Almost always missing layers / underextruding

[Nicolinux 288]

Hehe, I have transparent PLA here...

The material fed in ok, but hangs a bit where the teflon coupler and the nozzle meet. It doesn't hang if I feed it by hand when I take the bowden tube out though. But it passes this place and goes on.

 

[takei-naodar 0]

Hehe, I have transparent PLA here...

The material fed in ok, but hangs a bit where the teflon coupler and the nozzle meet. It doesn't hang if I feed it by hand when I take the bowden tube out though. But it passes this place and goes on.

 

i meant how it was fed into the feeder..... against its natural bending, with, neutral or straightend by hand.

 

[Nicolinux 288]

Fed in the standard way. Spool on the spool holder and filament fed in following its natural curvature.

 

[takei-naodar 0]

Ok i just did Illu's Extrusion test with 120% Material Flow and my feeder never clicked back. the lines also measured around 0.48ish so i think i can say i can now print with 12mm³/s (although i had to go up to 240°C to get that material through the nozzle)

 

[gr5 2,170]

1) Nicolinux your photo above of the 3 test prints is USELESS without including a temperature. My printer is worse than that if I print cold enough.

2) I'm not sure that printing at a max 6mm^3/sec is a problem. The fastest I have printed so far on my UM2 is 3mm^3/sec and most things I print at about 1.2mm^3/sec. The quality is just much better if you keep it well under 2mm^3/sec. Even if your printer could do 20mm^3/sec I think you would want to keep it under 3 for anything you want to look good.

Now I understand - some people print parts that are hidden inside something and don't have to look good. And for those parts it sucks that you are limited to 6mm (although even then a little underextrusion sometimes shouldn't ruin the functionality of most prints as long as it is only occasional). But I bet you printed colder than 250C and if you instead up it to 250C maybe you can get 12mm^3/sec just like Takei here in the previous post.

So I'm not quite sure if there is a problem here.

 

[Nicolinux 288]

1) Nicolinux your photo above of the 3 test prints is USELESS without including a temperature. My printer is worse than that if I print cold enough.

 

I am printing all test objects at 230°.

 

2) I'm not sure that printing at a max 6mm^3/sec is a problem. The fastest I have printed so far on my UM2 is 3mm^3/sec and most things I print at about 1.2mm^3/sec. The quality is just much better if you keep it well under 2mm^3/sec. Even if your printer could do 20mm^3/sec I think you would want to keep it under 3 for anything you want to look good.

Now I understand - some people print parts that are hidden inside something and don't have to look good. And for those parts it sucks that you are limited to 6mm (although even then a little underextrusion sometimes shouldn't ruin the functionality of most prints as long as it is only occasional). But I bet you printed colder than 250C and if you instead up it to 250C maybe you can get 12mm^3/sec just like Takei here in the previous post.

So I'm not quite sure if there is a problem here.

 

The thing is, I am not printing test objects day in day out just to prove some fabrication tolerances for the UM2. I do print stuff I want and most of the time I stay well under 4mm^3/s and still get underextrusion. Take this vase for example. Printed at 0.2 layer height, 40mm/s speed (3.2mm^3/s) and 230°:

Some prints are taking forever and since I live in an apartment I can't afford to print overnight because I am a nice guy and don't want to disturb my neighbors. So I am trying to balance speed and quality.

Besides, I see that other UM2 owners can achieve what I am looking for - printing with the same settings (illuminarti for example). I am not trying to optimize the last 5%, I just want to get rid of underextrusion. And I don't think that going almost max temperature is a solution either because this has problems on its own.

EDIT:

Another note. This underextrusion problem creeped in over time. I printed objects earlier without underextrusion. Maybe I got lucky and used some settings that didn't favor this problem, but if I remember well, the underextrusion issue got worse over time.

 

[cor3ys 28]

Hi Guys

About a week ago i was getting under extrusion printing at 0.2 with a temp of 230 speed 50mm, i was also getting filament stuck at the hot end when doing a material change.

I stumbled across this thread and decided to give the test ago that you was all doing and i could only manage to do 3mm and 4mm bands and as soon as it hit 5mm i got massive under extrusion..

At this point i thought i had a blockage and decided to strip down my hotend, when i tried to remove the white teflon it was well and truly stuck and it fell apart ( i don't know if it was like this already hence my under extrusion or happened when i pulled it)

I then heated the nozzle up to try and loss en it but i was still unable to pull it out...

I then removed the retaining screw for the nozzle and had to force it out with some force from the other end, it seemed to be well and truly stuck..

