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14. Molding and Casting

Assignment on Moulding and Casting

Group assignment:

  • Review the safety data sheets for each of your molding and casting materials Make and compare test casts with each of them
  • Compare printing vs milling molds

Individual assignment:

  • Design a mold around the process you’ll be using, produce it with a smooth surface finish that does not show the production process, and use it to cast parts.

Learning outcomes

  • Design appropriate objects within the limitations of your process
  • Demonstrate workflows used in mold design, construction and casting

Have you answered these questions?

  • Linked to the group assignment page and reflected on your individual page what you have learned
  • Reviewed the safety data sheets for each of your molding and casting materials, then made and compared test casts with each of them
  • Documented how you designed and created your 3D mold, including machine settings
  • Ensured your mold has smooth surface finish, that does not show the production process (by postprocessing if necessary)
  • Shown how you safely made your mold and cast the parts
  • Described problems and how you fixed them
  • Included your design files and ‘hero shot’ of the mold and the final object

Experiments on Moulding and Casting

Experiment with Silicone

Silicone

As part of the Fab Academy molding and casting assignment, I designed and fabricated a molding form with external dimensions of 10 cm × 5 cm. The internal geometry included both ellipse and round shapes, arranged to test the molding of complex curved forms.

To create a flexible casting mold, I used construction-grade silicone. The process involved pouring the silicone into the plastic mold. However, a critical mistake occurred: we forgot to add the hardener to the silicone mixture. As a result, the material did not cure and remained soft and unusable for casting purposes.

Despite this setback, the initial idea was to use the resulting (blue and red) silicone molds — once properly prepared — as forms into which we could pour epoxy resin. This epoxy mixture included a component of liquid glass to achieve a semi-transparent, glossy effect in the final product. The objective was to explore how colored silicone molds (blue and red) would work in shaping the epoxy and how well the combined epoxy and liquid glass mix would replicate fine details from the mold.

This experiment highlighted a key lesson: precise material handling — especially when working with curing agents — is essential for a successful molding and casting process.

### Experiment with Epoxy

Epoxy

In this experiment, we used epoxy resin combined with its hardener to cast chess figures. For this purpose, we utilized pre-made silicone casting molds specifically designed for chess pieces.

To explore material aesthetics, we conducted experiments both with and without added color pigments. Some figures were cast using transparent epoxy, while others were colored using various dyes. This allowed us to observe how pigmentation affected visual clarity and final appearance.

We also attempted to create a full chessboard using epoxy poured into a segmented mold. However, during the casting process, a slight hand shake caused some of the liquid resin to spill and mix across segment boundaries. As a result, the chessboard did not form clean, separate squares, and the overall shape was compromised.

This experiment highlighted not only the versatility of epoxy resin in fine casting applications but also the importance of precision and a steady hand during the pouring process to avoid cross-contamination between mold sections.

Experiment with Gypsum

Gypsum

In this part of the assignment, we experimented with gypsum as a casting material. We used two types of silicone casting forms: one was a flat plate mold with a decorative surface ornament, and the other was a 3D mold in the shape of a toy pig.

To prepare the gypsum mixture, we combined gypsum powder with water in appropriate proportions until it reached a smooth, pourable consistency. The liquid mixture was then carefully poured into both molds.

Due to the fast-setting chemical nature of gypsum, the material began to harden almost immediately after pouring. This required quick and precise handling. After curing, both the plate and toy pig forms solidified successfully, retaining the detailed patterns and shapes of the original molds.

This experiment demonstrated the suitability of gypsum for both surface-detail and 3D casting and emphasized the importance of working quickly once the material is mixed.