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1 Molding and Casting: Fabricating FabLab Badge Coins

1.1 Introduction​

This task is an individual assignment for FabAcademy, aiming to create a FabLab logo coin through digital modeling, 3D printing, silicone mold casting, and resin/metal casting processes. The project demonstrates key manufacturing steps while emphasizing surface finish quality and rational mold design.

1.2. Mold Design Using FreeCAD​

1.2.1 Design Concept​

The coin features FabLab's classic logo as a relief pattern, with dimensions of 30mm diameter and 4mm thickness. The minimalist design ensures easy demolding while maintaining visual impact.

1.2.2 Modeling Process​

  1. Create a 40×40mm square sketch in FreeCAD
  2. Generate a 3D box using padding and shell operations

  3. Sketch a Ø30mm circle as the coin boundary
  4. Apply 2mm extrusion to create the base structure
  5. Import FabLab logo in SVG format and convert to 3D path



  6. Adjust logo dimensions through scaling and extrusion

  7. Create relief effect using Pocket/Pad tools

1.2.3 STL Export​

The complete mold with integrated sprue was exported as an STL file for 3D printing.

1.3. 3D Printing the Master Model​

1.3.1 Printing Parameters​

• Printer: Bambu Lab A1 mini

• Layer height: 0.2mm

• Infill density: 100%

• Material: Yellow PLA

1.3.2 Post-processing​

The surface was sanded with fine grit sandpaper to eliminate layer lines. Critical details were cleaned with a brush and coated with glossy spray for enhanced finish.

1.4. Silicone Mold Fabrication​

1.4.1 Silicone Preparation​

RTV-2 silicone (10:1 mixing ratio) was degassed and poured into the containment frame.

1.4.2 Curing Process​

12-hour room temperature curing with vibration isolation.

1.4.3 Demolding​

The master model was carefully removed after complete curing. The mold showed intact patterns without significant air bubbles.

1.5. Resin Casting (Epoxy)​

1.5.1 Material Preparation​

Transparent epoxy resin (1:1 volume ratio) was mixed thoroughly for 1 minute.

1.5.2 Mold Filling​

The mixture was poured through the sprue using controlled flow.

1.5.3 Curing​

24-hour ambient curing on a leveled surface.

1.5.4 Final Result​

The resin coin retained design details though slight surface imperfections from 3D printing remained visible.

6. Tin Alloy Casting​

1.6.1 Metal Preparation​

Tin was melted in a 100°C water bath with continuous stirring.

1.6.2 Injection Process​

Molten tin was injected into the mold using a syringe.

1.6.3 Rapid Cooling​

5-minute quenching in cold water ensured complete solidification.

1.6.4 Final Product​

The metal casting replicated the design accurately, with surface texture limitations inherited from the 3D printed master.

1.7 Resources​