Silicone Overmolding on Metal: Precision Encapsulation of Metal Inserts with LSR

Overview of Silicone Overmolding on Metal

Silicone overmolding on metal is an advanced composite manufacturing technology that encapsulates metal inserts (stainless steel, aluminum alloy, copper alloy, titanium alloy, etc.) with Liquid Silicone Rubber (LSR) through precision injection molding. This technology combines the high strength, rigidity, thermal conductivity, and precision machinability of metals with the elastic sealing, vibration damping, insulation, and ergonomic comfort of LSR. It finds extensive applications in automotive manufacturing, aerospace, medical devices, electronics, and sanitary hardware.

2. Metal-LSR Bonding Principles

Reliable metal-LSR bonding is achieved through: Chemical bonding using sulfur-containing or silane-functionalized adhesion promoters that form chemical bridges between the metal surface and LSR; Mechanical locking through preset grooves, knurling, perforations, or undercuts on metal inserts; Surface micro-treatment including sandblasting (Ra 1-5um), chemical etching, anodizing for aluminum, and laser texturing for nano-micro composite structures.

3. Mold Design and Process Control

Key mold design elements: precise insert positioning with elastic locating pins, slide clamping, or vacuum adsorption; thermal isolation design to manage the high thermal conductivity of metal inserts; sealing design to prevent LSR overflow. Process parameters: mold temperature 150-190C, injection speed 25-45mm/s, holding pressure 60-130bar, curing time 10-20 seconds per mm of wall thickness.

4. Applications

Automotive: sensor encapsulation, connector seals, charging gun handle overmolding. Aerospace: aviation plug seals, instrument panel cushions. Medical devices: surgical instrument grips, dental tool overmolding. Electronics: power connector seals, cooling fan vibration pads. Sanitary hardware: shower head grips, faucet handle soft-touch overmolding.