Silicone Transfer Molding
Silicone transfer molding is a manufacturing process used to shape silicone rubber into various products. It combines elements of injection molding and compression molding, using a pre-measured amount of uncured silicone placed in a pot, which is then forced into a heated mold cavity under pressure. This process is particularly useful for creating complex parts with tight tolerances and is considered a cost-effective method for medium-volume production.
Steps of Silicone Transfer Molding
Material Preparation
Solid silicone rubber (HCR) is pre-weighed, cut, and prepared into blanks of appropriate size and weight.
Loading the Pot
The silicone blank is placed into a “transfer pot” (a chamber located above the mold cavities).
Mold Closing
The mold is closed tightly, and the transfer ram (plunger) is positioned above the transfer pot.
Material Transfer
Under heat and pressure, the plunger forces the silicone from the pot through sprues and runners into the mold cavities.
Curing
The silicone cures inside the cavities at elevated temperature, taking the exact shape of the product design.
Mold Opening
Once cured, the mold is opened and the finished silicone parts are removed. Excess flash or runner material may be trimmed if necessary.
Silicone Transfer Molding vs Silicone Injection Molding
Silicone transfer molding uses solid silicone pressed from a transfer pot into mold cavities, making it suitable for medium-volume production, insert molding, and moderately complex parts. Silicone injection molding uses liquid silicone injected directly into the mold, offering faster cycles, higher precision, and excellent consistency, ideal for large-volume, complex, and high-accuracy products such as medical devices and baby care items.
Silicone Transfer Molding vs Silicone Compression Molding
Silicone compression molding places solid silicone directly into the mold cavity and cures it under heat and pressure. It has a simpler process and lower mold cost, making it ideal for large, thick-walled, or low-volume parts such as gaskets, seals, and dampers. Silicone transfer molding, on the other hand, uses a plunger to press silicone from a transfer pot into the cavities, allowing more uniform filling and better dimensional accuracy. It is well-suited for insert molding and moderately complex parts, though it requires more complex molds and higher cost compared to compression molding.
Key Features of Silicone Transfer Molding
Silicone transfer molding offers higher dimensional accuracy, uniform material flow, and strong compatibility with insert molding, while keeping mold costs moderate. These features make it especially suitable for producing seals, gaskets, connectors, and other silicone parts that require reliable precision and embedded components.
