<p>What could cause that? </p>

<p>When linear_advance (v1.5) is "off" (<code>M900 K0</code>) - everything is uniform and smooth, only corners are protruding as expected. </p>

<p>When it is "on", I get these horizontal defects. My calibrated K-value is 2, I am getting same defects with K=1 as well as K=2. Position of defects is repeatable, so it is not random mechanics-caused underextrusion. </p>

<p>My setup uses a BMG Bowden extruder, A4988 drivers for Z and extruder with diode smoothers (X, Y are on TMC2209). I print the PETG with 245 °C, Perimeters at 50 mm/s, Gyroid Infill at 120 mm/s.</p>

<p><strong><em>After the original posting of the question I tried the following:</em></strong></p>

<ul>
<li><p>Removed diode smoothers on extruder and Z - <strong>no improvement</strong>. </p></li>
<li><p>It seems defect is somewhat connected to infill. Without infill print is nearly perfect. 50x50 box without infill prints perfectly, so it does not look like outer-wall speed-related. Reduced outer wall to 33&nbsp;mm/s, infill to 100&nbsp;mm/s (accelerations are also down 750->500, 1000->750), no improvement. Returned to A4988 on all axis - no improvement. Switched to 1/8 step on extruder (maybe it is step speed-related) - no improvement. Disabled infill before walls - <strong>no improvement</strong>. </p></li>
<li><p>Starting shooting time-lapses, and outer perimeter is extremely weird on some layers (see below)</p></li>
<li><p>Migrated configuration to latest Marlin 2.0. Enabled SQUARE_WAVE_STEPPING - no improvement. Gcode is uploaded here: <a href="https://s.14.by/3d_issue.gcode" rel="nofollow noreferrer">https://s.14.by/3d_issue.gcode</a></p></li>
<li><p>After inspecting larger parts printed before linear_advance (on large 100&nbsp;mm circular parts) - I also noticed this defect, more rare though. </p></li>
<li><p>Connected to oversized lab power supply, to ensure there is no power sag during high load. 24V 16A max power consumption. Print defects remain exactly the same though. </p></li>
</ul>

<p><a href="https://i.sstatic.net/rHbCY.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/rHbCY.jpg" alt="enter image description here"></a></p>

<p><a href="https://i.sstatic.net/LCWl3.jpg" rel="nofollow noreferrer" title="3D print showing horizontal defects"><img src="https://i.sstatic.net/LCWl3.jpg" alt="3D print showing horizontal defects" title="3D print showing horizontal defects"></a></p>

