This is my fifth attempt to build a good nozzle. After many failures and carefully reading all the available info, this is what I have come up with. Nods to Adrian and to Nophead for all their hard work. I have borrowed ideas from both. I spent many hours trying to push squishy plastic through the extruder before I realized what was going on. The PTFE was getting hot enough to melt the ABS, in the full length of the hot zone, and then some, making it difficult to push. This incorporates three features to resolve this. Firstly, the hot zone is at the very tip of the extruder, so I am not heating the whole thing up. Secondly, I used silicon bronze (you could use brass) instead of aluminum because of the lower thermal conductivity. I wanted to keep the hot zone at the very tip. Thirdly I used cooling for the ptfe, to keep it from getting hot enough to melt the ABS. So far I have had zero problems with this, it works very well. Note that I used nichrome specifically because I could put it at the very tip. With a heated block and a resistor you are heating the whole extruder hot part, and I didn't want this. Also, 99.9% of electric heaters in the world use nichrome... it seems to work pretty good. And I kept loosing the power resistors I used for the heated bed...