Nozzle Problems

[printbus]

Let's try to clarify a few things and get some questions on the table.

You had been printing ABS OK. When you wanted to try PLA, you used the "atomic method" or cold-pull technique to clean the ABS out of the hot end. Now, when printing PLA the extrusion stops within a few minutes of starting the print. Correct so far?

How did the cold-pull plugs look? Did you repeat the cold-pull until the plug came out clean, as best you could tell?

Providing some key print settings would be helpful. For example, what temperature and print speeds are you trying to use? Have you tried any higher temperatures or slower print speeds?

Your picture suggests other, possibly unrelated issues. Isn't the first layer supposed to be solid? The extrusion on the first layer also seems to vary quite a bit - but maybe that's a result of whatever else is going on with the first layer. If it were me, I'd first focus on getting the first layer nailed.

To answer some of your questions - your problem could be any of a number things and not the nozzle. Short of a complete hot end teardown, I think the cold-pull technique is pretty helpful in cleaning crap from the hot end, when done properly and the right temps are used. And no, you shouldn't have to dedicate nozzles to a particular filament type.