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chrisp

More Clogging Issues

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Maybe someone can help me understand why I am having these clogging issues.

I'm using a UM2 with PLA only.

In two weeks I have had to take the hot-end completely apart 3 times and the extruder I had to take apart twice out of those three times. The clogging is getting so bad that when I go to change the material, the extruder grinds away most of the matrerial so that it cannot be moved anymore. This is because the clog happens inside the nylon fitting that is attached to the nozzle. When this happens, I have to cut the PLA, remove the bowden tube from the extruder, then heat up the hot-end to 255C in order to remove the PLA by pulling it out with my bare hands. Anything less than that temperature will not suffice. I'm starting to get worried I might damage other parts if I have to keep using this method.

I'm currently using the orange PLA from the Ultimaker store at these settings:

Layers 0.08

Shell 0.8

Bottom/Top Thickness 0.8

Fill Density 100% (I'm making solid parts for my new printer)

Speed 50 mm/s

Support Brim

Buildplate 55C

Nozzle Temp 220C-221C

Everything else is default

Is it possible this temperature is too hot for too long so the heat is able to creep up to the PLA in the nylon?

Is there a recommended nozzle temperature when doing 10+ hour prints?

Also, I was wondering if anyone has come up with a chart for Layer quality and which speeds and temperatures are good to stick with at those different layer settings?

If there is such a way to figure out these numbers?

Something like this:

Layer Height: .02=20-30 mm/s + temps?

Layer Height: .04=30-40 mm/s + temps?

Layer Height: .06=50-60 mm/s + temps?

etc.........

 

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Sounds (reads) the same as with my old UM1, when I want to change filament, I have to extrude a little bit by hand first.

And only than! retract. The (clogged) Pla is softened and deforms when you pull it out the hotend.

Might be old-fashioned for a Ultra Modern UM2 but it might work :)

 

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1) Is your third fan working? It should always be on and keeps the region cool that you are discussing. It comes on even before the lights come on. If not it is very easy to fix (usually).

2) Your temp/speed/layer height looks quite reasonable. What is more likely causing this is retraction which raises warmer PLA upwards thus transfering heat upwards. Then it goes back in, heats up PLA higher up, retraction occurs again and heat is transferred still further upwards. Melting temp of PLA is around 170C but the "glass temp" is around 50 or 60C. Above this temp it starts to get soft and stickier and can jam. So reducing from 220 to 210C is not going to make much of a difference compared to the 50-60C needed to cause problems.

Having said that, Illuminarti did a 30 or so hour print on a UM2 with over a kilometer of retracions. Yes, that's right. A kilometer! Actually 1.6 kilometers. And he had no problems.

3) Something is wrong with your extruder. It should never grind the filament to dust. It should not have enough power. I think the tension is not strong enough - the tension indicator (the white square) should be at the top but maybe it's a little too loose? Are you aware of how to adjust this? You need to insert an allen wrench or similar into the screw that is accessible from the top. Turn it until the white square starts moving downwards and then back off so that it has moved down only the tiniest amount.

4) Ultimaker sells great PLA but... I recommend trying another spool/color/brand - someone recently had similar problems with a bad batch of PLA (not from ultimaker) and changing filament fixed everything. The grinding *and* the clogging.

 

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1) Is your third fan working? It should always be on and keeps the region cool that you are discussing. It comes on even before the lights come on. If not it is very easy to fix (usually).

2) Your temp/speed/layer height looks quite reasonable. What is more likely causing this is retraction which raises warmer PLA upwards thus transfering heat upwards. Then it goes back in, heats up PLA higher up, retraction occurs again and heat is transferred still further upwards. Melting temp of PLA is around 170C but the "glass temp" is around 50 or 60C. Above this temp it starts to get soft and stickier and can jam. So reducing from 220 to 210C is not going to make much of a difference compared to the 50-60C needed to cause problems.

 

Having said that, Illuminarti did a 30 or so hour print on a UM2 with over a kilometer of retracions. Yes, that's right. A kilometer! Actually 1.6 kilometers. And he had no problems.

 

3) Something is wrong with your extruder. It should never grind the filament to dust. It should not have enough power. I think the tension is not strong enough - the tension indicator (the white square) should be at the top but maybe it's a little too loose? Are you aware of how to adjust this? You need to insert an allen wrench or similar into the screw that is accessible from the top. Turn it until the white square starts moving downwards and then back off so that it has moved down only the tiniest amount.

 

4) Ultimaker sells great PLA but... I recommend trying another spool/color/brand - someone recently had similar problems with a bad batch of PLA (not from ultimaker) and changing filament fixed everything. The grinding *and* the clogging.

 

1. All fans are working.

2. What is a better setting for retraction other than the factory default settings?

3. Extruder is set to its default position all the way up. I'll try adjusting it.

4. I also have another PLA I'll try.

Thanks for the info!

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I'm having the same issues. I was getting great prints when I first received my UM2 but since then, have been having all the issues you describe above... my girlfriend is now calling my UM2 a "high maintenance girlfriend" I spend more time pulling it apart, then I do printing.

I suspect some of my issues are weather related, heat and high humidity. What's the weather like where you are? I'm in Sydney, the middle of summer.

 

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So... extrapolating from a few cases now... is the issue that the extruder tensioner can work loose? 'Very Low' tension setting is good but zero tension is bad? That would be analogous to the problems folks have with a UM1 extruder if they don't slide the lever all the way down...

The other thing you might check in these circumstances is whether the Bowden tube is properly seated all the way into the hot end, and doesn't move around during retractions.

I use 5.5mm at 35mm/s for retractions.

 

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What you should also keep in mind, when taking your head apart, is to put everything back in the right tension.

