Filament getting jammed when entering the printhead

[43tesseracts 0]

[EDIT: Ultimaker 2]

I'm having problems where sometimes (quickly becoming all the time) my filament will get jammed when trying to enter the printhead. It appears to occur at the bowdentube/printhead transition, in that white cap thing (nylon?).

If I cut a nice point on the filament, then it will enter properly and print good for a while as the stiffness of the filament keeps it going in )I'm guessing), but it seems like after it heats up a bit and softens, the slight mis-alignment of parts becomes too much for the filament and it jams on entry.

When I remove the filament it has a little "ledge" on the end, as if it was misaligned and trying to push down on the edge of the hole (also makes it difficult to remove, because the tip of the filament is not mishaped/fat and gets stuck in the tube on extraction...)

Even waiting for the bed to heat after changing filament seems to be too long of a wait. If I pre-heat the bed, change the filament and print right away, it at least starts ok.

Any tips or tricks? I can post some photos if that would help.

Edit: This occurs regardless whether I use 2.85mm official Ultimaker filament that shipped with the printer, or my 2.9-3.0mm Amazon Jet stuff.

 

[gr5 2,168]

That white teflon part is called the "isolator".

I also cut the tip of my filament to a point before inserting it but once it gets past all the lips it's good until the next time I decide to change filament.

Your issue is strange as the temperature shouldn't matter. I'm thinking your 3rd fan is broken. The 3rd fan is behind the print head. Make sure it is working and that it is blowing (not sucking) air towards the front. The fan comes on as soon as you turn on power - even before the lights come on.

If the fan was broken and you fix it, you probably need a new isolator as it has been too hot all this time.

Even if the fan wasn't broken you should probably remove the isolator and drill it out with a 3mm drill to get rid of that lip.

The isolator deforms under pressure especially with temperatures above 240C. So after you drill it out it might help to keep the head temperatures at 230C or lower.

edit: although I've occasionally printed 250C and 260C no problem.

 

[43tesseracts 0]

Upon further inspection, I think you're right, it's not a heat problem.

I think the problem occurs after the large retraction that happens at the end of a filament change, this causes the problem area to pull back, then it can't get back in again.

Here's what the tip looks like:

Thanks for the idea about drilling out the isolator. Should I bevel the top so the filament is fed into the printhead better?

 

[gr5 2,168]

Please don't use imgur. I don't know how long they host pics but I doubt it is for as many years as this forum will. To post a picture click "gallery" on the top left of this page, then click blue "upload" button, then make a post (or edit your old posts for future people to learn) and click "my media" next to smile icon.

 

Should I bevel the top so the filament is fed into the printhead better?

 

I don't think that's a good idea. I think if you take the isolator out you will see it has migrated inwards and drilling it out is enough. You should test the resistance to some filament before and after you drill.

Adding a bevel is just giving the softened PLA more places to flow into and offer resistance.

 

[gr5 2,168]

By the way, what country do you live in? Please update your profile location.

 

[43tesseracts 0]

Thanks for the help, I'll give it a try.

 

[43tesseracts 0]

"Even if the fan wasn't broken you should probably remove the isolator and drill it out with a 3mm drill to get rid of that lip."

Are there instructions anywhere how to disassemble the print head assembly? I couldn't find any.

 

[gr5 2,168]

Yes. Lots of people have posted instructions but I'm not going to look right now. There's also this:

https://github.com/Ultimaker/Ultimaker2/blob/master/um2%20assembly%20manual%20V1.1%20_english.pdf

Click "RAW" to download the pdf.

It's not hard. Just start. Remove the fans first and let them hang. Then remove the 4 long thumb screws. It all kind of hangs down at this point. Next remove the 2 screws that hold in the "3rd fan" aka the "rear fan". Careful - there is a strong spring as you can see.

Then the white teflon comes right out.

If you unscrew the nozzle be careful as PLA or ABS can get in the threads and lock it tight and it is not very strong so heat it to 180C first if you do this. But you don't need to do this to work on the white piece.