Moulding and Casting

Compare Printing vs Milling Molds

For this group assignment, we worked with the design of the Virgin of Guadalupe. The STL file was downloaded from Cults3D. Once we had the STL design, we followed a workflow to prepare the model for CNC milling and later compare it with the 3D printed mold.

Reference model: Virgin / Virgen Candle Chibi Kawaii - Cults3D

1. Milling Molds

Model preparation in Blender

1. We imported the 3D design in .OBJ format into Blender.
2. We measured and scaled the 3D object proportionally.
3. We drew a rectangular cube to simulate the material to be machined.
4. We moved and centered the figure inside the material block.
5. In Edit Mode, we selected the top face and used the “I” key to create an inward offset.
6. Using the Extrude command, we subtracted the block down to almost half of the figure.
7. In Edit Mode, we deleted the excess geometry below the figure.
8. Finally, we exported the mold in .OBJ or .STL format to machine it in Aspire.

Img. 1 - Importing the 3D design into Blender

Img. 2 - Measuring and scaling the object

Img. 3 - Creating the material block

Img. 4 - Centering the figure in the material

Img. 5 - Creating an inward offset

Img. 6 - Extruding the block

Img. 7 - Removing excess geometry

Img. 8 - Exporting the mold file

Machining with Aspire 10.5

1. We created a new file and configured it with the dimensions of the material to be machined.
2. In the Modeling tab, we selected the option “Import 3D Model”.
3. We oriented and scaled the mold according to the material and clicked “Apply” and then “Accept”.
4. We verified the imported 3D mold.
5. We selected the “3D Roughing Toolpath” option to perform the first roughing machining pass.
6. We configured the tool. We used a 3.175 mm compression bit because it was the tool available. The parameters were: RPM 15000, feedrate 2500 mm/min, pass depth 2.5 mm, rest machining 40%. Then we clicked “Calculate”.
7. Before the finishing toolpath, we drew a curved polyline in the 2D View tab around only the Virgin figure, so the finishing process would focus only on this area.
8. We selected the “3D Finishing Toolpath” option.
9. We configured the finishing tool. We used a 0.5 mm conical ball nose bit with 6 mm diameter. The parameters were: RPM 14000, feedrate 3000 mm/min, pass depth 0.2 mm, rest machining 10%. Then we selected the Virgin vector and clicked “Calculate”.
10. We verified the toolpaths through simulation.
11. We saved the toolpaths independently in .nc format for CNC machining.
12. We positioned the material. In this case, we used a 5 cm thick polyethylene block. We opened the file in NcStudio and started the first roughing machining process.
13. Once roughing was finished, we continued with the 3D finishing process. We changed to the ball nose bit, set the Z reference again, and started machining.

Img. 9 - New Aspire file setup

Img. 10 - Importing the 3D model

Img. 11 - Orienting and scaling the model

Img. 12 - Imported 3D mold verification

Img. 13 - 3D roughing toolpath

Img. 14 - Roughing tool parameters

Img. 15 - Curved polyline around the figure

Img. 16 - 3D finishing toolpath

Img. 17 - Finishing tool parameters

Img. 18 - Toolpath simulation

Img. 19 - Saving .nc toolpaths

Img. 20 - CNC roughing process

Silicone RTV Mold Fabrication

Process Description

As part of the group work, a silicone mold was developed using a rigid master fabricated through CNC machining. The mold geometry corresponds to a cavity with positive relief features, designed to accurately reproduce fine details and variations in depth in the final casted piece.

Due to the level of detail required, special attention was given to surface preparation, pouring, and curing stages to ensure high-fidelity geometric reproduction.

Rigid Mold Preparation

Before casting, the CNC-machined master was thoroughly cleaned to remove dust, residues, and any surface contaminants that could affect the final result.

Unlike FDM fabrication, CNC machining provided a significantly smoother and more continuous surface finish. However, minor toolpath marks were still present, so the surface was inspected to ensure it met the required quality for molding. For this reason, the mold was sanded and resin was applied to improve the surface finish and obtain a more professional result.

Img. 21 - Sanding process on CNC mold surface

Img. 22 - Resin coating to improve mold finish

A liquid release agent was then applied evenly across the entire cavity, paying special attention to detailed and recessed areas. This layer prevents adhesion between the silicone and the master, allowing for safe and clean demolding.

Img. 23 - Applying release agent

Materials Used

The mold was produced using RTV silicone F-20 Plus from Silicon Perú, along with its corresponding catalyst.

