Group Assignment:

  • Review the safety data sheets for each of your molding and casting materials
  • Make and compare test casts with each of them
  • Compare printing vs milling molds

Individual Assignment:

  • Design a mold around the process you'll be using, produce it with a smooth surface finish that does not show the production process, and use it to cast parts

Have you answered these questions?

  • Linked to the group assignment page and reflected on your individual page what you have learned ✅
  • Reviewed the safety data sheets for each of your molding and casting materials, then made and compared test casts with each of them ✅
  • Documented how you designed and created your 3D mold, including machine settings ✅
  • Ensured your mold has smooth surface finish, that does not show the production process (by postprocessing if necessary) ✅
  • Shown how you safely made your mold and cast the parts ✅
  • Described problems and how you fixed them ✅
  • Included your design files and ‘hero shot’ of the mold and the final object ✅
Group Assignment

  • Review the safety data sheets for each of your molding and casting materials
  • Make and compare test casts with each of them
  • Compare printing vs milling molds
Group assignment

Teamwork

For this project, I met with my colleague Evelyn via Meet to compare and show her the materials we were using to make the mold. In this case, I made a 3D print for the positive and negative molds. The progress of the group assignment can be found on the group page.


Reflections

  • This week, I delved into the use of gypsum (calcium sulfate hemihydrate), which is used to make the positive mold. The manufacturing process was easy to mix and mold, as it hardens quickly upon contact with water. It is also ideal for reproducing fine details in artisanal molds. The material I used for the casting process was wax, used as a moldable material within the plaster mold. It melts at a low temperature (~60°C) and is poured onto the mold. When cooled, it preserves the details well. It can be easily removed for processes such as lost-wax casting. The combination of gypsum and wax allows for the manufacture of molds with high precision and ease of replication. I also learned about the thermal behavior of wax and the setting of plaster, thus reinforcing the concepts of casting, modeling, and material safety.
  • On the other hand, having used the combination of 3D printing and silicone molding, I found it to be a surprising technique, as it allows for the creation of highly precise, custom molds. It's a versatile technique, useful for both prototyping and artisanal production, but it also requires careful mixing and curing of the silicone to ensure a clean, bubble-free result.

Individual Assignment


  • Design a mold around the process you'll be using, produce it with a smooth surface finish that does not show the production process, and use it to cast parts

To make my mold, which in this case will be a replica of the Fab Academy logo, I chose to use plaster as the base material and a CNC machining process based on an ArtCAM design. This digital fabrication process includes computer-aided design, CNC machining, and casting.

1.-3D logo design

I began designing the logo in AutoCAD software, as I wanted to work with an existing design that clearly represented Fab Academy's identity. I used this base to draw the main contours of the logo in 2D, which were then exported for 3D modeling in ArtCAM. This initial stage was key to accurately defining the shapes and proportions that would be replicated in the final mold.

2.-Import into ArtCAM

The DXF file was imported into ArtCAM, and a positive relief 3D model was generated from the vectors, where the logo stands out from the surface of the block.

3.-Creating 3D relief and defining trajectories

The relief depth was adjusted, and modeling tools were applied to give volume to the design. The toolpaths were then defined, starting with roughing to quickly remove material, followed by finishing to achieve greater detail and a smooth surface.

Toolpath Configuration in ArtCAM

Screenshot of the ArtCAM software during the setup of the toolpath for machining the plaster block. The interface shows the selection of the cutting tool (End Mill 3mm), safety height, ramp movement, and material thickness (12mm). Tool libraries such as “Roughing and 2D Finishing” and “3D Finishing” were also reviewed for optimal results.

G-code generation

After completing the setup in the program, the next step is to export the design in G-code (millimeter) format, a crucial step to ensure the machine can accurately interpret the machining instructions. This preparation stage is essential, as it ensures effective communication between the software and the machine, allowing the work process to begin smoothly.


