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need help with failed sponge-like printout

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I upgraded from ultimaker 2 to ultimaker 2+. I am using 2 mm PLA filament and 100% infill. At the beginning, it prints well. After about 100 hours printing, the printouts start having holes and are very fragile. I tried increasing the temperature to 230 but did not solve the problem. Any idea why this is happening and how to fix ? Thanks.


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Please post a photo. It's probably underextrusion but I want to see a photo to be sure. If it's underextrusion it should get better if you slow it down to half speed - while printing just go to TUNE menu and slow it down to 30% and up to 240C also. If it looks better then you had underextrusion which has many causes and lots of easy solutions.

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Thank you the reply. Picture is as below. I tried slowing the speed and increasing temperature to 240.  Though I got better results than before, the same issue still exists. The prints are still fragile and brittle. Is there other reason or how to resolve the underextrusion problem?



Edited by Guest

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I don't see any brittle spots or underextrusion. Well I guess I see two tiny spots near the top edge of the part in this orientation but not as much as I thought. Not enough to make it brittle. Are you sure this is PLA and not ABS? ABS can be quite brittle if you print it the way PLA should be printed.

Well if you only have underextrusino on a single layer then it could be a filament tangle. Consider putting the filament on the floor.

I'm very hesitant to give you more information because from this photo I do not see anything related to serious underextrusion but here it is anyway - here are the causes that I know of for underextrusion, how to diagnose, and fix:

As far as underextrusion causes - there's just so damn many. none of the issues seem to cause more than 20% of problems so you need to know the top 5 issues to cover 75% of the possibilities and 1/4 people still won't have the right issue. Some of the top issues:

1) Print slower and hotter! Here are top recommended speeds for .2mm layers (twice as fast for .1mm layers) and .4mm nozzle:

20mm/sec at 200C

30mm/sec at 210C

40mm/sec at 225C

50mm/sec at 240C

The printer can do double these speeds but with huge difficulty and usually with a loss in part quality due to underextrusion. Different colors print best at quite different temperatures and due to imperfect temp sensors, some printers print 10C cool so use these values as an initial starting guideline and if you are still underextruding try raising the temp. But don't go over 240C with PLA.

2) Shell width confusion. Shell width must be a multiple of nozzle size. For example if nozzle size is .4mm and shell width is 1mm cura will make the printer do 2 passes with .5mm line width which is possible but requires you to slow down much more to make a .5mm line out of a .4mm nozzle. If you really want this then set nozzle size to .5mm so it's clear what you are asking Cura to do for you.

3) Isolator - this is most common if you've printed extra hot (>240C) for a few hours or regular temps (220C) for 500 hours. It gets soft and compresses the filament under pressure. It's the white part touching the heater block. It's very hard to test when not under full pressure (spring and bowden) so sometimes it's best to just replace it. Also if you notice parts of it are very soft (the blacker end where it touches higher heat) then it's too old and needs replacing.

4) Curved filament at end of spool - if you are past half way on spool, try a fresh spool as a test.

5) curved angle feeding into feeder - put the filament on the floor -makes a MASSIVE difference.

6) Head too tight? Bizarrely MANY people loosen the 4 screws on the head by just a bit maybe 1/2 mm and suddenly they can print just fine! Has to do with pressure on the white teflon isolator.

6b) Bowden pushing too hard - for the same reason you don't want the bowden pushing too hard on the isolator.

6c) Spring pushing too hard. Although you want a gap you want as small as possible a gap between teflon isolator and steel isolator nut such that the spring is compressed as little as possible.

7) clogged nozzle - the number one problem of course - even if it seems clear. There can be build up on the inside of the nozzle that only burning with a flame can turn to ash and remove. Sometimes a grain of sand gets in there but that's more obvious (it just won't print). Atomic method (cold pull) helps but occasionally you need to remove the entire heater block/nozzle assembly and use flame. Or soak it in acetone overnight (after removing 90% of the material with cold pull).

8) Temp Sensor bad - even the good ones vary by +/- 5C and bad ones can be any amount off - they usually read high and a working sensor can (rarely) fail high slowly over time. Meaning the sensor thinks you are at 220C but actually you are at 170C. At 170C the plastic is so viscous it can barely get out of the nozzle. You can verify your temp sensor using this simple video at youtube - on you tube search for this: mrZbX-SfftU

9) feeder spring issues - too tight, too loose

10) Other feeder issues, one of the nuts holding machine together often interferes with the feeder motor tilting it enough so that it still works but not very well. Other things that tilt the feeder motor, sleeve misaligned so it doesn't get a good grip. Gunk clogging the mechanism in there.

11) Filament diameter too big - 3mm is too much. 3mm filament is usually 2.85mm nominal or sometimes 2.9mm +/- .05. But some manufacturers (especially in china) make true 3.0mm filament with a tolerance of .1mm which is useless in an Ultimaker. It will print for a few meters and then clog so tight in the bowden you will have to remove the bowden from both ends to get the filament out. Throw that filament in the trash! It will save you weeks of pain

11b) Something wedged in with the filament. I was setting up 5 printers at once and ran filament change on all of them. One was slowly moving the filament through the tube and was almost to the head when I pushed the button and it sped up and ground the filament badly. I didn't think it was a problem and went ahead and printed something but there was a ground up spot followed by a flap of filament that got jammed in the bowden tube. Having the "plus" upgrade or using the IRobertI feeder helps you feel this with your hand by sliding the filament through the bowden a bit to see if it is stuck.

