Casting in silicone

Guidelines

Mixing procedure

  1. Have a calculator, a disposable plastic mixing container, a disposable plastic fork/spoon and some cleaning paper available
  2. Put the empty mixing container on the scale
  3. Press the tare button to reset the scale
  4. Pour in the silicone part A, and leave some room for part B (or Catalyst T21 if Elatosil4511 is used)
  5. Type in the weight of the silicone in to the calculator and calculate the weight of part B (or T21)
  6. Press the tare button
  7. Pour in part B (or T21) until the weight is right
  8. Mix it well
  9. Pour it in the casting mold

Types of silicone

(Elatosil4511 is now available in the lab)

  • Wacker Elastosil M 4511
    • Extremely high elongation and flexibility, not very strong
    • Very low Shore A hardness (approx. 12)
    • Curing time - 10h (NOT dependent on temp)
    • Mixing ratio (by weight) with Wacker Catalyst T21: 5%
  • Wacker Elastosil RT 625A (M4601)
    • Sensitive chemistry, not suited for Objet mold
    • High elongation, outstanding tensile strength
    • Excellent tear strength
    • Translucent and colorless
    • Can be pigmented with 1 - 4 % ELASTOSIL┬« Pigment Pastes FL
    • Low hardness (Shore A approx. 25)
    • Mixing ratio (by weight) A/B 9 : 1
    • Curing time - 12h (dependent on temp)
  • Wacker Elastosil RT 601 A/B
    • Sensitive chemistry, not suited for Objet mold
    • Transparent, colorless
    • Shore A hardness (approx. 45)
    • Curing time - 24h (dependent on temp)
    • Mixing ratio (by weight) A/B 9 : 1

SolidWorks mold making examples

A simple form:

A "true shape" form: (CNTR-A selects all faces)