I have been waiting for a replacement Teflon (PTFE) That Sander kindly replaced for me which was due to be delivered today so i have taken the morning of work to get it all back together again and wow i can now print the full test print with no under extrusion first time...

faberdashery at 230

Measurement of old Teflon

 

Measurement of new teflon

 

[Nicolinux 288]

Aha! Thanks, I am not crazy after all

 

[IRobertI 520]

Just got done pulling the head apart to check the teflon piece. PLA offered no resistance. A 3mm drill bit inserted ass end first went through fine and a 3.2mm bit went through all the way although there was a wee bit of resistance from a tiny lip at the exit of the teflon. I carefully removed that lip just in case but I have no reason to think that's the issue for me.

 

[aaronalai 2]

Hi Guys

About a week ago i was getting under extrusion printing at 0.2 with a temp of 230 speed 50mm, i was als.......

 

Thanks for posting this! Was there any instance of you printing for long durations of time without the third fan moving?

 

[cor3ys 28]

Hi Aaron

If you mean when i got my ultimaker back in November, then no not really depends on how you gauge long though, i was doing small prints of about half an hour to an hour and a couple at about 3 hours if remember correctly over a 2 day period. then i boxed it up and sent it back to Imaker for repairs...

But i like your thinking as it did not cross my mind, i assume you think due to the 3rd fan not working when i first got it, this could have caused the Teflon to get burnt and jammed/stuck in the nozzle retainer.

I would have thought i would have suffered before now though as its been a good few months since and i only suffered from under extrusion over the last couple of weeks , but who knows :???:

 

[aaronalai 2]

I was asking because it may be that the teflon piece is not designed to withstand high printing temperatures for long durations of time, and that excessive heat may degrade it. Creep (deformation): http://en.wikipedia.org/wiki/Creep_(deformation)

As teflon seems to have a melting point of 327 C http://www2.dupont.com/Teflon_Industrial/en_US/tech_info/techinfo_compare.html, just how close you need to get to this temperature to induce significant deformations is beyond me, but I believe something to consider.

Edit:Being dumb today.

 

[Nicolinux 288]

I have printed Robert's awesome low friction spool holder (http://www.thingiverse.com/thing:235925). It really makes the reel rotation very smooth.

Printed another test object and it fails early. So this time I am pretty sure it is not the weak extruder. I will focus on the head/nozzle again.

 

[Nicolinux 288]

Another update.

I disassembled the head and enlarged the exit of the teflon coupler. I made sure there is no lip anymore. Ran the extrusion test again after assembly ...and ...nothing changed :angry:

Still fails right after 4mm^3/s.

Sander offered to send me a new teflon coupler. I'll try it as soon as it arrives. I hope it works, because that's one of the last things I'll try with this printer.

On the bright side - I am now fairly familiar with the head/nozzle and can take this thing apart and put it together in a few minutes. You know, army drill style when cleaning weapons

 

[gr5 2,170]

Wow - nicolinux - check this out! This might be the solution?

http://umforum.ultimaker.com/index.php?/topic/4145-small-question-about-material-feeder/?p=35649

When we did the weight test, it was straight down. Maybe when it comes in at an angle you get rubbing on the extruder? There is certainly wear in there. Maybe the friction is excessive?

 

[Nicolinux 288]

Hi,

Thanks for the hint. I'll check the extruder entry hole. Sadly I don't have a spare bowden tube, but I'll try to re-route the filament by other means.

On another note, this weak extruder of mine is still bugging me. Provided that I measured accurately, 30% difference is a lot. I'd like to understand (and fix) it. If it is a normal manufacturing variation I wonder which factors could facilitate such a big difference. Given that all components are identical, only the stepper driver config could be it - right? One thing I noticed (I removed the cover for the extruder stepper) - during and after a print the extruder stepper is fairly cool compared to the other steppers.

I'd love to have some documentation on this, but UM is taking its sweet time (or I didn't find it).

 

[takei-naodar 0]

You could always get another stepper motor to compare? They are not that costly.

This is the model: https://www.sparkfun.com/products/10846

German Seller: http://www.exp-tech.de/Servos-und-Motoren/Stepper-Motor-68-oz-in-400-steps-rev.html

 

[Nicolinux 288]

Thanks for the links. But I don't know... Already spent so much time (and a bit of money) on this issue. I will pursue one more idea until the coupler arrives (looking to build a filament re-routing guide right now).

 

[illuminarti 18]

One other thing you might try - adjusting the tension of the screws holding the motor/extruder together. Looking at my printer in detail today, it seemed like the screws might possibly tighten too much, and squeeze the sides down onto the lever, preventing it moving freely and/or preventing the bearing from turning. Don't know if it can; but might be worth seeing if loosening it a bit helps any. Unless you already did that... which is possible in this huge thread now.

