1Import the mesh

The STL file was imported into Fusion 360 using Insert → Insert Mesh. Fusion 360 accepts STL geometry directly as a mesh body, making it straightforward to work with models sourced from repositories like MakerWorld without rebuilding the geometry from scratch. The Snoopy-on-doghouse model appears in the canvas with visible triangle facets.

2Convert the mesh to a solid

The mesh was converted to a solid body using Mesh → Modify → Convert Mesh. This step is required to enable all subsequent boolean and sketch operations — Fusion 360's solid design tools do not operate on mesh triangles. After conversion, the Snoopy body appears in the browser as a solid (BRep), and the MESH tab is replaced by the SOLID workflow.

3Cut the solid in half using the XZ plane

The converted solid was split into two halves using Modify → Split Body, with the XZ plane as the cutting tool. This defines the parting line — the plane where the two mold halves will meet. The XZ plane passes through the widest cross-section of the Snoopy figure so each half can demold cleanly without undercut interference. After the split, two solid bodies appear in the browser: snoopystl_scaled and snoopystl_scaled (1).

4Create a rectangle sketch

A new sketch was created on the parting plane (XZ) and a rectangle was drawn around the half-model. The dimensions — 74 mm wide × 100 mm tall — were set to provide sufficient wall clearance on all sides of the Snoopy figure. This rectangle defines the outer footprint of the mold container box that will hold the silicone.

5Create the mold box (Extrude + Shell)

The rectangle profile was extruded 37 mm in height to form a solid block. A Shell operation with a 5 mm wall thickness was then applied, hollowing the block from the open top face and leaving uniform 5 mm walls on all sides and the base. The result is a sturdy open-top container — the mold matrix — that holds the master model in position and contains the silicone during the pour.

6Convert to components and combine the pieces

Both solids — the mold box and the embedded Snoopy half — were converted to Fusion 360 components and brought together as a single assembly. This ensures the half-model is correctly positioned inside its container, and that subsequent operations (sketches for the registration pins) reference the correct geometry.

7Sketch the registration pin positions

A new sketch was created on the interior base face of the mold container. Four circles of Ø 5 mm were placed at the corners, offset 5 mm from each wall edge. These circles define the footprints of the alignment cylinders that will ensure the two mold halves register precisely when assembled — any lateral offset between the halves during a resin pour would produce a misaligned cast part.

8Extrude the registration pins

The four circles were extruded upward as solid cylinders. These pins press into the soft silicone of the opposite mold half when the two halves are first assembled, creating matching holes. When the mold is reassembled for casting, the pins and holes interlock and prevent any lateral shift between the two silicone halves during the resin pour.

Steps 4–8 were repeated symmetrically for the second Snoopy half, producing the complementary mold container (Side_02, shown in yellow/gold) with matching registration features. Both completed mold matrix halves are shown here side by side. Each was then exported as an STL file — Snoopy_sideA.stl and Snoopy_sideB.stl — ready for 3D printing.

103D print the mold containers

Both STL files were sliced in Bambu Studio and printed simultaneously on the same plate on the Bambu Lab X1 Carbon. The Slicing Result panel confirms all print statistics:

1Assemble and secure the mold containers

The master model was placed inside one half of the mold container, positioned precisely so the parting line would fall at the widest cross-section of the house. The registration pins on the container halves were used to align the two halves correctly. The assembled container was placed on the kraft-paper-covered workbench, ready to receive the silicone pour.

No release agent was required between the silicone and the 3D-printed PLA+ container, since silicone does not bond permanently to PLA. However, a thin coat of petroleum jelly was applied to the master model surface to ensure clean demolding after the silicone cured.

2Measure the silicone and catalyst by weight

The Silicon Perú Silicona F-10 PLUS uses a base + catalyst system: the white silicone paste is the base, and the blue liquid is the catalyst that triggers the curing reaction. The mixing ratio by weight is specified in the product datasheet — the catalyst was added at the percentage indicated and the combined mixture was placed on the digital scale to confirm the correct total weight before mixing.

Measuring by weight rather than by volume is more accurate for silicone systems, since the base and catalyst have different densities. An incorrect ratio produces silicone that either does not cure fully (too little catalyst) or cures with a compromised surface quality (too much catalyst).

3Mix the silicone

The catalyst was added to the silicone base in the mixing cup and stirred slowly and thoroughly for the time specified in the datasheet — typically 3–5 minutes for this product. Mixing was done with a wooden stir stick in a circular motion, regularly scraping the sides and bottom of the cup to incorporate all the material evenly.

Slow, deliberate mixing is critical. Aggressive or rapid stirring introduces air into the silicone, which produces bubbles in the finished mold surface. Any bubble that appears on the face of the mold that contacts the master will be transferred as a raised bump to every cast part produced from that mold.

4Pour the silicone

The mixed silicone was poured in a thin, continuous stream from a height of approximately 20–30 cm above the mold opening. Pouring from a height helps break any surface bubbles as the stream falls. The pour was directed to one corner of the mold first, allowing the silicone to flow naturally toward the master model and push any air ahead of it toward the vents.

Once the first half was filled, the process was repeated for the second half of the mold container. Both halves were then left on a flat, vibration-free surface to cure overnight.

5Cure and demold

The silicone was left to cure overnight at room temperature. After curing, the mold container halves were separated by removing the registration pins and gently pulling the two blue PLA+ halves apart. The flexible silicone block was then carefully peeled away from the master model — silicone's flexibility makes this process straightforward even for shapes with moderate undercuts.

The result was two matching flexible silicone mold halves with the negative impression of the doghouse enclosure captured cleanly on the interior face of each half.