Almost always missing layers / underextruding

[illuminarti 18]

Hey Simon,

 

I have re-read parts of this thread since underextrusion strikes again and I am looking for clues. The sound accompanied by the blob comes from the extruder. It skips on the first extrusion. Also the bowden tube buckles at the head end which indicates that there is way to much pressure building up very quickly.

 

Sorry, I've been off on vacation for almost two weeks. I think that you're finding a firmware bug, whereby the e-counter isn't getting reset properly sometimes, and so it tries to extrude a ton at the start of the print. I'll check the firmware source when I get a chance, see if I can spot anything.

[eldrick 65]

The extrusion test is a good one for a number of issues - it is a sensitive indicator for print echo.

I found that echo trailing the text was visible at 5mm/s on my UM2, but was barely visible at 8mm/s after I replaced the OEM metal fan shroud with a 14g-lighter printed version.

 

[shurik 87]

And here we go again. There's something that I probably fundamentally miss in this old saga of the underextrusion.

Look:

 

After an hour of happy printing, there was the devil click of the underextrusion, and yet another print is going to go to the trash bin. In the tests, my printer went well up to 13mm³.

Colorfabb White, 210C, 30mm/s. There even were no retractions in the last layers before the problem, just the perimeter layers. The retraction settings:

Minimum travel: 1.5mm

Combing: off

Minimum extrusion before retracting: 0.1mm

Z hop: 0.075mm

Cura 14.04-RC1

Very unhappy. :-(

 

[Nicolinux 288]

Shurik, this could just be bad luck. If the filament thickens in one spot and won't pass the teflon piece in the head - you'd get underextrusion.

I have the feeling that there are a million possible causes for underextrusion and only a few of them are under your control (like not doing something stupid that prevents the extruder from feeding filament).

But I agree, I have more prints that were ruined by underextrusion than for any other reason.

 

[fingerpuk 0]

I had this issue a ton, Faberdashery filament solved it straight away. Never using a spool again.

[Nicolinux 288]

I had a very long failed print and had to disassemble the head because the nozzle was partially clogged (http://umforum.ultimaker.com/index.php?/topic/5595-resume-long-print/). After the failed print I cleaned the nozzle as best I could without taking it apart. The filament flow was normal but when I printed Robert's feeder, I got some of the worst prints ever on an UM2 :(

My idea was to print the feeder, then disassemble the head _and_ mount the new feeder (to avoid further ABS contamination). I disassembled everything, burned the inside of the nozzle and put it in acetone for a few hours. However I did also inspect the teflon piece and the ridge/lip is clearly visible:

No wonder the extrusion tests failed after 6mm^3/s. And this is a newish UM2 (two months old). I wonder if my use case promotes the early failing of the teflon piece. I do change filament quite often (almost every print). When the filament tip passes the teflon piece, the sharp edge may scratch the same spot over and over again until it forms this ridge. Or the teflon piece is very sensitive when the nozzle is hot and there is no filament (while changing it). I try to change filament as fast as possible but because I do it often, the time when the teflon piece is hot and alone adds up (this sounds unnecessarly kinky, I wonder which of my fellow horny squirrels will jump on it ).

Oh and my first attempt to print Robert's feeder was interrupted by the temperature sensor who couldn't decide if it wants to report the temperature or not (just to spice things up a bit). There was also some underextrusion, because why not?

 

[andrew-white 0]

This is why it sucks to be a newbie, I have downloaded the UM2 extrusion test & can't work out how to get it to print. tried opening it in cura & tried putting it onto the sd card to see if it would read. Any and all help gratefully received.

 

[cyan 0]

This is why it sucks to be a newbie, I have downloaded the UM2 extrusion test & can't work out how to get it to print. tried opening it in cura & tried putting it onto the sd card to see if it would read. Any and all help gratefully received.

 

It should be a .gcode file, which is what the printer reads, so you should just be able to put it on the SD card and it will work.

