Almost always missing layers / underextruding

[nallath 1,120]

We (R&D) are looking into the underextrusion. There are several options on the table, in various stages of completion. But we don't want to rush things, so they are being tested over and over again to ensure that we don't get everyones hopes up with a poor solution.

 

[Nicolinux 288]

Ok, thanks for the info. So is there a main cause for underextrusion or is it really a compound of many issues?

 

[nallath 1,120]

There doesn't seem to be just one. This is also why we're testing a bit more fundamental instead of rushing a patch job. This should prevent issues in the future aswell.

 

[DidierKlein 729]

Hi all,

Just putting my 2 cents here too as i never really experienced under extrusion. Maybe my answers a worth some info (or maybe not)

 

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

Before i changed the filament the standard way but now i manually heat up to 90°c and pull out by hand. I don't think this has an impact on underextrusion.

 

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

No i usually just cut it straight, i never felt it hang in the teflon piece

 

• How often do you change filament?
  

Usually once a day at least but i can stay with the same colour for a couple of days

 

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

The nozzle is heated up only when print or when i feed the new filament. I never let it heat up when not printing

 

• Do you perform _very_ long prints?
  

I did a couple of prints of 13h to 14h but never more for the moment.

 

• Room temperature where the printer is stored.
  

20°c to 24°c when it's hot like this weekend

 

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

Ultimaker and mostly Colorfabb both on spool. I ordered Faberdashery filament and printed a spool for it.

 

• Did you change motion settings?
  

Nope

 

• Did you increase stepper motor current?
  

Nope

 

• Do you use an alternative feeder?
  

Yes Robert's design, altough the first cylinder test was perfect with the old stock feeder. I'm able to go up to 13 - 14mm3/s for the moment.

 

• Do you have a filament dust filter?
  

I printed one but used it once (i always forget to put it on)

 

• 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

 

 

I also have an alternative spoolholder (Robert's design again) but again the first cylinder test was made with all standard parts.

 

I have some underextrusion with Ultimaker White PLA, all the others are doing good except when i reach the end of the spool, but that's normal i guess.

 

[skint 61]

 

• How do you change filament? Standard way or heating up and pulling the filament out?
  
• Standard way, always.
  
• Do you "sharpen" the filament tip so it doesn't get hung up inside the teflon piece?
  
• If the material has a sharp bend near the start I will often just clip with pliers.
  
• How often do you change filament?
  
• Varies, but usually after a print finishes.
  
• Do you let the nozzle heated up for a long time?
  
• Only at normal stages, printing and material change.
  
• Do you perform _very_ long prints?
  
• Longest so far is about 14 hours.
  
• Room temperature where the printer is stored.
  
• 20+ degrees
  
• Wich filament do you use (spool, loose, brand)?
  
• Faberdashery 95%. Intend to trial others soon.
  
• Did you change motion settings?
  
• Nope
  
• Did you increase stepper motor current?
  
• Nope
  
• Do you use an alternative feeder?
  
• Nope
  
• Do you have a filament dust filter?
  
• Nope
  
• 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
  

 

[johna 0]

So I got a new 'isolater' and installed it. And things looked promising!

First try got to 7mm / sec no problem, but started skipping in the 8 band. This is still one of my better results, especially with silver Ultimaker filament.

It's still not fixed, but it's closer.

 

[johna 0]

So I got a new 'isolater' and installed it. And things looked promising!

First try got to 7mm / sec no problem, but started skipping in the 8 band. This is still one of my better results, especially with silver Ultimaker filament.

It's still not fixed, but it's closer.

 

Just got word that new bowden tubing arrived, so tonight I'll probably swap in new tube, the new isolator is installed. Maybe I'll pull it apart and go nuclear on the hotend as well.

 

[johna 0]

Just got word that new bowden tubing arrived, so tonight I'll probably swap in new tube, the new isolator is installed. Maybe I'll pull it apart and go nuclear on the hotend as well.

• New isolator
  
• New bowden tube
  

No fix. Same as before. I think next move is full torch-out of hotend.

