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Top Layers not touching - UM2


Nicolinux
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Posted · Top Layers not touching - UM2

Here is another hint that it is related to under extrusion. I was testing an experimental nozzle and had this result:

u1.thumb.jpg.c276cd5c782348466d66dfd2387e7d1b.jpg

u2.thumb.jpg.c58233f9e00021a096696c705966fc34.jpg

 

Crazy idea #309

Has anyone with the flow sollution to the problem ever did a propper esteps calibration or just use a caliper to check if the knurted bolts has the propper diameter?

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    Posted · Top Layers not touching - UM2

    Well, it looks like @Nicolinux is not alone.

    Recently, I switched to the truly wonderful Olsson's block, but the same problem remains:

    WP_20150923_14_12_40_Pro.thumb.jpg.f7e68edee8335cca23bcfb4595c3eeeb.jpg

    WP_20150923_14_11_26_Pro.thumb.jpg.9a4cafc6cc51217c4b6fff54b9a2d51f.jpg

    Faberdashery or Colorfabb PLA, 0.4mm nozzle (0.8mm one gives the same results), 20-50mm/sec, 210-230C. There are no clicks of underextrusion. It simply doesn't push enough plastic through as it goes.

    The white teflon was replaced to the new on the occasion. The glass-coated one didn't hold that much good, apparently.

    What could it be?

    The idea #309 of @neotko might not be that crazy but it is a complete Chinese for me. :-)

    WP_20150923_14_12_40_Pro.thumb.jpg.f7e68edee8335cca23bcfb4595c3eeeb.jpg

    WP_20150923_14_11_26_Pro.thumb.jpg.9a4cafc6cc51217c4b6fff54b9a2d51f.jpg

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    Posted · Top Layers not touching - UM2

    The idea it's to take out the bowden from the feeder and mark the filament. Then make the machine move 10cm or better 100cm and the mark again. If the filament moved its 90cm then the esteps are wrong by a 10% and so on. The other thing it's to get a caliper and measure the diameter of the metal diamond shaped bolt that pushes the filament to see if it's the correct diameter.

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    Posted · Top Layers not touching - UM2

    Hmmm i really doubt that some feeders would have different diameters for the feeder knurled wheel... i guess it could happen.

    Maybe it all lies in the tension of the feeder, if it's too low it can slip on the filament and not move the requested value.

    It's a good idea to test that the requested amount of filament is moved by the way @neotko describes and can be very simply done with some piece of gcode (i can search for it if needed). But you cannot say by 100% that it's because of the knurled wheel diameter (my opinion)

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    Posted · Top Layers not touching - UM2

    If you are going to measure I would start measuring exactly where the filament enters the feeder. Extrude a certain amount and mark it again. Measure if that distance is similar to what you made it extrude. I think if you would measure from the top it will be difficult to measure the exact filament, since the top will be melted and can stretch.

    Besides, I believe the bowden tube is only like 68cm long, so 100cm would be difficult.

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    Posted · Top Layers not touching - UM2

    Indeed I doubt that the feeder bolt might have a different diameter. The esteps calibration should just work, unless there's some gnome inside the board playing with the extruded numbers.

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    Posted · Top Layers not touching - UM2

    Damn gnomes!

    Wild guess: maybe the knurled wheel is dirty and has some "melted" filament in the "holes" ? That could slightly change the diameter i guess and have some kind of negative influence on the requested amount

    Damn gnomes 8)

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    Posted · Top Layers not touching - UM2

    A very important factor that I've noticed, which is often overlooked, is humidity. I've had extrusion issues that I could not explain. One day the printer works perfectly. The next day, it can't complete the same exact print, no matter what I try. After ruling out nozzle clogs, filament tension, and other bugaboos, I put a thermometer/humidity gauge in the room, and I noticed a correlation between the days there was high humidity and poor extrusion. After putting a dehumidifier in the room, closing the doors/windows, and getting humidity down to about 30%, I never had those extrusion issues again. I've not done a quantitative analysis of the humidity issue, but I HAVE completed an analysis of several other factors affecting dimensional precision.

    Some of the perceived inconsistencies/drawbacks of the more economical FDM 3D printers like Ultimakers are not, in fact, inherent to the technology. Lack of detailed operational documentation, user inexperience, and anecdotal evidence not backed by quantitative numbers all contribute to the idea that some of these printers are not to be used as professional tools. A paper I recently published (in the International Journal of Aviation, Aeronautics, and Aerospace) on dimensional accuracy in consumer 3D printing refutes this: http://commons.erau.edu/cgi/viewcontent.cgi?article=1085&context=ijaaa ; I'm using my Ultimaker 2 printer to make very precise engineering components for airflow measurement - components that would cost thousands of dollars to purchase, but constitute a few dollars of filament material (and a lot of know-how). At first, I didn't know if this was possible, based on word of mouth about these printers. Spread the word! The limitations aren't as clear-cut!

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    Posted (edited) · Top Layers not touching - UM2

    teh_layers.thumb.jpg.0df333f26e5d55e0551f5c8f7ed1b8ad.jpg

     

    Just noticed that it looks like your walls and infill are not overlapping. So even in the "Good" area it looks like you are underextruding.

    This ColorFabb material does not list the specific plastic but that its loaded with carbon fibers. I am using a material at work that is PETG + CNT (Carbon Nano Tube) to make the filament ESD Safe. I've found that the filament tends to slip easily even with a good deal of force from the bearing side.

    Try this, when you see the underextrusion, assist the feeder by pushing the filament into the stepper. If the underextrusion goes away then your issue is mechanical and we can start following this path of correction. If the issue persist then its in a setting such as temp or speed, etc.

    Edited by Guest
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    Posted · Top Layers not touching - UM2

    @esteban-pacheco: I owe you a test print like a said a while ago. Since you did not provide all print settings I printed a 25mm X 25mm x 5mm square with the following additional settings:

     

    • layer height - 0.2
    • speed - 40

     

    It looks like this:

    square.thumb.jpg.8f0c14f9036d70362c8c0250a55619e9.jpg

    Perfect surface - WTH!?!??

    square.thumb.jpg.8f0c14f9036d70362c8c0250a55619e9.jpg

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    Posted · Top Layers not touching - UM2

    Another day, another fail.

    WP_20151001_00_19_59_Pro.thumb.jpg.59989009af30c69ca9f0bbf87d602d86.jpg

    It feels like a Russian roulette - you never know how it will go. In this case, all started well, but not for very long.

    So, what could it be?

    WP_20151001_00_19_59_Pro.thumb.jpg.59989009af30c69ca9f0bbf87d602d86.jpg

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    Posted · Top Layers not touching - UM2

    This doesn't look like top layers are not touching, but some underextruded layers halfway.

    Did the filament get tangled up or something?

    Even though the print is failed I find it amazing how it can still recover..

    There are some areas for improvement, like stringing too, but it doesn't look like the top layers are not closing. Or am I not seeing it right?

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    Posted (edited) · Top Layers not touching - UM2

    Well that just looks like classic under-extrusion. Could be quite a few factors, Filament tangle maybe?

    hehehe @SandervG beat me to it :)

    Edited by Guest
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    Posted · Top Layers not touching - UM2

    Check if at that layer moment the fan did hit at full and caused the nozzle to lower the temp. That would explain the recover? If so, up the temp to compensate the fan hit.

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    Posted · Top Layers not touching - UM2

     

    @DoctorH , great comment on humidity. I've observed that in some of my prints with my UMO as well. Now that we are heading into fall and the basement isn't muggy anymore, my prints of late have been great. I need to replace my dehumidifier to maintain the low humidity more consistently.

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    Posted · Top Layers not touching - UM2

    Yes, my post shows not the top layers but the same problem - irregular and unpredictive underextrusion. If you think the post doesn't belong here - by all means, please move it to more appropriate topic.

