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donmilne

Filament stuck

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I've been printing with relative success for the last week or two, but last night I seem to have had some kind of disaster.

I was giving KISSlicer a first test print, printing a kind of cylinder (a motor mount / noseplate). I went off to get something to eat, when I came back the PLA print had detached from the plate and stuck to the nozzle, which was waving it around. It was about 1mm thick by that point, but a lot was caked around the nozzle. I pulled all that off the nozzle while still hot and then aborted the print. (The KISSlicer UM1 profile I tried didn't seem to heat the bed, hence the print came loose).

I was going to upload pictures, but if there's any way for mere mortals to upload pictures on this site then the method escapes me. I can view my own (empty) gallery, but damned if I can see any way to add to it.

After the KISSlicer failure I decided to revert to Cura. It started off ok, and again I went off to do something else. When I came back about an hour later, the UM2 was "air printing". Head moving around, bed had decended about 20mm, no filament coming out. The feeder was a bit dusty but not excessively so. It had printed the first 5mm of the fairly dense base, so it filament flow hadn't stopped immediately. Quite strange. I aborted the print of course.

Next day (today) I tried to change the filament. The head heated up, the feeder motor went into reverse, but the filament didn't budge, not even with my assistance.

I then tried following the troubleshooting advice in the manual, i.e. printing at 260C for 10 minutes. Nothing came out during the print, and I still couldn't change the material after.

Does anyone recognize this failure, and tell me what the cure is? Telling me how to upload pics would be useful too.

 

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What print settings are you using? Temp, speed etc.

Sounds like you're going to have to do a bit of mechanical work to get the filament outa there. Time to see what the head looks like when disassembled :) Bring the head up to printing temp to keep the PLA soft. Then undo the four big bolts on the head. While holding the bowden tube firmly (to prevent it from moving down) carefully grab the lower part of the head (remember it's hot!) and wiggle it until it comes loose. Once the head is separated it should be easy to get the old filament out of there.

To clean out your nozzle, after having removed the big old pieces of PLA, cut off a piece of fresh PLA and insert it into the head. Now lower the temperature to 70-80C or so, once the head has cooled down to this temperature pull on the filament and hopefully you'll get a nozzle shaped blob of PLA coming out of there. Look through the nozzle to make sure you can see daylight. The nozzle should now be clean and you can re-assemble.

To upload pictures:

Click on the gallery link on the left of your screen, on the new page you click the blue "Upload" button towards the top right. From there just follow the instructions.

Once you've uploaded your images you can start a new post. When writing the post there's a toolbar above the area where you type in your post. Click on the "My media" button and a popup will be shown, click on the "Gallery images" link on the left and your images should show. Click on the ones you want to insert and then click on "Finished".

I know, it's really bloody convoluted... You're not the first one to be confused by it, trust me.

 

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Thanks for the quick reply.

The Cura was set to 45mm/s, 230C. Shell thickness 1.2mm, 20% fill. I've had some good prints recently with these settings, if only the damn support structures wasn't so strong!

Are you saying that if I undo the top four bolts then the major part of the print head (nozzle, fans etc) should pull off downwards? and I only need to avoid pulling the Bowden tube down with it?

 

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DonMilne

Have you checked the feeder on the back of the machine, check if you have ground down the filament so much that it will not reveres past the knurled bit if you have you will need to give a big tug on the filament when its in reverse or take the cover off and heat up the nozzle and pull it out by hand...

Just my 2 cents worth....

 

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I already checked the feeder, I mentioned it in my first post: there's a bit of dust in there, but it doesn't seem excessive. I have already given the filament as big a pull as I dared - this is what I referred to when I said that it wouldn't budge even with my assistance. I also tried loosening off the tension screw and tried the same thing again. I get about 5mm of movement in the filament, nothing more.

Whether or not this is the cause, IMHO it would be useful to know how to take the print head apart, so I'd appreciate answers to the Qs in my last two posts?

 

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I think the last comments regarding the likelyhood that the filament has been ground down is extremely likely. When this happens the auto reverse will not be able to move the filament without extra help.....by pulling the filament downwards firmly by hand, as the auto reverse is started up.

If that doesn't work, then you may have to take the extruder apart and pull it through by hand, once the nozzle is pre-heated up to about 100*c. Be careful when unscrewing the extruder housing because this also holds the drive motor in place....so unscrew it carefully and make sure you see how all the parts fit together when you pull the cover off.

If you're absolutely sure that the filament is not ground down in the drive mechanism and the at the mechanism is working ok..then I guess the next area to focus on is the nozzle assembly.....First check if the nozzle is heating up properly, before you start stripping the head down.

 

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When you say "extruder" I assume you're referring to what I call the feeder (IMHO the "extruder" is the hot end, where plastic changes shape). Luckily I had experience on day one of taking the feeder apart. That doesn't faze me, but nor, given my previous experience, do I believe that to be the problem this time.

 

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Ok, I have the feeder disassembled and lying beside me in pieces on my desk. The filament is still in the printer and still stuck. Hopefully we can now all agree that the feeder is not the problem.

I had a go at undoing the screws on the printhead. The stack all opened up concertina style, I can see that the filament doesn't go all the way through to the nozzle, but it still doesn't seem to want to withdraw.

 

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Have you read GR5 post in this thread ? is more related to a blocked nozzle

http://umforum.ultimaker.com/index.php?/topic/4118-blocked-nozzle/?hl=%2Bremove+%2Bbowden&do=findComment&comment=33691

I have stripped my head down but i did not have Filament stuck in the system you should remove filament before dismantle i think.