• Type: General-purpose RTV silicone
• Application: Casting mold fabrication
• Mixing ratio: 3% catalyst by weight

This silicone has medium viscosity, allowing it to flow into detailed geometries, and medium hardness, providing enough flexibility for demolding without compromising structural stability.

Mixing Process

The silicone was manually mixed with the catalyst following the specified ratio. Care was taken to achieve a homogeneous mixture to ensure uniform curing throughout the material.

During this process, air incorporation was identified as an inherent limitation of manual mixing, so additional measures were taken during pouring to minimize bubble formation.

Casting Process

The silicone was poured slowly and in a controlled manner, starting from a single point to allow the material to flow progressively into the cavity. This technique helps reduce air entrapment in deeper regions.

Additionally, the mold was gently tapped against the working surface to help release trapped air bubbles. Although this method improves results, it has limitations compared to vacuum degassing.

The cavity was filled completely to ensure full reproduction of all geometric details.

Img. 24 - Pouring RTV silicone into the mold

Curing

After pouring, the silicone was left to cure at room temperature for the recommended time specified by the manufacturer.

During this stage, the mold was not manipulated in order to avoid deformation or defects in the final structure.

Demolding and Evaluation

Once fully cured, the silicone mold was carefully demolded. The release agent performed effectively, allowing separation without damage to either the mold or the master.

The resulting mold showed a high level of detail reproduction, with clean edges and consistent surface quality across the entire geometry.

Img. 25 - Final RTV silicone mold

Img. 26 - Chocolate casting test with good surface finish

Process Conclusion

The use of a CNC-machined master significantly improved the final mold quality compared to additive manufacturing alternatives. The smoother initial surface reduced the need for post-processing and resulted in better surface finish in the silicone mold.

The final mold is suitable for casting applications requiring good detail resolution and structural reliability.

2. 3D Printing Molds Fabrication

Process Description

As part of the group work, two 3D printed molds were developed using a Bambu Lab A1. We printed with PLA. The mold geometry corresponds to a cavity with positive-relief features, designed to accurately reproduce fine details and depth variations in the final cast piece.

Print Settings

• Layer height: 0.08 mm
• Layer initial height: 0.2 mm
• Line width: 0.42 mm
• Line initial layer: 0.50 mm
• External wall: 0.42 mm
• Internal wall: 0.45 mm

These are the Bambu Studio mold designs, with different measures:

Img. 27 - Bambu Studio mold design

Img. 28 - Mold design with different measures

3D Printer Mold

The 3D Printer molds had a clear, smooth surface. This method is useful, and the mold can receive hot materials at temperatures below 180 °C.

Img. 29 - 3D printed mold

Img. 30 - Surface finish of the 3D printed mold

Bio-Silicone Mold Fabrication – Regen

As part of the group assignment, Regen Bio was used, a digital biomaterials platform linked to REGEN, an initiative publicly presented as a Fab Lab Peru project focused on promoting a regenerative economy in the Amazon.

REGEN was also recognized as one of the winning projects of the Biodiversity Small Funds Initiative, promoted by the Global Plastic Action Partnership (GPAP) within the framework of the World Economic Forum and announced during the UN Ocean Conference 2025.

In this context, the project was highlighted for its work with indigenous communities in Peru in the creation of biodegradable alternatives based on natural materials.

During this activity, the platform Regen Bio Platform was used as support to define the properties, ingredients, and preparation conditions of the biosilicone evaluated during the group practice.

Img. 31 - Regen Bio biomaterials platform

Img. 32 - Biomaterial information used during the experiment

Biomaterial Test: Biosilicone

As part of the group assignment, a molding test was performed using a biosilicone made from accessible ingredients, following a biomaterial recipe obtained from a biomaterials platform.

The objective of this test was to observe the behavior of the material during preparation, pouring, and solidification, as well as evaluate its surface finish and response when poured into a 3D printed mold.

For this test, a group mold fabricated by 3D printing was used, shaped as a small Virgin with flowers. The mixture showed good overall behavior and produced a visually satisfactory final piece.

Ingredients Used

• 520 g of gelatin sheets (Colapiz)
• 500 ml of water
• 50 ml of glycerin
• 15 drops of clove essential oil

Properties of the Ingredients Used

Preparation Procedure

Before starting, we first measured the mold capacity using water to estimate how much material would be needed for the biosilicone preparation.

