Structural Design of Double-color Overmolding Synchronous Molds

Double-color synchronous overmolding molds are widely used in smart home and electronic product parts, which can complete hard plastic base and soft rubber integrated molding in one clamping cycle. Compared with traditional secondary molding molds, synchronous molding has higher precision, fewer assembly lines and more stable appearance quality. Reasonable structural design is the core to ensure balanced filling, reliable sealing and stable mass production.

1. Mold Base and Rotation Positioning Structure Design

Special reinforced double-color mold base is adopted to bear dual injection high pressure and avoid template deformation. The internal double-station rotating disc structure realizes synchronous hard rubber molding and soft rubber overmolding. The hydraulic rotating mechanism is matched with high-precision conical positioning pins to control the rotation positioning accuracy within 0.01mm, effectively preventing overmolding offset and uneven rubber thickness. Large-area products are equipped with auxiliary supporting top blocks to resist injection pressure deformation. Independent temperature control water circuits are configured for hard and soft rubber cavities to adapt to different molding temperatures.

2. Double Independent Gating System Balance Design

Two completely independent flow channel systems are adopted to thoroughly avoid material mixing. The hard rubber side adopts hot runner and hidden submarine gates to ensure perfect appearance. The soft rubber side adopts fine point gates arranged on the inner non-appearance surface to reduce gate residue. The flow channel length and cross-section are optimized through mold flow analysis to ensure synchronous filling speed and balanced injection pressure of the two materials. A closed rubber retaining step is set at the junction to prevent high-pressure overflow and flash.

3. Parting Surface Sealing and Anti-overflow Structure Design

The junction of hard and soft rubber adopts stepped embedded structure to increase bonding area and improve adhesion strength, while forming physical anti-overflow limit. The soft rubber molding area is inlaid with high-hardness wear-resistant sealing inserts to prevent long-term pressure collapse. The exhaust groove depth of the parting surface is precisely controlled to ensure smooth exhaust without glue leakage. Independent exhaust inserts are added at weld lines and filling terminals to eliminate trapped air, scorching and incomplete bonding defects. Waterproof products adopt tooth-shaped occlusal structure to enhance sealing performance.

4. Zoned Temperature Control, Ejection and Exhaust System Design

The hard rubber cavity adopts dense water channels for rapid cooling and shaping to control shrinkage and deformation. The soft rubber area adopts spaced slow cooling water channels to prolong melt fitting time and improve bonding firmness. Partitioned independent ejection structure is used to avoid tearing soft rubber edges during demolding. The fit clearance of thimble parts is precisely matched to prevent soft rubber penetration and flash. A three-dimensional exhaust system is formed at flow channels, cavities and bonding lines to ensure smooth synchronous filling.

5. Mass Production Wear-resistant Reinforcement Design

Key sealing positions, positioning pins and nozzle parts are made of high-polish stainless steel for wear resistance and rust prevention. The main mold inserts adopt pre-hardened steel to ensure structural stability. All vulnerable parts are designed with independent insert structures for convenient replacement and low maintenance cost. The rotating friction surface is provided with lubricating oil grooves to ensure smooth rotation without jamming. The mold base is equipped with pressure balance blocks to balance dual injection pressure and prolong mold service life.