<p>Promoted from comment: if you had switched from a higher temperature filament to lower temperature, you need to purge the hot end at the higher printing temperature to ensure the old filament is sufficiently fluid for the new to push out.</p>
<p>If you don't do this, pulling the old filament may leave a &quot;core&quot; passage that lets the new filament get to the nozzle, more or less, but the lining of old filament in the nozzle will both limit thermal transfer (plastics are generally poor conductors) and restrict flow even when the new filament is well melted.</p>
<p>This will result in a preheated nozzle printing acceptably until the filament carries away too much heat, then grossly underextruding when the flow rate rises (larger layers, print speed increasing after initial layer slowdown), and potentially partially recovering when the layers get smaller or (due to slicer settings) the print speed slows near the top of a tall part.</p>
<p>Solution: when switching filament, ensure that your purge cycle (whether manual or automatic) is done at the higher temperature for the two filaments involved -- if switching from PETG to PLA, for instance, you'll likely need to purge at 220 °C or higher, even though you'd print your PLA at 180-220 °C,</p>

CC BY-SA 4.0
2021-08-13T11:12:46.207Z
2021-08-13T11:12:46.207Z
Zeiss Ikon
<p>Assuming you do have a direct drive system as described.
Is this correct?</p>
<blockquote>
<p>Retraction Distance 6 mm speed 25 mm/s</p>
</blockquote>
<p>A retraction distance of 6 mm for direct a drive is huge and could easily be pulling the filament out so far it might become problematic. Most of my direct drive printers are 0.4 to 1 mm. In addition the 25 mm/s appears to me to be on the low side, though it would not surprise me if it's highly extruder specific. Most of my retraction speeds are 60 to 90 mm/s.
Faster retraction speeds can actually be more effective at stringing reduction then adding distance as. Faster travel will also reduce stringing as the nozzle has less time to ooze.</p>
<p>Are you incorrectly a using a Bowden profile?</p>

CC BY-SA 4.0
2021-08-07T17:48:35.987Z
Enders are normally bowden machines and OP didn't mention converting it.
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2021-08-07T22:16:28.030Z
@R..GitHubSTOPHELPINGICE Added at note of that discrepancy, thanks.
Kezat
CC BY-SA 4.0
2021-08-10T19:38:23.957Z
I was indeed still using my former bowden tube settings and never looked into what the direct drive retraction settings should be, so thank you for pointing this out and giving me a place to start.  Unfortunately the more I try the worse it is getting for all PLA prints now, but PETG is still printing fine with the same setup.  I am noticing a clunking sound occasionally during the print, so I probed the bed again but still getting the same results.  The nozzle is clean and only been used on a dozen prints or so, is it ok to use the same nozzle for PLA and PETG?  Could that be a cause?
Eric Archer
CC BY-SA 4.0
2021-08-11T17:29:42.877Z
@EricArcher I've switched back and forth between PETG and PLA a couple times; you just need to be sure you purge while within PETG temperature range (usually a bit hotter than PLA) to clear the nozzle and heat break when you switch back to PLA.  If you didn't purge the PETG within its print range, it may not be soft enough for PLA to push out at PLA temperature.
Zeiss Ikon
CC BY-SA 4.0
2021-08-12T20:42:21.203Z
@ZeissIkon As soon as I read this it was a facepalm moment, of course I need to purge at the hotter temp, but I failed to do so!  How much material do you feed through when you purge?  I am using OctoPi as well so I just set it to extrude 25mm and ran it three times.  I am running a test print now and will report back.  I am also noticing that my rollers are starting so show some ware and my gantry has a little play to it. I have ran this thing almost every day for 8 months, I think it is time for some serious maintenance.
Eric Archer
CC BY-SA 4.0
2021-08-13T11:06:40.407Z
@EricArcher I generally have a color change, so I feed until the extrusion is cleanly the new color.  Usually takes, IIRC, 10+ mm of extruder movement, might be as much as 20.  I don't watch that, and often just hand push the filament with the extruder disengaged.
Zeiss Ikon
CC BY-SA 4.0
2021-08-06T22:57:59.613Z
2021-08-07T22:18:24.400Z
2021-08-07T22:18:24.400Z
Kezat
<p>You appear to have severe underextrusion. It may be that you are trying to melt plastic faster than your printer can physically accomplish which would explain why it starts good and then the nozzle gets cold and then as the layers get small it comes good.
That doesn't explain why reducing the print speed doesn't help. Double check that it is actually slower.
I have had similar issues with cura that were fixed by altering the configuration, like tilting the model slightly or changing print orientation.</p>

