While trying to print out the LCD mount for the “Internet Radio” project. I returned later to check the progress on the print after it finally starting due to temperature issues. I found this:
The temperature sensor had pulled free and had a piece of plastic lodged between it and the hot end. When I removed the hot end for inspection, the sensor broke apart. Clearly it was time to replace the entire hot end. It has served me well and is only the second one used in my Prusa Mendel i2.
The new hot end is 95% metal with a short piece of PTFE tube in the centre. I’ve used it twice and it had already jammed. Pulling it apart, I found the PTFE tube had been damaged preventing the filament from being pushed to the hotend block. I’ve cleaned the jam and it’s working OK for now:
Update: I’ve added a poormans’ hot end fan to cool the barrel and prevent warping of the inner PTFE tube, which was causing the filament to jam after a minute or so of starting.