Preparation of the plaster block

Before machining, I prepared the plaster block by mixing gypsum powder with water in the appropriate proportions until I obtained a homogeneous, lump-free mixture. I then poured the mixture into a rectangular mold, taking care to eliminate air bubbles, and let it dry completely for several hours until it hardened. This solid, flat block served as the base for machining the master mold using the CNC milling machine.

Components shown: plaster powder, water, mixing bowl, spatula, container mold, and level surface.

The plaster block is allowed to rest on a level surface for at least 24 hours to ensure complete drying before machining.


Molde terminado

master plaster block ready for machining



Machining in plaster block

  • The plaster block is fixed to the CNC bed.
  • The G-code generated in ArtCAM is executed.
  • The process is carried out in two phases (roughing and finishing) until the master mold is obtained.


CNC Machining Demonstration of a Plaster Mold

The video included in this section shows the complete CNC machining process of the plaster mold. You can see how the machine executes the toolpaths previously generated in ArtCAM, beginning with roughing, where material is removed in large volumes, and continuing with finishing, which profiles and details the positive relief logo. This visual record allows a clearer understanding of the system's operation and the final mold result.


we proceed to clean the mold

Our positive part mold is ready


Negative Mold Preparation

For this process, For this process, I used paraffin wax as a negative mold, as it is a solid, white or transparent substance derived from petroleum. It melts easily at temperatures between 46 and 68°C, making it ideal for modeling, candlemaking, and casting. It is easy to demold, flexible, and reusable. Below are the steps I followed to fill the plaster mold with melted wax.

the melted wax was applied to the plaster

The wax is left to cool for an average of 2 hours, until it hardens.


Molde de cera

Once hardened, the wax can be removed from the plaster mold.


Molde terminado

Ready, our mold is perfect!

Workflow for Silicone Molding with 3D Printed Molds

1. Mold Design

The piece, in this case a connecting rod type arm, was obtained by downloading a 3D model from an online source. The model was then reviewed and prepared for fabrication, including any necessary adjustments before proceeding with 3D printing or CNC machining.

2.- 3D printing of the mold

Then import the 3D design into Bambulab Studio. The mold was 3D printed using PLA filament to obtain the exact cavities that will shape the poured silicone. After cooling, the parts were carefully removed from the print bed. Light cleaning or sanding was performed, if necessary, to remove any burrs or imperfections.

Molde terminado

Preparation for printing

The printing parameters were configured as: material type, fill, resolution and supports.


The video shows the mold printing process


3.-Mold Preparation

Both halves of the mold were cleaned, and a release agent was then applied to facilitate removal of the cured piece.

  • The two mold halves were assembled and secured using rubber bands or screws.
  • A mold release agent was applied to the internal cavity to ensure easy removal of the cured piece.
  • Liquid silicone was prepared and poured into the mold through the top filling channel.
  • The mold was left to cure for several hours, depending on the type of silicone used.
Molde terminado


Did you have any problems?

While creating the plaster mold, one of the main issues I encountered was the drying time. When I poured the plaster mixture into the mold, it took longer than expected to fully harden. This raised concerns about whether the mixture was properly prepared or if factors like room temperature or water ratio were affecting the process.

Despite following the correct water-to-plaster ratio, the setting was slower than expected, likely due to low ambient temperature and excess water. After allowing more curing time, the mold hardened properly, and the casting was completed with the desired finish.

Conclusions

In conclusion, this week has been quite productive. I enjoyed making both positive and negative molds, and also being able to use and test different materials. In my case, I made a mold combining plaster and wax as part of an artisanal casting process. First, a mixture of plaster and water was prepared and poured over a model to create a positive mold. This mold was then used to create my design. I used ArtCAM to design my plaster mold and then machine it on a CNC. Once hardened, molten wax was applied to the plaster mold, forming a detailed figure with the desired shape. After the wax cooled and solidified, a solid replica was obtained that can be used as a model for techniques such as lost-wax casting. This procedure allows for the manufacture of pieces with a high level of detail and is ideal for low-volume artistic or technical processes.



Link to files used this week

1. CNC FAB LOGO.cnc
2. Super Jarv.stl