 

[illuminarti 18]

There's really not that much wrong with your printer if you can extrude at 7-8mm^3/s.

[johna 0]

There's really not that much wrong with your printer if you can extrude at 7-8mm^3/s.

 

Yeah, but it was bugging me.

So today I pulled it apart, torched out the hotend, and soaked it in acetone. Once it came out of the acetone, I mashed the end of some 3mm filament down a bit and then used it to scrape out the inside of the nozzle, just to make sure nothing else loose was in there.

Re-assembled. So now this is:

 

• new isolator

• new bowden tube

• cleaned out nozzle

 

And boom! Best result yet. Full speed, no skips. Repeated the test and it worked just as well.

 

Here's a selection (not even all of them) of the silver tests that I did....

 

Nothing worked for me other than burning out the nozzle. Seems like the 'ground down ABS in the hotend' idea may have been the culprit in my case.

 

[eldrick 65]

I strongly suspect that half the extrusion problems reported are simply due to people using much too high a temperature with PLA.

PLA is intended to print at 180-205C, and if you go much higher, you will carmelize/carbonize the stuff and leave high-friction brown crud (think burnt sugar) all over the inside of the nozzle. Even 215C can cook PLA when the printer temperature overshoots higher while heating. This brown stuff is Very difficult to get out without removing the nozzle for a thorough cleaning. Even the Nuclear cleaning option rarely gets it all out.

Here is an excellent reference to material selection and printing techniques: http://www.protoparadigm.com/blog/2012/06/3d-printer-filament-buyers-guide/

 

[illuminarti 18]

Personally, I rarely print PLA at less than 230º (as measured on a Ultimaker Original or Ultimaker²), and am notorious for having had no problems with under-extrusion. The increased viscosity of PLA at lower temperatures makes it much harder to extrude; in the http://www.extrudable.me/2013/04/18/exploring-extrusion-variability-and-limits/, I found that it was markedly more difficult at 200º or below. Only for very detailed prints at very low speeds would I print PLA in the 180-205º range you are quoting.

 

[eldrick 65]

Funny - that's not what any manufacturer recommends for their PLA. Have a look at the ProtoParadigm page.

I've run DiamondAge at 190 or so, Protoparadigm at 205C, and BTW, note that Ultimaker recommends 203C for their PLA, as set in the Robot test print. Ultimachine states: "This is Natureworks PLA4042D extruded into 3mm filament. Samples have been tested by various RepRap members and it is a wonderful build material. It prints at temperatures around 170C and has minimal warp when cooling."

YMMV, but I'd suspect a bad temp. sensor or high-friction nozzle if you have to print PLA at 230C. I personally find that running DiamondAge PLA over 210C leaves brown crap in the nozzle (revealed by the nuclear method) every time, after a few hours of printing.

BTW, the "testing I did" link seems to be busted.

 

[illuminarti 18]

It's certainly not necessary to print at 230, but it's perfectly reasonable to; it doesn't start to break down and become brittle until somewhere around 250 - and then it seems to require the plastic to sit hot for a while. On the other hand, temps around the low 200's or less can definitely cause problems if you're trying to print more than a few cubic mm per second. At higher temps, the extruder has to work much less hard, but the low viscosity of the plastic, and longer time to cool below the glass temperature can cause their own print quality problems.

It definitely varies by manufacturer as well, but pretty much every manufacturer gives a guide range that goes a lot higher than 205º. I think the last 'recommended' temp I saw on an Ultimaker reel was 220º, in fact. Colorfabb quotes a rough range for their filaments of 195-220, and says that users should also experiment with higher and lower temps than that. Protoparadigm quotes 180-220.

 

[eldrick 65]

Google "3d printing pla temperature" and tell me what you see. Almost every manufacturer recommends printing at 180-210C, and my results back that up.

