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I have a model that's placed on the bed exactly like on this picture:

sample model placement

I have constant quality degradation as the bed moves down to print in the upper left corner (1).

Everything is fine on the X (2)-(3) side. It does not have any visible artifacts. All hell goes along the (1)-(3) curve:

hell lines

Top left corner (1):

top left corner

On the way from (1) to (2) lines seem to disappear almost completely.

I used Cura slicer and these printing settings:

  • stock ender firmware
  • 0.2 mm layer height
  • supports
  • 2 bottom & top layers
  • PETG 235 °C nozzle
  • 80 °C bed
  • walls x2
  • 10 % infill gyroid
  • ironing
  • seam smart hiding
  • 50 mm/s print speed
  • 500 / 50 mm/s^2 acceleration / jerks

It looks like a mechanical issue, so I tried tightening/untightening bed bolts. It didn't help. They are a little bit tight, but not too much. The bed does not seem to be wobbling. Also, I tried the bed for wobbling in its top/bottom position. It looks fine along all the way.

What should I try next?

Extruder steps/mm are tweaked for this filament. Extruder produces exactly 97 mm of 100 mm of filament.

UPD

I decided to change my software/hardware settings step by step. This time I changed only my software settings to these:

  • Speed: 30 mm/s
  • Acceleration: 3000 mm/s^2
  • Retract: 4 mm
  • Combing: Not in Skin (previous print had the same value)
  • Overhanging wall speed 100% (same as the previous print)

Corners have become much sharper and there is a lot less of bulging on the arc.

arc

However, by X-axis (2) - (3) I see more artifacts:

x-axis bottom

Y-axis has become better:

y-axis bottom

Currently, I don't have any visible or sensible bed / X play. I tuned rollers to have enough tension not to slip if rotate them separately. So, if I rotate the roller, it moves the whole bed or X carriage. I'll try increasing the tension a little bit and then I'll share the result.

UPD2

I've made belts a little bit tighter and decided to print a new model. The layer height is 0.3 mm. Also, I tried increasing temperature up to 240 °C and changed the stock vent with a circular vent. The wall count is 50 to make the model solid. Coasting is off.

x-axis

x-axis curve

Now all artifacts are along the X-axis. There are many fewer of them at (1) than at (2). The model is a doorstep. On the build plate it's placed like this:

doorstep build plate placement

Now I think the problem has nothing to do with X/Y play and these two factors can be eliminated. I'll revert belt tensions back to their previous values and decrease the printing temperature down to 225-230 °C.

PS. USBASP is still in customs, so I'm doing all this on the stock firmware.

UPD3

I have finally figured out what was wrong. It was insufficient Z-belt tension on both sides. A close look at a DSLR camera shot gave me a clue: there was almost always a straight segment followed by a visible additional step down between layers.

There are still some artifacts but everything looks relatively tolerable now.

after z-axis has been fixed

Thanks to all of you guys!

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    $\begingroup$ On the Arc are retraction artifacts. What's your retraction setting? $\endgroup$ – Trish Jun 24 at 20:18
  • $\begingroup$ @Trish, I have 6mm retract. I tried 2, 4, and decided to stop at 6mm. Otherwise, there was a lot of stringing. $\endgroup$ – night-crawler Jun 24 at 21:55
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There are a lot of different print quality problems going on here, but the biggest I see is the bulging and sagging at the corners of each layer. This is a result of extrusion not being a zero-delay linear function of extruder motor motion, but subject to compression/pressure. This causes excess extrusion when printing slows down (approaching and rounding a corner) and underextrusion just after speeding back up. There are several possible fixes:

  • Upgrade to firmware with Linear Advance and calibrate it for your material. I find PETG needs about K=1.4 on an Ender 3.

  • Increase your acceleration limits (up to 3000 mm/s² should be ok for Ender 3) so that far less time is spent moving slow. You need to adjust the per-axis limits in config menu, not just the single acceleration setting in your slicer.

  • Decrease your print speed so that there's less difference in cornering speed and nominal speed (50 mm/s is too high for PETG anyway in my experience; you'll get underextrusion and bad layer bonding).

Also make sure you don't have your slicer set to slowdown on overhangs, as it makes this phenomenon far worse.

The other surface artifacts I'm less sure about, and you should probably look for other answers about resolving them. Trish is right that the lines look like a retraction problem - material intended to be there got lost somewhere else. It's probably due to combing (skipping retraction inside the model and letting material ooze out there). I would set combing to "not in skin" and set the max combing distance to something very small (around or slightly less than 1 mm) and see if that fixes the problem. Combing is especially bad with PETG in my experience.

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I see some possible issues at work here:

  1. Retraction issues on the arc. You might need to decrease your retraction length a little.
  2. Your bed might have a little play. tighten the eccentric nuts a tiny bit.
  3. As you are at it, check your X-belt, because accuracy on the Y move is affected by the accuracy of the X-head's position.
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