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Top Layers not touching - UM2

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Posted · Top Layers not touching - UM2

@illuminarti

 

i tested higher temps and the effect is like 10-20% improvement with 20°C higher temp (from 220° to 240°C) but looks still similar.

i would just expect that 12mm/s works fine on a simple cube..

 

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Posted · Top Layers not touching - UM2

COMPARE

 

you can even feel it with fingernails the other one feels nice flat

 

can i resize the image (how its shown in the post) somehow?

 

it cant be classical backlash cause my short belts on the new machine are tighter then the older ones

 

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Posted · Top Layers not touching - UM2

can i resize the image (how its shown in the post) somehow?

 

Don't worry about it. We all just click on it once. Note that when you post a picture - if you click on it you get a different experience than everyone else. Instead refresh the page and look at your posting and *then* click on it and it does a pop-up larger version.

Anyway so great - the left one is worse. Also I see the lines are in pairs so you seem to have a small amount of backlash or play or friction. More than my UM2. But more serious is the underextrusion. What were the settings for that exact cube? Can you post the gcode again? For *only* the left cube (please not two gcodes - I only want to see the "bad" one). And are there any special instructions? Override temp and speed and fan?

 

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Posted · Top Layers not touching - UM2

OK thanks.

Yes it could be friction but i'm not convinced that it would make up the whole problem.

But anyway it doesn't show up to me with for example 0.1 layers..?

Would the friction effect not be constant at similar speeds @ different layer heights?

0.2mm layer-height -settings i used :

 

  • 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
  • 100% fan

Cura will be reset to default before

No override. CURA Version is 14.11 -RC7, Ultigcode

gcode comes later, just have it on the sd-card wich is in the printing printer right now..

 

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Posted · Top Layers not touching - UM2

new information

on a new part with 0.1 layer it startet to have underextrusion as well i had to increase the flow to 120% to make it look closed.. means it seems like the problem gets worse and now affecting other prints as well

..and the speed actually is 35mm/s on that part..

whats the best way to check axis miss-alignment ? i can't see anything but i hear a little scratching sound when the printhead moves from side to side in about the middle..

and the left short belt touches the pulley side slightly..

 

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Posted · Top Layers not touching - UM2

You have two issues that are completely unrelated:

1) underextrusion (gaps between lines)

2) backlash (pattern of 2 lines touching, then a gap, then 2 lines touching).

These are independent and separate. The backlash is very minor and only noticable when you have underextrusion. Here is a diagram of why backlash causes the "2 lines touch, then gap" pattern (post #8):

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

So what can cause the backlash? Either play/looseness or high friction. The play means that the nozzle never catches up with the position that the motors move to. For example loose belts - most likely short belts to the steppers. Or defective head. You can test for loose head by pushing on the nozzle and seeing if it moves significantly without moving the belts. This is rare but it has definitely happened to people on this forum before. The other cause is high friction. What happens is friction is so amazingly high that when the stepper stops moving the head the belt is still very tight in that direction (and loosish in the other direction) because the friction is so high. You can test for this by pushing the head around with power off - see if both Axes are about the same.

But really I think the amount of backlash you have here is minor and might be normal.

The more serious problem is underextrusion. I know you printed the same gcode on 2 printers and they both had the gaps but I'm thinking it had to do with the .5mm walls issue and was printed too fast on the "good" printer. But the "bad" printer keeps doing the problem even when printing much slower. I think you should try the test cylinder again with the printer you used in the most recent picture above this post. I'm thinking that printer is getting worse. You might also want to test the temperature of the nozzle using that video technique I posted above.

 

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Posted · Top Layers not touching - UM2

@gr5 i agree that there are at least two issues

i guess it's high friction cause my short belts have a very high tension and the left one touches slightly

gonna try to push at the nozzle tomorrow..

moving around the head when turned off was one of the first things i tested and it felt a little heavier to move then the "good" um2 but not much, the printer doesnt move with the movement and it's a slippery surface on that table..

No! the prints on the older "good" UM2 never showed any significant lines and printed all nice even 0.5 i think you missunderstood or miss-readed that one somehow -> that's what's my problem that the newer um2 has gaps my older never has those..

But yes i think now it looks like underextrusion getting worse i will print a testcylinder at 230°C tomorrow but what if that turns out good?? (and i wll do the temperature test)

 

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Posted · Top Layers not touching - UM2

Just for reference since I might have the same issue. I can print the cylinder test up to 12-13mm/s^2 and the nozzle temp is fine (did the boiling water test - not very accurate but still).

 

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Posted · Top Layers not touching - UM2

Same here. Can't print anything above 0.1 mm layer and 20 mm/s without getting open surfaces and have no problems getting 10 mm^3/s with the test cylinders. I feel that we're moving in circles here :(

 

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Posted · Top Layers not touching - UM2

There are two types of underextrusion:

1) Extruder motor skips back - this is more obvious because you can hear it, you can see it happen, and you can see a huge lack of filament (usually none) for a short distance.

2) Filament moving but slower than it should be - this is less obvious. You can probably see it in the print if it's severe enough and also if you look at the "tread" pattern on the filament you can see that the diamond shaped holes are elongated or you get spots of "grinding" away.

The problem with the cylinder test is it detects #1 very well but not #2. You expect some underextrusion on the cylinder similar to #2 but caused instead by the high acceleration after "drawing" the letters on the cylinder. During speed up you normally get underextrusion until pressure builds and over extrusion as it slows down to do the letters again. So I'm not sure what the best test is for printers with issue #2.

when you have #1 you get huge gaps in the cylinder and it's not round in places (the filament takes a short-cut) but with issue #2 you just get something harder to quantify unless you have a "good" cylinder from another printer.