 

[Nicolinux 288]

Ok, thanks. Good idea, I'll try it. It would fit because I tend to over-tight things. Happened to me with the UM1 too.

By the way, I tried a makeshift filament guide so it enters the extruder straight from the bottom. Didn't work, so that's not it either. I am just documenting all failed attempts here in case there are others following along with the same problem.

 

[cor3ys 28]

Nicolinux

Did the retraction test for you as requested, using fabadashery at 230 using my own spool & holder.

 

 

i could only get to 9mm using ultimaker filament on the spool holder on the back.

 

[Nicolinux 288]

Thanks!

 

[Nicolinux 288]

Yeah - we are going to crack 20 pages soon! :eek:

I have loosened the screws on the extruder. Didn't help at first, but after I loosened them even more it helped a bit. Got to a point where I feared the stepper would fall off, but the extrusion test still failed at 6-7mm^3/s

And another peculiar thing I noticed. Don't know how it could be related though. The teeth marks on the filament inside the bowden tube do not form a straight line but somehow rotate around the filament. I haven't noticed it before, maybe it is normal (and due to the filament curvature).

 

[geeks 1]

I noticed the same thing at the marks left in the filament.

In addition, the filament chews the plastics. The filament guide, the casing which serves to the extruder ruined by the passage of the filament.

 

[aaronalai 2]

Another update.

I disassembled the head and enlarged the exit of the teflon coupler. I made sure there is no lip anymore. Ran the extrusion test again after assembly ...and ...nothing changed :angry:

Still fails right after 4mm^3/s.

Sander offered to send me a new teflon coupler. I'll try it as soon as it arrives. I hope it works, because that's one of the last things I'll try with this printer.

On the bright side - I am now fairly familiar with the head/nozzle and can take this thing apart and put it together in a few minutes. You know, army drill style when cleaning weapons

 

I thought I would do some somewhat limited tests on the deformation properties of the filament at different temperatures. I think this will help clear up what I've been saying about the teflon piece, although there are a few caveats. I only have filament of these types, all from ColorFabb:

Traffic Red 195-220C PLA/PHA

XT 220-240C not sure but website touts it can be used up to 70C

Standard White 195-220C PLA/PHA

So I took the traffic red and did some heat tests with it. Essentially what I did was heat the material next to the tip of a thermal probe sensor, record the temp, and apply a spring clamp to the end of the filament tip to test for deformation at a consistently prescribed pressure; what that pressure was though is unclear. I'll try to test it at work on a load cell or something and report back.

Alright so here is the setup:

In the upper left there is a thermal probe at a set distance from the exhaust of the hot air gun.

Closeup:

The filament was touching the probe for the heating events, it's just really hard to hold it steady, the camera steady, and focus at the same time.

This is a picture of the spring clamp.

It's not too terribly strong. I can hold it at the tip of my little finger and it's uncomfortable for sure, but it's not going to hurt me.

Below are some of the results:

There was significant deformation until 60C, the little bit of deformation at the tip is the cut from my wire cutters. Since this was only done with the force of a pinching spring clamp and not the same column type forces the filament would experience in the teflon coupler a one to one comparison cannot be made.

I believe it goes to show the large differences seemingly small temperatures can have on the filament, in the sense of deformation. I have tried to find the exact temperatures at the teflon interface in the UM2 to get a sense of how hot it is at the location where it mates with the metal body, but have come up short and have only found stuff from AYahoo's image album http://umforum.ultimaker.com/index.php?/gallery/image/526-hotend/ I don't know much about each image yet, how the simulations were performed, fan on/off, filament going through the hot-end....

To get back to what I was saying earlier, I think the teflon piece at the metal body interface can sometimes heat up to a temperature that allows for deformation at the pressures generated from the extruder. This probably isn't much of an issue if the inner walls of the hot-end are really smooth or the surface deformation is small, but if there is a significant surface deformation within the teflon piece at this interface then the filament could potentially get snagged and then dragged around inside the extruder (like the act of chewing gum) increasing the amount of force needed to push the filament through the hot-end, and thus under-extrusion.

If this is what Nicolinux is experiencing, I don't know. He cleared out the ID to remove the inner ring, but this could have had undesirable consequences related to the above rational. Now the surface deformation is from two IDs (the metal interface and teflon piece) being too disslmialr and forming another ring that only comes into existence when the teflon piece is mated with the metal piece.

I'll be interested to see the results of a teflon piece replacement, there seem to have been a few teflon malfunctions already that caused under-extrusion.