Img. 33 - Measuring mold volume with water

Img. 34 - Heating and mixing the biosilicone ingredients

To prepare the biosilicone, all ingredients were placed into a metal bowl and heated to integrate them uniformly.

The mixture was processed at approximately 70 °C, ensuring that the components melted and progressively combined into a homogeneous material.

Before pouring the biosilicone into the 3D printed mold, a layer of vaseline was applied to the internal surface of the mold.

This step facilitated demolding once the material solidified and reduced the risk of damaging either the mold or the final piece.

Once the mixture reached the appropriate consistency, it was carefully poured into the 3D printed mold corresponding to the group test.

The material was then left to rest and begin the solidification process inside the mold.

Img. 35 - Pouring biosilicone into the 3D printed mold

Img. 36 - Final biosilicone result

Observations During the Test

During preparation, the biosilicone showed good integration between its components. The mixture reached a uniform texture and could be poured without significant difficulty.

The material adapted well to the geometry of the mold, allowing the shape to be reproduced successfully.

The final result was very positive, presenting a pleasant appearance and attractive finish.

Problems Encountered and Solutions

During the heating stage, the mixture slightly stuck to the bottom of the container. This occurred because the metal container used was smaller than necessary and excessive heat was initially applied.

To solve this issue, the temperature was controlled more carefully and the mixture was continuously stirred to prevent further sticking or burning.

Fortunately, the problem did not significantly affect the final mixture, since the material continued melting correctly and maintained its properties.

Thanks to this, the biosilicone was successfully used and the final result was satisfactory.

Reflection About the Test

This test allowed us to understand that in biomaterials, not only the recipe matters, but also the heating conditions, the correct container size, and temperature control throughout the process.

We also learned that small mistakes at the beginning, such as excessive heat, can be corrected if handled carefully and in time.

Comparison Table of Results

Review the Safety Data Sheets for Each of Your Molding and Casting Materials and Make and Compare Test Casts with Each of Them

During the second part of the group assignment, on Sunday, April 26, we reviewed the Safety Data Sheets (SDS) of the different materials used during the molding and casting tests.

The objective was to identify risks, safe handling procedures, curing times, mold compatibility, and the final behavior of each material.

Before performing the tests, personal protective equipment (PPE) such as gloves, masks, and lab coats were used, especially with materials that generate vapors, heat, or chemical reactions during mixing and curing.

We also worked in ventilated environments and used appropriate containers for mixing and heating processes.

Casting tests were carried out using plaster, eco water resin, soy wax, glycerin soap base, white cement, epoxy resin, polyester resin, and plasticine for rapid molds.

Each material presented different behaviors in terms of fluidity, working time, surface finish, resistance, and ease of demolding.

Materials and Tools Used During the Tests

Img. 37 - Materials used during casting tests

Img. 38 - Materials and tools preparation

Img. 39 - Safety equipment and working environment

Img. 40 - Mixing and preparation process

Comparison Table of Materials Used

1. Soy Wax

For this assignment, we worked with soy wax, a 100% vegetal and refined material commonly used for candle making.

This material comes in small pellets, making it easier to handle and melt uniformly. One of its main advantages is its clean finish, neutral odor, and safe handling compared to other casting materials.

According to the specifications, its melting point ranges between 60 °C and 65 °C, making it suitable for controlled casting processes.

Melting Process (Double Boiler Method)

Img. 41 - Soy wax melting process

To melt the soy wax, the double boiler method (bain-marie) was used, allowing indirect and controlled heating.

Water was placed in a lower container and heated using a stove. Another container with soy wax pellets was placed above it.

This method prevents direct contact with heat, reducing the risk of burning or degrading the material.

Temperature Control and Safety

Temperature was continuously monitored during the process until the wax reached approximately 65 °C.

Maintaining the correct temperature was essential to avoid overheating, since soy wax can become flammable at excessive temperatures.

The work was performed in a ventilated area and containers were handled carefully to avoid burns or spills.

Img. 42 - Temperature control during melting

Preparation for Casting

Img. 43 - Preparing the mold for wax casting

Once the wax reached the proper liquid state, it was ready to be poured into the mold.

Before casting, the mold was cleaned and properly positioned to avoid misalignment or leakage.

The fluidity of the wax allowed it to fill the mold easily, capturing the shape with good detail.

Cooling and Final Result

After pouring the melted wax into the mold, it was left to cool at room temperature in a stable and ventilated environment.

Once completely cooled, the piece was removed from the mold, resulting in a clean and well-defined cast.

