Moulding and Casting

This week’s Fab Academy assignment was all about exploring the processes of molding and casting. The goal was to design and fabricate a mold, ensuring a smooth surface finish that hides the toolpath marks, and then use it to cast an object using a material of our choice. We had to plan the design based on the casting process we intended to use, choose appropriate materials, and learn to work with wax blocks, CNC milling, and liquid casting materials like silicone.

For most of us, it was our first time working with wax blocks and creating molds from scratch, so this week involved a lot of experimentation, problem-solving, and learning from mistakes. Since we had limited material, I worked in a team with Sohan and Mohir, and together we designed, milled, and cast multiple objects by sharing resources and ideas.

A. What is Molding & Casting?

Molding is the process of creating a hollow form (the mold) that captures the negative shape of an object. Casting is when you pour a liquid material (like silicone, resin, or metal) into this mold and let it harden to create a copy of the original object. It’s widely used in manufacturing for making tools, toys, product prototypes, jewelry, and more.

There are different types of molds:

One-part molds for flat or shallow objects.

Two-part molds for 3D and asymmetrical objects.

Materials commonly used: wax, silicon, clay, resin, 3D prints.

BASIC WORKFLOW OF MOULDING AND CASTING

Group Assignment

Safety First – Reviewing SDS of Casting Materials

Before working with any casting materials, we made sure to go through the Safety Data Sheets(SDS) to understand the precautions, handling instructions, and disposal methods. For the silicone casting we planned initially, we used a 1:10 ratio silicone and hardener, and reviewed its SDS to learn:

1. Wear gloves while mixing to avoid skin irritation

2. Mix in a well-ventilated area

3. Avoid direct inhalation of fumes (though silicone is low-risk, it’s still a best practice)

4. Store leftovers in airtight containers, away from sunlight

For the flour-water sealing paste and water casting, there weren’t any real hazards, but we kept the freezing process clean and safe just in case something spilled.

Material Test Casting – Silicone vs Water

Since resin wasn’t available, we used two different materials for test casting:

Material Test Casting – Silicone vs Water

Since resin wasn’t available, we used two different materials for test casting:

Material	Pros	Cons
Silicone	Smooth finish, flexible mold	Needs proper ratio, longer curing
Water (Ice)	Quick, low-cost, fun preview	Temporary, melts, not detailed edges

The silicone mold gave us more refined results and will last longer, while the frozen water cast was more of a creative experiment that helped us validate our mold design quickly.

Printing vs Milling Molds – What We Learned

We made molds using both 3D printing and CNC milling and here’s what we observed:

Method	Benefits	Drawbacks
Milling (Wax)	Smooth surface finish, no layer lines, durable	Long process (5–9 hrs), wax waste
3D Printing	Fast to produce, customizable, affordable	Layer lines visible, needs post-processing

Milling gave us better surface quality, but was time-intensive. On the other hand, the 3D printed mold was quicker to make and helpful for comparing cast quality. It was also useful when we didn’t have extra wax blocks.

If you're curious about this workflow and want to learn more, I’d recommend checking out work by Sohan , Mihir they’ve been super involved in testing out and comparing the mold outputs.

Individual Assignment

B. Tools & Materials Used

1. Wax blocks (for CNC milling)
2. Fusion 360 (for 3D modeling)
3. SRM-20 milling machine
4. 3mm round-end milling bit
5. Silicone and hardener (1:10 ratio)
6. Digital weighing scale
7. Sandpaper (for finishing)
8. Safety gloves and apron

C. Team Plan: Sharing Material, Sharing Learnings

Due to limited access to wax blocks, we decided to collaborate as a team of three — Mihir, Sohan, and I. Our idea was to create a single large mold block that combined three different parts — each designed by one of us.

Part 1

D. Designing Asymmetric Tool Molds

Each of us designed a different tool with an asymmetric shape:

I made a spanner

Sohan designed an axe

Mihir created a hammer

We modelled them individually in Fusion 360 and then arranged them on a single mold block file. While modeling, we ensured:

1. Correct depth of the cavity

2. Draft angle (taper) so the milling bit could move freely

3. Object thickness and clearance

Taping block of wax from behind so it doesn't move

For this we used 3mm Round bit

putting into the machine

setting the machine choosing the bit adjusting the layout layer for roughing

After finalizing the design, we generated the toolpaths using the Mods CAM software and began milling the wax block using the SRM-20. The file took five hours to finish.

The surface finish came out really clean, and we were excited — until we realized a major flaw: these asymmetric shapes required a two-part mold to cast properly. We only had the top halves! That hit us hard, but it also taught us our first big lesson in mold making.

