Ultimaker 2 Print head problems

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Hello all,

Over last week my Ultimaker 2 failed.

The head was blocked with both PLA and ABS.

I tried the 'Atomic' clean method and it didn’t help.

I tried heating to 260 and letting it sit for a while, and poking the end with a 0.35 drill bit but little success (the bit wont enter).

Since I cant use any chemicals to clean out the PLA (I believe NaOH will react with the brass and I don’t have proper way to dispose of chemicals) I dissembled the head completely and using a chefs blow torch, burnt out all the plastic.

Looking closely it looks like a shard of metal ended up in the nozzle. I am unsure where it has entered from, maybe from the plastic cant say?

So now I’m going to replace the brass hotend completely.

I just wanted to check, does the thermistor need to me inserted fully? - it was hard to take out and its hard to get back in fully. Right now I can get most of it in with a small amount of the metal jacket protruding, where as before it was completely in with no jacket showing.

does the ultimaker do its own temperature calibration or does that have to be initiated?

I did notice when reassembling the damaged print head, that it was finding it difficult to maintain the correct temperature, typically overshooting by 15*C

The inside of the bowden tube is sticky (most likely burnt PLA) can this be cleaned with caustic soda or is it best to replace that too and can I use the one listed in the store that is meant for the ultimaker 1

Thanks

Germano