Lost Wax Casting

The equipment on the Lost Wax Casting cart can be used for casting from wax models (the traditional method) or from 3D-printed PLA models. Very fine detail can be achieved. This is the casting method used by jewelers.

The Machines:

Master-Cast Vacuum machine

• Model No. 21.807.
• Brand - Stuller.
• 2 Amps
• For de-gassing plaster molds and pulling vacuum while pouring molten metal into molds
• https://www.stuller.com/products/22-1305/?groupId=193489

Electric Melting Furnace

• Model No. SY001.
• Brand - S.Y.
• 12.5 Amps (1500W)
• For metaling metal

Burnout Kiln

• Model No. S0720-SWEST
• Brand - Stuller/Swest
• 15 Amps
• For burning out wax/PLA from plaster molds and heating up mold prior to pouring
• https://www.stuller.com/products/22-1008/224288/?groupId=13241

Guides and Manuals

The following video explains how to use the casting equipment:

>>>Investment Casting Demonstration<<<

Instructions for Use

Prepare the part

We will only have details for making a 3D printed part for this process. For creating a wax part, please refer to other websites.

Settings for the print

• What you print is what you get. The casting process is very exact.
• You do need to get a volume measurement for your model, so you can use the right amount of metal when casting. If your slicer can do this, great. But if not, you can always print with 100% fill and then weigh the part afterward to get a volume estimate.
• PLA is 1.24 g/cc.

Type of filament to use - Natural PLA

• Use “Natural” PLA only (PLA with no pigment, which is yellowish clear in color).
• Anything other than PLA won’t burn away cleanly.
• And some PLA pigments leave ash behind and don’t burn away cleanly.
• From testing various brands, all unpigmented natural PLA filaments seem to work well. Use your favorite brand.

Features of the model

• The 3D print should have a sprue feature modeled into it.
• Sprue diameter must match the diameter of the hole in the black rubber lid of the casting cylinder. Measure the diameter of the hole in the lid you plan to use.

The Plaster Mold

Assemble the mold with your 3d printed part

• Materials: metal cylinder, rubber cap, 3D print, masking tape
• Tools: none

1. Insert sprue into rubber. You can also fill the hole with melted wax and squeeze the sprue into it to ensure a snug fit.
2. Put metal cylinder onto rubber cap
3. Put masking tape around the holes around the outside to prevent plaster from leaking out
4. Add a ridge of tape that goes above the metal cylinder

Mix and pour the plaster

• Materials: assembled cylinder with part, respirator or dust mask, water, plaster, rubber mixing bowl
• Tools: Vacuum Chamber, sink
• Safety: hazardous plaster dust

1. Get ratio of water to plaster from the chart in the binder
2. Calculate amount of mixture needed to fill the metal cylinder you chose
3. Put on respirator before handling plaster
4. Weigh water using a scale
5. Weight plaster using a scale
6. Always add plaster to water. Mix water and plaster in rubber mixing bowl, stir for 3 minutes
7. Put bowl of plaster mix in the vacuum chamber
8. Tun vacuum chamber to “Investment”
9. Turn vacuum on
10. Once the plaster starts to boil, count to 20 seconds
11. Turn off the vacuum and release air.
12. Pour plaster into mold
13. Put mold in vacuum chamber
14. Tun vacuum chamber to “Investment”
15. Turn vacuum on
16. Count to 90 seconds
17. Turn off the vacuum and release air.
18. Allow to harden for at least 2 hours
19. Peel tape off once hardened
20. Remove rubber lid. This will take some force and twisting. The plaster is sturdy.

The Burnout

• Materials: Your mold
• Tools: Burnout Kiln

1. Place mold in kiln with hole facing down on top of two metal rails (this will allow space for melted wax or PLA to drip out and smoke to escape)
2. Program the ramp for your part based on cylinder size. See binder.
   1. Default ramp rate is 9F per minute or 540F per hour
3. To finish programming, press 0, 0, Enter
4. Press Start to start program
5. During first 5 hours of burnout, keep area well ventilated as it will produce a lot of smoke
6. After 5 hours smoke should stop and doors/windows can be closed.
7. Let kiln sit overnight to finish the plaster curing process

Example program:

• Casting temp for metal: 1930 F
• Flask temp:1292 F
• Ramp 1: 300 F (8 hour ramp, 1 hour hold)
• R2 700 F (8 hour ramp, 2 hour hold)
• R3 900 F (1 hour hold)
• R4 1350 F (3 hour hold)
• R5 1292 F (99 hour hold)

The Casting

Melting

• Materials: your metal
• Tools: Electric Furnace, carbon stirring rod

1. Ensure all devices are plugged into different circuits. Circuit breaker may trip if all are on the same one.
2. Weigh appropriate amount of metal based on volume of mold and mass/volume ratio of metal (see example below)
3. Add your metal to the crucible
4. Set temperature on crucible to temp necessary to melt metal (note: it will need to be higher than the basic temp so it is very liquid and flows well)

Example calculation for weight of metal:

• Metal: Casting Bronze from Stuller
• Mass/Volume ratio: 8.75 g/cm3
• 3D print volume: 17.412 cm3
• Bronze mass: 152 g (plus a little extra)

Pouring

• Materials: your mold, your metal, firebrick, carbon block, correctly sized metal plate and red rubber casting gasket for vacuum pump
• Tools: Burnout Kiln, Vacuum Chamber, Electric Furnace, carbon stirring rod, tongs
• Safety: use welding goggles or appropriately shaded visor to protect your vision

1. Once metal is liquid, clean off dross from the top with a carbon rod
2. Adjust valve on vacuum machine to “Chamber”
3. Set red gasket on, the adapter ring, then gasket
4. Set mold in chamber
5. Turn vacuum on
6. Use tongs to grab hot crucible
7. Pour metal into mold carefully
8. Wait for a few seconds, then turn off vacuum pump, release pressure and use tongs tip to lever up the metal adapter plate to break seal.
9. Remove mold cylinder from vacuum chamber and set on carbon block
10. Set another carbon block on top
11. Allow to cool to a dark cherry-red color
12. Wash mold out in bucket of water and swish vigorously
13. Retrieve your part!

Parts and Consumables

• Casting metals
• Crucibles
• Investment plaster
• Red vacuum seal gaskets

Additional Resources

Other Instructions:

• Pepe Tools Lost Wax Investment Casting Manual

Other Videos:

• Basics of Lost Wax Casting with 3D Printing - KAYA-CAST

Suppliers:

• PMC Supplies