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Top Layers not touching - UM2


Nicolinux

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Posted · Top Layers not touching - UM2

Sorry, I thought I had posted about it already. I contacted Simon and he thinks it was simply a case of regular old slack short belts that got fixed rather than a fix for this particular issue. He never had a chance to see the before and after personally as he was with us over in the Netherlands at the time. Trust me, I'm just as (or probably more) sad about that as you :/

 

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    Posted · Top Layers not touching - UM2

    Funny because i got a brandnew Ultimaker 2 and have exactly the same problem if i make more then 0.1 Layer height.

    Allready checked all kinds of solutions that where discussed.. one rod is slightly excentric but wouldn't that affect also other layer heights?

    Here are my pictures of some tests:

    Overview of Surface Problem

     

    Usual Print setup

     

    25 percent speed

     

    240 degree temperature

     

    New firmware and different filament

     

    Layerheight set to half

     

    Z TOP

     

    The last pictures shows that the effect is constant from layer 2-3

    If i print with 0.1mm Layerheight its just fine.

    If i set the diameter to half or set flow to 200% it prints 0.2 layers fine as well^^

    hmm..

     

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    Posted · Top Layers not touching - UM2

    I'm not sure what you are trying to say in your pictures in the previous post. I see all kinds of different things in each picture and you don't seem to be saying which parts are "good" or "bad" or whatever. They all have different surfaces for different reasons.

    For example the bottom/last picture is normal quality - that's what i would expect from a properly tuned printer. The red one also. Do you consider this "bad" quality?

    The blue square above is definitely underextruded on it's top layer. This can be caused by sagging (top layers are bowed down into the cube) or lack of fan, printing too fast, too thick, or to cold.

    Some of the white surfaces are just not quite enough resolution to tell but they look like there isn't any backlash. But the blue one again - that one has a pattern of two diagonal stripes followed by a space, and then two stripes again. That is a sign of backlash which is rare on the UM2. And it's only a very slight backlash. It can be improved by tightening the short belts (loosen X and Y motors, slide them down the slots and hold them tight while tightening the screws). Here is a technical explanation of why backlash causes that pattern (post #8):

    http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/?p=14474

    Anyway, what is your point? That .1mm is better than .2mm? That's because you are printing less volume and so the feeder is strong enough to keep up. When you print too cold and too fast you get underextrusion (filament is slipping in the extruder). Here is a graph that shows you the max print speeds you can do at .2mm layers for a given temp (you can go twice as fast with .1mm layers of course as that's half as much plastic per second). Try to stay around half the speed of the dark blue line in this graph:

    http://umforum.ultimaker.com/index.php?/topic/4127-um2-extrusion-rates-revisited/

    If you are still getting underextrusion at half of the speeds of the dark blue line then you need to do an extrusion test although I suspect your machine is fine. Extrusion test must be done at 230C to be valid:

    http://umforum.ultimaker.com/index.php?/topic/4586-can-your-um2-printer-achieve-10mm3s-test-it-here/

     

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    Posted · Top Layers not touching - UM2

    George, seems that @VISU-AL has a SF UM2, so he knows what is talking about.

    And it is something related to the topic, which proved to be actually not an issue with top layer only, but also affecting other layers.

    And the story is that solid layers print fine, but not with 100% infill, for a reason that nobody actually found.

    And this appear to affect new machines.

    Forgetting about any axes misalignment, I begin to suspect a kind of limitation of the extruder speed. I don't see signs of underextrusion in the sense that is normally used. What I can see is that while the user is expecting that the settings will produce, at normal flow, a particular extrusion width (required for 100% infill), the result is less flow than required.

    So, at 0.1 mm it works, but at 0.2 mm (and com'on is only 4 cmm/s, not a reason for underextrusion at 240 C :) there is not enough filament extruded, but no skipping or any other obvious underextrusion reasons.

    Looks like the E speed and/or E steps/mm does not correlate to the actual printing speed.

     

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    Posted · Top Layers not touching - UM2

    @gr5: Apart from the first big pictures, all other pictures are hidef enough to spot the problem. His point is that with any combination of print settings a layer height of 0.2 seems to always produce a top surface that's not tight. Where as the red cube (layer height 0.1) has an almost perfect top surface. I say almost perfect because in the top right corner, the strands begin to drift apart again.

    I have the _exact_ same issue. I didn't make to connection between layer height and this problem but I will test it.

     

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    Posted · Top Layers not touching - UM2

    I am pretty sure this is again one of those weird issues where most others think we are crazy and then it turns out it is a software/hardware issue after all (like the Cura issue where the z - height was not consistent between prints and everyone thought we just couldn't level the damn bed properly...) :)

     

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    Posted · Top Layers not touching - UM2

    speaking of: have you tried it with the PID mode of the bed instead of the bang-bang mode?

     

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    Posted · Top Layers not touching - UM2

    His point is that with any combination of print settings a layer height of 0.2 seems to always produce a top surface that's not tight. Where as the red cube (layer height 0.1)

     

    Ah, okay. Sorry if I don't always get the context from older posts. I guess I read too many different topics and loose the thread in my mind and am too lazy to reread each time.

    It's simple enough to analyze the gcode - part of the final layer to make sure that the Z setting is correct (.2mm movement) and that the extrusion is correct. I have a little excel formula that calculates the amount of extrusion expected for any given move and compares that to the actual extrusion and cura produces excellent results normally.

    But it seems possible the top layer could be somehow messed up due to the height of the object not being integral with the layer height. Or some other bug. But I've tested very similar things before and Cura was usually correct. Someone should just check the "bad" gcode. But keep in mind that at .2mm you are DOUBLING the printing volume so of course you will get less extrusion than ideal (more underextrusion).

    Some printers (or filaments) skip backwards, but other filaments/um2 printers instead slip a bit and kind of quietly underextrude.

     

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    Posted · Top Layers not touching - UM2

    I just wanted to point out that this is not a problem that is connected to the top surface. We see this from the third or forth layer from the bed and upwards. It also seems to be surfacing on more and more machines which is very interesting.

     

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    Posted · Top Layers not touching - UM2

    Sounds like basic underextrusion which commonly gets worse over time on the UM2. Fortunately the various fixes aren't too hard. You can test by printing the test cylinder (see my 3rd link in post #205 above) at 230C.

     

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    Posted · Top Layers not touching - UM2

    Sorry, i forgot to mention that i exchanged the feeder with roberts version2 like i did on my other machine because i was thinking about underextrusion at first and i can run extrusioin test up to 13mm^3/s @ 240°C wich is enough i guess.

    Also i allready have an older UM2 wich prints all that stuff absolutely perfect compared to this and i couldnt find a reason just that at 0.1 it prints fine and it looks like the problem of nicolinux and the others and for some reason it extrudes just half of the amount it should at 0.2

    Also to mention that at first i had more kind of backlash sepearation between lines wich i kind of fixed a bit.

    @gr5 no the red print looks fine to me and everything i print with 0.1 looks normal to me like on my other machine (i have some of my prints on the older machine in my gallery)

    I have some experience with fixing underextrusion my older machine didn't always worked as well as it does now and i tried all the stuff on actual machine as well i have low resistance of the filament all the way trough the nozzle at normal temperature after some Taulman Nylon 618 atomic pulls it also didn't change and the tip was nice.. it's nearly impossible that this is an (mechanical feeder/bowden related) underextrusion problem in my eyes..

     

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    Posted · Top Layers not touching - UM2

    It could be that certain colors are near the end of the spool (blue) and so they have too much curvature for the white teflon isolator - it is amazing how much force it can take to get through the thing if the PLA is bent but how little force if the PLA is straight. So question: of the colors that do worse at .2mm, are any of them < one quarter remain on the spool?

     

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    Posted · Top Layers not touching - UM2

    I allready printed several rolls to the very end on my older um2, with roberts feeder (thank you robert) it is no problem at all maybe its really the teflon isolator but why is there no resistance with 0.1 at double speed and why does the flow set to 200% work nicely with 0.2 ? and why i get a good extrusion test?

    Anyway the spools are new, all of them so no special curvature effect im sure..

    for me it just looks like 50% Extrusion on 0.2 layers also because i see infill like stacked pipes instead of nice walls with the 0.2 setting on just 100% flow, i agree that its underextrusion but not related to mechanical problem because its like a switch on 0.2 it turns to half of the needed material not speed or temperature related

    Roberts feeder is really great as soon as i printed it for my old um2 i was able to print flexible PLA, Filaflex, Ninjaflex (with the guide) without any other change or oil. everything with the same tension, i even printed conductiv filament wich is just not so funny^^

    And i reached full 15 mm^3/s at 240° on the extrusion test :)

     

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    Posted · Top Layers not touching - UM2

    You really make it sound like the problem is with the gcode. The gcode is very easy to test. If you post the gcode somewhere I will be happy to check the top layer using excel. It's really not hard to do.

    Actually even better would be if you posted both gcode files so I can make sure the .1 version isn't *over* extruding. Which I doubt but we should test everything. Please don't reslice with cura. I want the *actual* gcode file that you printed that has a problem (it's possible that the tiniest change in the profile could change things - for example "cut off object bottom" or a plugin.

     

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    Posted · Top Layers not touching - UM2

    Ok i will but the other printer (and the sd card) is located at my workplace and i cant go there over the weekend.

    If i dont remember wrong it was also on the new um2 with gcodes i created with the same cura/computer at home with my other um2 were it prints well. And i printed files from the other cura i use with the new printer at home wich resultet in nice prints. Wouldn't that exclude that possibility? Of course i also installed an all new unofficial cura on another computer and sliced without any other changes.

    Is it impossible, that somewhere between the gcode and hardware steering its misscalculating something somehow by ignoring the layer height or something? i dont have any experience with this arduino electronics i just know the basic concept of it..

