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Complete head scratcher ... why?


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Posted (edited) · Complete head scratcher ... why?

Does anyone have any idea why this test print of a .1 mm layer (set layer height) would do this?

 

It seems almost like a checkerboard and I am a bit off on the bed level but a minor issue compared to the checkerboarding. Any ideas?

WeChat Image_20201206123314.jpg

Edited by A2k
forgot to link test print stl
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    Posted · Complete head scratcher ... why?

    Hi @A2k,

     

    This looks like the glass plate have small bumps, -hi where there is no filament seen.

    Maybe the plate is installed reverse side up? There's normally a heat warning on the up side..

     

    Thanks

     

    Torgeir

     

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    Posted · Complete head scratcher ... why?

    No bumps, the glass is smooth just a thin layer of glue wiped on with water like always. Glass is right side up, the sticker fell off while washing the glass and I never stuck it back on.

     

    Could this be something with the belts or axels or trapezoidal leadscrew?

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    Posted · Complete head scratcher ... why?

    I re-cleaned the bed, re-leveled it, tightened the belts and lubricated ( X,Y)and greased (Z) everything and no difference. Here is the 2nd print of the same .1 mm square

    WeChat Image_20201208021649.jpg

    WeChat Image_20201208021632.jpg

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    Posted · Complete head scratcher ... why?

    It could be the glass: glass is never totally flat, it has bumps and pits. If you look through a car window, especially on older cars, and in curved areas of the window, you will see the lens-deformations caused by this unflatness.

     

    But it could also be the rods not being totally straight. If they would only be 0.025mm curved, almost nothing, that would show up as a 0.05mm difference in layer height, in a sort of sine-wave. Thus a full layer in fine settings. If both rods have it, you could get a pattern like yours. Maybe you can check if the repeating frequency is one full turn of the rods?

     

    Bent rods could be caused by lifting the printer by the rods, instead of by the frame. Or by doing hard atomic pulls (which is why I use a much smoother method without pulling hard). Or it could have been in the rods from the beginning, if their extrusion was not perfect, or if they have been handled roughly during transport (e.g. if it were 3m or 5m long rods loaded on trucks by a crane).

     

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    Posted · Complete head scratcher ... why?

    Interesting, and which rods would I check the xy rods the hotend rides on or the pulley side rods also? How would I check such small potential warp? Would it be easier to just order new rods?

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    Posted (edited) · Complete head scratcher ... why?

    Hi @A2k,

     

    I'll think geert_2 is right, you have at least two "rotating" shaft that is slightly bent.

    If you measure the distance between the mid of "filament" bumps, this distance will match "one rev" distance the head will move on the bed. So one rotation of the "12mm" shaft will be equal to the distance between the bumps..

    Did you get this problem all of a sudden?

    Edited by Torgeir
    Name spelling.
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    Posted · Complete head scratcher ... why?

    Ah thank you, I will do another test and measure. 

     

    I have not used my printer for almost 3 years and started noticing some inconsistencies when started printing again. Maybe it got damaged during a move I had since then?

     

    Since the UM2 line is EOL does anyone know how I can approach the repair?

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    Posted · Complete head scratcher ... why?

    Thank you for the additional details Torgeir! I just did a larger test (stopped it after noticing it was about to do a 2md layer)and the distance seems to be between 40-45 mm from center of each 'hole' Does this align with the one rev or 12 mm shaft rotation theory you mentioned @Torgeir?

    WeChat Image_20201209130721.jpg

    WeChat Image_20201209130642.jpg

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    Posted (edited) · Complete head scratcher ... why?

    Yes, this is about right I'll think.

     

    I also took a measure and here's the pictures:

     

    Here is the distance along the X-axe (from left to right).

    1_Rev_Dist.thumb.jpg.e6b30cc20939c9a7ad6c4ce43abda50e.jpg

     

    Here is a temporary point made on the left inner pulley on the L/H X-axis.

     

    Aft_Left_X_Pulleye.thumb.jpg.1c234247ff33e63661eebec32db261d1.jpg

     

    This appear to be close to 40 mm.. 

     

    So this mean @geert_2 was absolutely right..

     

    Torgeir

     

     

    Edited by Torgeir
    Edit of text.
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    Posted · Complete head scratcher ... why?

