<p>Look at the gcode for those curves either manually in a text editor, or with a gcode analyzer tool (e.g. <a href="https://gcode.ws" rel="nofollow noreferrer">gcode.ws</a>) and see if there's anything strange about them. Cura is notorious for numeric instability problems with high resolution curves, where it will end up generating a few tiny moves (on the order of 0.005 mm) here and there that get truncated to zero motion on one axis and nonzero on the other (due to fixed rounding to 3 decimal places). To the printer firmware's motion planner, these look like sharp corners (because the angle changed severely from the last move), forcing it decelerate and re-accelerate.</p>
<p>The right fix for this is fixing Cura's numerical precision flaws. <a href="https://github.com/Piezoid/CuraEngine" rel="nofollow noreferrer">@piezoid</a> has a WIP branch doing this that might eventually push upstream to improve, but I wouldn't hold my breath. Short of that, there are a couple good workarounds:</p>
<ul>
<li><p>Check the &quot;Maximum Resolution&quot; and &quot;Maximum Deviation&quot; settings in Cura. You might have to unhide them if they're hidden. The defaults on modern Cura versions are 0.5 and 0.025 which tend to avoid the problem well, but older versions had bad values. (And of course, make sure you're using a recent version.)</p>
</li>
<li><p>Lowering the resolution (having it use a coarser triangle mesh) exported from your CAD software tends to avoid the problem.</p>
</li>
<li><p>Some people have reported success with the <a href="https://marketplace.ultimaker.com/app/cura/plugins/fieldofview/ArcWelderPlugin" rel="nofollow noreferrer">Arc Welder plugin</a>, but I'm not sure this is a good idea, and it depends on your printer having firmware that accepts the arc motion commands.</p>
</li>
</ul>

CC BY-SA 4.0
2022-03-20T19:33:47.167Z
2022-03-20T19:33:47.167Z
R.. GitHub STOP HELPING ICE
<p>If you haven't already, try rotating the object about the Z-axis to give a different orientation with respect to X and Y.  May not correct the problem but if the effect changes it may shed some light on the cause.</p>

CC BY-SA 4.0
2022-02-16T02:12:40.307Z
2022-02-16T02:12:40.307Z
allardjd
<p>It could be that the pressure in your nozzle is too high. I would switch on Coasting in Cura and see what effect that has.</p>

CC BY-SA 4.0
2022-02-18T17:43:11.480Z
2022-02-18T18:09:22.360Z
2022-02-18T18:09:22.360Z
Elric1997
<p>I'm trying to get good-quality thin wall prints with PLA on my Creality CR10s Pro V2 using Cura. After hours of calibration and testing, I'm getting quite good results. However, there is one issue I can't figure out. It seems that I'm getting uneven extrusion and blobs when the printer deaccelerates or accelerates. This issue causes problems with rounded corners on my test prints (see photos). In Cura, there is no retraction or anything in the arc, just accelerations. I have experimented with acceleration and jerk without success. I also tried to decrease the print speed from 50 mm/s to 20 mm/s, and it seems to have a minor positive effect. Anyone got any ideas on what values I need to change? Can this be a mechanical problem?</p>
<h3>General print settings:</h3>
<ul>
<li>Temp: 210 °C</li>
<li>Layer: 0.2 mm</li>
<li>Infill: 0 %</li>
<li>Retraction distance: 3 mm</li>
<li>Retraction speed: 60 mm/s</li>
<li>Cooling: 80 %</li>
<li>Flow: 102.5 %</li>
<li>Acceleration: 500 mm/s</li>
<li>Jerk: 20 mm/s (Tried values from 5 to 20)</li>
</ul>
<h3>Printed at 50 mm/s:</h3>
<p><a href="https://i.sstatic.net/OaIEh.jpg" rel="nofollow noreferrer" title="Printed model with blobs printing errors"><img src="https://i.sstatic.net/OaIEh.jpg" alt="Printed model with blobs printing errors" title="Printed model with blobs printing errors" /></a></p>
<h3>Printed at 20 mm/s:</h3>
<p><a href="https://i.sstatic.net/lNsIp.jpg" rel="nofollow noreferrer" title="Printed model that has been printed slower but still has blobs printing errors"><img src="https://i.sstatic.net/lNsIp.jpg" alt="Printed model that has been printed slower but still has blobs printing errors" title="Printed model that has been printed slower but still has blobs printing errors" /></a></p>
<h3>Cura:</h3>
<p><a href="https://i.sstatic.net/gFj1J.jpg" rel="nofollow noreferrer" title="Screenshot of the rendered model in Cura"><img src="https://i.sstatic.net/gFj1J.jpg" alt="Screenshot of the rendered model in Cura" title="Screenshot of the rendered model in Cura" /></a></p>

