Question: How small of a micro feature can be molded on a medical silicone part?

Answer: Silicone feature size is limited by the geometry, tooling, and process. Silicone will replicate surface finish features with less than 0.0005 inches in size. Features larger than 0.005 inch can often be manufactured with some considerations. Part geometries such as undercuts, large L/D pins and bosses can cause challenges in demolding, maintaining tool integrity, and forming full features without bubbles.

Shrink in micro parts is often not as much of an issue compared to larger parts since 2% on 0.005 inches is pretty small compared to 2% on a 3” part. Other issues may be magnified such as the difficulty in part removal from a mold, core deflection, and mismatch. Large undercuts in parts made with a high durometer and low tear strength material tend to tear more easily during removal. Large L/D parts holes (made by pins) may deflect during molding causing tool damage and/or features to be irregular. For perspective take a caliper or micrometer and set it to 0.005 inches. Simple features that are smaller than 0.005 inches may be possible but they are inherently difficult.