Img. 44 - Final soy wax casting result

2. Glycerin Soap Base

During this test, a glycerin soap base was used as casting material. This material is commonly used in handmade soap production because of its transparency, smooth finish, and easy handling.

One of its main advantages is that it melts quickly and solidifies without requiring complex curing processes.

The objective of this experiment was to evaluate the behavior of the glycerin base inside the mold and observe the level of detail and surface finish obtained after solidification.

Melting Process

Img. 45 - Melting the glycerin soap base

The glycerin soap base was cut into small pieces to facilitate uniform melting.

Heating was performed gradually using a controlled heat source to prevent burning or excessive bubbling.

During the process, the material became transparent and reached a homogeneous liquid consistency suitable for casting.

Casting Process

Once fully melted, the glycerin base was carefully poured into the mold. The pouring process was performed slowly to reduce air bubbles and improve detail reproduction.

The mold was kept stable during cooling to avoid deformation and maintain a uniform surface finish.

Img. 46 - Pouring the glycerin base into the mold

Img. 47 - Cooling and solidification process

Final Result

After cooling completely, the soap piece was demolded successfully. The final result showed good surface quality and clean edges, with a translucent appearance characteristic of glycerin-based materials.

3. White Cement

White cement was also tested as a casting material during this assignment. This material is commonly used for decorative rigid pieces because of its hardness and durability after curing.

Compared to other materials, white cement produces heavier pieces and requires careful proportion control during mixing.

Preparation and Mixing

The material was mixed gradually with water until obtaining a homogeneous and fluid consistency suitable for pouring.

During mixing, gloves and masks were used to avoid contact with the powder and prevent inhalation of fine particles.

Proper mixing was important to reduce bubbles and improve the final structural consistency of the piece.

Img. 48 - White cement preparation and mixing

Casting and Curing

After preparing the mixture, the material was poured slowly into the mold to avoid trapped air.

The mold was slightly tapped to help release bubbles and improve material distribution inside the cavity.

The piece was left to cure naturally until complete hardening was achieved.

Img. 49 - Pouring white cement into the mold

Img. 50 - Final white cement casting result

Observations

The final piece presented good rigidity and acceptable detail reproduction. However, compared to resin-based materials, the surface finish was less smooth and the weight of the final object was considerably higher.

4. Epoxy Resin

Epoxy resin was tested during the assignment because of its excellent transparency, smooth finish, and resistance after curing.

This material is widely used for decorative applications, encapsulation, and pieces requiring glossy surfaces.

Safety Considerations

During handling, gloves and ventilation were mandatory, since epoxy resin may release chemical vapors during mixing and curing.

Contact with skin was avoided throughout the process.

Img. 51 - Mixing epoxy resin components

The resin and hardener were mixed according to the manufacturer's ratio until achieving a completely homogeneous mixture.

Careful mixing helped reduce imperfections and incomplete curing areas.

Casting Process

Once mixed, the epoxy resin was poured carefully into the mold. The material showed high fluidity and adapted well to detailed areas.

During curing, the resin progressively became rigid and transparent.

Img. 52 - Pouring epoxy resin into the mold

Img. 53 - Final epoxy resin result

Final Evaluation

The final piece achieved excellent transparency and surface finish. Fine details were reproduced successfully and the material showed high structural resistance after curing.

5. Molding and Casting with Plaster

In this activity, we worked with plaster to obtain a solid and detailed piece. The process was documented as a technical recipe, including material preparation, safety measures, casting, vibration, curing, and final evaluation.

I. Technical Recipe

To ensure dimensional stability and acceptable hardness in the final piece, the following mixture parameters were established:

• Base ingredient: High-purity alpha hemihydrate plaster.
• Hydrating agent: Water.
• Mixing ratio: 1:2 by weight. For this practice, we used 150 ml of water and 300 g of plaster.
• Additive: Natural turmeric pigment for aesthetic contrast and flow analysis.
• Molds: Industrial-grade RTV-2 silicone molds with Shore A 25 hardness.

Img. 54 - Plaster materials and preparation

Img. 55 - Mold preparation for plaster casting

II. Operating Protocol

1. Safety and Biosecurity Management

Before starting the process, physical protection barriers were implemented. Since plaster is a fine mineral powder, respiratory protection was necessary to avoid irritation of the mucous membranes or inhalation of dust particles.

During this stage, the molds were checked and the work area was organized. Nitrile gloves and a surgical mask were used to reduce exposure and avoid contamination of the mixture.

