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.