W14 | Moulding and Casting

Their chocolates are currently sold only as tablets, so this project became an opportunity to explore the creation of custom-shaped chocolates using a silicone mold made from a 3D printed model. My friend's entrepreneurship, Kuska Yawarmasi, collaborates with this association to help bring their products to more people. You can follow her work here: Kuska Yawarmasi

Mold

The piece with the heart and bow design, which defines the final shape of the chocolate.

Countermold

A container that holds the mold in place during the silicone pour, avoiding wasting excess material.

⚠️ An important consideration when designing for casting is that any imperfection in the 3D model will be transferred to the silicone and from there to the final cast.

Both pieces were printed on a Bambu Lab X1-Carbon using ABS filament. The choice of ABS over PLA was deliberate. PLA is the most common 3D printing material and is easy to work with, but it tends to show layer lines more prominently on curved surfaces. ABS produces a smoother surface finish because its layers bond together more tightly during printing. This is important because the mold needs to capture and transfer the fine details of the design — the curves of the heart and the lines of the bow — but without transferring the layer lines from the printing process.

The print settings were the standard Bambu Lab profile for ABS, with the main difference being the temperature — ABS requires a higher nozzle and bed temperature than PLA to print correctly and achieve good layer adhesion.

The other materials prepared for the process were:

• Digital scale
• Mixing cup
• Wooden stir sticks
• Nitrile gloves
• Rubber bands
• Masking tape
• Paper towels

Step 2 — Prepare the silicone

The mixing cup was placed on the scale and tared to zero. Then 54g of part A and 54g of part B were measured separately and combined in the cup. Both components were mixed thoroughly for several minutes until fully combined and uniform.

📝 It is important to mix slowly and carefully to avoid introducing air bubbles into the silicone. Bubbles that form during mixing will be trapped in the mold once it cures, leaving small imperfections on the surface that will transfer to the final cast.

Step 3 — Pour the silicone

The mixed silicone was poured carefully and slowly into the mold. The mold was then moved and gently shaken to help the silicone reach all the fine details and corners. Once filled, it was left to cure overnight.

Step 4 — Demold

The following day, the rubber bands and tape were removed and the silicone mold was carefully separated from the 3D printed pieces. The result was a clean, flexible silicone mold with all the heart and bow details captured.

Before pouring, the chocolate was tempered — a process of carefully controlling the temperature of the melted chocolate to ensure it sets with the right texture and shine. Once tempered, the chocolate was poured into the silicone mold, left to set, and then carefully removed.

Problem 1 — Layer lines slightly visible on the final chocolate

Even though ABS was used for a smoother finish, some layer lines were slightly transferred to the silicone and from there to the final chocolate. This was partly due to the limitations of Autodesk Inventor for modeling organic curves. The assignment requires that the mold does not show the production process — ABS helped, but sanding the printed piece before casting would have eliminated the remaining layer lines completely.

✅ Fix for future iterations

Use software better suited for organic shapes and sand the printed piece before casting.

Problem 2 — Silicone did not reach the corners of the countermold

Due to the geometry of the countermold, the tight corners made it difficult for the silicone to flow in naturally. This can cause two issues — either the silicone does not reach those areas at all, leaving empty spots, or air gets trapped and forms bubbles. Both affect the final surface quality of the mold. Fortunately, the affected areas were only on the outer corners of the countermold — not in the cavity where the chocolate would be cast — so the final mold was not compromised and the result was not affected.

✅ Fix for future iterations

Redesign the countermold with more open, rounded corners to allow the silicone to flow freely and prevent air from getting trapped.

Problem 3 — Demolding the countermold was difficult

Once the silicone cured, removing the countermold was more difficult than expected because there was no good gripping point. The countermold needs small handles or tabs — called ears — on the sides so it can be pulled apart cleanly without forcing it.

✅ Fix for future iterations

Add small protruding tabs to the countermold design so there is a clear gripping point when separating the pieces after curing.

Safety considerations:

• Nitrile gloves were worn at all times when handling the silicone components to avoid skin contact.
• The work area was covered with paper to protect the surface and make cleanup easier.
• Since the silicone used was food-grade, no toxic fumes or hazardous chemicals were involved — making it safe to work with in a standard lab environment.
• For the chocolate casting, basic food hygiene measures were followed at the association's production facility.