CC BY-SA 4.0
2021-08-06T17:46:52.517Z
Welcome to 3D Printing SE and thank you for your contribution. When you get a chance, please take the [tour] to understand how the site works and how it is different than others.
agarza
CC BY-SA 4.0
2021-08-06T04:44:53.820Z
2021-08-06T05:24:47.627Z
2021-08-06T05:24:47.627Z
Samuel Comeau
<p>Printer: Ender 3 Pro - Direct drive, BLTouch, stock magnetic print bed surface<br />
Material: PLA - multiple brands</p>
<p>Slicer Settings:</p>
<ul>
<li>Layer Height .2 mm</li>
<li>Initial Layer Height .1 mm</li>
<li>Line Width .4 mm (with .4 mm nozzle) and also tried .39 mm</li>
<li>Wall thickness 1.2 mm (3 lines)</li>
<li>Hot End 210 °C</li>
<li>Bed 60 °C</li>
<li>Print Speed tried between 40 and 100 mm/s</li>
<li>Retraction Distance 6 mm  speed 25 mm/s</li>
<li>Print Cooling- Initial 3 layers 0 %, then 100 %, also tried 50 %</li>
</ul>
<p>I designed this in Tinkercad and sliced it with Cura for the Ender 3 Pro.  When I print this specific shape at this size the outer wall does not print properly, there are large gaps and it does not bond to the rest of the model so it just flakes off as soon as you handle it.  I can print other shapes fine- see the color swap example that was printed with the same settings successfully before AND after this series of failed prints of the same design.  Sometimes I get a clean first 15 layers then it goes to crap, and cleans up for the last 10% or so.  If I scale it down to 50 % it prints fine, but it will NOT print properly at full scale.</p>
<p>The infill and inner walls seem fine, but the walls are definitely not air-tight with what is left.</p>
<p>Looking for more things to try and troubleshoot, so please send me your ideas!</p>
<p>Troubleshooting steps so far:</p>
<ul>
<li>Re-downloaded the files and resliced with all new settings</li>
<li>Adjusted the print speed, wall line width and fan speeds</li>
<li>Tried multiple PLA types and brands</li>
</ul>
<p><a href="https://i.sstatic.net/4D9iC.jpg" rel="nofollow noreferrer" title="Printed model with printing errors"><img src="https://i.sstatic.net/4D9iC.jpg" alt="Printed model with printing errors" title="Printed model with printing errors" /></a></p>
<p><a href="https://i.sstatic.net/BNu8J.jpg" rel="nofollow noreferrer" title="Printed model without printing errors"><img src="https://i.sstatic.net/BNu8J.jpg" alt="Printed model without printing errors" title="Printed model without printing errors" /></a></p>

