Question: When molding medical silicone parts in the same mold will changing the durometer change the dimensions of the molded part?
Answer: The final part dimensions will depend on inherent shrink rate and processing conditions. Different materials molded in the same mold with the same shrink rate should produce the same size parts.
Durometer changes require different materials or additives which often changes the shrink rates. Higher durometer materials often have a greater raw viscosity and may achieve greater cavity pressures that can sometimes produce slightly larger parts compared to lower durometer materials. The difference has been shown to be less than 1% for a 40 durometer change without resetting the optimal processing conditions. Generally, changing durometer in the same series for most suppliers will not significantly affect the final dimensions but a first article is recommended. If you are considering trying multiple materials then I would recommend letting your molder know as early as possible.