<p>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:</p>
<ul>
<li><p>Upgrade to firmware with <a href="https://marlinfw.org/docs/features/lin_advance.html" rel="nofollow noreferrer">Linear Advance</a> and calibrate it for your material. I find PETG needs about K=1.4 on an Ender 3.</p>
</li>
<li><p>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.</p>
</li>
<li><p>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).</p>
</li>
</ul>
<p>Also make sure you don't have your slicer set to slowdown on overhangs, as it makes this phenomenon <strong>far</strong> worse.</p>
<p>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 &quot;not in skin&quot; 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.</p>

CC BY-SA 4.0
2020-06-24T21:04:12.710Z
2020-06-24T21:04:12.710Z
R.. GitHub STOP HELPING ICE
<p>I see some possible issues at work here:</p>
<ol>
<li>Retraction issues on the arc. You might need to decrease your retraction length a little.</li>
<li>Your bed might have a little play. tighten the eccentric nuts a tiny bit.</li>
<li>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.</li>
</ol>

CC BY-SA 4.0
2020-06-24T20:20:55.597Z
2020-06-24T20:20:55.597Z
Trish
<p>I have a model that's placed on the bed exactly like on this picture:</p>
<p><a href="https://i.sstatic.net/hDTcF.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/hDTcF.png" alt="sample model placement" /></a></p>
<p>I have constant quality degradation as the bed moves down to print in the upper left corner <strong>(1)</strong>.</p>
<p>Everything is fine on the X <strong>(2)-(3)</strong> side. It does not have any visible artifacts. All hell goes along the <strong>(1)-(3)</strong> curve:</p>
<p><a href="https://i.imgur.com/EvgyKFi.png" rel="nofollow noreferrer"><img src="https://i.imgur.com/EvgyKFi.png" alt="hell lines" /></a></p>
<p>Top left corner <strong>(1)</strong>:</p>
<p><a href="https://i.sstatic.net/oPGTi.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/oPGTi.jpg" alt="top left corner" /></a></p>
<p>On the way from <strong>(1)</strong> to <strong>(2)</strong> lines seem to disappear almost completely.</p>
<p>I used Cura slicer and these printing settings:</p>
<ul>
<li>stock ender firmware</li>
<li>0.2 mm layer height</li>
<li>supports</li>
<li>2 bottom &amp; top layers</li>
<li>PETG 235 °C nozzle</li>
<li>80 °C bed</li>
<li>walls x2</li>
<li>10 % infill gyroid</li>
<li>ironing</li>
<li>seam smart hiding</li>
<li>50 mm/s print speed</li>
<li>500 / 50 mm/s^2 acceleration / jerks</li>
</ul>
<p>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.</p>
<p>What should I try next?</p>
<p>Extruder steps/mm are tweaked for this filament. Extruder produces exactly 97 mm of 100 mm of filament.</p>
<h3>UPD</h3>
<p>I decided to change my software/hardware settings step by step. This time I changed only my software settings to these:</p>
<ul>
<li>Speed: 30 mm/s</li>
<li>Acceleration: 3000 mm/s^2</li>
<li>Retract: 4 mm</li>
<li>Combing: Not in Skin (previous print had the same value)</li>
<li>Overhanging wall speed 100% (same as the previous print)</li>
</ul>
<p>Corners have become much sharper and there is a lot less of bulging on the arc.</p>
<p><a href="https://i.sstatic.net/cpPQU.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/cpPQU.jpg" alt="arc" /></a></p>
<p>However, by X-axis <strong>(2) - (3)</strong> I see more artifacts:</p>
<p><a href="https://i.sstatic.net/zh7MP.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/zh7MP.jpg" alt="x-axis bottom" /></a></p>
<p>Y-axis has become better:</p>
<p><a href="https://i.sstatic.net/vMuZ5.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/vMuZ5.jpg" alt="y-axis bottom" /></a></p>
<p>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.</p>
<h3>UPD2</h3>
<p>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 <strong>240 °C</strong> and changed the stock vent with a circular vent. The wall count is 50 to make the model solid. Coasting is off.</p>
<p><a href="https://i.sstatic.net/3UgZQ.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/3UgZQ.jpg" alt="x-axis" /></a></p>
<p><a href="https://i.sstatic.net/OZnsB.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/OZnsB.jpg" alt="x-axis curve" /></a></p>
<p>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:</p>
<p><a href="https://i.sstatic.net/lYrF9.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/lYrF9.jpg" alt="doorstep build plate placement" /></a></p>
<p>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.</p>
<p>PS. USBASP is still in customs, so I'm doing all this on the stock firmware.</p>
<h3>UPD3</h3>
<p>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.</p>
<p>There are still some artifacts but everything looks relatively tolerable now.</p>
<p><a href="https://i.sstatic.net/ynYBN.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ynYBN.jpg" alt="after z-axis has been fixed" /></a></p>
<p>Thanks to all of you guys!</p>

CC BY-SA 4.0
2020-06-24T20:18:43.307Z
On the Arc are retraction artifacts. What's your retraction setting?
Trish
CC BY-SA 4.0
2020-06-24T21:55:05.740Z
@Trish, I have 6mm retract. I tried 2, 4, and decided to stop at 6mm. Otherwise, there was a lot of stringing.
night-crawler
<print-quality><creality-ender-3><petg><y-axis>
Visible lines along Y-axis on Ender 3 Pro
night-crawler
# Visible lines along Y-axis on Ender 3 Pro

(Asked by: username_0 on 2020-06-24)

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

[![sample model placement](https://i.sstatic.net/hDTcF.png)](https://i.sstatic.net/hDTcF.png)

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](https://i.imgur.com/EvgyKFi.png)](https://i.imgur.com/EvgyKFi.png)

Top left corner **(1)**:

[![top left corner](https://i.sstatic.net/oPGTi.jpg)](https://i.sstatic.net/oPGTi.jpg)

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](https://i.sstatic.net/cpPQU.jpg)](https://i.sstatic.net/cpPQU.jpg)

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

[![x-axis bottom](https://i.sstatic.net/zh7MP.jpg)](https://i.sstatic.net/zh7MP.jpg)

Y-axis has become better:

[![y-axis bottom](https://i.sstatic.net/vMuZ5.jpg)](https://i.sstatic.net/vMuZ5.jpg)

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](https://i.sstatic.net/3UgZQ.jpg)](https://i.sstatic.net/3UgZQ.jpg)

[![x-axis curve](https://i.sstatic.net/OZnsB.jpg)](https://i.sstatic.net/OZnsB.jpg)

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](https://i.sstatic.net/lYrF9.jpg)](https://i.sstatic.net/lYrF9.jpg)

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](https://i.sstatic.net/ynYBN.jpg)](https://i.sstatic.net/ynYBN.jpg)

Thanks to all of you guys!

**Tags:** print-quality, creality-ender-3, petg, y-axis
> **Comments:**
> **username_1**: On the Arc are retraction artifacts. What's your retraction setting?  
> **username_0**: @Trish, I have 6mm retract. I tried 2, 4, and decided to stop at 6mm. Otherwise, there was a lot of stringing.  

---

## 2 answers

### Answer by username_2 on 2020-06-24. Score: 2 | Accepted answer

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](https://marlinfw.org/docs/features/lin_advance.html) 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.


---

### Answer by username_1 on 2020-06-24. Score: 2

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.


---