[andrew-white 0]

for some reason when i download it on my mac the file is .gcode.txt

 

[andrew-white 0]

many thanks found an other file that is just .gcode in my downloads folder

 

[johna 0]

Having the same issue as other people....

 

First test:

 

 

Backed out filament a few times, got... slightly better?

 

 

Replaced stock spring in extruder with one slightly weaker. Now it's interesting in that I believe it's slipping and not doing the normal 'knock' type skip where the motor stops moving momentarily:

 

 

I've got probably 10-12 spools of plastic through this printer. Filament knurled gear isn't slipping. Printed at 230.

 

[Nicolinux 288]

Try the obvious things. Check for clogs (the atomic method works particularly well) and if it doesn't help, dismantle the head and check the teflon piece. The underextrusion issue is a bit of a mistery but deffinitely related to several factors.

By the way, now that I think of it, those of you who never had underextrusion problems and have put their printer through paces - maybe you're doing something inherently useful to counter underextrusion and/or wear to certain parts that may lead to underextrusion. And maybe you are completely unaware of it

So George, Simon, Aaron, Sander - could you please explain (in great detail if you have the time) how do you prepare a print, store filament (spool holder or floor), and in general - how you handle the printer. Here are some questions:

 

• How do you change filament? Standard way or heating up and pulling the filament out?
  
• Do you "sharpen" the filament tip so it doesn't get hung up inside the teflon piece?
  
• How often do you change filament?
  
• Do you let the nozzle heated up for a long time?
  
• Do you perform _very_ long prints?
  
• Room temperature where the printer is stored.
  
• Wich filament do you use (spool, loose, brand)?
  
• Did you change motion settings?
  
• Did you increase stepper motor current?
  
• Do you use an alternative feeder?
  
• Do you have a filament dust filter?
  
• Have you took the electronics cover off and checked where the extruder motor wires are guided? (maybe if they are guided wrong and are too close to other componentes, the extruder motor might be influenced during prints).
  
• ...
  

 

Sorry for the many questions, but maybe maybe this will lead somewhere.

Thanks,

Stefan

 

[johna 0]

Just tore it apart. Teflon piece seems fine, I can pull filament through it with no dragging at all. I did pass a loose drill bit through it by hand and it didn't snag at all.

Pulled the filament feeder off the back again, cleaned it out, and tried to smooth out a few rough parts where it's worn away.

Nozzle seems clean. Warming up for another test now.

<edit>

Failed! Got further than before, but still no dice. When it skipped once around 3, I upped the temp to 240, but it didn't seem to matter.

http://i.imgur.com/HaadDMd.jpg

One more test tonight before I give up. Loose coil, different brand PLA.

 

[SandervG 1,521]

 

• Who knows! I'll walk through the things I do.
  

I have an Ultimaker 2 on my desk which I use daily. I usually have the same one, but sometimes I need

to bring it to an event and it can happen that by now I have my colleagues and he has mine.

So I can not confirm with a full 100% I have been using the same machine always.

 

I am also not saying I have never suffered from under extrusion, however I have been able to fix it every time.

At 1 occasion I had the teflon part replaced.

 

• How do you change filament? Standard way or heating up and pulling the filament out?
  
• - When I change the filament I just use the change option in the menu. Nothing fancy about this action.
  
• Sometimes I change filament when I just need a different color for a different print. Sometimes when I notice some underextrusion it also helps to just use a different filament..
  
• 
  
• Do you "sharpen" the filament tip so it doesn't get hung up inside the teflon piece?
  
• - No. But I have experienced 2 / 3 times that it gets stuck at some kind of edge around the teflon-area.
  
• I notice because it is not feeding anymore when I have just fed in new. After a 'motivating push from the back', with a pair of pliers, I heard it get loose and squirt out of the nozzle. After that it worked normally. Also retraction was no problem.
  
• 
  
• How often do you change filament?
  
• - Hard to tell. Sometimes 3 times a day, sometimes I leave the same filament in for 3 days.
  
• 
  
• Do you let the nozzle heated up for a long time?
  
