m6 threaded aluminium tube for 3d printer

[jcb121]

A reamed finish would be great, I think brass may be a better material as it may hold the heat a bit more then Aluminium.

I don't want the heat to travel up into the cold end too quickly.

[FatFreddie]

Have you seen the reprappro hot ends - I have the older version and it has been very reliable (the only problem was with a section of oversize filament - 2mm instead of 1.75 - can't really blame them for that) - I've put well over a kilometre of filament through with no other problems.

New
http://reprap.org/wiki/RepRapPro_Men...t_end_assembly

Old
http://emakershop.com/RepRapPro_Mend...-2013-0205.pdf

The principle seems to be to create an abrupt transition between hot and cold zones by force cooling above the heater - this minimises the time the filament is semi molten and therefore the bulging which can cause jams.

The new version looks like it uses a PTFE liner which would remove the necessity for a smooth barrel as well as insulating the filament until it got to the melt zone.