CC BY-SA 4.0
2021-08-04T17:47:50.593Z
You say it prints fine at 50% scale -- have you closely examined the preview of the gcode in your slicer?  This looks like you're getting travels where you want print...
Zeiss Ikon
CC BY-SA 4.0
2021-08-11T16:42:06.880Z
Honestly, I have no idea how to inspect my gcode or what I am looking for, but I suppose that will be added to the list of top things to learn!
Eric Archer
CC BY-SA 4.0
2021-08-13T15:54:22.513Z
I was referring to the preview function in your slicer -- Cura, at least, lets you view the result of the slice operation, scolling up and down layers and along the extruder path within a layer.  Only available *after* "Slice" is completed, of course, because it's interpreting its own gcode.
Zeiss Ikon
CC BY-SA 4.0
2021-08-14T23:35:55.890Z
Do you still have this issue after reducing retraction distance?
Kezat
CC BY-SA 4.0
2021-08-16T17:05:08.150Z
I don't think reducing the retraction distance did a whole lot but it was still the right move. I purged the nozzle at a higher temp (and ultimately replaced it) and am still getting bad layers on PLA with any design I print.  I was down to one roll that has been open for several months and I live in the Pacific Northwest, so now I am suspecting I may have some moisture affecting the prints.  I ordered a new roll and am running a test print now that failed repeatedly with the old stuff, so far so good.  I increased my hot end temp to 220 and changed to a glass bed to get the flattest surface.
Eric Archer
<creality-ender-3><print-quality><pla><troubleshooting>
Why is my outer wall layer printing with gaps and flaking off on this specific shape?
Eric Archer
# Why is my outer wall layer printing with gaps and flaking off on this specific shape?

(Asked by: username_0 on 2021-08-04)

Printer: Ender 3 Pro - Direct drive, BLTouch, stock magnetic print bed surface  
Material: PLA - multiple brands

Slicer Settings:

* Layer Height .2 mm
* Initial Layer Height .1 mm
* Line Width .4 mm (with .4 mm nozzle) and also tried .39 mm
* Wall thickness 1.2 mm (3 lines)
* Hot End 210 °C
* Bed 60 °C
* Print Speed tried between 40 and 100 mm/s
* Retraction Distance 6 mm speed 25 mm/s
* Print Cooling- Initial 3 layers 0 %, then 100 %, also tried 50 %

I designed this in Tinkercad and sliced it with Cura for the Ender 3 Pro. When I print this specific shape at this size the outer wall does not print properly, there are large gaps and it does not bond to the rest of the model so it just flakes off as soon as you handle it. I can print other shapes fine- see the color swap example that was printed with the same settings successfully before AND after this series of failed prints of the same design. Sometimes I get a clean first 15 layers then it goes to crap, and cleans up for the last 10% or so. If I scale it down to 50 % it prints fine, but it will NOT print properly at full scale.

The infill and inner walls seem fine, but the walls are definitely not air-tight with what is left.

Looking for more things to try and troubleshoot, so please send me your ideas!

Troubleshooting steps so far:

* Re-downloaded the files and resliced with all new settings
* Adjusted the print speed, wall line width and fan speeds
* Tried multiple PLA types and brands

[![Printed model with printing errors](https://i.sstatic.net/4D9iC.jpg "Printed model with printing errors")](https://i.sstatic.net/4D9iC.jpg "Printed model with printing errors")

[![Printed model without printing errors](https://i.sstatic.net/BNu8J.jpg "Printed model without printing errors")](https://i.sstatic.net/BNu8J.jpg "Printed model without printing errors")

**Tags:** creality-ender-3, print-quality, pla, troubleshooting

> **Comments:**
> **username_1**: You say it prints fine at 50% scale -- have you closely examined the preview of the gcode in your slicer?  This looks like you're getting travels where you want print...  
> **username_0**: Honestly, I have no idea how to inspect my gcode or what I am looking for, but I suppose that will be added to the list of top things to learn!  
> **username_1**: I was referring to the preview function in your slicer -- Cura, at least, lets you view the result of the slice operation, scolling up and down layers and along the extruder path within a layer.  Only available *after* "Slice" is completed, of course, because it's interpreting its own gcode.  
> **username_2**: Do you still have this issue after reducing retraction distance?  
> **username_0**: I don't think reducing the retraction distance did a whole lot but it was still the right move. I purged the nozzle at a higher temp (and ultimately replaced it) and am still getting bad layers on PLA with any design I print.  I was down to one roll that has been open for several months and I live in the Pacific Northwest, so now I am suspecting I may have some moisture affecting the prints.  I ordered a new roll and am running a test print now that failed repeatedly with the old stuff, so far so good.  I increased my hot end temp to 220 and changed to a glass bed to get the flattest surface.  