• - Nope. I do also experience that with a second print sometimes I need to move material first.
  But the inconsistent bed leveling haven't really plagued me.
  
• For a second print my extrusion is sometimes lagging behind. What I do sometimes is after the first layer manually tilt the bed up very gently so when it starts extruding it still sticks to the bed. After this first second layer (makes sense) it usually just works and I can let go.
  

I have been printing hotter then I have before lately, around 220/230ºC for normal prints.

But I am getting good results.

 

• Do you perform _very_ long prints?
  
• - Usually it varies between 2-12 hours. Except for the weekend when I try to print bigger.
  
• 
  
• Room temperature where the printer is stored.
  
• - Around 17-20ºC. It is on my desk.
  
• 
  
• Wich filament do you use (spool, loose, brand)?
  
• - Ultimaker filament, sometimes Colorfabb.
  
• The amount of filament also varies, some are full some are almost empty.
  
• 
  
• Did you change motion settings?
  
• - Nope, basic set up. I do not intend to print faster then 50mm/s.
  
• 
  
• Did you increase stepper motor current?
  
• - Nope, basic settings.
  
• 
  
• Do you use an alternative feeder?
  
• - Nope. When I do have time I want to try Roberts, but so far I haven't and I am using the default one.
  
• 
  
• Do you have a filament dust filter?
  
• - Nope. However the filament is just in a closet in the office, so it is not really protected for dust either.
  
• I do think that for the under extrusion I have, the filament is partially to blame. I rather suspect moist then dust that has its affect on the filament.
  
• 
  
• Have you took the electronics cover off and checked where the extruder motor wires are guided? (maybe if they are guided wrong and are too close to other componentes, the extruder motor might be influenced during prints).
  
• - Nope. It is as how it is being shipping.
  

What reel holder do you use?

- I have the basic reel holder, however sometimes I do put the reel on the floor in front of my desk.

Sometimes this helps, sometimes it doesn't.

 

Have you used Atomic Method before?

- Yes, and it did help.

I did not particularly find a lot of black in the nozzle.. but it was under extruding before, and it worked fine afterwards so I guess I did something right

 

Any more questions?

 

[Nicolinux 288]

Wow, thank you Sander.

 

One more (hopefully not uncomfortable) question.

What is the official status of underextrusion on the UM2?

 

There has been written so much about it, and I am not sure how Ultimaker sees it. Do you recognize it as a real problem and are you working on a fix? Maybe a new feeder (not ABS) or a new teflon piece (new material)? Since this problem is so elusive, it might be hard to find a "be all end all" fix. But since the UM Original doesn't exhibit this problem, it must be something related to the new UM2 design. Because people and filament didn't change meanwhile, but the underextrusion was deffinitely en vogue with the appearance of the UM2.

I am not sure what to do about underextrusion. Well, my printer has its own weird problems (plz answer the other pm), but for others who experience underextrusion, it might be frustrating to have a hit/miss relationship with their prints (as if 3d printing wasn't hit/miss-y already )

The UM2 has been about to 9 months out in the wild - no pressure, just aking because in my mind it is the perfect consumer 3D printer and I'd like to see that underextrusion problem erased from its image. Or at least prevent underextrusion from beeing attached to UM2's image.

 

[SandervG 1,521]

Hi Nico,

Fair question. Given the fact under extrusion does exist.

Luckily, for us, it does not strike the majority of the users.

But enough users experience it for us to seriously look at the reasons on what is causing it, and more precisely; how to solve it!

So far we know that most existing causes of under extruding is a sum of various reasons.

Whether it be filament curvature, teflon deformation or something regarding the feeder.. it is usually a combined reason.

We are looking at all those points, to find out if there is any room for improvement or if we can rule out any room for play that may still existed. We are testing various solutions and once we have reliable outcomes you guys will all be the first to know

It makes sense that people who are in need of help go to the source of information (forum) and seek for help.

People with a solely positive and flawless experience may not feel that urge to connect with the community right away.

This may create a unbalanced view on how many people are actually suffering from this.

