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Top Layers not touching - UM2


Nicolinux
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Posted · Top Layers not touching - UM2

@gr5 - I'm working together with mevander on the same machine so I thought I'd get into the discussion just to make things more confusing. =) Thank you all for your help and brainpower put into solving this. To address two of your questions. We have already been in contact with Robert who got our gcode and could print the box with no problems, so I think we can take that off the list though of course I'm happy to post it for you if you would like. Come to think of it I believe we use the same one that was posted earlier in this thread.

We have also tested the temperature and basically got the same results as in the video.

The error occurs early, after a couple of layers as mevander said, and the pattern then holds through the entire print. I printed a 7cm tall "cylinder-ish" piece (lightsabre "heat sink" :-P) with the same result, non-connecting wall layers etc. though the bottom layer looks perfect.

gallery_36655_1357_305333.jpggallery_36655_1357_133819.jpg

What I find curious and which might give a clue to this problem is that thinner layers seems to give better coverage. Today I ran a print at .06mm layer, 70mm/s and 235 degrees C which came out with very nice surfaces (albeit with a bit of stringing).

gallery_36655_1357_93901.jpg

 

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    Posted · Top Layers not touching - UM2

    Can anyone prepare the GCODE of the test box 30x30x5mm for UM2 but generated in other slicer than Cura?

    0.2mm layer hight, 50mm/s print speed, 20% infill, 6-7 top layers.

     

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    Posted · Top Layers not touching - UM2

    Well at .06mm layer height you are extruding at half the speed as if printing at .1mm layer height so the feeder doesn't have to work so hard. So this sounds like underextrusion still. You could try printing at thicker layer but slower print speed to compensate and get the same volume of plastic. For example if you print layers 2.3 times thicker then try printing 2.3X slower.

     

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    Posted · Top Layers not touching - UM2

    I agree that it is a bit confusing with all the different users and input around this issue. Just to add to the confusion, I had to print a detail for a work setup today. I set it at 0.1 mm layer thickness, 20 mm/s and 220 C. It looked horrible already at the second layer. I increased the temperature to 230 and then the different lines barely managed to touch and it still looked pretty awful. I increased the flow to 120 % which made it look almost ok and at 130% flow things look like they should!

    I'm going to remove the hotend today, clean it and check it for any burnt material that might be creating resistance to the feeder. We have a spare hotend that we might install and test as well and I'll let you know what we find out.

     

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    Posted · Top Layers not touching - UM2

    Ultimaker is going to send us new nozzle block and new teflon isolator and hopefully that will solve our issue.

    In the meantime we're printing at 220C and 130% flow with ColorFabb Glowfill with pretty good results.

    We've tried 230-240C and 120% flow however all prints were really "hairy" (known issue with Colorfabb with higher temperatures).

    I've found one more issue with the printer head which might cause underextrusion but before I can tell what is this I need to confirm that with Ultimakers technical support.

     

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    Posted · Top Layers not touching - UM2

    I thought earlier in this thread the nozzle was stated not to be the issue, so yet again the nozzle?

    I have this phenomenom occuring sometimes too, but not all the time that's why I don't think the nozzle is the main problem. But perhaps it makes it even worse..

     

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    Posted · Top Layers not touching - UM2

    I just found something which might help to solve this case:

    When I switched off the fans to test something for a different issue, a close top surface was suddenly not closed (compare the middle and the right print in the picture below).

    Horizontal banding on my UM2

    So it has something to do with cooling...

     

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    Posted · Top Layers not touching - UM2

    Just wanted to update to let you know that a new PTFE-coupling and new hotend nozzle didn't solve the issues

     

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    Posted · Top Layers not touching - UM2

    I think I have also this problem. I printed unti yesterday only with Ultimaker PLA and testing now Colorfabb PLA. I print the Colorfabb with 200°C (higher temperature causes bubbles). With the Ultimaker PLA this problem not occurs. I have printed with 100% fan.

    I read through this thread but didn´t found a solution for this problem.

    Layern not touching

     

    EDIT: Ok also reproduced with Ultimaker PLA, set material flow to 120% and everything was "fine" now. Also interested in a better solution of this problem. Already printed the underextrusion test, everything fine up to 10mm³/s.

     

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    Posted · Top Layers not touching - UM2

    @stephanG that's called "pillowing". It's usually fixed by using:

    - thicker layers (layers < 0.1mm tend to be worse as the threads break)

    - more fan (most important of everything)

    - more top layers (as it eventually recovers). Usually 6 top layers are enough.

    Notice how the problem is more on the right side where the fan doesn't reach as well (because nozzle is closer to left fan)? (or did you turn the part around?)