CC BY-SA 4.0
2022-02-16T12:03:47.613Z
Have you tried setting linear advance? https://marlinfw.org/tools/lin_advance/k-factor.html
FarO
<print-quality><ultimaker-cura><pla><creality-cr-10>
Issue with uneven surface when printing speed changes
Martin Claesson
# Issue with uneven surface when printing speed changes

(Asked by: username_0 on 2022-02-15)

I'm trying to get good-quality thin wall prints with PLA on my Creality CR10s Pro V2 using Cura. After hours of calibration and testing, I'm getting quite good results. However, there is one issue I can't figure out. It seems that I'm getting uneven extrusion and blobs when the printer deaccelerates or accelerates. This issue causes problems with rounded corners on my test prints (see photos). In Cura, there is no retraction or anything in the arc, just accelerations. I have experimented with acceleration and jerk without success. I also tried to decrease the print speed from 50 mm/s to 20 mm/s, and it seems to have a minor positive effect. Anyone got any ideas on what values I need to change? Can this be a mechanical problem?

### General print settings:

* Temp: 210 °C
* Layer: 0.2 mm
* Infill: 0 %
* Retraction distance: 3 mm
* Retraction speed: 60 mm/s
* Cooling: 80 %
* Flow: 102.5 %
* Acceleration: 500 mm/s
* Jerk: 20 mm/s (Tried values from 5 to 20)

### Printed at 50 mm/s:

[![Printed model with blobs printing errors](https://i.sstatic.net/OaIEh.jpg "Printed model with blobs printing errors")](https://i.sstatic.net/OaIEh.jpg "Printed model with blobs printing errors")

### Printed at 20 mm/s:

[![Printed model that has been printed slower but still has blobs printing errors](https://i.sstatic.net/lNsIp.jpg "Printed model that has been printed slower but still has blobs printing errors")](https://i.sstatic.net/lNsIp.jpg "Printed model that has been printed slower but still has blobs printing errors")

### Cura:

[![Screenshot of the rendered model in Cura](https://i.sstatic.net/gFj1J.jpg "Screenshot of the rendered model in Cura")](https://i.sstatic.net/gFj1J.jpg "Screenshot of the rendered model in Cura")

**Tags:** print-quality, ultimaker-cura, pla, creality-cr-10
> **Comments:**
> **username_1**: Have you tried setting linear advance? https://marlinfw.org/tools/lin_advance/k-factor.html  

---

## 3 answers

### Answer by username_2 on 2022-03-20. Score: 2

Look at the gcode for those curves either manually in a text editor, or with a gcode analyzer tool (e.g. [gcode.ws](https://gcode.ws)) and see if there's anything strange about them. Cura is notorious for numeric instability problems with high resolution curves, where it will end up generating a few tiny moves (on the order of 0.005 mm) here and there that get truncated to zero motion on one axis and nonzero on the other (due to fixed rounding to 3 decimal places). To the printer firmware's motion planner, these look like sharp corners (because the angle changed severely from the last move), forcing it decelerate and re-accelerate.

The right fix for this is fixing Cura's numerical precision flaws. [@piezoid](https://github.com/Piezoid/CuraEngine) has a WIP branch doing this that might eventually push upstream to improve, but I wouldn't hold my breath. Short of that, there are a couple good workarounds:

* Check the "Maximum Resolution" and "Maximum Deviation" settings in Cura. You might have to unhide them if they're hidden. The defaults on modern Cura versions are 0.5 and 0.025 which tend to avoid the problem well, but older versions had bad values. (And of course, make sure you're using a recent version.)
* Lowering the resolution (having it use a coarser triangle mesh) exported from your CAD software tends to avoid the problem.
* Some people have reported success with the [Arc Welder plugin](https://marketplace.ultimaker.com/app/cura/plugins/fieldofview/ArcWelderPlugin), but I'm not sure this is a good idea, and it depends on your printer having firmware that accepts the arc motion commands.


---

### Answer by username_3 on 2022-02-16. Score: 0

If you haven't already, try rotating the object about the Z-axis to give a different orientation with respect to X and Y. May not correct the problem but if the effect changes it may shed some light on the cause.


---

### Answer by username_4 on 2022-02-18. Score: 0

It could be that the pressure in your nozzle is too high. I would switch on Coasting in Cura and see what effect that has.


---

