How to Select Two-Color Injection Molds
2025-12-19 10:29:22
Two-Color Injection Molds
Two-color injection molding is widely applied in automotive interiors, 3C products and medical devices for its one-shot molding benefits. Mold selection directly determines product precision, production efficiency and overall costs, requiring comprehensive consideration of product features, material properties and production demands to align with both current needs and industry tech trends.
Product Structure and DimensionsSimple-shaped products (e.g., keys, cup lids) suit simplified-structure molds, while complex products (e.g., dashboards, phone frames) demand molds with excellent cavity filling and demolding performance. Conventional products require mold positioning accuracy ≤0.02mm, and high-precision medical parts ≤0.01mm, with proper shrinkage compensation to prevent warpage.
Material Combination CompatibilityCommon combinations include hard-soft rubber (ABS+TPU) and hard-hard rubber (PC+ABS). Molds should be optimized for materials with large fluidity differences to avoid uneven filling; modular cavity structures are recommended when shrinkage rate differences exceed 1.5%. Wear-resistant designs are needed for glass fiber-reinforced materials.
Production Batch and EfficiencySmall-batch or customized production prefers versatile, low-modification-cost molds to control development cycles. Mass production (≥1 million pieces/year) requires high-stability molds with high-strength materials, ensuring a service life ≥500,000 cycles. The single-cycle time is 20–40 seconds for conventional products, and can be shortened by 10%–15% via optimized mold design.
Mold TypeMainstream types include rotary table, translational and stack molds. Rotary table molds fit small-medium products for high efficiency; translational molds ensure high positioning accuracy for large-precision products; stack molds with double-layer cavities boost capacity by over 80% for mass standardized production. Selection must match injection machine specs (clamping force, mold capacity) and product size.
Positioning Mechanism AccuracyRepeat positioning accuracy ≤0.01mm is the industry standard. Composite structures of taper and guide pillar positioning offset injection pressure deviations for high-precision products. Foolproof mechanisms are essential to avoid cavity misalignment.
Cavity and Core DesignConformal designs reduce material flow resistance, with draft angles of 1–3° for conventional products and 0.5–1° for high-precision ones. Micro-textures or grooves on cores enhance bonding force between hard and soft materials (peel strength ≥1.5N/mm). Cavity surface roughness should be ≤Ra0.8μm for smooth product appearance.
Cooling System OptimizationZoned cooling with independent circuits adapts to material temperature differences. Cooling channels (8–12mm in diameter) are 15–25mm away from cavity surfaces, keeping cooling time at 40%–60% of the total cycle. Special-shaped or 3D-printed conformal cooling improves efficiency for complex cavities.
Gating System SelectionPin gates suit high-fluidity materials to reduce marks; larger gates apply to low-fluidity materials to avoid insufficient filling. Gate positions for two injections must be rational to prevent structural damage, with cold slug wells set to ensure melt purity.
Mold Material AdaptationS136 and H13 steels (HRC52–58) are ideal for mass production for high wear resistance. P20 and 718H pre-hardened steels reduce costs for small-batch production. Nitriding or titanium plating is required for corrosive materials or high-polish products, increasing surface hardness to ≥HV1000.
Trial Molding VerificationTrial molding should check dimensional accuracy, material bonding strength, appearance and stability, ensuring defect rates ≤2%. Adjust mold structure and process parameters promptly if issues like uneven filling or warpage occur.
Industry Tech Trend AlignmentPrioritize molds with intelligent monitoring functions (real-time temperature/pressure sensors) for precise process control. Modular molds reduce modification costs, fitting the flexible production trend of multiple varieties and small batches.
Cost and After-Sales BalanceBalance manufacturing, maintenance costs and service life, avoiding low-cost molds prone to failures. Choose suppliers with sound after-sales systems and request maintenance guidelines to extend mold service life.
