<p>This looks a lot like <strong>under extrusion caused by heat creep</strong>.</p>

<p>Heat creep is when the nozzle temperature 'creeps' up through the filament and makes it melt (a bit) and form a blob (or just widen enough to get stuck) a centimeter or two before the nozzle.</p>

<p>The characteristic is usually that everything works perfectly well for some quite fix amount of time, then there is severe under extrusion.</p>

<p>Solutions:</p>

<ul>
<li>Lower the temperature (yes, as then the heat won't creep as much!)</li>
<li>Add a fan cooling down the cooling part of the print head</li>
</ul>

<p>I have the same print head as you it seems (E3D 1.75 all metal) and I had heat creep when I changed the fan to a less noisy one (but also less effective).</p>

CC BY-SA 4.0
2018-07-12T11:16:02.793Z
Thank you all for response. I will investigate the heat creap. I use the fan that came with the E3D. It's a 7 blade fan of good quality. But maybe I need to clean the cold-end and the fan blades. They catch dust after a while.
Toon
CC BY-SA 4.0
2018-07-13T07:21:33.890Z
I had something like that too, but in my case it was caused by retraction settings. The retraction made the filament get out of the nozzle hole and caused a jam and thus an under extrusion.
Petar Petrov
CC BY-SA 4.0
2018-07-12T10:59:32.913Z
2018-07-12T10:59:32.913Z
Valmond
<p>This suggestion may not apply in your specific case (you seem to have looked closely at the problem, and it doesn't really fit the apparent time-dependence) but you might have an issue with the extrusion drive. If your hobbed drive isn't tight on the stepper motor then the 'push' might not be enough to match the force you've tested by hand. This explains one way that the extruder can be more sensitive to small performance variations than you would normally expect (heat build up somehow contributing to those variations).</p>

CC BY-SA 4.0
2018-07-16T09:23:23.087Z
Actually I have. I added extra current to the stepper driver because it was skipping when I first started to print with XT I also added tension to the hobbed gear springs. When it get's stuck the hobbed gear grinds the filament away. So no tension issues here. XT is a tough cookie.
Toon
CC BY-SA 4.0
2018-07-12T14:54:19.373Z
2018-07-12T22:46:06.997Z
2018-07-12T22:46:06.997Z
Sean Houlihane
<p>I have a possible cause for my problems. XT is sensitive to moisture (hydrolytical stability) When I extruded 20mm filament manually, the string felt a bit rough. When I looked closer very tiny bubbels where visible. I baked the filament at 60°C for 2 hours.</p>

<p>The baked filament allowed me to print a perfect model. </p>

<p>But after one print the filament is again affected by moisture so I need to build a dry-box and do some more tests before I come to a conclusion. </p>

CC BY-SA 4.0
2018-07-16T10:16:05.760Z
Nice to post an answer, please update when you have more information. The only remarkable thing is that it prints fine in the beginning, and all parts fail at about the same height (or are the parts printed in one job?).
0scar
CC BY-SA 4.0
2018-07-16T11:11:29.700Z
Forgot to mention that the two parts on the left are printed in one job.
Toon
CC BY-SA 4.0
2018-07-16T09:35:23.443Z
2018-07-16T09:35:23.443Z
Toon
<p>I'm printing parts for a HEVO (<a href="https://www.thingiverse.com/thing:2254103" rel="nofollow noreferrer">HyperCube Evolution</a> CoreXY), using Colorfabb XT filament. After several successful prints. I'm having a lot of failed prints. They start off pretty well but after ~15 layers the filament starts to string and blob. </p>

<p>Printer details</p>

<pre><code>Model: RepRap i3 
Extruder: E3D 1.75 all metal hotend.
Nozzle: .4
Print temp: 260°C (max. recommended).
</code></pre>

<p>Steps I took to troubleshoot</p>

<ol>
<li>First I thought my nozzle was clogged. But it's not I can push the filament by hand without issues.</li>
<li>Lowered the speed to 35&nbsp;mm/s.</li>
<li>Disabled retraction / disabled part cooling.</li>
<li>increased the max temp with 10&nbsp;% to ensure the filament flow</li>
</ol>

<p>Printed parts that fail: </p>

<p><a href="https://i.sstatic.net/2wEjO.jpg" rel="nofollow noreferrer" title="Top view printed part"><img src="https://i.sstatic.net/2wEjO.jpg" alt="Top view printed part" title="Top view printed part"></a>
<em>Note: the two parts on the left are printed in one job</em></p>

<p><a href="https://i.sstatic.net/1jure.jpg" rel="nofollow noreferrer" title="Side view printed part"><img src="https://i.sstatic.net/1jure.jpg" alt="Side view printed part" title="Side view printed part"></a></p>

<p>UPDATE 26/07
Dit a few more prints with PETG to eliminate the moisture problem. Same results.</p>

