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kris

Possible countermeasure: Underextrusion

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Hi everyone,

I would quickly like to share with you how I managed to get rid of underextrusion on my UM2.

This first happened to me in the middle of a print. I then tried standard prints that used to work fine, so I could rule out Cura as a possible failure source. Then I tried every method I could find on the forum; the 'atomic' cleaning, readjusting the material flow, taking apart the extruder wheel. It seemed as if material was supplied to the nozzle just fine, but in retrospect the material that left the nozzle looked very rough. Nothing would help.

I finally took the entire extruder apart and soaked relevant parts in acetone for a few minutes, cleaned everything with a q-tip, soaked, cleaning etc. After 20min or so the parts were completely clean again.

Now the prints look exactly the way they did when I first received the machine.

Sounds easy, but I would not have though that the performance of the extruder would deteriorate over time to the point where it needed to be cleaned. This is probably the regular maintenance the machine requires in order to function properly.

Another theory is of course the contaminated filament. This happened while using white ABS from UM. A few days prior to the incident I found a huge piece of something very hard in the filament. If you miss something like that, it ends up in the nozzle.

Anyway, next time I experience underextrusion, I will again give the extruder a good acetone bath :-P .

Regards,

Kris

 

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I am afraid I did not take any pictures of the process, so I will try to explain in words.

First I removed the four long bolts at the top that hold the extrude together. That can be done without tools. Then you remove the side fans and the little screws that hold together the bottom aluminium part to which the nozzle is attached. Then you need to heat up the nozzle to >200°C. With the hexagon key you can now unscrew the ring that holds the nozzle in place (the one with the holes in the side). You can also do that with a hexagon key. Be careful not to touch the hot parts. I used a pair of flat nose pliers to hold the brass part. The nozzle can now gently be pulled free from the aluminium frame.

Regards,

Kris

 

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Tetrahydrofuran (THF) works very well for PLA, similar to acetone for ABS. But there are substances that are hazardous to health.

http://www.protoparadigm.com/blog/2013/06/vapor-smoothing-and-polishing-pla-with-tetrahydrofuran-thf/

THF is harmful and generally very dangerous. The handle is reserved experienced users, and safety regulations must be complied with mandatory. THF is a solvent for PVC, polyurethanes, cellulose nitrate, adhesives and coatings.

Markus

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I am afraid I did not take any pictures of the process, so I will try to explain in words.

First I removed the four long bolts at the top that hold the extrude together. That can be done without tools. Then you remove the side fans and the little screws that hold together the bottom aluminium part to which the nozzle is attached. Then you need to heat up the nozzle to >200°C. With the hexagon key you can now unscrew the ring that holds the nozzle in place (the one with the holes in the side). You can also do that with a hexagon key. Be careful not to touch the hot parts. I used a pair of flat nose pliers to hold the brass part. The nozzle can now gently be pulled free from the aluminium frame.

Regards,

Kris

 

thanks,

Arjan

 

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So you only soaked the nozzle?

 

plus the round piece with the holes in the side. I put a small cup of acetone on the build platform and raised it, so I could soak the nozzle without having to detach it from its cables. Didn't want to damage those.

I removed as much cotton from a cotton bud as I could to it would snuggly fit into the nozzle while turning it. I did this several times until nothing would come out anymore. The nozzle needs to be soaked a few times since the acetone will vaporize quickly.

Regards,

Kris

 

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After seeing extruder skips of both kinds on my UM2, I set the extruder current higher with M907 E1500 and (I hate to jinx it by mentioning it) skips are greatly reduced. I'm now printing faster and several degrees cooler, with no skips in the last 20 minutes (wouldn't have happened before the change).

Watching the edge of solid fill as it is printed, it seems to be better controlled, too - a straighter edge. We'll see if that shows up in print quality - I'm hopeful.

Perhaps a batch of motors came through that were at the low end of the performance spec, and that is exacerbating the problems from the poor design of the extruder?

 

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This brings up an interesting idea. Try removing ABS clogs by simply lowering the nozzle tip into some acetone for a while?

 

plus the round piece with the holes in the side. I put a small cup of acetone on the build platform and raised it, so I could soak the nozzle without having to detach it from its cables. Didn't want to damage those.

