Jeshua Lacock Presents Lost Shell Sand Casting for PLA 3D Printed Models

[3DTOPO]

So it's not about the size, but the energy required to melt that amount of metal?

Correct.

It seems odd, then, that the same rig that will melt 30 kg of copper will only melt 10 kg of aluminum, which is a lot easier to melt. Or am I missing something?

It is because while steel melts at much higher temperatures; aluminum conducts electricity much better than steel. When you heat metal with induction, you can essentially think of the work piece as being shorted out to your main. So the additional resistivity of steel allows more heat for the same amount of energy. Ferrous materials have an additional advantage too, in that they are heated by magnet eddy forces up to the currie temperature.

So while it seems counterintuitive, induction generators actually heat ferrous materials easier.

That said, one can use a conducive crucible (eg high purity graphite) and that is heated directly by the EM field and can be used to heat things that are both non-conductive and non-ferrous (eg you could melt glass). But in an ideal induction furnace, you want the metal to adsorb the energy directly; not the crucible.

The more I learned about induction; the more surprises it has reveled!