Img. 56 - Safety and biosecurity protocol before working with plaster

2. Master Geometry Prototyping

The process did not start directly with plaster. First, the master geometry was prepared through digital fabrication. FDM technology was used to create the negatives and structural supports that would define the silicone mold shape.

Img. 57 - Master geometry and mold support fabrication

3. Mixture Preparation

The “rain pouring” technique was applied. The plaster was not added all at once; instead, it was gradually sprinkled over the water to avoid trapped air and dry lumps.

1. Weighing: A digital scale was used for accurate measurement.
2. Resting: The plaster was allowed to absorb water by capillarity for approximately 30 seconds.
3. Mixing: Manual stirring was performed while keeping the tool near the bottom to reduce air incorporation.

Img. 58 - Plaster hydration and homogenization process

4. Casting Technique

Due to the hydrostatic pressure exerted by the liquid plaster on the flexible silicone mold walls, external support was required. The pouring process was carried out in a laminar and continuous way to improve filling and reduce bubbles.

5. Vibration, Setting and Thermal Control

After filling the mold, gentle mechanical tapping and vibration were applied to break surface tension and release microbubbles trapped in fine details.

Img. 59 - Vibration, setting and final plaster result

III. Laboratory Management Conclusions

• Technical cleaning: Containers were washed before final hardening to avoid solid residues in future samples.
• Quality: The final piece presented a smooth texture without visible surface porosity, validating the manual vibration method.
• Sustainability: Plaster waste was placed in dry waste containers, avoiding contamination of the Fab Lab drainage system.

6. Plasticine

1. Formula and Composition

Plasticine is a non-drying, oil- and wax-based modeling compound. It is manufactured by heating raw ingredients, homogenizing the mixture, cooling it, and extruding it into blocks.

Plasticine comes in different grades: professional, school or hobby, and industrial. The material softens near 40 °C and can become firmer when placed in a refrigerator.

2. General Uses

Plasticine is used in sculpture, animation, design, and prototyping. Its permanent pliability makes it useful wherever the material needs to be reworked repeatedly. In molding and casting, it functions mainly as an auxiliary mold-making material rather than a structural material.

3. Benefits for Molding and Casting

• Plasticine can be shaped as a figure before pouring liquid silicone or plaster.
• After the silicone cures and the plasticine is removed, the resulting void becomes a functional mold.
• For demolding, the plasticine is removed and the silicone surface can be cleaned with isopropyl alcohol before casting.

4. Limitations and Disadvantages

5. Plasticine in the Fab Academy Workflow

The workflow used was: design → define the quantity → mold making → add final material → demold.

Img. 60 - Plasticine mold preparation

Img. 61 - Adding casting material into the mold

Img. 62 - Product overview, demolding and final result

7. Eco Water Resin

Eco water resin was tested as an alternative casting material for decorative and experimental pieces. This material is useful because it has lower toxicity compared with conventional resins and can be handled more safely when basic protection measures are used.

During the test, the resin was prepared according to the working consistency required for pouring. The goal was to evaluate its flow, surface finish, demolding behavior, and final appearance inside the mold.

Safety and Handling

Although eco water resin is considered easier to handle than solvent-based resins, gloves were used to avoid direct skin contact. The workspace was kept clean and organized to prevent contamination of the mixture.

Casting and Result

The material flowed properly into the mold and allowed the reproduction of the main details of the design. The final result showed a uniform texture and a clean surface finish, making it suitable for decorative casting applications.

Img. 63 - Eco water resin preparation

Img. 64 - Eco water resin casting process

Img. 65 - Final eco water resin result

8. General-Purpose Polyester Resin

General-purpose polyester resin was tested as a rigid casting material. This material is commonly used to obtain resistant pieces, but it requires more careful handling due to its strong vapors and chemical reaction during curing.

Safety and Handling

During the preparation and pouring process, ventilation was necessary because polyester resin can release strong vapors. Gloves and a mask were used to reduce exposure and avoid direct contact with the skin.

The resin and catalyst were mixed carefully to obtain a homogeneous mixture. Correct proportions are important because too much catalyst can accelerate curing and generate excessive heat.

Casting and Final Result

After mixing, the resin was poured into the mold in a controlled way. The final piece showed good rigidity and resistance, with acceptable surface finish and detail reproduction.

Img. 66 - Polyester resin preparation and casting

Img. 67 - Final polyester resin result