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Under-extrusion at start of some lines


Zackorion15

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Posted · Under-extrusion at start of some lines

So, I had been seeing some under-extrusion at the start of some lines after travel moves. So I started testing to try and replicate it in a simple to repeat test print. 

under-extrusion.jpg.703171c752f74f57d04d25df00a32581.jpg

I first thought it was just filament oozed away on long moves, but in my testing i rules that out as the culprit by printing 4 single wall squares far apart.

Three out of the 4 squares looked fine, no matter the distance between them, but the 4th one was consistently under-extruding at the start of each line. Then i realized I had made a small mistake when setting up the test, I had been scaling the model i used to set up the test by 175%. But i had accidentally set one of the squares to 150%. The one square that was printing poorly was the one AFTER the 150% square.

So, this made me wonder if the issue i was seeing in the test print was a result of cura attempting to print the lines differently because the scale of the model called for different thickness walls (though still only one line). Basically my thought was that the pressure was lower after the 150% square, so after the retract and travel, the prime was not enough to get back to the required pressure for the line size of the 175% square.

So, I set up a new test, with 2 squares at 150% and two at 175%. Sure enough, the 175% squares now both had under-extrusion.

Test_under-extrusion.jpg.8cf0976c5c3baf9a7caf84246e718a26.jpg


I have attached images of the initial issue that started my testing, an image of a test print with the latest testing setup, my cura settings file, and the gcode of the final testing setup shown in the picture.

I have been playing around with this, and can't seem to think of a fix to the tested issue, or the initial issue (if they are not in fact related). Anyone seen this and know what im looking at here? 😄

A8_Testing_squares.gcode A8 - Fast.curaprofile

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    Posted · Under-extrusion at start of some lines

    Underextrusion is caused by 

    1. Your nozzle temperature is too low, and/or your speed is too high. This is a very common cause, check those settings.

    2. Your extruder/stepper motor is worn out, and you should upgrade your motor to a stronger, more durable motor
    3. Bed leveling. My bed was not leveled properly, so I leveled it and I realized that was the cause of my underextrusion.

    4.  Slicer settings. Make sure that your printer's profile matches up with your printer's volume, details, etc. Accuracy is better than speed if you are trying to print a sculpture for detail.

     

    Try changing these parameters and see if it helps. 😄

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    Posted · Under-extrusion at start of some lines

    Temp changed nothing on this particular issue.

    Motor is fine, has no issues in all other cases, simply this edge case issue.

    Bed level is good.

    Slicer settings is more likely part of it, but that's the rub, i'm not sure exactly what the slicer is doing that might result in the issue. 

    I'v varied anything i know to have an effect including:
    retraction speed/distance
    temp
    Acceleration
    extra prime amount
    linear advance
    etc.

    But none of them seemed to touch the issue noted in the test situation without being taken to extremes.

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    Posted (edited) · Under-extrusion at start of some lines
    12 hours ago, Zackorion15 said:

    Temp changed nothing on this particular issue.

    Motor is fine, has no issues in all other cases, simply this edge case issue.

    Bed level is good.

    Slicer settings is more likely part of it, but that's the rub, i'm not sure exactly what the slicer is doing that might result in the issue. 

    I'v varied anything i know to have an effect including:
    retraction speed/distance
    temp
    Acceleration
    extra prime amount
    linear advance
    etc.

    But none of them seemed to touch the issue noted in the test situation without being taken to extremes.

     

    Interesting. Which printer is it?

     

    Edit: Did you try to lower your speed? Your speed can be a key factor in extruding properly. If nozzle temperature doesn't help, try lowering your speed by around 5 mm/s at a time. 

    Try printing a few tests made specifically for under-extrusion, like literally anything. When it is printing, try lowering the speed bit by bit to see what works best. Too fast of a speed gives you under-extrusion, a missing of layers, while too slow of a speed gives your over-extrusion, so you have to find that sweet spot.

    (Which is like 40-50 mm/s for some, 70-80 mm/s for others, and 180-200 mm/s for legends)

    Edited by Thegladster
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    Posted · Under-extrusion at start of some lines
    2 hours ago, Thegladster said:

     

    Interesting. Which printer is it?