Where with the Ultimaker Original you had to be careful with the teflon insulator, with the Ultimaker 2 hot end you have to set the right tension again to the part just below the teflon insulator.

Print head Ultimaker 2

The area marked on the image above needs to be 1mm / 1.5mm.

If it is less, you have a chance of clogs or a leak. If you took the hot end apart and put it back together again, I think there is a fair chance this area is too small.

Can you verify?

gr5 edit: After further discussion, Sander says 1mm to 2mm is okay but less than 1mm is bad.

 

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The other thing you might check in these circumstances is whether the Bowden tube is properly seated all the way into the hot end, and doesn't move around during retractions.

As far as I can tell, nothing is moving and I am extremely careful to put everything back the way it was. I usually take pictures before and after to make sure.

 

I use 5.5mm at 35mm/s for retractions.

Thank you for these settings, I will try them.

 

The area marked on the image above needs to be slightly under 1mm.

If it is more, you have a chance of clogs or a leak. If you took the hot end apart and put it back together again, I think there is a fair chance this area is too large.

 

Can you verify?

 

I call it hitting home when we talk in terms of piping or fittings going all the way in to where they are supposed to sit.

In every case that I took apart the hot-end, the teflon insulator has hit home, with the 1mm gap visible. This is something I made sure to do everytime.

 

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Hi Sander, the gap in this image looks larger than 1mm. I haven't touched mine, but I would say it's closer to 2mm, as in this image you posted.

How do you adjust that gap?

 

What you should also keep in mind, when taking your head apart, is to put everything back in the right tension.

Where with the Ultimaker Original you had to be careful with the teflon insulator, with the Ultimaker 2 hot end you have to set the right tension again to the part just below the teflon insulator.

 

The area marked on the image above needs to be slightly under 1mm.

If it is more, you have a chance of clogs or a leak. If you took the hot end apart and put it back together again, I think there is a fair chance this area is too large.

Can you verify?

 

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Hi Braddock, Thank you for your reply.

I am glad you ask, because turns out there was some miscommunication and it needs to be 1mm minimal.

If you aim between 1mm - 2mm you should be fine. The spring needs to create tension on the teflon part, and if it area is too small (less them 1mm) it can not apply enough pressure.

Sorry for the mix up :)

 

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After more testing I found another issue that wasn't apparent before.

I printed all of these gears pretty much perfectly and left the machine running overnight to finish the final gear on the front right side of pic.

20140108 205333

20140108 205346

I wasn't quite sure what had happened, so I tried the change material option to remove the filament to see if it might be another clog. Before doing so, I noticed that the filament was ground down against the gear like the two times before. This made me aware that the extruder would not be able to retract the material properly so I gave it a slight pull to get the gears engaged on the cleaner filament. The material successfully retracted and here is what I noticed.

20140108 210036

The nubby shard was the culprit, keeping the filament from entering the bowden tube any further, causing the extruder to grind down the rest below that.

 

Something didn't add up because I didn't find a clog and I didn't understand why the extruder gear ground up the filament. Illuminarti mentioned this issue.

 

The other thing you might check in these circumstances is whether the Bowden tube is properly seated all the way into the hot end, and doesn't move around during retractions.

That's when I checked the bowden tube again (at both ends), and found that it was slightly loose where it sits into the teflon fitting in the hot-end. I can move it up and down about 1-2mm. The red clip is in properly and the gray coupling is probably messed up, even though I never removed it.

 

Can I get these parts?

 

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I'm not convinced you have diagnosed things properly - but you should know that if you somehow thicken that red clip or add a shim in there or put two clips in there (or you could print a clip) then you will get more force holding the Bowden. That clip lifts a ring and lifting the ring pushes some metal blades inward that dig into the bowden tube and hold it in place.

I think the proper solution might be to take the bottom area of the head apart, push the bowden in 1mm more and then put it back together. But I've never taken my head apart so I'm not sure how it all works.

 

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What you should also keep in mind, when taking your head apart, is to put everything back in the right tension.

Where with the Ultimaker Original you had to be careful with the teflon insulator, with the Ultimaker 2 hot end you have to set the right tension again to the part just below the teflon insulator.

 

The area marked on the image above needs to be 1mm / 1.5mm.

If it is less, you have a chance of clogs or a leak. If you took the hot end apart and put it back together again, I think there is a fair chance this area is too small.

Can you verify?

gr5 edit: After further discussion, Sander says 1mm to 2mm is okay but less than 1mm is bad.

 

i think is what happen to me.

Today i unmounted the head because my nozzle is again clogged.. and i saw a big clog under the teflon.. so the great distance between the teflon and the nozzle could be a problem. Now i'm on my way to reduce the distance but i think that less than 3 mm it's impossible. Seems that the metal part (the one you screw on the nozzle ) is somehow full of plastic that block the teflon to go down.

 

I'm not convinced you have diagnosed things properly - but you should know that if you somehow thicken that red clip or add a shim in there or put two clips in there (or you could print a clip) then you will get more force holding the Bowden. That clip lifts a ring and lifting the ring pushes some metal blades inward that dig into the bowden tube and hold it in place.

I think the proper solution might be to take the bottom area of the head apart, push the bowden in 1mm more and then put it back together. But I've never taken my head apart so I'm not sure how it all works.

 

I think that this is a big and common problem for what i read in the forum. The bowden tube pop up.. and i think that the responsible is the red clip that is too low to let the blades hold the tube.

 

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is somehow full of plastic that block the teflon to go down.

 

PLA melts around 170C. Teflon around 250C. Get the temp in between and the PLA will melt and you can wipe it away with paper towel. Even boiling water is plenty hot enough to remove the PLA.

 

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