How to Make an Electric Foundry

We’ve been loving our CNC and we’ve made so many things. One of the things we need to improve on is nesting designs to minimize waste. In order to reuse the scrap aluminum, we made this electric foundry so we can melt the pieces into an ingot that can be machined again.

To give a overview of this project, we spent about $200 USD to complete the build and with out 120VAC circuit at home, the calculated power of this foundry is about 1.6kW.

You can check out the entire build video on Youtube linked below. (We would also appreciate a like and sharing if you think it's worth it :))

DISCLAIMER: THIS PROJECT UTILIZES HIGH VOLTAGE POWER SUPPLIES AND PRESENTS A SERIOUS RISK OF PERSONAL INJURY (E.G. THE HEATING ELEMENT IS LIVE WHEN IN USE AND MAY HAVE ELECTRICAL POTENTIAL EVEN WHEN SHUT OFF). ALSO THE FOUNDRY CREATES EXTREMELY HIGH TEMPERATURES AND MOLTEN METAL THAT ALSO PRESENTS A SERIOUS RISK OF PERSONAL INJURY. USE ADEQUATE PRECAUTIONS AND SAFETY GEAR AND CONSULT A EXPERIENCED PROFESSIONAL. THANK YOU AND BE SAFE!

The links to all the materials we used for this project are listed below: (These are affiliate links that help us earn a commission and support more projects. Thank you!)

Insulating fire bricks: https://amzn.to/3fnsgYJ

Furnace cement: https://amzn.to/32dCGqe

Crucible tongs: https://amzn.to/2APBApk

Ceramic terminal blocks: https://amzn.to/3ehWefr

High Temperature wire: https://amzn.to/3foqkzt

Baking pan: https://amzn.to/2ZjCu78

Graphite crucible: https://amzn.to/3ekQUrN

K type thermocouple: https://amzn.to/38Rnkc9

Heating element coil wire: https://amzn.to/2ZmIZ9i

PID Controller: https://amzn.to/3fi9NwR

1” Angle Iron: https://amzn.to/301PMUW

125/250V toggle switch: https://amzn.to/328QmTk

14 gauge Power cord: https://amzn.to/38MktBw

We started off with 10 insulated fire bricks. There are a few different types so you want to be sure to use “soft” fire bricks like these larger white ones. They have better insulating properties compared to “hard” fire bricks.

We arranged the bricks to create a simple box to house the crucible, allowing it to be loaded from the top. We cut two bricks in half length wise to fill the corners. These bricks are very easy to cut and shape, so we used our old Japanese pull saw to cut them in half.

Next, we measured three evenly spaced lines from the floor of the foundry to the top rim around the perimeter of the inside. This marked the three rows the electric coil will seat into. Using a square file, we filed grooves into the bricks and used a scrap piece of the electric coil to ensure the correct depth. Meanwhile, we bonded the walls together with furnace cement.

Once grooves were made and walls were bonded, we set them aside for a couple of hours to let the cement cure. Next, we drilled the holes for the electric coil heating element inlet and outlet. The final walls were bonded together with more furnace cement to complete the structure.

We measured and cut 1 inch angle iron to fit along all the outside corners of the foundry. This will help keep the structure secure and minimize pieces breaking off when moving about because he bricks are very brittle. Once the angle iron were cut to size, we TIG welded all the joints together. To keep things simple, we made lap joints rather than mitering the connections.

Moving on to the electrical portion. We used a PID controller and solid state relay, thermal insulated wire, and a K type thermocouple that reads 0 – 1300 deg C. To house everything together, we 3d printed an enclosure and mounted a toggle switch and electrical outlet we salvaged from an old computer power supply.

We wired everything according to the directions of the PID controller and left two long pigtails that will be connected to each end of the electric coil. Once everything was wired and mounted to the enclosure, we bolted onto the metal structure of the foundry using nuts and bolts. We later found out that the structure gets a bit warm and softens the 3D printed enclosure, so having an insulated layer like wood would be helpful.

We made sure to connect the ground wire to the mounting bolt, so that the structure can be electrically grounded for safe operation. Then we measured and drilled a hole for the thermocouple. The temperature is picked up only 1 inch from the tip of the thermocouple, so we wanted to position this area closer to the floor of the foundry to get the most accurate reading. We made a small arm with a bit of adjustability for the thermocouple to mount to. After that was mounted, we closed up the enclosure.

Using steel wire coil as the heating element, we calculated a resistance of about 9 ohms to give us enough power, without overloading our 20 amp circuit and giving us a decent margin to run other tools on the circuit if needed.

To calculate using our 120v circuit with 9 ohms measured at the heating element:

Current = Voltage/Resistance

Current = 120 v / 9 ohms

Current = 13.3 amps , < This is well below our 20 amp circuit

Then we can figure out our total power:

Power = Current x Volts

Power = 13.3 amps x 120 v

Power = 1600 Watts

In order to coil around the foundry three times for even heat distribution, we calculated that we need the coil to be stretched out to 78 inches.

After using the bench vise to help pull the coils, we placed it into the grooves. We straightened out leftover steel wire and shaped staples with a plier to help secure the heating coils to the wall

With the heating elements placed into the interior grooves and the ends protruding through the holes we drilled earlier, we screwed the ceramic terminal block into the brick and attached the heating coils to one end of the terminal block and the wires from the PID controller to the other end. After that, it was ready to fire up!

This setup took about 20 mins to reach 900C and about 15 mins to melt some small scrap of aluminum.

This was such a rewarding project. We were able to mesh a lot of our skills like welding, 3d printing, electronics to make something so useful. We’re excited to melt all of our scraps and continue our CNC adventures.