    It looks like there is temporary underfeeding of the plastic during the print, occurring more or less at random. There are no clicks of the classical underextrusion. The filament is Colorfabb, last couple of meters of it freely hanging behind the printer, no obstructions whatsoever. The curvature radius should not be the problem, either, as it happens to me on other rolls, too. Like for @Nicolinux, there may be a few successful prints, and then - what you see.

    I use the latest stable 15.04.02 both for slicing and on the printer. Recently, installed the Olsson's block, and there where my troubles started. Could it be that I messed up something?

    Not sure which way to look...

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    Posted · Top Layers not touching - UM2

    Have you cleaned the feeder recently? Some have mentioned doing so helps.

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    Posted · Top Layers not touching - UM2

    I use Robert's feeder, there's nothing to clean there. The filament change is always done using the Atomic pull method, so the nozzle is clean, too.

    Maybe, the PLA of the feeder is worn out? I will probably re-print it, just in case.

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    Posted · Top Layers not touching - UM2

    I remember someone saying that indeed the feeder can wear out.. like that at some point it can't offer the same tension as in the beginning.

    But I am not sure exactly what caused it.. can you see some wear, or perhaps manually feel a difference?

    If it is locked and the printhead is heated, can you manually pull it out?

    I don't think you should.

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    Posted · Top Layers not touching - UM2

    If the feeder were to wear out, it wouldn't recover so well after the hickup.

    In @shurik's case (apart from tangled filament) I could think of bad filament where the diameter changed drastically in one spot.

    A friend of mine had another related error. He seems to have stored his filament in such a way that only one side of the filament roll was dried. His prints failed regularly because the diameter changed a lot on the dried out segments.

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    Posted · Top Layers not touching - UM2

    If the feeder were to wear out, it wouldn't recover so well after the hickup.

    In @shurik's case (apart from tangled filament) I could think of bad filament where the diameter changed drastically in one spot.

    A friend of mine had another related error. He seems to have stored his filament in such a way that only one side of the filament roll was dried. His prints failed regularly because the diameter changed a lot on the dried out segments.

     

    interesting idea.
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    Posted · Top Layers not touching - UM2

    But back to the initial issue. Many people have tried many things. It is hard to compare results because every printer is different _and_ the environment (humidity, temperature...) differs too.

    @SandervG I think it would be best if you could fetch one of those problematic printers and test it at the UM HQ. As far as I know, @Labern's printer should be available.

    Anyway, over time I have tested the following (mechanical) areas and I would exclude them as the reason for the problem. Of course I've done tons of firmware resets and upgraded the firmware too over time. But these are only the mechanical parts that I focused on:

     

    • Nozzle - tested it with the standard nozzle and the Olsson Block with tons of other nozzles
    • Feeder - tested with the standard one and Robert's feeder.
    • Bowden tube - Bought a new one and tested it.
    • PTFE coupler - Tested a few...
    • Metal collet - Is this the correct name? I mean the metal thingie where the PTFE coupler is inserted into. Swapped this one out too.

     

    There are two other components that I didn't test.

     

    1. Board - I've so had it with swapping boards between UM2's... So if someone has access to two UM2s might want to test this case.
    2. Feeder stepper - Might be something as easy as a faulty stepper of maybe some very ugly error that happens only under certain circumstances.
    3. Metal rods - Maybe some rods are bent in such a way that they move the head slightly up and down in some areas. This might produce the under extrusion like effect with the layers not touching.

     

    Next things I will try are the humidity test/problem and feeder calibration.

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    Posted · Top Layers not touching - UM2

    I think it would be best if you could fetch one of those problematic printers and test it at the UM HQ. As far as I know, 's printer should be available.

    We are! But like you say, it is difficult to test. A lot of things are already tested and replaced and compared, but it is difficult to find consistent results.

    We'll continue to investigate!

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