03.04.14 3 Ways Silicone is Keeping you Safe
Specifying Liquid Silicone Medical Rubber Parts
The following are some of the specification items. How demanding the specification determines the cost of the tooling and parts.
Material Supplier and Material: Example: Wacker 303060
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 or ink marking.
Dimensional Tolerances: Typical from +/- of .002inch or +/- 0.051 mm to +/- .005 inch or +/- 0.127 mm.
Note: in specifying tolerance of a silicone rubber part method of measuring the part tolerances should be considered.
Flash Tolerances: When the two halves of a mold come together there will be flash. It might not be visible without magnification. Typical flash tolerances for parts are projection down to 0.002inches / 0.127 mm and flash thickness of 0.003 inches to 0.0076 mm and up to what can be tolerated.
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 .002 inch or +/-0.051 mm.
Air Bubbles: Can effect part performance and vary from no visible to not visible under value of magnification.
Contamination: Surface and part vary from no visible to not visible under value of magnification.
Post Baking: Is important for medical application so 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 each bag sealed and labeled.
Validation: Should include material certification and your requirements.
Prototyping Liquid Silicone Medical Rubber Parts:
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.
- Reduce risk in building production tool.