<p><a href="https://i.sstatic.net/l6vj4.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/l6vj4.jpg" alt="PETG"></a></p>

<p><a href="https://i.sstatic.net/GL1IF.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/GL1IF.jpg" alt="PETG2"></a></p>

CC BY-SA 4.0
2018-07-11T21:41:59.303Z
Welcome! Very well written and documented first post! Lowering speed and increasing temperature is usually the opposite of what you want. Is the cold end properly cooled? The filament you use is of high quality, my favorite brand actually, their filaments print very well using their settings, you print at the maximum temperature and under the minimum suggested speed.
0scar
CC BY-SA 4.0
2018-07-12T09:29:09.833Z
could you add nozzle size and layer height
profesor79
<print-quality><filament><diy-3d-printer><print-material><colorfabb-xt>
Printing with colorfabb XT fails after several successful layers
Toon
# Printing with colorfabb XT fails after several successful layers

(Asked by: username_0 on 2018-07-11)

I'm printing parts for a HEVO (HyperCube Evolution CoreXY), using Colorfabb XT filament. After several successful prints. I'm having a lot of failed prints. They start off pretty well but after ~15 layers the filament starts to string and blob. 
Printer details
Model: RepRap i3 
Extruder: E3D 1.75 all metal hotend.
Nozzle: .4
Print temp: 260°C (max. recommended).

Steps I took to troubleshoot

First I thought my nozzle was clogged. But it's not I can push the filament by hand without issues.
Lowered the speed to 35 mm/s.
Disabled retraction / disabled part cooling.
increased the max temp with 10 % to ensure the filament flow

Printed parts that fail: 

Note: the two parts on the left are printed in one job

UPDATE 26/07
Dit a few more prints with PETG to eliminate the moisture problem. Same results.

**Tags:** print-quality, filament, diy-3d-printer, print-material, colorfabb-xt
> **Comments:**
> **username_1**: Welcome! Very well written and documented first post! Lowering speed and increasing temperature is usually the opposite of what you want. Is the cold end properly cooled? The filament you use is of high quality, my favorite brand actually, their filaments print very well using their settings, you print at the maximum temperature and under the minimum suggested speed.  
> **username_2**: could you add nozzle size and layer height  

---

## 3 answers

### Answer by username_3 on 2018-07-12. Score: 9

This looks a lot like **under extrusion caused by heat creep**.

Heat creep is when the nozzle temperature 'creeps' up through the filament and makes it melt (a bit) and form a blob (or just widen enough to get stuck) a centimeter or two before the nozzle.

The characteristic is usually that everything works perfectly well for some quite fix amount of time, then there is severe under extrusion.

Solutions:

* Lower the temperature (yes, as then the heat won't creep as much!)
* Add a fan cooling down the cooling part of the print head

I have the same print head as you it seems (E3D 1.75 all metal) and I had heat creep when I changed the fan to a less noisy one (but also less effective).

> **Comments:**
> **username_0**: Thank you all for response. I will investigate the heat creap. I use the fan that came with the E3D. It's a 7 blade fan of good quality. But maybe I need to clean the cold-end and the fan blades. They catch dust after a while.  
> **username_4**: I had something like that too, but in my case it was caused by retraction settings. The retraction made the filament get out of the nozzle hole and caused a jam and thus an under extrusion.  

---

### Answer by username_5 on 2018-07-12. Score: 5

This suggestion may not apply in your specific case (you seem to have looked closely at the problem, and it doesn't really fit the apparent time-dependence) but you might have an issue with the extrusion drive. If your hobbed drive isn't tight on the stepper motor then the 'push' might not be enough to match the force you've tested by hand. This explains one way that the extruder can be more sensitive to small performance variations than you would normally expect (heat build up somehow contributing to those variations).

> **Comments:**
> **username_0**: Actually I have. I added extra current to the stepper driver because it was skipping when I first started to print with XT I also added tension to the hobbed gear springs. When it get's stuck the hobbed gear grinds the filament away. So no tension issues here. XT is a tough cookie.  

---

### Answer by username_0 on 2018-07-16. Score: 3

I have a possible cause for my problems. XT is sensitive to moisture (hydrolytical stability) When I extruded 20mm filament manually, the string felt a bit rough. When I looked closer very tiny bubbels where visible. I baked the filament at 60°C for 2 hours.

The baked filament allowed me to print a perfect model.

But after one print the filament is again affected by moisture so I need to build a dry-box and do some more tests before I come to a conclusion.

> **Comments:**
> **username_1**: Nice to post an answer, please update when you have more information. The only remarkable thing is that it prints fine in the beginning, and all parts fail at about the same height (or are the parts printed in one job?).  
> **username_0**: Forgot to mention that the two parts on the left are printed in one job.  

---