CC BY-SA 4.0
2019-09-15T00:30:02.653Z
Which version of Linear Advance (1.0 or 1.5 - that is, pre-1.1.9 Marlin or >=1.1.9) are you using? The K values look like 1.5, but 2 is very high for normal PLA and even 1 is somewhat high. Did you use the calibration pattern to select a K or just guess?
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2019-09-15T00:54:01.093Z
It looks to me like you have severe underextrusion in the areas where the print head has accelerated to significant speeds, but just on some layers. I suspect the mechanism of the problem is that your extruder gearing or idler is not up to producing the pressure that linear advance with K=1 or K=2 is attempting to get, and the filament slips backward. Can you watch closely and see if that appears to be the case?
R.. GitHub STOP HELPING ICE
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2019-09-15T00:56:16.290Z
@R.. It's 1.5. This is PETG, I used calibration pattern.
BarsMonster
CC BY-SA 4.0
2019-09-15T00:58:11.900Z
@R..It's hard to catch this in real time, but it is fairly consistent. I printed like 6 of these, and defects are in the same positions. I will try to tighten BMG gear and see if it helps. Also, in previous attempts I was reducing Ejerk (20->10->5) and Eacceleration (20k->10k->6k) - without any changes.
BarsMonster
CC BY-SA 4.0
2019-09-15T01:01:03.107Z
@BarsMonster: What temperature? PETG is hard to move through a nozzle fast even at high temps, and at lower temps I would not be surprised at all if it slipped from too much pressure. K between 1 and 2 does make sense for PETG with a bowden though.
R.. GitHub STOP HELPING ICE
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2019-09-15T01:10:28.577Z
@R.. 245°C, at the upper recommended temperature range
BarsMonster
CC BY-SA 4.0
2019-09-15T01:13:55.490Z
@BarsMonster: OK, temp shouldn't be the problem then. Are you printing it too fast? Otherwise my guess is just that the tension holding the filament is not sufficient.
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2019-09-15T01:18:52.153Z
@R.. Perimeters where problem is visible are at 50mm/s. Infil at 120. Accelerations are 500 for perimeters and 1500 for infills. And puzzling part is that without LA these speeds are not the issue, before LA I was even pushing it to 80...
BarsMonster
CC BY-SA 4.0
2019-09-15T01:29:17.240Z
@R.. What makes it unlikely a random slip of gear is that it is very consistent. Every print defect is in the same place...
BarsMonster
CC BY-SA 4.0
2019-09-15T01:31:29.923Z
@BarsMonster: I don't think you can actually extrude PETG at 120 mm/s. At 0.2 mm layer height (guess) and 0.4 mm nozzle (guess) that's nearly 10 mm³/s volumetric extrusion. There are likely lots of issues going on that just show up more visibly with LA enabled.
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2019-09-15T01:35:15.107Z
@R.. You diameter guess is perfect in both cases. 0.2 / 0.4... Cracked the part open - infill (gyroid) looks ok, I guess it is unable to accelerate to 120mm/s anyway's.
BarsMonster
CC BY-SA 4.0
2019-09-15T01:46:54.593Z
@R..Tightened BMG's gear quite a bit - but defect is still at exactly the same place.
BarsMonster
CC BY-SA 4.0
2019-09-15T01:58:45.237Z
@BarsMonster: Yeah, I think you'd need some *extreme* acceleration limits to actually hit 120 mm/s while doing gyroid.
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2019-09-15T09:28:50.963Z
Can you try to print the tower with 40 mm/s for the outer shell? It seems to only have an effect on long lines...
Trish
CC BY-SA 4.0
2019-09-16T16:41:59.777Z
@Trish I will try, but I am not sure why quality is different for different identical layers, where speed profile on the perimeters should be identical.
BarsMonster
CC BY-SA 4.0
2019-09-16T16:45:04.043Z
hm, is the extruder bar plastic or metal?
Trish
CC BY-SA 4.0
2019-09-17T06:46:53.003Z
@Trish Hot part of extruder is mounted on extruded-aluminum plate with 2 press-fit steel linear bearings. Cold part of extruder (BMG) has injection molded plastic case, the rest of BMG is metal.
BarsMonster
CC BY-SA 4.0
2019-09-17T08:57:03.410Z
I had uneven extrusion when the lever pressing the filament to the hobbed gear had secretly broken. Checking the lever and/or spring for even pressure could help
Trish
CC BY-SA 4.0
2019-09-19T00:28:42.907Z
@Trish Extruder is solid, no slipped steps. Also, defect position is consistent - on every print it is on the same places.
BarsMonster
CC BY-SA 4.0
2019-09-19T03:17:07.483Z
Does disabling combing in the slicer make the problem go away? (Cura uses the name "combing"; other slicers may call it something different. It's the feature to allow moves without retraction over already-printed regions or infill regions, and combing over infill region can lead to loss-of-material problems as described here: https://github.com/Ultimaker/CuraEngine/issues/1084)
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2019-09-19T07:33:12.697Z
that the error is Height dependant might indicate that the error is in the Z axis... What kind of printer is it?
Trish
