Introduction: DIY Electric Foundry for Metal Casting (120V)

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About: We're Laura and Louis. Laura is an educator and Louis is an engineer. With our powers combined, we make things and try to show everyone how we tackle projects in hopes to inspire others to get up and create!

We’ve been loving our Shapeoko CNC and have made some fun projects recently. One thing we need to improve on is nesting designs to minimize waste. In order to reuse the scrap aluminum, we made this electric foundry to melt scraps 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 above. (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!

Supplies

Here is the list of supplies we used: (These are affiliate links where we earn a small commission at no extra cost to you, 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

Step 1: Insulated Fire Bricks

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 which are the smaller sand colored bricks and retain heat within the interior of the foundry.

You can use the "hard" bricks if you really wanted to, but since their function is primarily structural they conduct a lot of heat and it will take a very long time for the foundry to get to temperature, if at all, since there will be major heat loss through the surface of the bricks.

We arranged the bricks to create a simple box to house the crucible, allowing it to be loaded from the top.

Step 2: Cutting Bricks

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, making sure to keep the cut straight.

Step 3: Making Grooves for the Heating Element

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.

Step 4: Grinding and Bonding

We made a mini assembly line to make the process a bit manageable. We filed the grooves for all the interior walls and then bonded the finished pieces using furnace cement.

Step 5: Drilling and Final Bonding

For one of the short walls, we filed grooves in a ramping pattern which allows the heating coil to reach the next row. This is also where we wanted the ends of the heating coil to exit, so we drilled a small hole using a standard drill.

Then we bonded all the walls together with furnace cement and allowed it to cure overnight.

Step 6: Making the Outer Structure

Since the "soft" fire bricks are really brittle, we made a simple metal structure to protect the edges of the foundry.

Using 1" Steel angle iron, we measured the lengths of all the outside corners and welded them together.

To keep it simple, we just lapped the corresponding pieces rather than mitering each connection. If you don't have a welder, you can also use nuts and bolts by drilling a hole at each connection and tightening nuts and bolts.

Step 7: Electronics - the Temperature Controller

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 attached a general wiring diagram for reference, but different PIDs may have different wiring instructions so double check your model.

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.

Step 8: Mounting Thermocouple

Then we measured and drilled a hole for the thermocouple to fit into.

The temperature is picked up only 1inch 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

Step 9: Heating Element

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

Step 10: Final Wiring

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.

Step 11: Firing It Up!

With all the wiring complete, we can plug it into and wait for the foundry to get to temperature!

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

Step 12: Follow Us!

Thank you for reading our Instructable!

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You can check out our other projects here on Instructables as well as our Youtube channel IMEE MADE.