The following are some of the items that should be specified when designing silicone parts.

Material Supplier and Material: Example: Wacker LR 3030/60
Durometer – (with value): Example: Shore A 60 Durometer
Color: Typical choices are clear, transparent, color match for tint, solid color. Include color dispersion manufacturer product number and percent color.
Part Identification: Laser marking, ink marking or mold engraving
Dimensional Tolerances: X.XXX” to +/- 0.005″ inch or +/- 0.127 mm.
Flash Tolerances: When the two halves of a mold come together there will be flash. It might not be visible without magnification. Typical flash tolerance is 0.005″ inch or 0.127 mm.
Mitre Tolerances: (Mold Miss Match) Alignment of the two mold halves if critical should be specified could affect wall tolerances. Typical mitre could be tolerance of +/- of 0.002″ inch or +/-0.051 mm.
Inspection: Criteria for rejectable product including air bubbles, contamination and dimensions.
Air Bubbles: In parts with a thickness ≤ 0.1″, no bubbles at 12″ normal visual. In parts with a thickness of > 0.1″, no bubbles > 0.025″ at 12″ in normal visual.
Contamination: Surface and part vary from no visible to not visible under value of magnification.
Post Baking: Ensures that all cross-linking is completed. If cross-linking is not completed possible part will produce volatiles as it completes cross-linking. Post baking time and temperature relates to max part cross-section.
Packaging: Should be double poly bagged and labeled. Many shipping options are available
Special Considerations: Tear strength and conductive properties, among others.

 

Prototyping Liquid Silicone Rubber Parts: 

It is strongly recommended to:
  • Determine the correct silicone material for the properties required.
  • Choose a durometer and mold parts in that durometer and higher and lower value—note different durometers and manufactures effect the shrink.
  • Check Fits.
  • Determine shrink values for part.
  • Complete functionality testing.
  • Reduce risk in building production tool.

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