13. Moulding and Casting

group assignment:

• review the safety data sheets for each of your molding and casting materials,

• then make and compare test casts with each of them

• compare mold making processes

For this week we tried to cast metal, milled and 3D printed a mold, made a mold with plaster and casted with metal. We also did some trial casts with silicone.

Safety

Some safety rules when casting metal:

Everyone who works with metal must know how to handle it safely and how to use tools and machines, what to do in case of an emergency, and how to fix things if they break.

1. Read safety data sheet of each of material.

2. Check our tools and equipment for cracks and damage.

3. Protective equipment. Everyone needs to wear gloves, glasses, and a special uniform to protect themselves from burns.

4. Molds and casting metal must be comletely dry.

5. Monitoring temperature. We need to watch how hot things get and how long we can work with them.

6. Careful handling. Metal is hot and can burn us. We must be very careful when we work with it. We need to make plans for emergencies.

7. Good ventilation to keep the air clean. There are bad gases and dust when we work with metal.

Safety measures when using silicone

We used Sp Polymer polymers for casting. here is their safety instructions.

1. Wear gloves, goggles, and clothing to protect your skin and eyes. Also use a respirator or work in a well-ventilated place to prevent breathing the fumes.

2. Mix the two parts of the silicone together in a clean dry container. Don’t touch the silicone with hands. Clean any spills with isopropyl alcohol right away.

3. Keep the parts in a cool and dry place, away from fire and other chemicals. Throw away the waste according to the rules, so you don’t hurt the environment.

4. What to do in case of an accident: If you touch the skin, wash it with soap and water. If the eyes are hurt, wash them for 15 minutes with water and go to the doctor. If you breathe the dust, go to fresh air and see the doctor if you feel bad. For more information, read the Best Mold manual.

Making mold

For group assignment we made some panels using different casted materials. The design is made with Grasshoper.

Milling with Roland SRM-20

material: wax

mills: 1/8” Flat endmill - rough cuts, 1/8” endmill - finishing

Casting with metal

When the molds were milled, we covered them with silicone to make it easier to take the casting out of the mold.

We mixed the plaster to achieve the desired consistency and poured into the mold. To remove air bubbles, we used a vibrating surface. Since we didn’t have vibrating or vacuum table in the lab, we just used any shaking machine available in the lab to lightly vibrate the mold placed on top of the working machine.

After a few tries, we got a good consistency. Although the plaster that we used was only regular, it was not supposed to be used for molding at high temperatures. After we made another try with a jewelry plaster.

Poured the molten aluminium into the mold. After some time when it cooler, we take it out.

First try failed because of some issues. First is that our plaster isn’t high heat temperature resistant, and also it wasn’t fully dry, so we had a little vulcano when pouring in the metal.

Casting with pLastics

To cast with plastic materials we used both the milled mold and same shape mold produced with 3D printing.

Because the 3D printing had a little shrinkage when its cooled, we additionally fixed parts tightly to each other and isolated the edges with plasticine.

Mixed two components of the silicone. We used different hardness platinium based silicones, plyurethane plastics and completed some casts. Results and links below. To remove air bubbles we used a small device that we purchased on a Chinese marketplace. It was supposted to clean keys/glasses with ultrasound but actually it was just a vibrating device. This actually worked well for our mixtures and all the air bubbles were removed.

Results: Platinium based hard silicone:

Not fully dried plaster:

All tries to compare - Instamold, soft silicones, polyurethane plastic, plaster:

Conclusion

We completed mould production using two production techniques: milling and 3D printing. Both methods showed a high level of smoothness, but the mould produced by 3D printing had shrinkage, so if it wasn’t isolated additionally, it would leak. However, we had some problems during casting, and the main issue was time - we did not allow the plaster to fully dry.

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Last update: April 30, 2025