Mold Making and Casting

Resources

Local Services

• Reynolds, Silicone and More, Retail:
  • Reynolds is national, with a retail store in Tempe, just North of the 202, off McClintock
  • https://www.reynoldsam.com/location/phoenix/

Tutorials

• British Man makes Silicone Molds for Pewter Models
  • 1) Mold Making: https://www.youtube.com/watch?v=h_QD1ff3wJk
  • 2) Casting: https://www.youtube.com/watch?v=7atJo0iA5W4
• Ex Disney Guy Casting Urethane Resin in Silicone
  • Playlist: https://www.youtube.com/playlist?list=PLIy8UDigJ_ynP97e0sMtbKmRuBrCff1Ql
  • Same Guy, Doing Low-Temp Metal: https://www.youtube.com/watch?v=wRU-IlIBPKY
• Casting a mechanical part in low-temperature bismuth-tin:
  • https://www.youtube.com/watch?v=qqqVS_YyWzo
• Lost Styrofoam
  • https://www.youtube.com/watch?v=vvh0twfgzLM
• Electroplating
  • https://www.youtube.com/watch?v=G-PtnwtOR24
  • I haven't tried this on bismuth tin yet.
• Desktop Injection Molder
  • https://www.youtube.com/watch?v=HoSVPHVESiE
• Resin Printing for Beginners
  • https://www.youtube.com/watch?v=UU6tWhV010M

Materials

• High Temperature 3D Printer Resin (for directly printing molds)
  • 250C, $2.15/oz: https://www.amazon.com/dp/B08V8T9NZL
  • 180C, $1.15/oz: https://www.amazon.com/dp/B08GJTGPYQ
• Eutectic Bismuth Tin
  • 58% Bi 42% Sn by weight
  • 138C melting point (280F)
  • 150C / 300F casting
  • Tin (Sn) 232C / 450F
  • Bismuth (Bi) 272C / 521F
  • Bi-Sn tensile strength: 55 MPa, Mild Steel (the cheap stuff): 400-550 MPa, 6061 Aluminum (the cheap stuff): 290 MPa, Tin 220, 3003 aluminum: 186, HDPE plastic 20 - 30, epoxy resin 26 - 85
  • Bi-Sn Density: ~8,500 kg/cm3, Mild Steel: 7,850 kg/cm3
  • A little denser than steel and a lot weaker than most metal.
  • Roughly as strong as epoxy resin (which can be cast in the same molds and is less dense).
• Heat Stable Silicone Mold Release
  • https://www.amazon.com/dp/B0018NBE8A
• Cheaper Tin and Bismuth (free shipping over $150):
  • https://www.rotometals.com/tin-cut-wire-pieces-99-9-pure-1-pound-made-in-usa/

Equipment

• Elegoo Mars 1
  • 4.7x2.6x6.1 = 120x68x155

Examples

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Creating Magnet Models

Basic Process

Mars 1 Bed Size: 68mm x 120mm

1. Create a clip art style image in Inkscape.
   • I use layers as my checkpoint stack, so I can recover to a previous checkpoint if needed.
   • Draw outlines only.
   • Use Bezier curves and straight lines.
   • Minimize the number of control handles to get fair curves.
   • File > Document Properties > Page > Custom Size: printer bed size or smaller (portrait or landscape).
   • Set the line width to 0.5mm.
   • Set line ends to rounded.
   • Keep inset regions at least 2mm wide.
   • Clean up everything as much as possible.
     • Check where endpoints meet other curves. Close gaps, pull in dangling ends.
   • Path > Stroke to Path
   • Select 1 path, then all the rest, then Path -> Union
   • Save as SVG
2. Import Into Blender
3. Set Scene > Units > Length to Centimeters or Millimeters
4. Scale the image to smaller than printer bed size (portrait or landscape).
5. Convert to Mesh