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8. Moulding and casting

Group Assignment

  1. Team Formation: Our class was divided into smaller teams of two members.

  2. Research Objective: We researched different casting materials, focusing on their properties, safety guidelines, and best practices for use.

  3. Material Focus: My group focused on Graffiti Resin Multi Use.

  4. Outcome: We assessed and compared test casts of the selected materials. Visit our website for more details.

Individual Assignment

  1. Objective: Create a 3D design that meets specific design specifications and produce a final object.

  2. Milling Process: Utilize the Roland SRM-20 Compact Milling Machine to carve a positive mold from a rectangular wax block.

  3. Molding: Pour a material into the wax mold to create a negative mold.

  4. Final Casting: Cast the negative mold with a different material to produce the final object.

What is Moulding?

  • Moulding (or mouldmaking) is the process of creating a cavity or form that holds a negative or reverse impression of an original model.
  • Molds can be made from:
  • Rigid materials like plaster or plastic resin.
  • Flexible materials like rubber (more commonly used).
  • The choice of material depends on:
  • The type of model being used.
  • The material for the casting.
  • The presence of undercuts in the design.

What is Casting?

  • Casting is a positive manufacturing process in which a liquid material is poured into a mold with a hollow cavity of the desired shape.
  • After pouring, the liquid material solidifies into a solid part called a casting.
  • The casting is then removed or ejected from the mold.
  • Common casting materials include:
  • Metals.
  • Cold-setting substances such as epoxy, concrete, plaster, and clay.
  • These materials solidify through chemical reactions or cooling.

What is a Milling Machine?

A milling machine is a tool used to remove material from a workpiece by rotating a cutting tool (cutter) and feeding it into the material. Milling machines can be vertical or horizontal and are primarily used to machine flat or irregularly shaped surfaces. They are versatile and can also be used for tasks such as drilling, boring, and cutting gears, threads, and slots.

The milling machine operates around a circular cutting tool with multiple cutting edges arranged symmetrically on its axis. The workpiece is typically secured in a vise or similar device, which is then clamped to a movable table. This table can move in three perpendicular directions, allowing precise control over the cutting process.

In the FabLab, we use the Roland SRM-20 milling machine.

Group Assignment

In this week’s group assignment, we were divided into pairs and tasked with reviewing safety sheets for four different moulding and casting materials. Our goal was to create test casts with each material and compare the final results. You can review our findings through the following group link the material I worked on was material 1 the Graffiti Resin Multi Use.

My Experience with Resin

For this assignment, I was assigned to research and use resin as the casting material. I learned several important things during this process:

  1. To create a cast using resin, you must mix the resin and hardener in a 10:6 ratio respectively.
  2. Resin requires 8-12 hours to cure and has a work time of 45 minutes at room temperature.
  3. To ensure the resin has fully hardened, it is recommended to wait for 24 hours before handling.
  4. It is important to wear gloves and an apron to protect your skin and clothing from resin.
  5. If the end product is intended to be solid, you must use a flexible mold. Conversely, if the end product is to be flexible, a solid mold should be used. For example, when making an object from resin, the mold should ideally be made from silicone.

Individual Assignment

For our individual assignment, we were tasked with creating a 3D design that meets specific design specifications:

  • Design dimensions: 50x50x15mm
  • Maximum extrusion height: 15mm
  • Minimum gap between lines/details: 1mm (to allow the machine to cut effectively)

The steps involved in the assignment were as follows:

  1. Design: Create a 3D design according to the specified dimensions.
  2. Milling: Use the Roland SRM-20 Compact Milling Machine to carve the design from a rectangular wax block, creating the positive mold.
  3. Moulding: Pour material into the wax mold to create the negative mold.
  4. Casting: Cast the negative mold using a different material to produce the final object.

↪ 3D Design Process

Since I was the last to use the milling machine, I had the entire block of modeling wax to myself. This allowed me the flexibility to adjust the design dimensions beyond the original 50mm x 50mm limit. I chose to increase the dimensions to 60mm x 60mm and designed two different designs to be printed. The steps for both designs are as follows:

Design 01: Ice Cream Cone

  1. Download and Convert the Images
    I started by downloading the images I wanted to use as the bases for my designs. I then used an online converter to convert the JPG images into DXF format, making them compatible for use in Fusion 360.

  1. Insert the DXF into Fusion 360 I opened Fusion 360 and inserted the DXF file by selecting the “Insert” button and choosing “Insert DXF.”

  1. Cleaning up the Design I refined the design by removing unnecessary lines, adjusting the scale, and ensuring that the gaps were at least 1mm.

  1. Extruding: Select the design area and extrude it to various depths.

Design 02: keychain

  1. Download and Convert the Images
    I started by downloading the images I wanted to use as the bases for my designs. I then used an online converter to convert the JPG images into DXF format, making them compatible for use in Fusion 360.

  1. Insert the DXF into Fusion 360 I opened Fusion 360 and inserted the DXF file by selecting the “Insert” button and choosing “Insert DXF.”

  1. Cleaning up the Designs I refined the design by removing unnecessary lines, adjusting the scale, and ensuring that the gaps were at least 1mm.

Additionally, I modified the two inserted DXF files to create the desired final design.

  1. Extruding: Select the design area and extrude it to to various depths.

  1. Chamfering: Apply a chamfer to smooth out the edges.

  1. Hanger Design:
  2. Create a new sketch for the circular hanger.
  3. Use the Move tool to position the circle.

↪ Positive Mold Creation

  1. Combining Designs: Merge my design with my partner’s into a single .stl file using TinkerCAD.
  2. File Import: Import the combined file into SRP Player software to control the Roland SRM-20 Milling Machine.
  3. Machine Setup:
  4. Ensure the design meets the machine’s constraints (minimum detail of 1mm and maximum design height of 15mm).
  5. Apply a sticker to secure the wax block in place.
  6. Tool Path Creation:
  7. Select the appropriate milling type and click “Create Tool Path” to preview the cutting process.
  8. Adjust the settings if needed, based on the preview.
  9. Surfacing:
  10. In the software, select Surfacing and adjust the X/Y axis to set the cutting origin.
  11. Set the Z origin and replace the spindle tool with a 1/8 SE 4FL BN long Altin bit for surfacing.
  12. Click Start Surfacing to begin.
  13. Final Cutting:
  14. Once surfacing is complete, clean the workpiece and replace the spindle tool with a 3/32 inch BN bit.
  15. Click Start Cutting to carve the design.
  16. Milling Completion: After the cutting is done, remove the final positive mold from the milling machine.

↪ Negative Mold Creation

  1. Silicone Preparation:
  2. Fill the positive mold with water and measure its volume to determine the amount of silicone needed.
  3. Mix the silicone components A and B in the proper ratio.
  4. Pouring the Silicone:
  5. Carefully pour the silicone mixture into the wax mold, ensuring it fills all gaps and covers the surface.
  6. Curing: Allow the silicone to fully cure.
  7. Removing the Negative Mold: After curing, remove the negative mold from the wax block. The flexibility of the silicone makes it easy to extract the final cast.

↪ Final Casting

  1. Material Selection: Choose Graffiti Resin Multi-Use for the final casting, the same material used in the group assignment.
  2. Mixing:
  3. Mix the resin with the hardener according to the specified ratio.
  4. Add a small amount of color to the mixture for a unique effect.
  5. Pouring the Resin: Carefully pour the resin mixture into the silicone mold.
  6. Curing: Allow the resin to cure for 24 hours.
  7. Removing the Final Cast: After curing, remove the final cast from the mold, completing the process.
Last update: January 27, 2025