Can't print PLA

[JohnMHammond 0]

So I bought the Ultimaker 2 a few months ago and was pretty happy with it. After a few prints, the extruder clogged, but I was able to fix it using the Atomic Method. It began clogging frequently, but I was always able to fix it until last week. After trying everything short of taking apart the print head, I decided to switch from the gray PLA that came with the printer to some ABS that I had bought. Lo and behold, it worked perfectly (other than some warping issues). After a few prints, I figured I could go back to the PLA now that the nozzle was seemingly clear, but it didn't work.

Here's what happens:

When I am in the process of changing filament to PLA, I can get all the way to the step where I am waiting for the filament to begin extruding from the nozzle. When it gets to the nozzle, it starts making a loud clicking sound and won't come out. I tried using the "move filament" tool as well, moving it back and forth to no avail.

Any ideas as to what the problem may be? I can't really understand why one plastic would work (ABS) and another wouldn't (PLA)...

[ultiarjan 1,222]

Nr1 check your ptfe (the white thing) In the head. Take it out and check for damage. Abs is much more slippery so it's very well possible that it's still possible to print abs with a damaged ptfe.

There's tons of info on this forum on how to do it.... just ask again if you need more info..

[IRobertI 516]

Are you sure it's not just something trivial like the filament getting caught on one of the transitions in the head? It's quite common for the filament to get stuck on the transition between bowden and PTFE. Cutting the filament so that it is pointy helps with this. Sometimes giving it a good shove at the feeder end can also allow it to get past this point.

[JohnFox 25]

Wonder if your PLA is a little over size and getting caught in the head.

Also cut the end off. If I do a 'filament change' I often get a small blob on the end of the filament which is quite a bit larger than 3mm.

[JohnMHammond 0]

Update - it works!

So I put the PLA back in and removed the bowden tube when I initially forwarded the material.  I let the filament extrude several inches through the end of the bowden tube, then manually inserted it into the extruder.  I gently forced it through the nozzle until the bowden tube was back into place, and then everything worked normally!  It was getting stuck in between bowden tube and PTFE, like was said above.