4
$\begingroup$

I've had an Ender 5 Plus for a few weeks now. It's printing great and I've got my tuning pretty good at the moment. I've noticed some horizontal inconsistencies matching feature/geometry changes. It seems to be associated with maybe layer time(?) I only have a picture from two models, but the problem will appear in other places on different models, always matching some change in the layers.

The problem is consistent all around the model and changes position with different prints, so I know it's not a mechanical problem. Say I printed a 2x2 cm tower 20 cm tall, it will not have any of these imperfections because every layer is identical.

I highly suspect the layer time/temperature change, but I don't know how to fix this, I'm a bit stumped. They both were printed at 200 °C and I'm trying a new one at 210 °C (best temperature with the spool I have) and it has the same problem. All three models are from the same spool of PLA.

Also, I use Cura with mostly default settings for the Ender 5+.

Here are the pictures :

I tried to highlight the idea, but every line matches with some change in the model Model 1

On the benchy it's harder to see, but the hull line match with the solid floor of the model, and the top ones match with the top window sill starting.

Benchy

$\endgroup$
2
  • $\begingroup$ I still struggle with some of it. I've just upgraded to a 32 bit board with TMC2209 and now noticed a potential wobble in my lead screw (not linked with artifact in the post tho). So I'll fix this this week and come back to this problem which I think is due to the infill overlap pulling on outer walls while cooling. Sorry for going MIA $\endgroup$
    – GmodCake
    Commented Feb 2, 2021 at 14:36
  • $\begingroup$ I have exactly the same problem: " try print from outside to inside (outer walls > inner walls > infill). Then try to reduce "Flow" until you see no over extrusion (or even small gaps in the surface)." Doesn't work (just reduce slightly the problem" If I print SQUARE o RECTANGULAR shapes all is perfect, no over extrusion no nothing, simply perfect, but once the model make geometric changes the lines appear In another forum they said that is CURA related so change slicer, didn't test it yet; any updates or solves..?? $\endgroup$ Commented Apr 21, 2022 at 7:40

3 Answers 3

1
$\begingroup$

This is varying underextrusion due to loss of material to oozing in the interior of the model.

When printing the infill pattern, the nozzle doesn't follow a single continuous extrusion path, but moves from the end of one path to the beginning of the next, and under Cura defaults, does this without retracting the filament. This causes unpredictable amounts to ooze out during travel from one to the next, thereby desynchronizing the planned/intended amount of material extruded so far and the actual amount. This means, when the next outer-wall extrusion starts, there's an unpredictable deficiency between the amount of material at the nozzle to extrude, and the amount the slicer intended to extrude. The result is what you're seeing.

To fix it, you need to eliminate oozing, not just outside the model where it appears as visible stringing, but inside too. Either disable "Combing" entirely in Cura, or set "Max Comb Distance With No Retract" to something very low (0.8 mm or less). Also set "Minimum Extrusion Distance Window" to 0 to ensure Cura doesn't skip retractions for other reasons.

You may also want to play with extrusion length and speed. Too short or too long can be bad; 5-7 mm is the reasonable range for PLA with a bowden. Higher speed generally helps too; the printer should be able to handle 50 mm/s or faster.

$\endgroup$
11
  • $\begingroup$ I don't even have the slightest form of stringing or oozing on any of my prints actually. I'm not quite sure about this theory $\endgroup$
    – GmodCake
    Commented Jan 18, 2021 at 22:47
  • 1
    $\begingroup$ Can't the issue be related to some form of hysteresis? Not posted as an answer, just a genuine thought. The printer is decent, but not of super quality (carriages on aluminum extrusion profiles, belts not straight, etc.). These ridges are often seen when the geometry changes, so that a different path is followed by the print head causing it to result in a few tenths of a mm difference with respect to the previous layers?. My custom Pursa i3 printer has this also, but my Hypercube CoreXY does not (nor does my Ultimaker 3E). $\endgroup$
    – 0scar
    Commented Jan 19, 2021 at 14:15
  • 1
    $\begingroup$ These don't even look like tenths of a mm but hundredths, maybe 0.08-0.10 mm at most. Positional hysteresis seems like a possibility but I've fought with this type of issue a lot including where it's caused structural weakness, and it seems to be extrusion related. Maybe hysteresis of the Bowden tube or excess flow where extrusions prior are overhanging and have less backpressure. $\endgroup$ Commented Jan 19, 2021 at 14:47
  • 1
    $\begingroup$ @FarO: Because when the nozzle isn't properly primed after starting the perimeter, you don't just get a gap in extrusion then a normal perimeter. It will flow, just at a lower rate, until reaching an equilibrium where it's primed again. $\endgroup$ Commented Aug 15, 2022 at 17:35
  • 1
    $\begingroup$ @FarO: That only works with direct drive. With bowden, the spring model LA/PA use is insufficient to represent the behavior of the bowden tube and filament over such a long distance, and while it will improve things so that there's less pressure, you will still have significant residual pressure and oozing unless you choose a K factor so high that your corners start to disappear inward. $\endgroup$ Commented Aug 19, 2022 at 18:44
0
$\begingroup$

If this matches the horizontal planes - like "solid floor" than I would advice to check overlap settings. My suspicion is slight overextrusion, which might be the reason of many small horizontal differences. Using 3 mm filament I often suffer of similar inconsistencies, until I find proper flowrate to avoid overextrusion. Adding first to second, the solid plane will push walls more to sides.

Do you print "Infill Before Walls" (Cura setting)? You may try to disable this checkbox and observe if the result persisted. Also you may enable "Outer Before Inner Walls" - to ensure, that outer wall is printed first with least interference (though some other issues may appear after travel, layer change, etc.).

  • So try print from outside to inside (outer walls > inner walls > infill).
  • Then try to reduce "Flow" until you see no overextrusion (or even small gaps in the surface).
  • Finally revert these settings (infill > inner > outer) and check again.
$\endgroup$
1
  • $\begingroup$ You can reduce the issue with less overlap, but the issue is due to shrinkage. Some tests were performed, see my answer $\endgroup$
    – FarO
    Commented Aug 15, 2022 at 8:46
0
$\begingroup$

The issue with the "hull line" is known. It depends on the fact that the material shrinks after extrusion and faster layers give less time to the previous layer to shrink, so they appear continuous, while slower layers take more time, so the previous layer has more time to shrink and there will be a visible change in the outer dimensions.

So, larger layers are the slower ones. You can increase the temperature a bit, so that it will take more time to cool down to the shrinkage temperatures, you can print faster, you can increase chamber temperature to have more time before shrinkage, or you can cool more the part so that no matter the current layer time, the previous one will always be already shrunk.

In the Polymaker Discord server there is a channel about the "hull line". You can find an invitation to the server and check there.

$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .