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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Magnet Models

Models

Shown with example paint schemes.

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Suggestions

• Cactus
• HSL meatball on AZ shape (with rays and blue?)
• Flower
• Mandala
• Dinosaur
• Earth
• Darwin Fish

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 Millimeters
4. Scale the image to smaller than printer bed size (portrait or landscape).
5. Convert to Mesh
   • If your design has a lot of lines parallel to the X axis, rotate it 45 degrees before converting. Convert to Mesh has trouble with lines aligned with the X axis.
6. Edit Mode > Vertices > Select All > x > Limited Dissolve > 1 degree
7. Clean Up Excessive Vertices
   • Loop Select, Remove Critical Vertices, Dissolve by Distance 0.1m or 0.2m
   • Pay Special Attention to Inside Corner Vertices
   • Merge vertices at center or dissolve vertices as needed.
8. Loop Select and Create Face
9. Inset by 0.5mm
10. Clean Up Corners
11. Select Inset Face
12. Select More
13. Unselect Inset Face
14. Triangulate Faces
15. Select Inset Face
16. g > z > 0.7 > - (move face 0.7mm in the negative z direction)