---

## 3 answers

### Answer by username_1 on 2021-08-13. Score: 2

Promoted from comment: if you had switched from a higher temperature filament to lower temperature, you need to purge the hot end at the higher printing temperature to ensure the old filament is sufficiently fluid for the new to push out.

If you don't do this, pulling the old filament may leave a "core" passage that lets the new filament get to the nozzle, more or less, but the lining of old filament in the nozzle will both limit thermal transfer (plastics are generally poor conductors) and restrict flow even when the new filament is well melted.

This will result in a preheated nozzle printing acceptably until the filament carries away too much heat, then grossly underextruding when the flow rate rises (larger layers, print speed increasing after initial layer slowdown), and potentially partially recovering when the layers get smaller or (due to slicer settings) the print speed slows near the top of a tall part.

Solution: when switching filament, ensure that your purge cycle (whether manual or automatic) is done at the higher temperature for the two filaments involved -- if switching from PETG to PLA, for instance, you'll likely need to purge at 220 °C or higher, even though you'd print your PLA at 180-220 °C,


---

### Answer by username_2 on 2021-08-06. Score: 1

Assuming you do have a direct drive system as described.
Is this correct?

> Retraction Distance 6 mm speed 25 mm/s

A retraction distance of 6 mm for direct a drive is huge and could easily be pulling the filament out so far it might become problematic. Most of my direct drive printers are 0.4 to 1 mm. In addition the 25 mm/s appears to me to be on the low side, though it would not surprise me if it's highly extruder specific. Most of my retraction speeds are 60 to 90 mm/s.
Faster retraction speeds can actually be more effective at stringing reduction then adding distance as. Faster travel will also reduce stringing as the nozzle has less time to ooze.

Are you incorrectly a using a Bowden profile?

> **Comments:**
> **username_3**: Enders are normally bowden machines and OP didn't mention converting it.  
> **username_2**: @username_3 Added at note of that discrepancy, thanks.  
> **username_0**: I was indeed still using my former bowden tube settings and never looked into what the direct drive retraction settings should be, so thank you for pointing this out and giving me a place to start.  Unfortunately the more I try the worse it is getting for all PLA prints now, but PETG is still printing fine with the same setup.  I am noticing a clunking sound occasionally during the print, so I probed the bed again but still getting the same results.  The nozzle is clean and only been used on a dozen prints or so, is it ok to use the same nozzle for PLA and PETG?  Could that be a cause?  
> **username_1**: @username_0 I've switched back and forth between PETG and PLA a couple times; you just need to be sure you purge while within PETG temperature range (usually a bit hotter than PLA) to clear the nozzle and heat break when you switch back to PLA.  If you didn't purge the PETG within its print range, it may not be soft enough for PLA to push out at PLA temperature.  
> **username_0**: @username_1 As soon as I read this it was a facepalm moment, of course I need to purge at the hotter temp, but I failed to do so!  How much material do you feed through when you purge?  I am using OctoPi as well so I just set it to extrude 25mm and ran it three times.  I am running a test print now and will report back.  I am also noticing that my rollers are starting so show some ware and my gantry has a little play to it. I have ran this thing almost every day for 8 months, I think it is time for some serious maintenance.  
> **username_1**: @username_0 I generally have a color change, so I feed until the extrusion is cleanly the new color.  Usually takes, IIRC, 10+ mm of extruder movement, might be as much as 20.  I don't watch that, and often just hand push the filament with the extruder disengaged.  

---

### Answer by username_4 on 2021-08-06. Score: 0

You appear to have severe underextrusion. It may be that you are trying to melt plastic faster than your printer can physically accomplish which would explain why it starts good and then the nozzle gets cold and then as the layers get small it comes good.
That doesn't explain why reducing the print speed doesn't help. Double check that it is actually slower.
I have had similar issues with cura that were fixed by altering the configuration, like tilting the model slightly or changing print orientation.

> **Comments:**
> **username_5**: Welcome to 3D Printing SE and thank you for your contribution. When you get a chance, please take the [tour] to understand how the site works and how it is different than others.  

---

