How We Made a Taiwan Mahjong Silicone Mold From an SLA Master

This workshop project shows how we made a reusable silicone mold for a Taiwan mahjong piece from an SLA 3D-printed master. The process covers preparing the master, weighing and mixing the silicone, vacuum degassing, pouring, curing, and compressed-air-assisted demolding.

The 0.04 mm value shown in the video is the SLA printing layer height, not a dimensional tolerance. The four-hour cure shown here applies only to this recorded project; always follow the instructions for your own silicone system.

Materials and tools used:

• SLA 3D-printed mahjong master

• Mold box or retaining frame

• Two-part mold-making silicone suitable for the master

• Digital scale

• Mixing cups and stirring tools

• Vacuum chamber and vacuum pump

• Compressed-air nozzle for demolding

• Gloves and normal workshop safety equipment

Start with a clean SLA 3D-printed master and place it securely in the mold box. Check the surfaces, edges, and orientation before pouring. The 0.04 mm figure shown in the video refers to the print layer height only; it is not a claim about the final mold's dimensional accuracy.

Weigh the two silicone components accurately using a digital scale. Use the mixing ratio specified by the manufacturer of your silicone system; this project does not establish a universal ratio. Prepare only the amount you can mix and process within the material's working time.

Combine the measured components and mix thoroughly, scraping the sides and bottom of the container. Continue until the material is uniform. Avoid whipping unnecessary air into the mixture and follow the working-time guidance for the silicone you are using.

Place the mixed silicone in a vacuum chamber to remove entrapped air before pouring. Leave enough headroom in the container because the silicone can expand significantly under vacuum. Release the vacuum carefully once the bubbling subsides.

Pour the degassed silicone slowly into the mold box, starting at a low point and allowing the material to rise around the master. A controlled, narrow stream helps reduce newly trapped air. Continue until the master is fully surrounded at the required mold thickness.

Allow the silicone to cure without disturbing the mold box. In this recorded project, the mold was demolded after four hours; this is project-specific, not a universal cure time. After full cure, remove the retaining frame and use compressed air carefully to help separate the master from the flexible mold. Inspect the cavity and edges before use.

A longer process record is available here: https://www.bksilicone.com/taiwan-mahjong-silicone-mold-making/