- as a response on your assumption that under extrusion is associated with the Ultimaker 2.

I know about your own problems, and I will get back with you on those soon, ok?

 

[illuminarti 18]

The main reason that this sort of under-extrusion is only seen on the Ultimaker² is because of the 'skip-back' feature in how the motor is set up, combined with the relatively low torque created by an non-geared system. The Ultimaker Original can generate more than enough torque to be able to strip the filament, so that becomes the limiting factor.

As my tests showed, the Ultimaker Original under-extrudes chronically by up to 20% as you print faster - it just does it at a constant rate, so that it's hard to spot in most cases. On the Ultimaker² there is the skip-back failure mode where all extrusion totally stops for a moment, making the failure very obvious.

[Nicolinux 288]

@Sander: Thanks Sander. I knew that you are taking it seriously, but it is nice to have a confirmation.

@Illuminarti: Good explanation. So I am not sure what's better. Having underextrusion and never spot it, or as soon as there is underextrusion, totally make it visible and potentially ruin the model (stability wise). I mean both scenarios aren't ideal since stripped filament leads to a failed print and severe underextrusion too.

 

[johna 0]

So here's my latest update.

Tried different PLA that was a big 18" coil, and fed it by hand. No dice:

Still stopped early. Or started skipping, so I stopped it.

The only change I made after that was to narrow the gap between the barrel adjuster (I don't know the right name) and the teflon piece. I cut it to half of what it was (I don't have a great way to measure it currently) and tried again, this time just leaving the loose coil on a table.

 

Whoa, HUGE improvement. My best result yet. No other changes to machine, other than closing that gap. I just cut the gap in half again, and I'm running another one now. Will report back.

 

[johna 0]

And... almost total success! Almost.

I cut the gap between the adjuster and the white teflon part in half again. Now it looks like this:

 

And re-ran it, everything else the same:

 

That's by far my best yet, it printed up into the 10 area, but had a few skips in the 8 and 9 rings....

So closing the gap is making / has made a measurable difference for me. I'll go back to the silver Ultimaker PLA shortly and try that.

 

[fuh 1]

I'm not sure if everybody has noticed my findings about filament friction which allowed me to at least double the extrusion rate before underextrusion occurs. http://umforum.ultimaker.com/index.php?/topic/5454-ultimaker2-reduce-filament-friction-in-the-bowden-tube/&do=findComment&comment=52713. It might help.

 

[aaronalai 2]

Not sure why I've been summoned as I got my printer around March 10th, coming up on 3 months soon :-P. But I'll answer as I like to inspect and watch the machine a lot :shock:. I too print daily and have only missed a handful of printing days since I got my machine.

 

• How do you change filament? Standard way or heating up and pulling the filament out?
  
• Standard way sort of. I'm using the latest stable firmware of Cura, but have always had an issue where sometimes the extruder motor will stop before it has moved all of the filament out during the change filament route. I power the machine off briefly pull out the filament then turn it back on again. I try to get out as much of the string as possible while doing this, if it's PLA I just leave it in the Bowden tube, if it's ABS I clean it out with a paper towel.
  

 

 

• Do you "sharpen" the filament tip so it doesn't get hung up inside the teflon piece?
  
• I have not felt the filament hang on the teflon coupler, but I do cut the filament at an angle to prevent squishing the cut surface and deforming it.
  

 

 

• How often do you change filament?
  
• I have 14 spools of filament (I ordered overseas and it's to justify the shipping). Out of these spools 4 are empty or only have about 2 meters on them. They consist of PLA, ABS, XT, PET+, and flexable PLA; out of these I have not yet printed out of XT or flexable PLA. I switch the filament out about 1.5 times a week.
  

 

 

• Do you let the nozzle heated up for a long time?
  
• Nope, definitely always conscious to keep the filament flowing through the hot end and if I'm not I get it out of the hot zone as quickly as I can. There was one instance where PLA was sitting in the nozzle heated for an entire day without any issue. The filament wrapped under itself and knotted almost at the beginning of the print and I didn't see it until I got back late from work that day. The motor just ground the filament down.
  