I removed as much cotton from a cotton bud as I could to it would snuggly fit into the nozzle while turning it. I did this several times until nothing would come out anymore. The nozzle needs to be soaked a few times since the acetone will vaporize quickly.

Regards,

Kris

 

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I'm glad none of the cotton got lost inside the nozzle! That would be bad as it would cause it's own clog.

 

I thought about that too. But I figured that the cotton fibres are far too small and thin to get caught in the nozzle.

And whatever I tried, nothing else would help. After a while you just do not care any more.

Anyway, although the methods works to clean the nozzle, it does not eradicate the cause of the irregular extrusion.

But I believe these guys were on to something: http://umforum.ultimaker.com/index.php?/topic/3976-almost-always-missing-layers-underextruding/page-2

As far as I have understood the extruder design suffers form a design flaw. Seems as if turning of retraction helps...

 

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After weeks of slowly-worsening under-extrusion with PLA, the machine threw a temp sensor error last night, and now won't print for more than a minute or two before halting.

Oh well, it gave me a chance to open up the print head and clean out the nozzle. While I had it open, I shortened the Bowden tube by a couple of mm, and noticed that the teflon tube is not completely square to the metal heat sink. I don't know if a slight angle would make a difference in extrusion, but it seems like it could.

So anyway, I heated up the nozzle while it was hanging there, and stuck a needle in from the intake side. Stirred it around for a bit, and pulled out a lot of black fragments that a half-dozen nuclear treatments had not extracted. I poked the needle all the way thru the nozzle until I could see the tip, then after reassembly, ran the nuclear treatment another 4-5 times, and still got black chunks out of it. This is pretty annoying, after I had been printing white PLA for a couple of weeks.

Bottom line is that I think I addressed the under-extrusion (which pretty much had to be caused by chunks of the poorly-designed extruder getting in there) but now the machine won't print due to the temp. sensor.

Sigh...

 

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I used the atomic method a few times and was printing fine again in PLA.

today I was printing in ColorFabXT, at 260 C, and got a lot of black spots. I assume ABS from the material feeder.

I heard a new feeder for the UM2 is being tested by UM at the moment... anyone have an idea when it will be made available ??

ColorFabbXT 260degrees blackSpots

 

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I assume ABS from the material feeder.

 

Probably, yes. Or you could be carbonizing the PLA. I don't know much about XT but 260 is a bit hot for most PLAs and if you leave it for a few minutes at that temp without printing (or if you print slowly) it can also turn black. But more likely it's the feeder grinding up. I strongly recomend you keep your PLA on the floor and not on the back of the printer so there is less grinding. That has worked very well for me.

spool On floor

 

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but now the machine won't print due to the temp. sensor.

 

Which one - bed or nozzle? If it's the bed it specifically says "bed" but if it's the nozzle I think it doesn't mention nozzle or head or anything.

You should get a new temp sensor. Are you in the USA Eldrick? If so I can get you one quickly. Otherwise you need to open a ticket. Please update your location in your profile to indicate what country you are in.

I'm thinking you have bad wiring somewhere - could be at the head or it could be underneath the printer (I recommend removing the larger cover on the bottom - only 2 screws - very easy to do - and check the wiring for the temp sensors to see if they are loose or fell out. If it's at the head you might want to just get a new one.

If instead it's the bed sensor that is the problem you likely don't need a new one - just need to check the wiring at each end and likely need to reheat the solder at the 4 conductor connector on the heated bed.

 

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After seeing extruder skips of both kinds on my UM2, I set the extruder current higher with M907 E1500 and (I hate to jinx it by mentioning it) skips are greatly reduced. I'm now printing faster and several degrees cooler, with no skips in the last 20 minutes (wouldn't have happened before the change).

Watching the edge of solid fill as it is printed, it seems to be better controlled, too - a straighter edge. We'll see if that shows up in print quality - I'm hopeful.

Perhaps a batch of motors came through that were at the low end of the performance spec, and that is exacerbating the problems from the poor design of the extruder?

 

Eldrick,

Where did you typed the m907 e1500 code? In Cura, when you choose Ultimaker 2, the star/end geode tab disappears. So, I am wondering where do you out the code. Anyone?

 

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