Help! Random molten (water like molten) blobs

Hi,

I was printing multiple items lately when suddenly a problem started of which I have absolutely no idea what could cause it.
After ~8 hours printing without problems yesterday suddenly a part had a big blob of PLA on it's surface. Since the nozzle dragged through it I though "Oh well, seems there did something go wrong" but didn't care about it because it was not crucial to be nice looking.
Today I started printing the next parts and it immediately became obvious that there is a bigger problem:
Randomly (but often, like every 5-10 minutes) the flow of PLA is broken, there comes nothing out of the nozzle for a few seconds and then suddenly there comes out a big fat blob of molten plastic which is so liquid that it's like water. It just blobs out of the nozzle, ruins my prints and after the blob came out everything is going completely normal - until the next blob comes.

I'm running a Kossel Mini with a 3mm bowden system and a E3D v5 hotend with a 0.4mm nozzle. The extruder is a normal Wades one which is ghetto-modified for bowden. This setup did run without any problems at all for ~60 print hours now.
I tried cleaning the hobbed bolt multiple times, changed the filament (I only have 2 different PLA filaments currently), pushed a piece of filament through the nozzle manually, pulled it out at ~130°C to clean out the nozzle.

I have absolutely no idea what is happening here...
Does anyone have any idea?

Thanks!

I'm not an expert in bowden systems but looks like your filament it's snaking inside the tube and once forces are too strong it released with an over extrusion, your tube might be worn out, fittings might be loosened some or simply your tube is too long?. Just some ideas for you to play with.
Hope you can find your problem.

Just one more question:
Are you cooling your e3d hot end right?
If you don't, that might also be your problem since filament might get heated up the barrel and create that big liquefied blob.

Edited 1 time(s). Last edit at 10/20/2014 09:31AM by ggherbaz.

Thank you for your tips! I tried changing the bowden tube but sadly it didn't make any difference. I also made sure that the thermistor is in place and the E3D is not overheating.
I tried printing with ABS which works absolutely flawlessly (apart from warping, but that's expected without an heated bed) and I could print some very high quality objects with ABS (again, apart from warping).

This lead me to suspecting that it's one of the infamous problems of the E3D with PLA. So I tried some tips from around the internet (seasoning etc) but it did not make any difference.

Since I wanted to upgrade to the E3D v6 anyways (for the screw-secured thermistor, I don't like the kapton securing method at all) I did order an E3D v6 and an extra nozzle for the E3D v5 (the new ones are compatible) so I can try if somehow some PLA crystalized within the nozzle or whatever...

Interesting though: When I printed with white ABS I noticed that even after flushing out the old material until only new material (ABS) was coming out of the nozzle there were some not-so-small blobs of PLA after printing 2-3 layers pure ABS, so it seems that some PLA indeed was stuck somewhere in the hotend...

Thanks again for your tips!
Best
Nils