     

    Edit: Did you try to lower your speed? Your speed can be a key factor in extruding properly. If nozzle temperature doesn't help, try lowering your speed by around 5 mm/s at a time. 

    Try printing a few tests made specifically for under-extrusion, like literally anything. When it is printing, try lowering the speed bit by bit to see what works best. Too fast of a speed gives you under-extrusion, a missing of layers, while too slow of a speed gives your over-extrusion, so you have to find that sweet spot.

    (Which is like 40-50 mm/s for some, 70-80 mm/s for others, and 180-200 mm/s for legends)



    It is on my Anet A8.

    Yeah, I'v tested a lot on print speed too, and for all other cases i'v found the speeds i use are just fine.
    20mm/s for initial layer
    30mm/s for top skin layer
    45mm/s for walls
    60mm/s for support/infill
    All with 1000mm/s^2 acceleration
    Small perimeter features printed at 50% of standard speeds.

    I'm definitely not running the fastest here, nor the slowest. My testing found that the issue was less pronounced but still present with speeds cut in half. So, that tells me that the core issue is not caused by speed, just exaggerated by it. 

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    Posted (edited) · Under-extrusion at start of some lines

    After extensive research this post seemed to describe the problem I was having the best: 5-10mm of some but not all single width line segments were underextruded as shown after a travel move, and none of the settings that would logically fix the issue really addressed it properly. My model also has several single walled features which would be consistent with the OP's hypothesis of cura not slicing properly when switching between different width thin features. After a large amount of time playing with every setting that could remotely have anything to do with outer perimeters, I found that disabling the "Compensate outer wall overlaps" setting made the single wall extrusions behave as intended. Phew! Hopefully that helps anyone else who is seeing this issue. I don't know why this setting would change the way a single wall feature is extruded. I'm inclined to think it is a bug.

    Edited by ganadyne
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    Posted · Under-extrusion at start of some lines
    On 11/30/2020 at 9:47 AM, ganadyne said:

    After extensive research this post seemed to describe the problem I was having the best: 5-10mm of some but not all single width line segments were underextruded as shown after a travel move, and none of the settings that would logically fix the issue really addressed it properly. My model also has several single walled features which would be consistent with the OP's hypothesis of cura not slicing properly when switching between different width thin features. After a large amount of time playing with every setting that could remotely have anything to do with outer perimeters, I found that disabling the "Compensate outer wall overlaps" setting made the single wall extrusions behave as intended. Phew! Hopefully that helps anyone else who is seeing this issue. I don't know why this setting would change the way a single wall feature is extruded. I'm inclined to think it is a bug.

    Thank you for sharing this, in my case I disabled both inner and outer wall. Solved a problem I had been battling for days now!

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    Posted · Under-extrusion at start of some lines
    On 11/30/2020 at 9:47 AM, ganadyne said:

    After extensive research this post seemed to describe the problem I was having the best: 5-10mm of some but not all single width line segments were underextruded as shown after a travel move, and none of the settings that would logically fix the issue really addressed it properly. My model also has several single walled features which would be consistent with the OP's hypothesis of cura not slicing properly when switching between different width thin features. After a large amount of time playing with every setting that could remotely have anything to do with outer perimeters, I found that disabling the "Compensate outer wall overlaps" setting made the single wall extrusions behave as intended. Phew! Hopefully that helps anyone else who is seeing this issue. I don't know why this setting would change the way a single wall feature is extruded. I'm inclined to think it is a bug.


    Hi, I can't find the setting you are mentioning. Do you know what it is called in Cura 5? 🙏

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    Posted (edited) · Under-extrusion at start of some lines

    I started having this problem after Cura 5 was released. I believe in my case it has a lot to do with the new "Flow Equalization Ratio" setting under the 'SPEED' menu - which affects the way the slicer decides to change line width. A '0' value makes it change the flow to adjust line width. A '100' value makes it change the printhead speed to adjust line width. Anything in between is a blend of the two at the given ratio. Try changing this value and see if it affects the line start positions after re-slicing. After trying this myself, my start points shifted and it fixed the issue. Prior to learning this, I had found that setting 'Outer Wall Wipe Distance' to '0' also helped alleviate some of the problem, by keeping more pressure in the nozzle after the travel move prior to the new line start. I hope this helps!

    Edited by filamentalPW
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