    I think slowing down the top layers by 50% would help also giving the filament an extra few milliseconds to cool, shrink, thin as it's being laid down before it touches the layer below. Once it touches the layer below further shrinking can break the thread.

     

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    Posted · Top Layers not touching - UM2

    Hi,

     

    I haven't posted here for a long time because I didn't have anything new to report (still not checked the rods and I don't think I will do it anymore). But now I have found something interesting.

    Back when Renthal shared his .gcode for the square, I printed it and it came out almost perfect:

    surface1

     

    I did some other tests and started again with Renthal's cube:

    cube original

    There are some very feint gaps, but nothing like I was used to.

    Then I took his settings (load profile from gcode in Cura) but printed the full 20mm cube with two different filament colors:

    cube original big

    cube original big2

    This time - perfect surface. No gaps at all!

    Ok, then I gradually started to change settings (one setting at a time) to see what would cause it:

    Infill 0%

    cube empty

     

    Lots of gaps.

     

    Early cooling (advanced setting fan full on at height)

    cube early cool

    Again, some gaps.

    Combing off

    cube comb off

     

    Some gaps. The weird thing is, another test with combing on (which should be just the default setting from Renthal) showed some feint gaps too.

    cube comb on

     

     

    And from here on, every other setting I changed, did not influence the print. The surface was perfect without any gaps!

     

    Layer height 0.2

    cube layer 0.2

     

    Top/bottom 0.6

    cube Top 0.6

     

    Travel speed 200

    cube travel 200

    I don't know what to make of it. I still think it is something mechanical that only manifests under certain circumstances. I'd be interesting if others could print some of these cubes. I have attaced the .gcode (UM2 .gcode flavor) below. Everything was printed at 230°.

     

     

    A while ago I have also printed one flat layer where a recurring pattern was visible. I have re-printed it again. Did two runs, 0.1 and 0.15 layer height (only one layer and took care of the Cura setting about the first layer height. This thing is really only 0.1/0.15mm high).

    0.1

    flat 0.1

     

    0.15

    flat 0.15

     

    A few pages back Illuminarti suggested to measure the distance between the center of these spots. I did - it isn't very accurate, but after several measurements it boils down to the same value. From each center of one spot to each adjacent center of another, the distance amounts to 40mm.

    So there you have it, added more entropy to an already chaotic problem :)

    EDIT

    Forgot to mention - If anyone is interested, I have added the flat layer .gcode files (beware UM2 gcode flavor):

     

     

     

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    Posted · Top Layers not touching - UM2

    How many teeth has the GT2 pulleys? 20? :)

    Seems that, for a reason or another, at each turn of the smooth rods there is a slight lack of parallelism between the pairs, hence the carriage is moving up and down on a 20x2 mm pattern on both X and Y.

     

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    Posted · Top Layers not touching - UM2

    :evil: 20 it is. So the rods might be it eh?

    Ok, I have ordered a new teflon piece and bowden tube as well as another 3rd fan with higher cooling capacity. Right now I am also printing the replacement fan holder with improved air flow for the right fan. I will dismantle the head, soak the nozzle in acetone (there are some dark spots inside that I can't get out with the atomic method). I will use this opportunity and take half of the machine apart and check the rods. And while I am at it I'll try to find out why the z-screw wobbles (a bit).

    Whish me luck!

     

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    Posted · Top Layers not touching - UM2

    Nicolinux -

    Power the printer off, and put the head in the middle of the bed. Then move it left to right by hand, back and forth, and look carefully at the left and right sliding blocks that aren't moving (much). I imagine that you'll see at least one of the blocks bouncing up and down a bit.

    Similarly when moving the head front to back, the front and/or rear blocks are probably also bouncing up and down. This could be caused by the pulleys being eccentric, or, more likely, bent axis rods. As the axis spins to slide the head on the opposite axis, a bent rod lifts the sliding block (and hence head) up and down - moving it closer and further away from the bed, causing the pattern you are seeing.

    I don't know how this affecting the top layer issue, but it probably isn't helping.

     

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    Posted · Top Layers not touching - UM2

    It's peculiar anyway.

    If it should have been bent, the pattern would have normally appeared in the center only. As it looks is rather that the rods are... oval!? Eccentric pulleys would produce the same effect, since they will tend to bend the rods that are fixed at the ends.

    And if the rods are oval then the pattern will be repeat on each layer, but differently I think, due to the 90 degrees change in the orientation of the infill and to the very little difference between the starting and ending point of the perimeters on each layer (at least for the very simple square shape in the test). As a result, the different thickness/width is not appearing only in the first layer, but in all the layers. If this is the case, than printing a "flat cube" with 100% infill will perhaps expose this peculiar effect on all layers.

