Extruder body with the motor installed and the pieces of the E3D V6 hot end. The hot end for the Prusa came preassembled, and the Bear Exxa build manual assumes you are removing your hot end from a stock Prusa extruder, so I had to go to YT to see how this was supposed to go together.
Lower left of the hot end parts is the heat sink, which is the part actually held in the extruder body, upper left is the heater block, top center is the heat break that goes between the heat sink and the heater block and actually holds the two together, and continuing clockwise are the PTFE tube, collet clip, and collet, with the brass nozzle in the center. Not shown are the heater cartridge and thermistor which also go in the heater block once the rest is assembled. One of the printed parts for the Bear design was a different collet clip which I used instead of the one shown, although I don't think it makes any difference.
Assembly was not difficult but once the printer can be powered up, I will need to heat the hot end to some high temperature and re-tighten, so nothing will loosen in use due to heating and cooling cycles. The PTFE tube is inserted from the top and is held in place by the collet. There's a printed tool for trimming it to exact length and putting the specified taper on the nose, then the upper end gets a 60 degree internal chamfer which I did with a small center drill. The PTFE tube is a wear part so I made up several of them.
Assembled hot end placed in the extruder body. The extruder cover goes over this and holds it in place.
This is the fully assembled extruder, ready to go on the X axis. The fan on the left is the cooling fan for the hot end, which blows air across the heat sink. I used a fan that is supposed to have a higher flow than the stock Prusa fan. The fan on the front is the part cooling fan, which blows cooling air across the part as it is being printed. This is the same part as the stock Prusa extruder uses (I bought it directly from Prusa along with some other spares). One of the benefits of the Bear extruder over the Prusa is the Bear mounts this fan vertically instead of at an angle, which is supposed to extend the life of the bearings.
The printed ASA fan shroud attaches to the bottom of the print fan and directs cooling air to the part. This is the part closest to the heater block and the work piece which is why it is printed from a higher temp material. Because it's vulnerable to damage in the event of a failed print, it's a good idea to have extras on hand. Once I have 2 printers running, having spare printed parts will be less important since I'll be able to use the printer that's not broken to print pieces for one that is.
Extruder hanging on the printer. I have gone about as far as I can with this until the drive pulleys show up.
