<p>Have you tried adjusting the Extra Restart Distance in Simplify3D or Retraction Extra Prime in Ultimaker Cura?  Most slicers should have a similar setting, perhaps named just slightly differently.  A small positive value can help prime the nozzle after a long travel when you've lost back pressure or oozed a little.</p>

CC BY-SA 4.0
2018-09-26T23:09:05.450Z
2018-09-27T05:52:07.650Z
2018-09-27T05:52:07.650Z
Brian Chow
<p>Zero retraction is just a special (worst) case of under-retraction. You'll pretty much always lose material to oozing if you don't retract before travel. At best this ends up hidden inside the print (but can still affect weight and weight balance); usually it'll also harm the surface.</p>

<p>Ensure that retraction is set to <em>always</em> happen (not skipping short travel), and at least 5-6 mm for bowden extruders. Direct extruders can get away with less but I'm not sure exactly how much less. Less-rigid materials need more retraction to make up for compression of the filament between the extruder gear and the nozzle.</p>

CC BY-SA 4.0
2019-06-07T09:05:27.870Z
The second part of your answer implies Bowden style printers considering the rather large retraction, I think it is best to state that explicitly.
0scar
CC BY-SA 4.0
2019-06-06T17:16:28.740Z
2019-06-07T12:22:17.350Z
2019-06-07T12:22:17.350Z
R.. GitHub STOP HELPING ICE
<p>I came across several issues which seem to have been lowered.
Firstly, I changed from a 0.4 to a 0.5 mm nozzle. Because of the backpressure I was not able to print my PETG (Colorfabb XT filament) below 270°C which caused unresolvable oozing. After that I was able to extrude till 230°C.</p>

<p>The left print below shows the result. I disassembled the hotend, there was no leak or whatsoever. Maybe it was too cold for printing. However, the temperature displayed was 250°C. Then I replaced the cheap aluminum heat block with a copper alloy based one. After that my PIDs did not work anymore. I had to greatly enhance the d-term, otherwise there was a big overshoot. Guess there was a serious heat conducting issue with the old BQ hotend. </p>

<p><a href="https://i.sstatic.net/uxd43.jpg" rel="nofollow noreferrer" title="Prints using BQ Alu Heatblock (left) and Copper alloy heatblock (right)"><img src="https://i.sstatic.net/uxd43.jpg" alt="Prints using BQ Alu Heatblock (left) and Copper alloy Heatblock (right)" title="Prints using BQ Alu Heatblock (left) and Copper alloy heatblock (right)"></a></p>

<p>Anyway, from there it became better. However, I noticed that I still have severe underextrusion after travel moves (second piece, first picture, first piece, second picture). I use Cura, so I activated retraction with the feature to prime after travel moves. I got the wall closed just after 0.35 mm³. </p>

<p><a href="https://i.sstatic.net/Oj1Ey.jpg" rel="nofollow noreferrer" title="Prints using Copper alloy Heatblock (left)"><img src="https://i.sstatic.net/Oj1Ey.jpg" alt="Prints using Copper alloy Heatblock (left)" title="Prints using Copper alloy Heatblock (left)"></a></p>

<p>My Question: Is this underextrusion after travel moves normal for PETG/XT? I did not discover such behavior with PLA or ABS in the past. </p>

<p>Current Site Advice: Despite the weight, copper heat blocks seem to be worth the upgrade. </p>

CC BY-SA 4.0
2018-07-07T21:57:07.613Z
What is your retraction length?
0scar
CC BY-SA 4.0
2018-07-08T11:25:03.933Z
I need 2.5 mm for PETG. But the underextrusion happens also if no retraction is active.
dgrat
<extrusion><colorfabb-xt>
Underextrusion after travel moves with PETG/Colorfab XT
dgrat
# Underextrusion after travel moves with PETG/Colorfab XT

(Asked by: username_0 on 2018-07-07)

I came across several issues which seem to have been lowered.
Firstly, I changed from a 0.4 to a 0.5 mm nozzle. Because of the backpressure I was not able to print my PETG (Colorfabb XT filament) below 270°C which caused unresolvable oozing. After that I was able to extrude till 230°C.

The left print below shows the result. I disassembled the hotend, there was no leak or whatsoever. Maybe it was too cold for printing. However, the temperature displayed was 250°C. Then I replaced the cheap aluminum heat block with a copper alloy based one. After that my PIDs did not work anymore. I had to greatly enhance the d-term, otherwise there was a big overshoot. Guess there was a serious heat conducting issue with the old BQ hotend.

[![Prints using BQ Alu Heatblock (left) and Copper alloy Heatblock (right)](https://i.sstatic.net/uxd43.jpg "Prints using BQ Alu Heatblock (left) and Copper alloy heatblock (right)")](https://i.sstatic.net/uxd43.jpg "Prints using BQ Alu Heatblock (left) and Copper alloy heatblock (right)")

Anyway, from there it became better. However, I noticed that I still have severe underextrusion after travel moves (second piece, first picture, first piece, second picture). I use Cura, so I activated retraction with the feature to prime after travel moves. I got the wall closed just after 0.35 mm³.

[![Prints using Copper alloy Heatblock (left)](https://i.sstatic.net/Oj1Ey.jpg "Prints using Copper alloy Heatblock (left)")](https://i.sstatic.net/Oj1Ey.jpg "Prints using Copper alloy Heatblock (left)")

My Question: Is this underextrusion after travel moves normal for PETG/XT? I did not discover such behavior with PLA or ABS in the past.

Current Site Advice: Despite the weight, copper heat blocks seem to be worth the upgrade.

**Tags:** extrusion, colorfabb-xt

> **Comments:**
> **username_1**: What is your retraction length?  
> **username_0**: I need 2.5 mm for PETG. But the underextrusion happens also if no retraction is active.  

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## 2 answers

### Answer by username_2 on 2018-09-26. Score: 3 | Accepted answer

Have you tried adjusting the Extra Restart Distance in Simplify3D or Retraction Extra Prime in Ultimaker Cura? Most slicers should have a similar setting, perhaps named just slightly differently. A small positive value can help prime the nozzle after a long travel when you've lost back pressure or oozed a little.


---

### Answer by username_3 on 2019-06-06. Score: 0

Zero retraction is just a special (worst) case of under-retraction. You'll pretty much always lose material to oozing if you don't retract before travel. At best this ends up hidden inside the print (but can still affect weight and weight balance); usually it'll also harm the surface.

Ensure that retraction is set to *always* happen (not skipping short travel), and at least 5-6 mm for bowden extruders. Direct extruders can get away with less but I'm not sure exactly how much less. Less-rigid materials need more retraction to make up for compression of the filament between the extruder gear and the nozzle.

> **Comments:**
> **username_1**: The second part of your answer implies Bowden style printers considering the rather large retraction, I think it is best to state that explicitly.  

---