E. Realization & Redesign: Keep It Symmetric!

After discussing what went wrong, we decided to pivot the project. The new idea had to be:

• Simple and fun
• Symmetrical
• Possible to cast using a single-sided mold (for now)

We came up with the idea of making spinning tops. Each of us modeled a different design and combined them again into one wax block layout.

This time, we made sure the mold:

• Was completely symmetric
• Had proper walls and alignment holes
• Maintained even height and placement

Part 2

F.Milling the Spin Top Mold (Wax)

This was our final wax block, so everything had to go right. We set the job with a 3mm round-end bit and began roughing followed by finishing. The new file took around 9 hours.

But again, we faced a challenge. We hadn’t extended the milling bit beyond 20 mm from the nozzle, so it couldn’t reach the deeper regions of the wax. The bit started scraping the sides, ruining the clean walls.

We paused the milling, adjusted the bit height, and restarted the job. This time, it worked better, but two of the tops still had rough surfaces from the earlier mistake. We decided to use sandpaper later to smoothen those parts manually.

G. Creating the Other Side of the Mold – 3D Printing

To turn this into a working two-part mold, we 3D printed the opposite side of the mold using the same measurements as the wax mold. This would allow us to:

• Match both halves
• Cast complete spinning tops
• Test which material (wax vs. 3D print) worked better for silicone casting

• Print dowels to match moulding framing cases
• The 3D printed mold had the same frame, hole positions, and heights as the wax block, which helped us align both sides accurately.

Part 3

I. Silicone Casting

With both mold halves ready (wax and 3D print), we began casting using silicone.

We prepared the silicone mix in a 1:10 ratio (silicone base to hardener). For 700 ml of silicone, we added 70 ml of hardener. The process was:

1. Wearing gloves and mask for safety.
2. Weighing the components properly.
3. Mixing in circular motion, not back and forth, to avoid air bubbles.
4. Pouring the mix slowly into the molds.
5. Tapping the molds lightly to release trapped bubbles.
6. Leaving them to cure overnight in a clean space.

We cast into both the wax mold and 3D printed mold to compare the results and understand how the materials affect the casting process.

J. Demolding – Peeling the Results

After allowing the silicone to cure overnight, we moved to the final and most satisfying part of the process: demolding. This step had to be done slowly and carefully to avoid tearing the silicone or damaging the mold.

We first loosened the edges gently using a flat tool and then peeled back the mold gradually to release the cast objects. Since we had used both wax and 3D printed molds, the demolding experience was slightly different for each:

From the wax mold, the tops came out clean and smooth, with very few surface marks.

The 3D printed mold, however, left behind minor texture lines due to the layer lines from FDM printing.

Two of the tops needed some light sanding because of earlier milling issues, but they were still functional and looked great overall.

Demolding also helped us understand how material choice and mold surface finish affect the final cast. This comparison between wax and 3D printed mold results gave us useful insight for future projects.

K. Alternative Casting with Water – A Quick and Creative Jugaad

Since resin wasn’t available in the lab at the time we wanted to cast, we decided to experiment by using water as our casting material. It was easily available, safe to handle, and a fun way to test the mold quickly without waiting for any curing chemical process. Our goal was to freeze the water inside the mold overnight and observe how well the shapes turned out

Creating a Homemade Sealant – Flour Paste

made a thick paste using flour and water, which acted like a natural, sticky dough. This traditional "jugaad" method worked surprisingly well:

Mixed small amounts of atta (flour) and water until a dough-like consistency was formed.

Applied this paste carefully around the mold's edges and openings.

Used transparent cello tape over the paste to secure everything in place and prevent leaks.

Pouring the Water

gently poured water into the mold cavity through the top, making sure it filled every part. We tapped the mold a few times to release any trapped air bubbles.

Freezing

Once filled and sealed, placed the mold carefully in a freezer overnight. This step was simple but exciting, as we couldn’t wait to see if the frozen water would take the shape properly.

Demolding the Ice

The next morning, carefully demolded the spin tops. The ice castings came out beautifully detailed and surprisingly accurate, considering the simplicity of the material and sealing method.

🧊 Outcome & Reflections The frozen tops looked really nice, and the details from the mold were clearly visible. Although this wasn’t a permanent material, this process gave us a quick preview of our design and helped test the mold quality without using costly casting materials.

This spontaneous method taught us a lot about the flexibility of casting processes. It also showed how creative thinking and low-cost alternatives can still lead to meaningful results—even when traditional materials aren’t available.

Original Code Files

TOP DESIGN FILE