CC BY-SA 4.0
2019-09-19T09:10:36.733Z
@R.. I see, interesting. In my case combing was enabled only in infill (Cura)
BarsMonster
CC BY-SA 4.0
2019-09-19T09:11:37.570Z
@Trish It's Flyingbear Ghost4. If it's Z-axis-related, then it is not clear why it disappears when linear advance = 0....
BarsMonster
CC BY-SA 4.0
2019-09-19T10:24:44.703Z
@BarsMonster Have you disabled "pressure compensation" in the slicer? when you use linear (or "pressure") advance in the firmware the similar feature in the slicer must be turned off.
FarO
CC BY-SA 4.0
2019-09-19T10:32:10.827Z
@BarsMonster: In infill is exactly where combing has this problem.
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2019-09-19T11:00:33.253Z
@R..Disabled combing everywhere - no changes :-/
BarsMonster
CC BY-SA 4.0
2019-09-19T13:28:04.170Z
@FarO: I think the only "pressure compensation" Cura has is "coasting". That should definitely be off. `speed_equalize_flow_enabled` ("Equalize filament flow") should also be off. It's a feature to compensate for lack of linear advance, and produces problematically-fast moves while extruding.
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2019-09-19T16:15:29.090Z
@R.. "Equalize filament flow" is disabled for all prints. Coasting is also disabled.
BarsMonster
CC BY-SA 4.0
2019-09-19T17:40:12.090Z
@BarsMonster: Can you observe the affected layers while they're being printed (maybe even take some video so you can go back and review) to figure out what was printed *just before* the problematic parts? If you know the exact height you could do this by reading the gcode too.
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2019-09-20T00:57:44.853Z
By chance are you doing the outer perimeter before or after the inner wall? That might be somewhat related.
craftxbox
CC BY-SA 4.0
2019-09-20T01:21:36.270Z
@craftxbox Tried both options. Currently outer perimeter first.
BarsMonster
CC BY-SA 4.0
2019-09-21T21:40:10.480Z
@R.. craftxbox FarO Please see photo of the layer in the middle of the print...
BarsMonster
CC BY-SA 4.0
2019-09-22T01:32:24.527Z
@BarsMonster: The infill looks *really* weird in that new image. Could you perhaps share the gcode file somewhere?
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2019-09-23T16:00:51.980Z
@BarsMonster Try to ask Marlin developers, maybe they know more. Interesting case. Does it happen with other STLs? From the middle layer it looks like that underextrusion alternates with overextrusion.
FarO
CC BY-SA 4.0
2019-09-24T00:14:43.130Z
@R..gcode uploaded, https://s.14.by/3d_issue.gcode
BarsMonster
CC BY-SA 4.0
2019-09-24T00:16:28.180Z
@FarO No issues for STLs which do not require infill... Will try to ask at reprap.org firmware section...
BarsMonster
CC BY-SA 4.0
2019-09-24T03:40:40.283Z
@BarsMonster: Have you tested without whatever extension you're using to do the timelapse camera shots? It looks like it's corrupting your gcode; at least in the analyzers I'm using, the motion back from the head-partking position seems to have *replaced* the first line of each layer, and your photo seems to show material wrongly deposited along that path.
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2019-09-24T03:41:58.457Z
@BarsMonster: It also really looks like you have coasting enabled, despite having previously said you don't. Can you make sure it's off? Coasting would definitely cause the type of problem you're seeing, and make it worse with LA.
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2019-09-24T03:53:06.927Z
@BarsMonster: I tried editing out the timelapse-inserted stuff and the missing first lines are no longer missing, so it's possible my analyzers are just barfing on it but it's not the problem. It still looks like the infill ends with coasting on each layer though, leaving insufficient material when starting the next layer's outer wall.
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2019-09-24T11:53:33.590Z
Does changing slicer affect the result?
FarO
CC BY-SA 4.0
2019-09-24T23:42:19.597Z
On second review, the infill doesn't necessarily look coasted; the slicer just stops the last line in weird ways (weird with respect to what I'd expect from zig-zaggify-infill) when no more gyroid oscillations will fit.
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2019-09-24T23:44:04.583Z
Could your problem just be fan? I see from the gcode your fan speed is being dynamically adjusted but is generally 75-100%. In my experience fan messes up PETG badly, and should be either off or at most something like 20-40% depending on your printer.
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2019-09-25T09:59:38.520Z
Is it only me, or the infill on the left, first photo, looks way too thick? when I print it's usually as wide as the outer layers, here it's very fat and not constant. I think there may be more issues with the printer than just some settings for perimeters or linear advance.
FarO
<petg><bowden><flyingbear-ghost-4>
Horizontal defects when linear_advance enabled?
BarsMonster
# Horizontal defects when linear_advance enabled?