 

 

• Do you perform _very_ long prints?
  
• Yup, I've had a couple of multi-day prints with no problem. I often am working the printer for most of the weekend.
  

 

 

• Room temperature where the printer is stored.
  
• 20 - 27.5 C
  

 

 

• Wich filament do you use (spool, loose, brand)?
  
• Ultimaker, ColorFabb, MadeSolid
  

 

 

• Did you change motion settings?
  
• Yeah, heated bed 50-60 for PLA, default settings for ABS, acceleration 2000; I believe it's 3000 in the newest firmware by default.
  
• 
  
• Did you increase stepper motor current?
  
• Nope.
  

 

 

• Do you use an alternative feeder?
  
• Nope. I do use a filament guide and an existing bolt hole on the UM2 frame. This significantly reduces grinding down of the extruder motor casing.
  

 

 

• Do you have a filament dust filter?
  
• Yup, ziptied paper towel around filament tightly. This assemblage sits at the enterance to the stepper motor box. I also blow out little bits of ground down filament from the extruder motor case frequently just using my breath.
  

 

 

• Have you took the electronics cover off and checked where the extruder motor wires are guided? (maybe if they are guided wrong and are too close to other componentes, the extruder motor might be influenced during prints).
  
• I took the electronics cover off and didn't notice anything odd with the wire guiding. Unlikely RF interference would change the stepper's behavior.
  

 

I've also had under-extrusion a couple of times but it was usually because of something I did that ended up grinding the filament down, like printing way too cold or knoting up the filament on the reel. I have had two clogs that were easily remedied by a hypodermic needle. And there have been a few times where I did not clean the nozzle well enough, but have only had to do the Atomic Bob method twice.

 

To clean out the nozzle I usually use the move filament command, if I'm switching from ABS to PLA I tell the machine I'm putting in ABS so it heats up real hot. After the install filament sequence I quickly go to "move material" and start pumping out PLA as fast as it will come out of the machine, I frequently induce skipping during this action. Once I'm satisfied with the speed and consistency by which the filament comes out of the nozzle; thick, smooth, and straight down out of the nozzle, almost like dispensing a liquid, I move the filament backwards until it's barely out of the teflon coupler then let everything cool like normal with the 3rd fan on.

 

Once cool I'll take the Bowden tube off at the print head end; clip the bit of melted plastic at an angle; with the machine off, spin the filament reel backwards manually to get it completely out of the Bowden tube; remove the other end of the Bowden tube and clean the tube with a rolled up paper towel.

 

If I've been printing with ABS for only a short time I skip cleaning out the Bowden tube, I notice ABS collects over time.

 

Once I got a really stubborn clog after using PLA for a while, and I didn't have a suspicion as to what the material could be. I was too lazy to do the Atomic method so I just used move material at I think 220 to plunge the filament into the nozzle and back out again. The clog eventually went away.

 

I recently inspected my teflon coupler and could not identify any deformation to the interior cylinder wall, and did notice an almost invisible deformation to the surface of the teflon coupler that interfaces with the nozzle. I could only see it when light was reflecting off the surface.

 

Also, I used a beta firmware once and the new filament start sequence tried to push filament through the nozzle too quickly and usually ended up grinding it down.

 

Hmm, I think this response is getting long enough, I'll answer any more questions if needed or for clarification.

 

[illuminarti 18]

Ok, here are my answers... I don't think I'm doing anything unusual...

 

• How do you change filament? Standard way or heating up and pulling the filament out?
  

Standard way.

 

• Do you "sharpen" the filament tip so it doesn't get hung up inside the teflon piece?
  

Not particularly - I either cut the tip off at a slight angle with wire cutters, or often just bend the filament back and forth until it breaks. I avoid inserting particularly jagged or deformed tips, but any kind of clean break is fine.

 

• How often do you change filament?
  

It depends - often several times a day.

 

• Do you let the nozzle heated up for a long time?
  