    Pure induction and I might be wrong :)

     

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    Posted · Top Layers not touching - UM2

    @illuminarti: Ok the sliding blocks bounce considerably. Left and right quite a lot - I'd say around 2mm height difference. The rear sliding block maybe half of that and the front sliding block not at all.

    @3Dmaker4U: Your thinking about eccentric pulleys is not far fetched. It is not a secret that they are pretty bad. So far I had 4 Ultimakers and they all had bad pulleys. They do the job, but I really can't understand why Ultimaker who sells machines for 1k-2k € uses pulleys that look like they only cost 10ct each...

    I don't think that the rod manufacturer managed to produce oval rods, but who knows. I will test it for sure.

    Regarding the 100% flat cube, I already printed it and it produces the same pattern as the others.

    It looks something like this:

    Top layer pattern

     

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    Posted · Top Layers not touching - UM2

    Same results here on both our UM2's, same pattern.

    After proper calibration is much better now.

    X axis was almost ok but Y axis was miscalibrated on both machines.

    On the old one that was 4mm !! You could see it with naked eye. New UM2 was off by 2mm (difference between two yellow lines on the picture below)

    IMG 0500

    Next common problem, build plate screws sticking out so proper bed levelling was impossible to achieve (come on Ultimaker, are you serious ?! )

    IMG 0461

     

    Quick fix, take the dremel into your hand :)

    IMG 0498

     

    Also, I don't like new LED lights. Old were very bright and white, new ones are bit dimmer with purple tint

    IMG 0469

     

    They did some changes to the electronics as well IMO. New UM2 is whisper quiet, you can't hear the motors at all (motors are exactly the same IMO). Old one is not too bad but new one is really amazing.

     

    Other than that still, cheap pulleys, even cheaper fans (first thing to replace in every machine).

     

    Ohh, and one more difference between them two (everything is well put together and tight)

    IMG 0501

    IMG 0502

     

     

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    Posted · Top Layers not touching - UM2

    Interesting comparison..

    looking at the last picture, the advice would be to turn the hot-end-isolator until the gap with the teflon part gets to 1 mm. In your picture, with a bigger gap, the pressure from the spring on the teflon part is to high (page 56 of the assembly manual...)

     

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    Posted · Top Layers not touching - UM2

    Hey guys,

    I don't know if this idea has been bounced around before - but which firmware version do you use?

    Right now I have 14.09.

     

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    Posted · Top Layers not touching - UM2

    14.07 before and 14.09 right now, same result

     

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    Posted · Top Layers not touching - UM2

    Ok, same here - forgot to mention that I had 14.07 before.

     

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    Posted · Top Layers not touching - UM2

    illuminarti got a very interesting message the other day concerning three printers that showed similar top fill issues that were fixed by a very weird adjustment. I'm not entirely sure I remember correctly but if I understood it right the fix was to rotate the X and Y motors ever so slightly... as in, undo the screws slightly and twist the motor so that it's straight up and down. Super weird and it really shouldn't make a difference, we were all a bit baffled I think. Let's wait for illuminarti to give the precise details once he has a chance (btw, all you US customers should thank him a bit extra, that man works hard for you guys even when he's on "vacation").

     

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    Posted · Top Layers not touching - UM2

    @nicolinux regarding post #187 from 10 days ago...

    The orange top gets underextrusion on 0% infill because the top isn't perfectly level - it bows down a bit when doing the first top layer as it is printing over empty space. Each layer gets a bit better but it doesn't recover in time for the last layer. If you increase top/bottom layer thickness to add 1 or 2 more layers it should become "perfect" or as good as the other layers.

    Regarding that dark/light pattern it could either be not-round pulleys which cause the X/Y to move more in some areas and less in others creating a slightly more extruded areas and slightly less extruded areas. Or more likely (as you already confirmed) the X,Y rods are bent/bowed such that the head is moving up and down as it prints. This will cause high spots and low spots exactly as shown in the picture you posted.

    Ultimaker is working on newer/better shipping boxes. Personally I don't think it's enough but it will help some of the shipping issues. I'm not surprised at all that after shipping the X/Y rods all got bowed downwards in the middle. Something during shipping put massive forces on that printer.

     

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    Posted · Top Layers not touching - UM2

    I don't know. I have also printed objects with infill and still got that problem.

    Regarding shipping. I don't understand how the rods got bent because the box of the last UM2 I got looked pretty good. They have already four pillars of cardboard on in the corner of the box thus allowing for some free space between the rods and the top of the box. I don't think the rods could be bent while shipping. At least it would have left dents and other marks on the box.

     

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    Posted · Top Layers not touching - UM2

    Hey Robert / Simon,

    do you have any news on this very intriguing info (rotating the x / y motors)?

     

    Or did anyone try it yet?

     

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