This design is based on Adrians design from HERE
I found a weakness in the this and other similar designes. The PTFE heat Shield fails where it screws into the nozzle.
My design gets around this issue by using the PEEK block to support the PTFE heat shield.
The PTFE is made with an additional 10.5 mm shoulder
The PEEK Support block is drilled 8mm to hold the nozzle then 6mm deep at 10.5mm
I found that the 10mm thick heater blocks made the melt zone a little to long.
I make my heater blocks ~8 mm thick and have shortened the nozzle length by ~2mm.
The result is a strong and durable Hot End based on a very well tested and proven design.