I don't generally heat the head up for long periods of time other than the duration of the print. I generally allow the built-in start and end gcode to do its thing, as much as I hate it.

 

• Do you perform _very_ long prints?
  

The longest print I've done is about 2 days. It printed fine. Tons of retractions. No problems.

 

• Room temperature where the printer is stored.
  

About 21-25ºC

 

• Wich filament do you use (spool, loose, brand)?
  

Ultimaker, Faberdashery. Definitely get less problems with loose faberdashery placed on floor behind printer.

 

• Did you change motion settings?
  

No

 

• Did you increase stepper motor current?
  

No

 

• Do you use an alternative feeder?
  

No

 

• Do you have a filament dust filter?
  

No - and I keep the filament in a closet. And I have a very hairy cat who likes to play in the coils behind the printer sometimes. And I've never *ever* had a take-it-apart head clog in two years of printing.

 

• Have you took the electronics cover off and checked where the extruder motor wires are guided? (maybe if they are guided wrong and are too close to other componentes, the extruder motor might be influenced during prints).
  

My main printer doesn't have an electronics cover - never has. However, I've also extrusion tested many other printers now, in my work, and I don't think there's anything particularly special about the routing of the wiring on my own, or those.

 

[gr5 2,172]

 

• How do you change filament? Standard way or heating up and pulling the filament out?
  

Standard way until about month ago. Now I heat up to 90C, pull damn hard with my hand and hand insert the new piece. I haven't used "change filament" in a while.

 

• Do you "sharpen" the filament tip so it doesn't get hung up inside the teflon piece?
  

Now I have to as inserting by hand is a pain. I almost always cut the pla to a nice tip. Partly to discard the old tip.

 

• How often do you change filament?
  

Every other print or so. I'm always changing colors.

 

• Do you let the nozzle heated up for a long time?
  

Never. I'm afraid to let it stay hot very long at all. 240C is my max temp for the most part.

 

• Do you perform _very_ long prints?
  

I've done 3 prints > 12 hours. One was about 30 hours.

 

• Room temperature where the printer is stored.
  

UM says 20C. I have AC in summer, heat in winter. Never gets very humid. UM2 in the fall so haven't run AC yet.

 

• Wich filament do you use (spool, loose, brand)?
  

Mostly UM but also printbl. I have had some underextrusion on spools down to the last 1/4. I now only run those spools on the UM original.

 

• Did you change motion settings?
  

no.

 

• Did you increase stepper motor current?
  

no.

 

• Do you use an alternative feeder?
  

no. Haven't taken mine off yet or looked inside yet.

 

• Do you have a filament dust filter?
  

Not really. Tried it - was a mess.

 

• Have you took the electronics cover off and checked where the extruder motor wires are guided? (maybe if they are guided wrong and are too close to other componentes, the extruder motor might be influenced during prints).
  

My cover has been off for a very long time.

The one thing I do that not many do - and I think it's important - I always print with filament on the floor. I think the feeder is too low and/or the filament spool too high and that creates a 45 degree angle as the filament enters the feeder.

Other things:

I've had many tangle problems. Now when I remove filament I hang on to the end and tuck it through a spool hole so it can't get tangled. I can't print 10mm^3/sec usually but I rarely need to go that fast - I mean I can print the cylinder to 10mm^3 but it isn't dependable - not safe. I feel comfortable printing 3mm^3/sec at 230C.

I have 2 printers and I've never been able to keep them both going. So I'm really not in a rush, so I tend to print slow. When I push it to 5m^3/sec I'm bound to get a single ugly underextruded layer.

I love the atomic bob method and so basically do it on all filament changes now.

I have had at least 2 nozzle clogs that needed combination of atomic method and sometimes also some hypodermic needle.

 

[gr5 2,172]

barrel adjuster (I don't know the right name) and the teflon piece.

 

The white teflon piece is the "isolator" (that's what UM calls it). The "barrel adjuster" seems to be officially called the "isolator nut" (it has (6?) holes through it). The isolator nut is probably the most delicate thing in there as the walls are very very thin where it is threaded.