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UM2: Under extrusion


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Posted · UM2: Under extrusion

Hello there! 😄 


I am trying to figure out why my UM2 have so much problems with under extrusion and I have really done my homework:


* Replaced to new heat cartridge (35W) since the old one (25W) was a bit old and slow

* Replaced bowden

* Replaced PTFE coupler

* Added the new kind of metal distance at the PTFE coupler

* Bought new filament (testing with black PET)

* I use 0.4mm nozzle when testing

* Olsson Block is installed


The ESTEPs showed 282 when I for the first time since I bought it checked them with M503 in OctoPrint. Fine. I try to feed 100mm at F40 speed and get various results (98 - 102mm) depending on ESTEP values I try. None of them seem consistent.


Even if I ramp it up to 290 from 282 I still get serious under extrusion even at 7m3 with the attached test file.


With this said... I have done some testing with the same ESTEP that UM2+ use (369) and I get WAY better result.


What ESTEP value should I use for my beautiful UM2 and how can I calculate it properly?


I hope someone can explain this to me 🙂


/ Oskar


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    Posted · UM2: Under extrusion

    Hi @oskars & @GregValiant,


    Well, thanks for the invitation.. 🙂


    First, I would not use "PET" as -a first material to refer too after all this modifications.

    Just use the good (old) PLA as reference for testing in general..

    You still have an UM2 that's upgraded, -but it's still not an UM2+ (as your feeder is still the original one)!

    So your E-step should NOT be changed, you should use 282, as you have not changed to the UM2+ "feeder". OK.?


    This is just my "briefly" thoughts.








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    Posted (edited) · UM2: Under extrusion

    Thank you! I went back to E282 now and red old ColorFabb PLA. 


    I did not mention that I use a custom fan mount which make me have to turn down fan speed to 30% to not get even more under extrusion because of too effective cooling. 


    I still get under extrusion. 


    I have NO idea way at this point. I have replaced so many parts by this point.


    Edit: lol. Pictures are up side down 😂




    Edited by oskars
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    Posted · UM2: Under extrusion

    Hi @oskars,


    Not a problem at all 🙂..


    I do not think your new fan mount create any problem here.


    What we're seeing here is "kind of" typical for a standard UM2 printing this model for "filament flow test".


    The problem might be a reduced diameter where the coupler meet the flange of the Olsson block, so if the torque is a little to hard -the pressure and "some" high temperature may lead to squeezing this critical part of the coupler.


    If you try to feed the filament by pushing it by hand, it should feed easily, if not check the coupler.


    Check the coupler passage and the nozzle/housing for "old" collected debris (by using atomic pull). 


    The tension of the special steel nut, holding the nozzle and delivering cooling to the upper part of the extruder.

    Tip: (Put a little marker on this "special nut" and the base plate so you can check that the nut stay in place.)


    You also need to use copper paste (to improve the heat transfer) where this nut connect to the base plate of the aluminum "house" containing the cooling radiator.


    You've to screw this nut until you feel it just met the stop, then turn it a quarter of turn more (90 deg.).

    This is what I'm using, -sure I print regularly at +255 deg., C.


    There is a little spacer, that can be printed an installed to space up the aft cooling fan from the aluminum rib. This little "modification" really improve the flow through the radiator. Yes, I'm been using this from day one.


    Another thing you can do, is to install the black feeder the reverse way, yes turn it 180 deg. This will make your filament go the wrong way, but this can be corrected by swapping two off the wires at the stepper motor connector.

    This will move the grooved groove from the outside to the inside of the bent filament that runs through the bowden tube. The result of this is less friction, that's reduce the force needed to feed the filament.


    Since you did not upgrade the feeder unit, this might help to get it working again.


    That's a bit to do, -but will "normally" work..


    Good luck




    Ps. I've been writing about all this before, I've to look around a bit.







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    Posted · UM2: Under extrusion
    On 12/18/2021 at 6:19 PM, Torgeir said:

    little spacer, that can be printed an installed to space up the aft cooling fan from the aluminum rib

    Hello @Torgeir, happy new year. Would you mind pointing me to where can I find it?


    Anyway, I am also having problems with extrusion.

    UM2 with Bondtech DDG, 3DSolex 0.4 nozzle, PETg. Draft, 0,6 line width, 2 walls, infill gyroid at 20%,  custom speeds, 230-235 nozzle temp and 75 bed temp, I really don't know why but custom flow gets 97% flow top/bottom layer in Cura.

    While printing everything seemed OK: walls ok, infill ok, first layer ok. But to the end...IMG_9729.jpg.zip

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    Posted (edited) · UM2: Under extrusion

    I have a lot of images but can't upload, don't know why. It says "There was a problem uploading the file.

    Please contact us for assistance."
    Edited by my3DBr
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    Posted · UM2: Under extrusion

    Hi @my3DBr,


    I've been looking inside here for this spacer (fan duct), -but by some reason this posting is gone.

    However, I have the gcode file (for an UM2) printer.

    It's printed at 205 deg. C. with a 0.4 mm nozzle and using PLA. (Sliced with Cura 2.3.1 I'll think).


    The file is attached here:






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