The all metal hotend I use for printing with recycled plastic from my filament extruder (http://forums.reprap.org/read.php?1,205005,205005#msg-205005 )
I used the following:-
A stainless steel hypodermic tube (available at Amazon and Mcmaster's) 0.084" ID
Two m6 brass bolts with holes drilled through
a copper heater block with holes for a 12v/40w stainless steel heater cartridge, a thermistor and for the stainless steel tube and a small hole for a 3 mm bolt to fix the cartridge in the block
a copper round bar with a hole drilled through and 6 groves cut in the copper
6 pieces of flat copper (from 15 mm plumbers copper pipe cut lengthwise and flattened )
a 6 mm brass dome nut for the nozzle with a .5 mm hole drilled in.
6 mm copper washer between the dome nut and the heater block
The first to solder - the heatsink to the stainless steel and at the same time the flat copper to the heatsink.
Once that was done i soldered the heater block to the one brass bolt(head partially filed away) with the stainless steel tube through both and then the other bolt that will be used to fasten the hotend to the mounting plate and the bowden tube.
I used silver solder with a 56% silver content with a handy gas flame and stainless steel flux.The inside of the stainless steel tube and all areas that were not supposed to be soldered were covered with milk of magnesia(one can use tippex as well). The Milk of Magnesia not only keeps the silver solder from flowing beyond the joint, but it seems to protect the stainless from getting that hard black coating from being heated.
After cleaning the hotend the tube was polished with a string and brasso to clear the inside of the tube and the heater cartridge and thermistor installed. I used thermal paste on the cartridge.
Working great with my recycled filament on a delta printer - did not test it with any other plastic.
The first one I made the heater block was insulated with cuttlefish bone held together with silicone. It worked great but you cannot change nozzles without damaging the cuttlefish bone.
Advantages:
One continuous barrel - no gaps for jams
small meltzone
small transition zone
easy to clean - just remove the tube at the top and ram a steel rod down the barrel.
easy to change nozzles
heat up quickly
can be manufactured without any fancy machinery - only need a drill and handy gas.
I used the following:-
A stainless steel hypodermic tube (available at Amazon and Mcmaster's) 0.084" ID
Two m6 brass bolts with holes drilled through
a copper heater block with holes for a 12v/40w stainless steel heater cartridge, a thermistor and for the stainless steel tube and a small hole for a 3 mm bolt to fix the cartridge in the block
a copper round bar with a hole drilled through and 6 groves cut in the copper
6 pieces of flat copper (from 15 mm plumbers copper pipe cut lengthwise and flattened )
a 6 mm brass dome nut for the nozzle with a .5 mm hole drilled in.
6 mm copper washer between the dome nut and the heater block
The first to solder - the heatsink to the stainless steel and at the same time the flat copper to the heatsink.
Once that was done i soldered the heater block to the one brass bolt(head partially filed away) with the stainless steel tube through both and then the other bolt that will be used to fasten the hotend to the mounting plate and the bowden tube.
I used silver solder with a 56% silver content with a handy gas flame and stainless steel flux.The inside of the stainless steel tube and all areas that were not supposed to be soldered were covered with milk of magnesia(one can use tippex as well). The Milk of Magnesia not only keeps the silver solder from flowing beyond the joint, but it seems to protect the stainless from getting that hard black coating from being heated.
After cleaning the hotend the tube was polished with a string and brasso to clear the inside of the tube and the heater cartridge and thermistor installed. I used thermal paste on the cartridge.
Working great with my recycled filament on a delta printer - did not test it with any other plastic.
The first one I made the heater block was insulated with cuttlefish bone held together with silicone. It worked great but you cannot change nozzles without damaging the cuttlefish bone.
Advantages:
One continuous barrel - no gaps for jams
small meltzone
small transition zone
easy to clean - just remove the tube at the top and ram a steel rod down the barrel.
easy to change nozzles
heat up quickly
can be manufactured without any fancy machinery - only need a drill and handy gas.