Week 13: Molding and Casting
This week's assignment involves designing, fabricating, and casting a mold with a smooth finish. I chose to create an octopus model, which I designed using Autodesk Inventor Professional. After designing the octopus, I made a frame to facilitate the casting process with food-grade silicone. The frame ensures that the casting process is easier and results in a smooth, high-quality finish. The octopus design was then 3D printed to create a master model, which I used to prepare the silicone mold.
For the mold design, I incorporated a tapered shape to facilitate easy removal of the silicone mold. Additionally, the base and sides are two separate pieces, allowing for effortless demolding by simply pushing the base upwards. This design ensures that the silicon mold can be removed smoothly.
For the slicer, I used Chitubox, a popular slicing software for 3D printing. Chitubox offers a user-friendly interface with advanced features like customizable support structures, print settings optimization, and a preview function to ensure accurate slicing of the 3D model. It allows for precise control over the slicing process, making it easier to achieve high-quality prints.
For printing, I used the Phrozen Sonic Mega 8K SLA printer. The Sonic Mega 8K is renowned for its ultra-high resolution, thanks to its 8K monochrome LCD screen, which allows for exceptionally detailed and precise prints. This printer is designed for large-scale projects, offering a substantial build volume of 330 x 185 x 400 mm, which is perfect for creating larger molds or multiple parts in a single print. The printer's robust build quality, combined with its high resolution and large build volume, makes it ideal for producing intricate and detailed models.
For the mold assembly, I opted to use double-sided tape to securely mount the SLA-printed octopus in the correct position. To prevent any leakage, I sealed the mold using packing tape, which provided an effective barrier without the need for more complicated sealing methods. This approach was both cost-effective and time-efficient, allowing for quick setup and reliable results. By using these simple materials, I was able to create a well-sealed mold that performed effectively during the silicon casting process.
For the silicone casting, I used food-grade silicone that I found in the lab. According to the instructions, I needed to mix equal parts of Part A and Part B (50% each). Using a scale, I measured the exact amounts to ensure a perfect mixture of silicone.
Next, I carefully mixed the two parts together, taking care not to generate too many bubbles since the fab lab doesn't have a vacuum chamber to remove them. To minimize bubbles, I mixed slowly and thoroughly. After mixing, I tapped the mold on the table several times to encourage any remaining bubbles to rise to the top.
I then let the mold rest for 48 hours to ensure that the silicone cured completely and evenly throughout. This extended curing time helped to ensure that the final mold was fully set and ready for use.
During the demolding process, I used a spatula to gently release the sides of the mold first. This careful approach helped to ensure that the edges separated cleanly without tearing or damaging the silicone. After loosening the sides, I pushed the bottom piece upwards, which allowed for smooth and easy removal of the mold. The tapered design of the mold significantly facilitated this process, ensuring that the silicone came out without any hassle.
The entire demolding procedure was efficient and straightforward, thanks to the thoughtful design and the use of appropriate tools. The successful demolding confirmed the effectiveness of the preparation and curing steps, resulting in a high-quality silicone mold ready for jelly soap casting.
For this recipe, I used strawberry-flavored gelatin. Although it worked to some extent, it didn't produce the result I wanted. The flavors and sugars in the gelatin reacted poorly with the liquid soap. As a result, half of the mixture didn't harden properly, and the other half didn't make good jelly soap due to inconsistent texture and undesirable aromas.
For this recipe, I used unflavored gelatin with a clear yellow liquid soap. I used 1 cup of soap and 1 teaspoon of unflavored gelatin. The result was better, although the jelly soap was very soft and delicate. It was a matter of finding the right ratio of liquid soap to gelatin. Additionally, the jelly soap ended up with a lot of bubbles or cavities, which affected the texture.
To improve the recipe, I need to adjust the gelatin-to-soap ratio and find a method to reduce bubbles for a smoother finish.
For the third version of the recipe, I noticed that mixing all the components at 60°C helped the unflavored gelatin dissolve properly and created a lighter mixture. As the mixture is runny at this temperature, it allows any bubbles to rise to the surface, resulting in a smoother jelly soap. The mixture I used was 1 cup of liquid soap with 3 tablespoons of unflavored gelatin. This adjustment improved the consistency and reduced the presence of bubbles in the final product.
When working with jelly soap, mixing the recipe can generate bubbles. To minimize this, it is recommended to stir slowly and then spray USP alcohol on the surface to remove any bubbles from the mold. This will help ensure a smooth and consistent texture in your final jelly soap product.
This week's group assigment, I learned about various materials in the fab lab based on their safety data sheets and molding properties. Specifically, I analyzed RTV PLATINUM 1510 Silicone Rubber, Mold Release Wax, Polyurethane Rubber, as well as castings such as Glycerin Soap with Chlorhexidine, Chocolate, and Ceramic Plaster. Understanding the properties of each material provided a better overview of the options and applications for each.
Understanding the properties of each material provided a better overview of their options and applications. This material comparison helped me select the best silicone for my personal assignment.
I was in charge of casting a material and decided to use a glycerin soap bar. I melted the bar of soap using a double boiler for a consistent and slow melting process. Then, I poured the melted soap into the mold and waited for the results.
The density of the soap did not help in reproducing small details like the eyes and mouth of the octopus. I learned that the different flow properties of casting materials affect the final result. Higher density materials are poor at capturing small details, while lighter materials flow better into every feature of the model. However, I am moderately satisfied with the result. There is room for improvement.