Please try my video in the link earlier (previous page I think) for testing temperature of nozzle - I think it's more accurate than the boil test plus sometimes the head is fine at 110C but not at 200C as this is where solder starts to melt.

 

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Posted · Top Layers not touching - UM2

amazing maze haha but take it easy, we will find it.. at least we can print at all ;-)

 

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Posted · Top Layers not touching - UM2

@gr5 very interesting i guess it's #2 cause not long ago i made a testcylinder up to 13mm3/s without problems

i'll also check the pattern on the filament

 

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Posted · Top Layers not touching - UM2

Thansk for the more detailed underextrusion explanation. I've tested the temperature and that is not the problem in my case. I've also tested measuring the temperature inside the hotend (without filament in there of course) and was a bit surprised to see it being 20C higher than what the machine thermocouple measured. I'm still measuring at a different place than the machine so I'm not too surprised that it didn't match but rather by the large difference in temperature .

I've previously seen that when pushing the filament towards the feeder rather forcefully, separating lines can merge again and as soon as you release the filament they separate back again. I've always assumed that I would not be able to push more material this way (as the motor while being powered should prevent this right?) but rather that I helped the motor overcome some of the torque needed to work against the friction in the bowden tube. This would be an indication of #2 then I guess?

 

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Posted · Top Layers not touching - UM2

Here is my Result, the usual cylinder worked perfectly fine up to 10mm3/s but the bigger one failed @ 10mm3/s see here:

printed @ 230°

CylinderTest_20-11-14

printed @ 230°

BigCylinderTest_20-11-14

Temperatur also seems fine, also the pattern on the filament doesn't look wrong maybe i'll take a picture of that too..

 

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Posted · Top Layers not touching - UM2

Ok, here's some new input from me. I did a test today with a test cube that always produces gaps. I printed it at 220 C and marked the filament at the beginning and the end of the print. I then did the same thing but let the filament go out into the air (without bowden tube or anything). I also took pictures of the filament pattern on the two runs.

The amount of filament that was pushed through the hotend when printing the cube was 44.4 mm while the amount for the free filament was 51.3 mm! Cura says that it is supposed to be 51 mm. In other words, there seems to be a fairly large amount of slipping during the print.

Here is the picture of the pattern on the "free" filament:

gallery_36523_1334_42452.jpeg

and here is the pattern of the filament that went through the bowden tube and hotend:

gallery_36523_1334_125237.jpeg

I unfortunately reversed the filament to get it out of the machine so there are two sets of pattern. There is still a pretty big difference in the patterns though and you can see that the "diamonds" are skewed.

So, the question is how to solve this. More pressure on the filament? A better knurl pattern?

 

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Posted · Top Layers not touching - UM2

mine looks like this

Filament Pattern After Underextruisioned Print

Doesn't look good closeup

Maybe it's combination of

-high pressure caused by any resistance

-not really having as much temp as it shows and

-new knurled design?

-heat @ the knurled bolt?

@mevander how the f*** could you maximize your image??

 

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Posted · Top Layers not touching - UM2

Hi everybody!

Just to give some input: I know that Illuminarti did some research about this as well: http://www.extrudable.me/2013/04/18/exploring-extrusion-variability-and-limits/

Besides this Erik van der Zalm also took some measurements with a rotary encoder on the filament (see attached graph).

buddy.thumb.jpg.5e9df516f4ac1dd5e6fbf3f989a9a777.jpg

As far as I know, these results were all measured on a UM original.

-Bas

 

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Posted · Top Layers not touching - UM2

Thanks Bas, that was very interesting. I think that one difference is that what we see here is at fairly low flow rates. My test box was printed at 4 mm^3/s and we've seen it at much lower flowrates too. If we go really slow, 0.05-0.1 mm layers at 20 mm/s we get very nice prints but that is also the only settings we can use more or less.

 

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Posted · Top Layers not touching - UM2

@ Bas van Deursen

i have readed all this and information in the forum over and over but..

..in my eyes this has nothing to do with my problem not being able to print 10mm/s @ 0.1mm layer without underextrusion while the extrusion test works up to 10mm3/s!

he wrote how to determine the limits and the actual limit of my printer seems something around 0.5 mm3/s wich is 30 times less then my older UM2 but i'm still able to print the usual extrusion test fully

so:

Limit of my printers:

older UM2: 10mm3/s still very nice surface

newer UM2: 0.5mm3/s still a little underextrusion

 

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Posted · Top Layers not touching - UM2

Hi,

I understand, that is of course unacceptable. I know that the current feeder design is critical, which means that only slight changes in the resistance in the "extrusion train" can make the difference between a nice and a bad print.

From the material feeder perspective (which is the area of the printer I am working on) I can say that I am doing my best to get some more grip and torque.

-Bas

 

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Posted · Top Layers not touching - UM2

@ Bas

I Exchanged the feeder to Roberts V2 because on my older UM2 i can print everything with it without change the tension.

As my older UM2 shows the overall design of the setup can't be so wrong..

..but what makes a 30 times difference on my newer machine, when everything looks good even the extrusion test?

 

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Posted · Top Layers not touching - UM2

Hey Bas,

 

I think the problem lies elsewhere since different UM2 owners with seemingly identical feeders, still have very different results.

I suspect a firmware problem or a combination of bad pulleys and bent rods. I wanted to test the rods for ages but now that my 3DR Delta build is finished and I need to fine tune it, I got sidetracked.

However, for the firmware idea, a few posts ago I asked around about the combination of firmwares used. But in order to structure the data a bit more, I have started a new thread/poll. I see there are 12 people following this thread so please be so kind and vote here:

 

 

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Posted · Top Layers not touching - UM2

Btw. I didn't remember all firmware names/numbers. If you find a complete list, please change the poll or tell me to do it.

 

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