Very basic tutorial for mixing, casting, and curing silicone rubber in molds. This technique is a starting point for silicone-based soft robotics.
Video
Materials
- 40g (depends on the mold’s size) of Ecoflex silicone rubber 00-30 (Smooth-on, Inc.)
- Disposable cup
- Disposable mixing stick (chopsticks)
- Disposable gloves
Tools and Equipments
- Non-silicone molds
- Kitchen scale
- Oven (optional)
Directions
Scale Molds
First, let’s see how much silicone rubber is needed for the mold. Pour water into the molds instead of silicone rubber. Gather the water into a cup and weigh it. This value is about the same amount of silicone rubber necessary to fill the molds. When measuring the silicon rubber, we will add an extra 10-20% to this amount.
Measure
Pour Ecoflex part A into a cup. It should be half of the required amount of silicon rubber. Pour the exact same amount of Ecoflex part B into the same cup. If you have poured more than the required amount of part B, then add more part A so that they are the equal amount.
Mix
Slowly mix the silicone with a mixing stick for 1 minute. Avoid brisk mixing movements to prevent from making bubbles. Mix well while scraping the silicone from bottom and side of the cup.
Cast
The molds should be made of non-silicone material such as PP (polypropylene), PE (polyethylene), and PET (polyethylene terephthalate), otherwise the silicone mold will fuse with the casted silicone. Pour the silicone into the molds. Wipe off the overflowed silicon with a paper towel.
Rest and degas
Leave the silicon rubber for 10 minutes for degassing. For simple molds, vacuum pumps are not necessary because Ecoflex’s viscosity is not that high.
Bake
Bake in an oven at 60°C (140°F) for 20 minutes to accelerate curing. If you don’t have a oven, just wait for 4 hours at room temperature.
Demold
Take out the silicone rubber from molds. Cut off the excess silicon on the edges with scissors.
Bon Appétit! (but don’t eat)
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