Question: Are micro medical silicone parts easier to mold than medical thermal plastic parts?
Answer: The difficulty of molding micro parts is driven by challenges in tooling, processing, demolding, and handling. Silicone and plastic have a wide range of advantages and disadvantages and should be chosen for properties that best serves your application. The following is a few micro molding points to consider that may not be addressed in your standard data sheets.
Micro tooling for both plastic and silicone parts require small features and the mismatch between the plates is very accurate. For example, a 0.003” mismatch or tolerance in a 0.500” part represents a 0.6% difference compared to a 20% difference for 0.015” part. Most silicones have excellent formation of micro features and surface finishes even as small as or smaller than 0.0001”. The pressures and melt viscosity for plastics tend to be very high compared to silicone and may cause greater core or feature deflection compared to silicone but silicone may flash more easily.
Medical molding does run into some extra challenges because materials are more limited. Also releases and additives tend to be restricted in many medical applications so release and processing may require alternative approaches. The handling processes may be challenged by little space or no options for knock out pins or push plates but brushes, mechanical, or hand pull may be an option depending on the size and scale of the molding. Many times, molding a micro part onto a large runner or with a puddle can ease handling issues by providing a handle and address parts approaching the minimum shot size of molding equipment.