 

[illuminarti 18]

I'm not saying you can't print at lower temps. But it is a lot harder on the equipment. I fixed the link now, btw. And yes, I googled it:

Makerbot says 220 - 230º

http://www.makerbot.com/support/guides/pla/

Matterhackers recommends 205 - 220

http://www.matterhackers.com/articles/how-to-succeed-when-printing-in-pla

MakerGeeks says 195-215:

http://www.makergeeks.com/pla-vs-abs2.html

As noted above, Colorfabb says 195-220

(see the tricks and tips tab on any filament store page, although admittedly that's not pure PLA ) .

Protoparadigm also lists 220 as the upper end of the range

http://www.protoparadigm.com/about-3d-printer-plastic-filament

I just looked the roll of green Ultimaker filament on the back of my printer. It quotes 260º (!!) as the top end. I have actually printed PLA that hot - and it basically works, but it does get brittle, and I certainly wouldn't recommend it as a long term strategy. The fact that the robot might have been printed at 203º doesn't mean that that is the optimum temp in general, nor the top end temp. It was just the temp that UM found worked well for that print when they wanted to print a bunch of robots as quickly as possible but with reasonable quality.

And none of them suggest that anything bad is going to happen if you hit 230, or 240. I agree that you don't want to keep any plastic cooking in the nozzle any longer than you have to. And that at some point the PLA will degrade if it sits too hot. But that point is much nearer 250 than 200, and plenty of people routinely print PLA much hotter than 205º and don't experience any problems at all.

Bear in mind also, that it is notoriously hard to compare temperatures between different brands of printers, and that the Ultimaker² is also more likely to need higher temps than many other printers because it has a very tiny melt zone; as a result the plastic spends less time being heated, and may not come to thermal equilibrium with the heater block before it gets extruded when printing fast.

 

[johna 0]

I think there is something to be said for how and where the temp is measured, and the idea of temps being relative.

I have taken a spool of PLA from one of my repraps that printed it at 195, and moved it to the Ultimaker where it wouldn't print at less than 220.

I don't think the filament changed in the 5 minutes / 3ft move... I just think they're measuring temp differently.

I always just assumed that '230' on my UM and UM2 wasn't actually 230 if I was running it on the repraps. That's why I figured Ultimaker filament says '260' on it. It might be 260 on an ultimaker, but for all we know it's 220 in other systems.

 

[eldrick 65]

I suspect that JohnA has it right. I have also had to raise the temps to print material on UM2 that printed at lower indicated temps on another RepRap printer.

 

[eldrick 65]

I've now got evidence that too-high PLA temperatures cause clogs.

When extrusion slowed down on my UM2, I had been printing a part with White DiamondAge PLA at 220C (while the nozzle had a buildup of brown crud in it). After removing and cleaning the nozzle thoroughly, I resumed printing, but dropped the temperature to 215C. It printed fine, but I started checking the nozzle by the heat/cool/pull method after each print.

Sure enough, after each 8-hour print, I found brown crud on the filament after pulling it out, so I started dropping the temperature back toward what I had always used in my TrinityLabs printer. At 210C, brown junk in the nozzle again, and the same at 208C.

So I dropped back to 201C which is what I had always used with this filament, and I'm now getting a completely clean end when I heat/cool/pull the filament after each print. No problems at all with extrusion at this 201C, as it is above the melt temperature of this filament.

DiamondAge PLA is known to print a bit cooler than others - I've used it down as low as 185C with no issues, but I conclude that as expected, overheating PLA carmelizes it, and causes clogging over time, to the point where high-friction in the nozzle causes high pressure, slow extrusion, and increasingly poor performance as it deposits more and more brown hard stuff in the nozzle.

If you have a known-clean nozzle, I'd strongly suggest paying attention to the manufacturers recommendations on temperatures. PLA is known to cook and harden, causing clogs. If you have to go more than a couple degrees above the recommendation, you've probably already got the problem, and are making it worse as you jack up the temps to compensate.

 

[Nicolinux 288]

Hi,

I've got another idea about the cause of underextrusion. New filament tends to have a sharp edge where it is cut off. When it travels through the bowden tube, it will scratch the inside of the tube leaving tiny specs that catch on the filament itself. These are transported into the nozzle and lead to clogs. Since Bowden material (PFA) has a very high melting temperature, it would even withstand brief "torching" with a hot flame (around 500°).

