<p>Here's your problem:</p>

<blockquote>
  <ul>
  <li>1&nbsp;mm retraction distance -> stringing...</li>
  </ul>
</blockquote>

<p>If you have stringing, that means that material that was supposed to end up as part of printed lines instead ended up somewhere else, leaving less material (underextrusion) where it was actually wanted. This particular test piece may not exhibit stringing, but it's likely that it occurred interior to the piece, in the infill region. Contrary to widespread(?) opinion, stringing here is not harmless. It's just not visibly ugly. But it still messes up the surface quality, and even more importantly the strength, of your print.</p>

<p>You don't say if your printer has a bowden extruder or direct drive. If a Bowden, the 1&nbsp;mm of retraction is virtually useless; a typical Bowden system has more than 1&nbsp;mm just of <em>compression</em> between the extruder gear and the hotend, meaning that retracting by 1&nbsp;mm does not pull the filament back out of the hotend at all, and doesn't even relieve all the pressure that's pushing melted material out. I would recommend an absolute minimum of 5&nbsp;mm for Bowden type extruders, unless your printer firmware has linear advance (Marlin 1.1.9+ or comparable features in other firmware) in which case you might be able to reduce it some. For direct drive, I don't have experience, but 1&nbsp;mm is still probably too low; 2.5&nbsp;mm is the believable recommendation I've heard.</p>

<p>In addition to retraction, you can further reduce material loss to stringing/oozing in the infill region by turning on Ultimaker Cura's "Zig-zaggify infill" option, which helps avoid in generating travel without retraction over unprinted area within the infill zone (see e.g. <a href="https://github.com/Ultimaker/CuraEngine/issues/1084" rel="nofollow noreferrer">this issue</a>). Turning slicer setting "combing" to "off" is an even more extreme option here. Of course make sure retraction is really on (not "retract at layer change", which is a separate, mostly useless option) and make sure "retraction minimum travel" is set low (something like 150&nbsp;% of the nozzle width or less) to prevent retraction from getting skipped on short travel moves.</p>

<p>I also just noticed you wrote:</p>

<blockquote>
  <p>I've tried smaller retracting distances...</p>
</blockquote>

<p>This was probably based on erroneous advice. Reducing or eliminating retraction does not mitigate these sorts of problems; it creates them. The only reasons to reduce retraction distance are to fight problems with the extruder gear grinding down the filament after repeated retraction, and problems with jamming the path into the hotend due to pulling molten material back into the cool part where it then solidifies and jams. If you're not having such problems you should not reduce retraction. If you are having such problems, you should try to fix them in other ways that still let you keep the necessary amount of retraction not to have catastrophic print quality problems from material coming out in the wrong places.</p>

CC BY-SA 4.0
2019-08-31T21:46:29.487Z
2019-09-01T20:49:00.830Z
2019-09-01T20:49:00.830Z
R.. GitHub STOP HELPING ICE
<p>I increased the retracting distance to 1.5mm. Speed was set to 30mm/s
Printing temperature is still 245°C</p>

<p>The screw which is pressing the filament to the drive gear was too tight.
So the stepper lost steps.</p>

<p>-> No stringing and no under extrusion anymore. prints are looking good now.</p>

CC BY-SA 4.0
2019-09-02T15:18:03.460Z
2019-09-02T15:18:03.460Z
rusky
<p>You can see small gaps in the print which looks like under extrusion (see image below).
What is the reason for that?</p>

<p>I've tried smaller retracting distances. Temperature looks stable.</p>

<p>Print settings:</p>

<ul>
<li>PETG from Extruder</li>
<li>245&nbsp;°C Printing temperature</li>
<li>50&nbsp;mm/s print speed</li>
<li>25&nbsp;mm/s wall speed</li>
<li>30&nbsp;mm/s retracting speed</li>
<li>1&nbsp;mm retraction distance -> stringing...</li>
<li>Print cooling fan is enabled</li>
</ul>

<p>Setup:</p>

<ul>
<li>E3D Titan Aero</li>
<li>Duet Wifi</li>
<li>1,5&nbsp;A Motor current for feeder motor</li>
<li>250&nbsp;mm/s<sup>2</sup> feeder max acceleration </li>
</ul>

<p>Slicer:</p>

<ul>
<li>Ultimaker Cura 4.0</li>
</ul>

<p><a href="https://i.sstatic.net/yXGPn.jpg" rel="nofollow noreferrer" title="Small gaps in the print"><img src="https://i.sstatic.net/yXGPn.jpg" alt="Small gaps in the print" title="Small gaps in the print"></a></p>