(Asked by: username_0 on 2019-09-14)

What could cause that?

When linear\_advance (v1.5) is "off" (`M900 K0`) - everything is uniform and smooth, only corners are protruding as expected.

When it is "on", I get these horizontal defects. My calibrated K-value is 2, I am getting same defects with K=1 as well as K=2. Position of defects is repeatable, so it is not random mechanics-caused underextrusion.

My setup uses a BMG Bowden extruder, A4988 drivers for Z and extruder with diode smoothers (X, Y are on TMC2209). I print the PETG with 245 °C, Perimeters at 50 mm/s, Gyroid Infill at 120 mm/s.

***After the original posting of the question I tried the following:***

* Removed diode smoothers on extruder and Z - **no improvement**.
* It seems defect is somewhat connected to infill. Without infill print is nearly perfect. 50x50 box without infill prints perfectly, so it does not look like outer-wall speed-related. Reduced outer wall to 33 mm/s, infill to 100 mm/s (accelerations are also down 750->500, 1000->750), no improvement. Returned to A4988 on all axis - no improvement. Switched to 1/8 step on extruder (maybe it is step speed-related) - no improvement. Disabled infill before walls - **no improvement**.
* Starting shooting time-lapses, and outer perimeter is extremely weird on some layers (see below)
* Migrated configuration to latest Marlin 2.0. Enabled SQUARE\_WAVE\_STEPPING - no improvement. Gcode is uploaded here: <https://s.14.by/3d_issue.gcode>
* After inspecting larger parts printed before linear\_advance (on large 100 mm circular parts) - I also noticed this defect, more rare though.
* Connected to oversized lab power supply, to ensure there is no power sag during high load. 24V 16A max power consumption. Print defects remain exactly the same though.

[![enter image description here](https://i.sstatic.net/rHbCY.jpg)](https://i.sstatic.net/rHbCY.jpg)

[![3D print showing horizontal defects](https://i.sstatic.net/LCWl3.jpg "3D print showing horizontal defects")](https://i.sstatic.net/LCWl3.jpg "3D print showing horizontal defects")