So depending on the way filament tips are cut off, a sharp edge may form or not. Maybe that's the reason why only some people have problems with it.

What do you think?

 

[svanbennekom 0]

There seems to be alot of confusion going along in this thread!

Let me please start off by asking anyone here to be careful with their claims. Speculation is fine, but please refrain from stating it as truth.

As far as we know here at Ultimaker, there seems to be no issue with printing the PLA's we've tested at higher temperatures. We regularly print PLAs at 210-260 degrees, as others in this thread have done.

JohnA is exactly on the mark. When you print faster, the material has less time to be heated, so higher temperatures are required.

Keep in mind that thermoplasts degrade when you heat them. In fact the filament you have is probably already somewhat degraded with respects to the original base material it was made of. So obviously, when you print PLA at high temperatures, it will degrade faster. But that's bound to be true for *all* thermoplastic filaments!

Also keep in mind that every PLA is different. There are different compositions out there, with different fillers, additives, etc. This makes it harder to find out what's going wrong when someone experienced failure with 'PLA'. If you read about such things, or experience them yourself, please, keep that in mind. The problem you have with your particular PLA might not be present with other PLA's. No doubt you've found out for yourself that certain colours give better prints, or that one brand is easier to print than another.

I hope this clears up some of the confusion. Feel free to PM me if you have any questions!

 

[Nicolinux 288]

Hi Svan (did I guess your first name correctly?).

Thank you for the clarification. You are right, filament varies greatly. So can we settle on a common underextrusion pattern when - say at least 3 different filament brands fail illuminarti's underextrusion test below 5mm^3/s (printed at 230°)?

By the way - team Ultimaker - cool! What are you doing at UM? What is your main task?

 

[gr5 2,172]

EldRick - very interesting. When I started reading your post I was thinking maybe you were getting the black teflon stuff from the feeder into your prints (black and brown are similar colors) but now you say at 201C you don't get any brown spots inside the nozzle? Well I find this all hard to believe but I will keep this in mind! Very interesting.

I also have some white diamond age filament. It definitely flows nicely at lower temps. I've been printing it mostly at 220C lately but it's been small parts and I have been changing filament often and always change filament by pulling at 90C (atomic cleaning) so I clean the nozzle a lot! Unintentionally. And I always cut the end off and discard.

I mostly use the 90C pull technique not to clean the nozzle but to make it so I can change colors instantly (no mixing of colors).

Anyway this idea of slow cooking PLA over 8 hours causing problems - seems believable - I've just never noticed it before and I'll have to pay more attention and keep it in mind.

 

[svanbennekom 0]

Hi Nico!

Van is my middle name, so, try again

 

can we settle on a common underextrusion pattern when - say at least 3 different filament brands fail illuminarti's underextrusion test below 5mm^3/s (printed at 230°)?

 

Well, we've seen that a well adjusted UM2 with a new nozzle and teflon part should be able to extrude PLA at 10 mm/s without problems. That said, in older printers differences between PLA's are highlighted. Some PLA's still extrude well, while others don't. I hope to be able to publish a report here soon where you can see the differences that I'm talking about.

My main task at Ultimaker is materials research. This encompasses improving printing and understanding of new materials, as well as developing new materials!

So if you have any serious questions about materials, drop me a message!

 

[gr5 2,172]

I hope to be able to publish a report here soon where you can see the differences that I'm talking about.

 

That would be nice!

If even one PLA is failing at 5mm at 230C and you have experienced underextrusion in "real" parts you *probably* should look into some remedies. Especially remedies involving cleaning nozzle, inspecting and replacing or redrilling out the isolator, and putting the filament on the floor instead of the rear of the printer.

@svanbennekom. What material is the black feeder on the back of the UM2? I thought it was ABS originally but now I'm told it is glass impregnated teflon. I get little pieces of it traveling along my filament and out through the nozzle all the time although they are so tiny it's not much of a problem (not really visible in my prints even with white filament).