Liquid cooling your hot-end?

[Greg. L]

Many problems, especially with PLA and jamming, occur because the hot part of your hot-end really shouldn't be hot. The best-case scenario would be an isothermal temp at the nozzle tip (say, 190C) and an isothermal temp at the entry point of the hot-end (say, 100C). Of course, the heat travels up the hot-end, warming the entrance, so we need a fan, etc.

Today, while I was waiting for some paperwork, I realized that I could bend some copper 0.25" tubing around the top of a hot-end (in my head, a Trinity Magma, only because they have that long, thin metal neck), a few times to make a simple heat exchanger (I could even solder it on if I was feeling crazy), and leave both ends up the tube pointing "up" a few inches. Clamp on some flexible hose that heads to the top of the printer, where I'd have a standard PC-style watercooling radiator block (I wouldn't want the extra thermal mass on my moving hot end).

I don't think I'd even need a pump - the heat from the hot-end would force the heated water to rise, where it would cool at the radiator. I know I'd get an isothermal point at the point of contact, or at least near enough to one, as the water would boil off at 100C, rising up, cooling, and condensing back down. Admittedly, the first dozen times I'd run this, I'd watch it like a hawk for evaporation (I'd leave it open to the air, as I don't want a pressure vessel). Alternately, I could use a higher-temp rated coolant than water.

As long as the thermal conductivity between the part we want hot and the liquid coolant loop isn't too high (overpowering the resistor) it might really help eliminate PLA jams with some of the higher-speed and high-temp capable hot-ends.

Having said all of this, has anyone tried anything similar? It sounds like the kind of thermo problem a sophomore MechEng could tackle mathematically, so it's not like I'm proposing aetheric science or anything...

[Misha]

There are people working on water-cooling motors. http://kuehlingkuehling.de/2013/02/13/the-kuhlingkuhling-reprap-industrial/

If you figure out the water cooling then you can cover the whole thing up and get a nice hot box to print in.

[JohnD]

Misha - I know then are water cooling the cold end of the hot end - didn't see the bit on the motors.

[Tim Rastall]

The reprappro guys have been doing water cooled hotends for a while now - The cad files for the head are on github.

http://blog.reprap.org/2012/07/water-cooled-hot-end.html