I've decided to take a different approach for melting the aluminum.
This is based on a couple of factors. The first is that we can use the principle of induction heating to raise the temperature of the aluminum well past it's melting temperature.
The effect that this has on the aluminum is that any impurities are burned away in the process. This is important as we don't need a separate heater for removing the BPA epoxy liner and the paint on the aluminum soda cans.
It also allows for a much safer method of melting. Raising and lowering a graphite curcible within the work coil means we can effectively create a system that requires no human interaction.
Remember that the whole the whole point of this project is to build something that an operator can dump a bag of aluminum cans into the hopper, turn the unit on and leave unattended. The system should ideally be capable of taking care of every step in the process on it's own.
A Raspberry Pi and/or an Arduino controls the shredder, feeds the shredded aluminum into the crucible, and turns the induction heater on and off, all while monitoring current to detect jams and the state of the metal in the crucible.
An interesting phenomenon exists with the induction heating method. Once the shredded aluminum is dumped into the crucible, the current rises until a certain point. When the aluminum melts, the current drops. This can be used as a signal to feed more shredded aluminum into the crucible.
In order to detect when there's enough molten aluminum to fill an ingot, a load cell will be needed to detect the tare weight of the crucible before being filled and once that point is reached, stepper motors will lower the crucible platform and tip it in order to dump the contents into a mold.
This process is quite a bit safer in terms of semi-automated operation,