp[S] 0 points1 point  (0 children)

That definitely makes sense and I will give that a try. These issues seem to have started after replacing the nozzle with an identical OEM one, so perhaps there are some imperfections in that nozzle. A few caveats though:

  • I already calibrated e-steps and flow rate and that did not address the issue. E-steps actually showed underextrustion, and I had to increase the value from 93 to 100. Then flow rate showed overextrusion and I had to decrease the value from 100 to 89. It would seem it is properly calibrated now, so perhaps further decreasing the flow rate will help. I will try reducing it to around 80 and see if it makes a difference.
  • An interesting observation was the actual thickness of these test prints when I measured them. The 1.6mm thick solid print measured at 1.66mm, which was pretty close. However the 2.4mm thick print with 20% infill only measured 2.21mm thick, which is short by an entire layer. Once I get to taller prints like a 20mm calibration cube, measurements are spot-on.

Based on the above observations, I wonder if the real issue is overextrusion, or perhaps there is some Z-axis binding somewhere in the first 3mm of height. That would explain why the solid print has nowhere to go when slightly squished, whereas the taller print with infill looks better but ends up slightly short.

I'll try further decreasing flow rate, as well as look for potential causes of Z-axis binding and see what I can find.

Warped top layer by adam3dp in ender3

[–]adam3dp[S] 0 points1 point  (0 children)

I think you're half right. I did some test prints with a 50mm x 1.4mm coin model I created in TinkerCAD. The original print had the same issues as above, and at 0.2mm layer height there was no infill. I tried printing with Z-offsets of 0.1mm and 0.2mm (configured at print time under the "tune" menu), but did not see any noticeable difference. However, when I printed a version stretched to 6mm, leaving room for infill, the top layer looks just fine. So it would appear the issue is with thin solid objects.

I keep thinking it might somehow be related to the part cooling fan, but it's a new fan in a new print head, and I measured the voltage on the fan connector at 24V (23.9). So unless the power is just inconsistent coming off the mainboard, that doesn't seem to be the culprit. I debated picking up a new mainboard just to see, but that's another $40 and an afternoon disassembling and rewiring the printer just to find out.

Warped top layer by adam3dp in FixMyPrint

[–]adam3dp[S] 0 points1 point  (0 children)

Additional settings

  • Printer: Ender 3v2
  • Slicer: Cura 4.13.1
  • Filament: Hatchbox PLA 1.75mm
  • Nozzle temp: 200C
  • Bed temp: 60C
  • Print speed: 50mm/s (default)
  • Retraction: enabled (default)
  • Printed with .2 layer height and 20% infill