    To repair: trying to bend the rods the other way round, doesn't seem like a good idea to me: chances are that it gets far worse. So I wouldn't do that.

     

    I would say: now that you know the most probable cause: if you can work around this by using a slightly thicker first layer, then try to live with it?

     

    To rule out the glass for sure as a cause, what you could try is: mark and measure the exact centers of the "dots" you see, from the edge of the glass. Then rotate the glass 180°, and do the test again. If the cause is the glass, then the pattern should have rotated also. If the rods, it should not have rotated.

     

    To prevent further damage, never lift the printer by the rods, so don't grab into the top opening, but grab from the bottom. And use very smooth and soft atomic pulls to clean the nozzle. Have a look at my method here (and then scroll down a little bit):

    https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/

     

    Note: do copy any of my manuals and models that you find usefull, as I am not sure I can keep them up here on our website, since our website-engine, layout, functionality and rules are changing here (e.g. in the future we can no longer upload zip-files).

     

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    Posted (edited) · Complete head scratcher ... why?

    Thank you so much, so based on the measurements would you say that if it is not the glass it is the center rods and not the outer pulley rods right?

     

    Here are some additional photos after I flipped the glass and releveled, which is showing it is not yet level but does hide it like you said.

     

    I will finally try to rotate the glass per your suggestion with the same leveling to ensure it is not the glass.

     

    I will open a support ticket to replace whatever part the issue is.

     

    Does anyone know the actual names of the rods? I'd like to be more educated and describe the issue better in the support ticket.

    WeChat Image_20201210105624.jpg

    WeChat Image_20201210105607.jpg

    Edited by A2k
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    Posted · Complete head scratcher ... why?
    2 hours ago, A2k said:

    Does anyone know the actual names of the rods? I'd like to be more educated and describe the issue better in the support ticket.

     

    The source files for older printers are published on Github:

    https://github.com/Ultimaker/Ultimaker2Extended#ultimaker2extended

     

    I guess, you are asking for "print head shaft x" and "... y"?

     

    grafik.thumb.png.ef03c98ea0df3f358c8fee2975563986.png

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    Posted · Complete head scratcher ... why?

    If it are rods, then it should be the *outer rotating rods*, those with the belts. Because it is their wobbly rotation that causes the pattern (I think). Try measuring and calculating if the circumference of the pulley wheel and belt matches the distance between the spots? Visually guestimating, it could.

     

    Or you could make it more easy: using a marker, mark a spot on the pulley and on the belt, rotate the pulley, and each time it comes along the belt, then mark the belt as well on that same matching spot. After a few rotations, your belt should have marks with the exact same distance as the pattern. If that is the cause.

     

    I am not saying it can't be the inner rods which are carrying the head, but that seems *very* unlikely, since they do not rotate. So they would have to have a sine-wave or zigzag deformation all along their whole length, and that seems unlikely.

     

    But when printing, after 2 or 3 layers, you will most likely not see anything anymore of this deformation. It will probably be less noticable than the layer-lines and print-lines. So the question is whether it is worth worrying about? My experience with disassembling and repairing complex equipment (like cameras and stuff) is that it sometimes ends worse than it was before. If it was my printer, I wouldn't want to fall into the trap of "keep repairing it until it is broken", a risk that is always there with any fine and complex equipment.

     

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    Posted · Complete head scratcher ... why?

    I hear you @geert_2 but I would really rather it work how it is supposed to especially when I will want to print with different nozzles and even smaller layer heights.

     

    Here are some images where I made white marks in the belts per your suggestion and overlaid lines to represent the relationship to the print. I think they are lining up.

     

    What seems to show an even clearer case is the pulley gears themselves which seems to show the wobble fairly clearly in the video I took in the zip attached. 

     

    The last two image is where I rotated the glass 180 and left bed leveling exactly the same to rule out that it is the glass or bed. This double confirms it is not the glass since I both flipped it and rotated.

     

    Thank you everyone for the help! Next stop UM Support and replacement parts 😞

    WeChat Image_20201210214628.jpg

    WeChat Image_20201210214639.jpg

    WeChat Image_20201210231634.jpg

    WeChat Image_20201210231724.jpg

    pulleyGears_20201210215954.zip

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