All i did was remove the red clip on the bowden retainer

Push down on the grey retainer and pull the bowden tube out (how this will work with filament in it i dont know)

Remove the 4 screws that hold the fan shroud on. 2 each side

You need to unscrew the back fan 2 screws

Then unscrew the 4 long screws in each corner, (i stick some tape on the black housing so it did not fall apart.. i only removed the back 2 long screws and left the front 2 in place so the black housing did not fall down...

Remove 2 screws from the aluminum block this will give you access to the spring and white Teflon be careful if you remove the Teflon i broke mine it was jammed in the nozzle hence i had to replace mine...

you will now have the aluminum block with the nozzle in it free to look in...

There is some pics in this thread page 4 by Chrisp of the head dismantled

http://umforum.ultimaker.com/index.php?/topic/3976-almost-always-missing-layers-underextruding/page-4?hl=%20strip%20%20down%20%20head

There is lots of pictures through out that thread as lots of people have been stripping there heads down should give you an idea....

hope that helps in some way

 

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Focusing on your point that the filament doesn't appear to go into the nozzle....so my next question would be....Is the filament stuck inside the white plastic sleeve? This could happen if the filament had melted and expanded in diameter below the plastic sleeve and then solidified again. The in that case, heating up the nozzle wouldn't help the release of the filament.

So......if you can therefore remove the filament from the nozzle by unscrewing the nozzle/fan assembly, you could cut the filament higher up and pull it through by hand from the other end. (the nozzle end).

 

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FYI - leaving pla at 250C or hotter is a bad idea unless things are flowing nicely. 250C is enough to turn it into a hard sticky gunk that you will have to burn out with a gas flame later. 260C of course is even worse. Leaving PLA at 260C for 10 minutes is a very very bad idea. Please don't ever do this again :)

You are going to have to take the whole head apart. It's not so hard - just get started. Read the link carefully about removing the bowden tube as that is the only tricky part where you can damage it if you just pull up on it without retracting the 4 metal blades first.

You will probably need to heat all the parts up to around 100C -180C to get everything apart. It sounds like there is melted PLA all over the upper parts of the head. Possibly stick parts in boiling water before pulling apart if they are stuck.

When you get a chance check to see if your 3rd head fan is working. If it isn't it would explain all your original symptoms that lead up to this problem. The rear head fan should come on as soon as you power up the UM - even before the lights come on.

 

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Anyway, thanks to all for your advice, especially the advice on how to correctly remove the Bowden tube. Once I did that I found that the white bit could only be pushed down with difficulty, but once I did the filament did come out quite easily, everything looks clean inside.

I'm glad I didn't have to disassemble the entire print head.

On inspecting the business end of the filament the problem is obvious. I still don't know how to upload pictures so I'll have to describe it: the PLA has softened and created a nice little collar for itself around its entire diameter, about 8mm from the end of the filament (I would guess there must be a small (~1mm) gap between the end of the Bowden tube and whatever it butts up against). In my earlier mishaps described in my OP I assume the printhead has got too hot, the PLA has softened and filled that gap, then cooled again, and then it couldn't move. The collar is over 4mm at the widest, so there's no way that was ever going to reverse through the tube. I don't know what was stopping it going forward, I assume there's a similar constraint in that direction.

I've replaced the tube now, I'll put the feeder back later on. I'm hopeful it will now work.

I hope there's no trick to getting the tube back in place. I assume you push it in as far as it'll go, then push the white bit down and put the retaining clip back?

 

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I hope there's no trick to getting the tube back in place. I assume you push it in as far as it'll go, then push the white bit down and put the retaining clip back?

 

The trick is explained here. This is the third reference to the below link in this topic:

http://umforum.ultimaker.com/index.php?/topic/4118-blocked-nozzle/?hl=%2Bremove+%2Bbowden&do=findComment&comment=33691

Quick answer: loosen the 4 long screws first, get the bowden as tight as possible, then tightening the 4 screws will get it nice and tight.

It's very easy to damage your bowden when removing. I hope you read the above link before you removed it. Too late now of course.

 

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@gr5: the idea of printing PLA for at least 10 minutes at 260C in order to clear a print head blockage is the recommended procedure given in the current UM2 User Manual, "Troubleshooting" section.

 

Yes of course, but if no plastic is flowing this will have the opposite effect - create more blockage. Don't go over 240C for more than a minute if no plastic is flowing.

 

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When you get a chance check to see if your 3rd head fan is working. If it isn't it would explain all your original symptoms that lead up to this problem. The rear head fan should come on as soon as you power up the UM - even before the lights come on.

 

Did you check this yet? This would explain why the pla softened enough to create that disk in the first place. Although more likely your bowden just wasn't seated properly.

 

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Yes of course, but if no plastic is flowing this will have the opposite effect - create more blockage. Don't go over 240C for more than a minute if no plastic is flowing.

 

Hindsight is wonderful, but how should one establish that in advance, and I wonder why no mention of this caveat in the manual?

 

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Thanks for the advice on posting of images. Ok, if this works then it shows what the filament looks like.

gallery_33340_597_54329.jpg

Wow, that was some rigmarole to post a picture. Thank heavens this site won't care much about how things look, right?

As to the links to other discussions, they seemed to involve clearing a nozzle blockage and completely dismantling the print head - neither of which I thought I needed. I still don't.

 

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Hooray! Filament feeder reassembled and bolted back in place (feeder motor too), material change went flawlessly and the printer is now printing again.... actually I just had to abort it because I forgot to enable support, but it looks like I'm up and running again, thanks for everyone's help.

 

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