**Tags:** petg, bowden, flyingbear-ghost-4

> **Comments:**
> **username_1**: Which version of Linear Advance (1.0 or 1.5 - that is, pre-1.1.9 Marlin or >=1.1.9) are you using? The K values look like 1.5, but 2 is very high for normal PLA and even 1 is somewhat high. Did you use the calibration pattern to select a K or just guess?  
> **username_1**: It looks to me like you have severe underextrusion in the areas where the print head has accelerated to significant speeds, but just on some layers. I suspect the mechanism of the problem is that your extruder gearing or idler is not up to producing the pressure that linear advance with K=1 or K=2 is attempting to get, and the filament slips backward. Can you watch closely and see if that appears to be the case?  
> **username_0**: @R.. It's 1.5. This is PETG, I used calibration pattern.  
> **username_0**: @R..It's hard to catch this in real time, but it is fairly consistent. I printed like 6 of these, and defects are in the same positions. I will try to tighten BMG gear and see if it helps. Also, in previous attempts I was reducing Ejerk (20->10->5) and Eacceleration (20k->10k->6k) - without any changes.  
> **username_1**: @username_0: What temperature? PETG is hard to move through a nozzle fast even at high temps, and at lower temps I would not be surprised at all if it slipped from too much pressure. K between 1 and 2 does make sense for PETG with a bowden though.  
> **username_0**: @R.. 245°C, at the upper recommended temperature range  
> **username_1**: @username_0: OK, temp shouldn't be the problem then. Are you printing it too fast? Otherwise my guess is just that the tension holding the filament is not sufficient.  
> **username_0**: @R.. Perimeters where problem is visible are at 50mm/s. Infil at 120. Accelerations are 500 for perimeters and 1500 for infills. And puzzling part is that without LA these speeds are not the issue, before LA I was even pushing it to 80...  
> **username_0**: @R.. What makes it unlikely a random slip of gear is that it is very consistent. Every print defect is in the same place...  
> **username_1**: @username_0: I don't think you can actually extrude PETG at 120 mm/s. At 0.2 mm layer height (guess) and 0.4 mm nozzle (guess) that's nearly 10 mm³/s volumetric extrusion. There are likely lots of issues going on that just show up more visibly with LA enabled.  
> **username_0**: @R.. You diameter guess is perfect in both cases. 0.2 / 0.4... Cracked the part open - infill (gyroid) looks ok, I guess it is unable to accelerate to 120mm/s anyway's.  
> **username_0**: @R..Tightened BMG's gear quite a bit - but defect is still at exactly the same place.  
> **username_1**: @username_0: Yeah, I think you'd need some *extreme* acceleration limits to actually hit 120 mm/s while doing gyroid.  
> **username_2**: Can you try to print the tower with 40 mm/s for the outer shell? It seems to only have an effect on long lines...  
> **username_0**: @username_2 I will try, but I am not sure why quality is different for different identical layers, where speed profile on the perimeters should be identical.  
> **username_2**: hm, is the extruder bar plastic or metal?  
> **username_0**: @username_2 Hot part of extruder is mounted on extruded-aluminum plate with 2 press-fit steel linear bearings. Cold part of extruder (BMG) has injection molded plastic case, the rest of BMG is metal.  
> **username_2**: I had uneven extrusion when the lever pressing the filament to the hobbed gear had secretly broken. Checking the lever and/or spring for even pressure could help  
> **username_0**: @username_2 Extruder is solid, no slipped steps. Also, defect position is consistent - on every print it is on the same places.  
> **username_1**: Does disabling combing in the slicer make the problem go away? (Cura uses the name "combing"; other slicers may call it something different. It's the feature to allow moves without retraction over already-printed regions or infill regions, and combing over infill region can lead to loss-of-material problems as described here: https://github.com/Ultimaker/CuraEngine/issues/1084)  
> **username_2**: that the error is Height dependant might indicate that the error is in the Z axis... What kind of printer is it?  
> **username_0**: @R.. I see, interesting. In my case combing was enabled only in infill (Cura)  
> **username_0**: @username_2 It's Flyingbear Ghost4. If it's Z-axis-related, then it is not clear why it disappears when linear advance = 0....  
> **username_3**: @username_0 Have you disabled "pressure compensation" in the slicer? when you use linear (or "pressure") advance in the firmware the similar feature in the slicer must be turned off.  
> **username_1**: @username_0: In infill is exactly where combing has this problem.  
> **username_0**: @R..Disabled combing everywhere - no changes :-/  
> **username_1**: @username_3: I think the only "pressure compensation" Cura has is "coasting". That should definitely be off. `speed_equalize_flow_enabled` ("Equalize filament flow") should also be off. It's a feature to compensate for lack of linear advance, and produces problematically-fast moves while extruding.  
> **username_0**: @R.. "Equalize filament flow" is disabled for all prints. Coasting is also disabled.  
> **username_1**: @username_0: Can you observe the affected layers while they're being printed (maybe even take some video so you can go back and review) to figure out what was printed *just before* the problematic parts? If you know the exact height you could do this by reading the gcode too.  
> **username_4**: By chance are you doing the outer perimeter before or after the inner wall? That might be somewhat related.  
> **username_0**: @username_4 Tried both options. Currently outer perimeter first.  
> **username_0**: @R.. username_4 username_3 Please see photo of the layer in the middle of the print...  
> **username_1**: @username_0: The infill looks *really* weird in that new image. Could you perhaps share the gcode file somewhere?  
> **username_3**: @username_0 Try to ask Marlin developers, maybe they know more. Interesting case. Does it happen with other STLs? From the middle layer it looks like that underextrusion alternates with overextrusion.  
> **username_0**: @R..gcode uploaded, https://s.14.by/3d_issue.gcode  
> **username_0**: @username_3 No issues for STLs which do not require infill... Will try to ask at reprap.org firmware section...  
> **username_1**: @username_0: Have you tested without whatever extension you're using to do the timelapse camera shots? It looks like it's corrupting your gcode; at least in the analyzers I'm using, the motion back from the head-partking position seems to have *replaced* the first line of each layer, and your photo seems to show material wrongly deposited along that path.  
> **username_1**: @username_0: It also really looks like you have coasting enabled, despite having previously said you don't. Can you make sure it's off? Coasting would definitely cause the type of problem you're seeing, and make it worse with LA.  
> **username_1**: @username_0: I tried editing out the timelapse-inserted stuff and the missing first lines are no longer missing, so it's possible my analyzers are just barfing on it but it's not the problem. It still looks like the infill ends with coasting on each layer though, leaving insufficient material when starting the next layer's outer wall.  
> **username_3**: Does changing slicer affect the result?  
> **username_1**: On second review, the infill doesn't necessarily look coasted; the slicer just stops the last line in weird ways (weird with respect to what I'd expect from zig-zaggify-infill) when no more gyroid oscillations will fit.  
> **username_1**: Could your problem just be fan? I see from the gcode your fan speed is being dynamically adjusted but is generally 75-100%. In my experience fan messes up PETG badly, and should be either off or at most something like 20-40% depending on your printer.  
> **username_3**: Is it only me, or the infill on the left, first photo, looks way too thick? when I print it's usually as wide as the outer layers, here it's very fat and not constant. I think there may be more issues with the printer than just some settings for perimeters or linear advance.  

---

## 0 answers

