【Technical Challenges】
High-frequency vehicle vibrations often caused the manually installed O-ring to slip, leading to leakage and short circuits. Thus, the client chose to implement plastic-to-silicone overmolding. The challenge was that the bonding interface was very narrow, requiring tight adhesion without delamination under high injection pressures.
【Jun-Hsiang's Solutions】
We injected the PA66 frame in the first station, and then a robotic arm precisely located the frame into the second LSR injection mold cavity, holding positioning tolerance within ±0.01mm to prevent flash. We tested and selected a specialty self-adhesive LSR that bonds chemically with PA66, eliminating the primer step. We designed custom mold cavity venting and gating configurations to ensure optimal molecular cross-linking at the polymer-silicone interface, maintaining shear strengths >4.5 MPa after thermal cycling.
【Mass Production Benefits】
Successfully passed the automotive OEM's IP69K waterproof standard and vibration tests. This eliminated post-mold manual assembly costs and increased sealing reliability to 100%.
▲ LSR liquid silicone double-shot overmolded directly onto hard PA66 plastic automotive connector plug