The process is simple but you will need to take safety seriously. Object 3d printed in PLA is coated with susceptor that transforms microwaves into heat. Susceptor is made from mixture of silicon carbide, sugar, water, and alcohol. The part is then placed in a mold made of plaster of paris with perlite and heated in an unmodified household microwave to burn out the PLA.
A second microwave with a top emitter is used to melt aluminum, which is then poured into the prepared mold. When the metal cools down, the mold is broken to take out the metal part for post-processing
From project description:
Our system uses consumer microwave units to perform burn-out of PLA from molds, and a second microwave to liquify aluminium, to be poured into the mold. 3d printer inspired mechanics will move the aluminium from the microwave, into the target mold under human control across the network, so that there is no risk to the person operating the machine.
What is working and what we're working towards:
What works now is that we are able to successfully melt aluminum inside a microwave and supply our molds to get fine quality crafted aluminium parts.
The vision is to automate the process and build machines so that the system can be remotely run by a human being safely from their terminal.
Automation will be as simple as two to three machines powered by arduino with minimum axes.
One machine will be a forklift to pickup the item and deposit it safely onto a pair of fire bricks. One is a crane to pickup the top from the kiln, and one is a combination of forklift and a x,y table. This will pickup the cup, place over target, and pour through a heated steel funnel into the mold.
Ideally, we see an operator walking to the machine, starting the microwave on the mold & aluminium. When notified the machine is done, the operator can use gloves to pickup and bury the mold in sand, then walk back to their workstation, and pour the aluminum remotely. This will reduce the risk of injury to an operator to near 0, and not require any dangerous gasses to perform the melt.
All of the software will be released under the GNU GPL V3 as the project advances, with the hardware designs released under the TAPR OHL.
Detailed project page and build log on hackaday.io:
Here is very detailed video presentation by Julia Longtin on Chaos Computer Club 31th Chaos Communication Congress. It is a great how-to guide on casting high quality 6040 aluminum pieces using a 3D printer and commercially available consumer microwaves
Here is a more detailed guide on how to make and use microwave oven DIY smelter for silver or tin solder:
Here is a different approach to melting aluminum in a microwave oven: