On 2013-06-06 6:12 PM, John Ferrell wrote:
> How about giving up the copper pipe and hunting down something like a=20
> ceramic Tea Pot or a Coffee cup?
> If the copper pipe is essential, how about clamping one (or more) $4=20
> soldering irons to the copper pipe with hose clamps?
> Also a hot air gun will do it.  Or just set it on a hot plate?
> {snip-snip}

It has to be temperature regulated to around 80'C. Too cold and the wax
won't flow well. Too hot and air bubbles will form and the wax may foam,
burn, or become unusable. It's tolerant enough that I can control NiCr
wire with the help of a temperature sensor, but not tolerant enough for
a crude soldering iron or a hot plate. Also, the temperature should be
maintained right up until the point where you pour it into the mold. So
what better way than a heated copper pipe? Copper is easy because I can
properly drill and mount a temperature sensor right inside where the wax
should be. There's also a large inner surface area for the wax to melt
quickly, but not too fast such that it could burn.

Indeed, it would be far simpler to coil the NiCr wire and put it right
inside the copper pipe such that no copper is touched. My only concern
is that the high point temperature at the wire will overheat the wax
initially. Could be solved by reducing maximum power to the NiCr heating
element, but that would make initial melting from a solid very slow. Not
too bad a price to pay for mounting simplicity, I suppose.

Next best thing would be a ceramic cup. A very tiny flower pot maybe.
Hard to find in the size/shape I need though.

Thermal pads, as suggested by Bill, would be perfect if they weren't so
hard to obtain/expensive.

Kapton tape would do, but hard to obtain as well.
--=20
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