CC BY-SA 4.0
2019-08-31T18:58:05.400Z
Welcome to 3dPrinting.SE! What is the filament size and layer thickness?
Pᴀᴜʟsᴛᴇʀ2
CC BY-SA 4.0
2019-08-31T22:13:32.823Z
Try lowering the hotend temperature with 10 °C.
0scar
<petg><retraction><underextrusion><e3d-titan>
Under extrusion... sometimes
rusky
# Under extrusion... sometimes

(Asked by: username_0 on 2019-08-31)

You can see small gaps in the print which looks like under extrusion (see image below).
What is the reason for that?

I've tried smaller retracting distances. Temperature looks stable.

Print settings:

* PETG from Extruder
* 245 °C Printing temperature
* 50 mm/s print speed
* 25 mm/s wall speed
* 30 mm/s retracting speed
* 1 mm retraction distance -> stringing...
* Print cooling fan is enabled

Setup:

* E3D Titan Aero
* Duet Wifi
* 1,5 A Motor current for feeder motor
* 250 mm/s2 feeder max acceleration

Slicer:

* Ultimaker Cura 4.0

[![Small gaps in the print](https://i.sstatic.net/yXGPn.jpg "Small gaps in the print")](https://i.sstatic.net/yXGPn.jpg "Small gaps in the print")

**Tags:** petg, retraction, underextrusion, e3d-titan
> **Comments:**
> **username_1**: Welcome to 3dPrinting.SE! What is the filament size and layer thickness?  
> **username_2**: Try lowering the hotend temperature with 10 °C.  

---

## 2 answers

### Answer by username_3 on 2019-08-31. Score: 1 | Accepted answer

Here's your problem:

> * 1 mm retraction distance -> stringing...

If you have stringing, that means that material that was supposed to end up as part of printed lines instead ended up somewhere else, leaving less material (underextrusion) where it was actually wanted. This particular test piece may not exhibit stringing, but it's likely that it occurred interior to the piece, in the infill region. Contrary to widespread(?) opinion, stringing here is not harmless. It's just not visibly ugly. But it still messes up the surface quality, and even more importantly the strength, of your print.

You don't say if your printer has a bowden extruder or direct drive. If a Bowden, the 1 mm of retraction is virtually useless; a typical Bowden system has more than 1 mm just of *compression* between the extruder gear and the hotend, meaning that retracting by 1 mm does not pull the filament back out of the hotend at all, and doesn't even relieve all the pressure that's pushing melted material out. I would recommend an absolute minimum of 5 mm for Bowden type extruders, unless your printer firmware has linear advance (Marlin 1.1.9+ or comparable features in other firmware) in which case you might be able to reduce it some. For direct drive, I don't have experience, but 1 mm is still probably too low; 2.5 mm is the believable recommendation I've heard.

In addition to retraction, you can further reduce material loss to stringing/oozing in the infill region by turning on Ultimaker Cura's "Zig-zaggify infill" option, which helps avoid in generating travel without retraction over unprinted area within the infill zone (see e.g. [this issue](https://github.com/Ultimaker/CuraEngine/issues/1084)). Turning slicer setting "combing" to "off" is an even more extreme option here. Of course make sure retraction is really on (not "retract at layer change", which is a separate, mostly useless option) and make sure "retraction minimum travel" is set low (something like 150 % of the nozzle width or less) to prevent retraction from getting skipped on short travel moves.

I also just noticed you wrote:

> I've tried smaller retracting distances...

This was probably based on erroneous advice. Reducing or eliminating retraction does not mitigate these sorts of problems; it creates them. The only reasons to reduce retraction distance are to fight problems with the extruder gear grinding down the filament after repeated retraction, and problems with jamming the path into the hotend due to pulling molten material back into the cool part where it then solidifies and jams. If you're not having such problems you should not reduce retraction. If you are having such problems, you should try to fix them in other ways that still let you keep the necessary amount of retraction not to have catastrophic print quality problems from material coming out in the wrong places.


---

### Answer by username_0 on 2019-09-02. Score: 0

I increased the retracting distance to 1.5mm. Speed was set to 30mm/s
Printing temperature is still 245°C

The screw which is pressing the filament to the drive gear was too tight.
So the stepper lost steps.

-> No stringing and no under extrusion anymore. prints are looking good now.


---