12) Hot weather. If air is above 30C or even possibly 25C, the air temperature combined with the extruder temperature can soften the filament inside the feeder such that it is getting squeezed flat as it passes through the feeder - this is obvious as you can see the problem in the bowden. The fix is to add a desk fan blowing on the back of the printer. Not an issue on the UM2 "plus" series.

13) Crimped bowden. At least one person had an issue where the bowden was crimped a bit too much at the feeder and although the printer worked fine when new it eventually got worse and had underextrusion on random layers. it's easy to pull the bowden out of the feeder end and examine it.

14) Small nozzle. Rumor has it some of the .4mm nozzles are closer to .35mm. Not sure if this is actually true. I'm a bit skeptical but try a .6mm nozzle maybe.

15) CF filament. The knurled sleeve in the extruder can get ground down smooth - particularly from carbon fill. 4 spools of CF will destroy not just nozzles but the knurled sleeve also. Look at it visually where the filament touches the "pyramids". Make sure the pyramids are sharp.

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I see that you print with 2mm filament? I guess by that you mean: "2.00mm", is that correct? could you check that again?

Normally, the filament should be 2.85mm (which is sometimes referred to as "3mm filament"). So, if you use 2.00mm filament indeed, you will sure get underextrusion, since the printer expects a much thicker filament. The surface area of 2.85mm filament is about twice that of 2.00mm filament.

So you need to accurately measure the filament diameter and set this correctly in the settings (but I don't know where to find that setting), or you need to adjust flow rate accordingly manually.

If this is the cause indeed, then increasing temperature will make the layers bond better, even with underextrusion, but it will not cure the real cause: not enough material. A too hot temperature might even burn the PLA in the nozzle, or make it decompose chemically and reduce strenght.

Using filament that is too thin will also cause other issues, such as back flow in the nozzle, and twisting in the bowden tube.

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The PLA filament is fine. I measured the diameter and the number is 2.85mm.  I have been using the same filament and setup. I got good prints on upgraded 2+ until this issue showed up.   I tried slowing the speed only to 30% but there is little extrusion at 210. If I increase the temperature to 230 and above, it can extrude but the quality of printing is much worse (fragile prints and higher failure rate).  I also tried lowering temperature to 90 and then pulling the filament out of extruder to clean up , which seems not working.  

Before I made the upgrade from ultimaker 2 to 2+ (changing both the extruder head and feeder), I also had the same problem with ultimaker 2. After the upgrade, the issue does not exist any more for a while. But after using the upgraded ultimkaer 2+ for 100 hours, the same issue appeared again.

I could not got a good measurement of temperature following the youtube video, so can not tell whether the temperature sensor has broken or not. If the issue can not be solved myself, is there any technical support or repair center in US I can ship the product to ?

Edited by Guest

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@penglu - this additional information about how it worked for a while is very very helpful.  That eliminates all but issues above except #3 #4 #7 #15.

If you have more than half a spool that eliminates #4.

If you have never printed carbon fiber then that eliminates #15

That leaves #7 and #3.  #3 can be checked by swapping with another same-size nozzle.  But really #7 is the most likely of all of these.  You probably need a new teflon part.  I sell the latest high tech expensive teflon (much better than what Ultimaker used to sell).  Ultimaker now also sells the better teflon.  In USA you can get the teflon part from my store here:


Or you can get official UM parts from fbrc8.com

Going through one part every 100 hours seems a little fast unless maybe you were printing some ABS parts?  But not too unbelievable.

Edited by Guest

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I agree with your analysis. So there are two possible reasons

3) Isolator - this is most common if you've printed extra hot (>240C) for a few hours or regular temps (220C) for 500 hours.

7) clogged nozzle -

I have not done printing at high temp so clogging is most likely the issue. Since I have tried cooling and pulling out filament, is there any video showing how to disassemble the extruder and do a more though cleaning? BTW, what official UM parts do you think I need to fix the issue ?

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Well I see you have the UM2+ so you already have 4 different nozzle sizes and the Olsson block. Just heat block to 150C and take a wrench and remove the existing nozzle. Once up to temperature it takes maybe 5 seconds.

You can burn that nozzle in a flame until everything is ash. Or spend the $8 for a new nozzle plus $3 shipping. While the nozzle is off and after it cools to < 40C try pushing some filament up through from below. If the teflon part is bad you will feel significant friction. If it is bad I recommend ordering one asap and temprarily drilling the bad one out from below gently by hand (not electric powered! Don't want to drill out the brass block).

I don't recommend "official UM" parts. I recommend the ones from my store. I recommend getting a new TFT and a spare 0.4mm nozzle. I also recommend you try out the 0.6mm nozzle you already have - it prints so much faster than the 0.4mm nozzle (twice as fast) and the resolution is excellent.

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