     

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    Posted · Top Layers not touching - UM2

    By all means retest the gcode, but I checked Nicolinux's somewhere earlier in this saga, and it was spot on.

    When it's printing, the printer doesn't know or care what the layer height is - it just does what the gcode says, based on the e coordinates. So thicker layers will have larger e amounts for the same line segments, but the printer has no understanding of how far below the nozzle the previous layer is.

    Ultigcode uses volumetric e coordinates - cubic mm to extrude - while normal gcode has linear mm of plastic to feed in for the e coordinates.

    One test that might be interesting is to slice the same piece with ultigcode and regular gcode, keeping all the settings and temp the same, and see if there is a difference between the results - which, if both gcodes look correct, would imply an issue in how Marlin is converting ultigcode volumetric e coords into linear ones.

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    Posted · Top Layers not touching - UM2

    by the way thank you all for the great support here!

    well i will do the following steps:

     

    • upload my tested gcode file/s and post the link here

     

     

    • slice 7 new cubes
      • Cura @home
        • 0.1mm layer (Ultigcode)
        • 0.2mm layer (Ultigcode)
        • 0.2mm layer (regular gcode) @illuminarti wich in Cura? RepRap (Marlin/Sprinter)?

         

        [*]Cura @work1

         

        • 0.1mm layer (Ultigcode)
        • 0.2mm layer (Ultigcode)

         

        [*]Cura @work2

         

        • 0.1mm layer (Ultigcode)
        • 0.2mm layer (Ultigcode)

         

         

       

       

     

     

    • testprint 14 new « cubes » :
      • one set of 7 on the older UM2 @home
      • one set of 7 on the new UM2 @work

       

       

     

    0.1mm layer-height-settings i will use :

     

    • First layer height 0.1
    • 50mm/s (25mm/s @ bottom layer)
    • 220°C @ 100% flow and 2.85mm
    • 0.8mm shell thickness
    • 0.7mm bottom/top-thickness
    • 20% infill /speed 0
    • Disabled retraction
    • 0.4 nozzle size
    • Travel speed 150mm/s
    • Outer and inner shell speed 0

     

    0.2mm layer-height -settings i will use :

     

    • First layer height 0.2
    • 25mm/s
    • 220°C @ 100% flow and 2.85mm
    • 0.8mm shell .
    • 1.2mm top-bottom
    • 20% infill /speed 0
    • Disabled retraction
    • 0.4 nozzle size
    • Travel speed 150mm/s
    • Outer and inner shell speed 0

    Cura will be reset to default before

    So then all combination of my printer and Cura installs on both layer height will be tested to compare and i will also upload the files and pictures then for you guys to check

     

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    Posted · Top Layers not touching - UM2

    When it's printing, the printer doesn't know or care what the layer height is - it just does what the gcode says...

     

    But what if the firmware received some wrong configuration and the extruder does not want to feed more than a value. Which is not necessary a firmware parameter.

    This behavior was reported on new printers only and in all cases it's about the same behavior: reduced infill when it should be 100%, most visible on top layers, but not present on first layer.

    Gcode was checked and if VISU-AL codes will confirm, gcode reasons are excluded.

    Then only the firmware could make the difference.

    Don't know how production flow is, but it does not have to be for all printers.

     

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    Posted · Top Layers not touching - UM2

    (regular gcode) @illuminarti wich in Cura? RepRap (Marlin/Sprinter)?

     

    Corect - "marlin/sprinter".

     

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    Posted · Top Layers not touching - UM2

    Marlin itself is very well tested and I doubt there are any changes in the movement code in Marlin. It should be the same code on every reprap machine out there. Same as on UMO and UM2. It doesn't know what layer it is on so if there was a Marlin bug regarding flow it would happen on every layer. Much more likely to be a bug in Cura. And even more likely a operator/hardware error (something causing underextrusion).

    On top of this I print about half my prints .1mm layers and half .2mm layers and they all have good top surfaces. I have looked at all kinds of complicated, fascinating bugs, and there have bugs in Marlin but none like this.

     

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    Posted · Top Layers not touching - UM2

    @gr5 thanks

    im printing the one with regular gcode (0.2 lh) right now and it looks better, the infill lines are more like a wall then the stacked pipes before..

    also allready printed new sliced 0.2 layer from both curas and both have still the stacked-pipes effect even if the surfaces for some reasons look better(but still not perfect) filled now..

     

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    Posted · Top Layers not touching - UM2

    I downloaded you gcode files. The "calibc.gcode" looks wonky though. If I import the settings in Cura 14.07, it shows me a layer height of .05 which would be 0.05. Top/bottom set at 0.6.

     

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    Posted · Top Layers not touching - UM2

    @Nicolinux Yes the second one i sliced to test very small layers. unfortunately the 0.1 before was overwritten^^

    I saw the top layer of the new print were i used regular gcode and it still looks ugly and the same..

    i will upload my results soon..

     

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