Overheating Extruder???

All,

So two nights ago I was having a bunch of problems like my nozzle was plugged so I torn it apart and checked it and my teflon tube inside my tube going to my nozzle had black marks like it was burning and then yesterday when I went to print I had a big puddle on top of the block my nozzle and tube attach to. So I took it apart and my teflon tube that the filament goes through to the nozzle is completely gone. Is this normal wear for the teflon tube to wear out or could this be an overheating hot end? I just ordered two new tubes and two new nozzles but I don't want to put them on if it is overheating and ruining stuff.

The easiest way to find out, is to watch the temp rising and judge yourself.
It can't get worse than it is now...
-Olaf

I looked at the data log for temperatures and it is always within the plus or minus 5 degree C. I wasn't sure if it could be a bad thermistor?

What temperature are you running at? Teflon is most useful for pla, in which case you rarely need to go much over 210. If you are running hot, you are probably using a high temperature filament like nylon or pc, in which case you would probably be better off getting an all metal heat break and not having to worry about the ptfe liner. That said, I've been printing nylon at 265 with a ptfe liner with no problems so far.

Edited 1 time(s). Last edit at 01/06/2016 08:42AM by JamesK.

I am printing PLA and printing at 200C extruder which I wouldn't think would melt teflon but the glass temperature of Teflon is 120C which means it starts getting soft and I'm curious as to if I did not have the PLA in the teflon tube but instead on the top corner of it and it was sitting there trying to push the Teflon down into my nozzle and plugged it up then filled up with PLA and came out the top of the block? I'll add a picture in about an hour when I get home from work of the blob that I had on my hot end and also a somewhat decent picture of the threads of my nozzle. They look as though it was burning or something burned onto it such as Teflon tube which has disappeared completely..... Thanks for you suggestion JamesK

There's a big difference between getting a bit soft and deforming and being fluid enough to exit the cooled heat break. I can't really see that happening below 300C or more. I hate to say this, but are you sure you put the teflon liner back in?

I understand that question because I could see that mistake being easily made however I am certain that I replaced it when I reassembled it because I slide my filament through everything as I was reassembling it. But once it was put back together I changed filaments. So I know the tube was in there. So my next question is how likely is it for a thermistor or heating element to go bad and overheat? I feel like if anything it would be the thermistor because it reads temperatures and increases to 200C and the reading doesn't change more than the set +/- 5C.

That's possible - a low reading means too high a resistance which could happen if there was a bad connection somewhere. But for that to be plausible we'd have to accept that your hotend had run at ptfe melting temperatures - what would that have done to the pla? I can't imagine it's good. You'd also expect to see a bad reading at room temperature if the thermistor was the problem.
Perhaps a more likely explanation is that the liner you got wasn't really ptfe but some other plastic that had either been used by mistake or to save a few cents.

Yeah PTFE melts around 650F not sure in Celsius. So my reading would have to be way off and the PLA would likely look like water pouring out. Ha. and the thermistor reads the same as my hot plate when cooled so that's a good point there. As well that is very possibly that the tube was not PTFE being as people are so cheap they could have tried to save money. I will post response later with pictures as well as when I get the new tubes and nozzle to verify if something was just plugged or if something is wrong with my hot end.