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11. Molding and casting

This week I worked on Molding and Casting processes followed by safety guidance in the safety data sheets of each material.

group assignment: - review the safety data sheets for each of your molding and casting materials, - then make and compare test casts with each of them

Materials used and safety data sheets(SDS)

We used below materials. For safety work, we read through SDS and learned personal protections beforehand as below.

1 2

  • machinable wax : Ferris File-A-Wax : blue

    • SDS
      • Section 8 Exposure Controls/Personal Protection
        • Provide exhaust ventilation
        • Eye/face protection, Use a full-face shield and safety glasses
        • Hand protection, use disposable nitrile, neoprene or butyl rubber gloves
        • Body protection, Prevent skin contact
        • Safety Stations, washing facilities
        • General Hygienic Practices, Avoid breathing dust, vapor or mist
  • Silicone rubber : Mold Star 31T for molding

    • SDS

      • Section 8 - Exposure Controls / Personal Protection
        • Hand protection, Wear any liquid-tight gloves such as butyl rubber, neoprene or PVC.
        • Eye Protection, Safety glasses with side shields per OSHA eye- and face-protection regulations 29 CFR 1910.
        • Other Protective Clothing/Equipment, Additional protective clothing or equipment is not normally required.
        • Comments, Never eat, drink, or smoke in work areas.
    • Mix ratio by Volume or weight : 1A:1B

    • Pot life: 5 min & cure time: 23 min
    • color: Translucent
  • Urethanes resin : Smooth-cast 320 for casting

    • SDS
    • Section 8 - Exposure Controls / Personal Protection, safety contents the same as Mold Star 31T

    • Mix ratio by Volume: 1A:1B

    • Mix ratio by Weight: 100A:90B
    • pot life: 3 min & cure time: 10 min
    • color: Off-white
  • Color Tints for Urethane : SO-Strong™ liquid urethane colorants

    • SDS
    • Section 8 - Exposure Controls / Personal Protection, safety contents the same as Mold Star 31T

    • Recommended loading range is .01% to 3% of total system weight

    • try to put a few drops

We put on a safety glasses, disposable nitrile gloves and wore long sleeves.

Test materials of molding and casting

  • We used MDF patterns for this testing.

  • Prepare molding materials and casting materials. Each material needs similar preparation processes.

  • Shake well bottles.(Smooth-cast 320)
  • Check mix ratio, Part A vs. Part B
  • Measure weight of Part A and Part B respectively
  • Mix Part A and Part B and stir well. Once get mixed, the chemical reaction starts, which means Pot time starts.
  • Pouring mixed material into a model.
  • Cure time starts. Waiting for completion.

Testing Results

Due to the condition (weather was not good and a bit cold in the room), it needed to take longer time to set or harden.

  • molding

We thought that silicon would be soaked into MDF and we might no be able to take off it from MDF pattern. Contrary to that, we could take the silicon from the MDF. The mold was very soft, like a jelly.

  • casting

We put some silicon splay to a MDF before pouring casting material for removing the MDF from hardened cast. However it didn’t work and we was not able to take off the cast. That was hard.

Last update: April 20, 2021