Why Co Injection Molding Lowers Material Packaging Costs

Manufacturing cost-effective structural enclosures and multi-functional plastic hardware requires balancing pristine surface aesthetics with low raw material expenses. Solid single-material components using virgin engineering resins drive up production costs, whereas using 100% recycled polymers compromises surface cosmetics and impact strength. Specifying professional co injection molding resolves these conflicting requirements by encapsulating a low-cost or recycled polymer core inside a high-purity virgin outer skin. JUCHENG operates specialized multi-barrel co-injection machinery, delivering multi-layer structural parts strictly according to customer technical CAD drawings.

目次

• 1. Sandwich Molding: Virgin Outer Skin with Recycled/Regrind Core
• 2. Material Interlayer Adhesion & Viscosity Matching in Dual Injections
• 3. Cost-Effective Structural Panels & EMI Shielded Enclosures

Sandwich Molding: Virgin Outer Skin with Recycled/Regrind Core

Executing multi-layer processing utilizes sandwich molding technology through specialized dual-concentric nozzles or sequential manifold valves. First-stage injection introduces the virgin skin resin, filling the cavity walls to form a pristine outer surface. Second-stage injection introduces the core material directly into the warm center of the skin melt, expanding the core from within. Enclosing a regrind core or recycled polymer inside a virgin skin cuts raw material costs by up to 30% to 50% without altering surface finish. Final skin-purge injection seals the sprue gate with virgin resin, ensuring zero recycled material remains exposed on external surfaces.

Co-injection sandwich sequence steps include:

1. Virgin skin injection—高純度スキン樹脂を射出することで、冷たい金型壁面に対して欠陥のない表面層を形成します。.
2. コアメルト置換—センターマニホールドからコア樹脂を射出することで、サンドイッチ層を均一に拡張します。.
3. ゲートスキンパージ—バージンスキン樹脂の短い最終ショットを射出してゲートを封止し、コアの露出を防ぎます。.
4. キャビティ圧力パッキング—パッキング圧力を保持することで、均一な密度を確保し、ヒケの形成を防ぎます。.

二重射出における材料層間接着と粘度マッチング

安定したサンドイッチ層を実現するには、スキンとコアのメルトストリーム間の正確な 粘度マッチング が必要です。メルト粘度差が20%を超えると、コア材料がスキンを突破し、 スキンブレークスルー. が発生します。スキンブレークスルーは、部品表面に内部コア材料を露出させ、外観不良を引き起こします。 PC/ABS または ポリプロピレン（PP） のような互換性のある熱可塑性プラスチックを選択することで、層間境界に沿った強力な化学融合が保証されます。適切な温度プロファイリングにより、同様のレオロジー流動フロントが維持され、コアが外側スキン内で同心円状に保たれます。.

Cost-Effective Structural Panels & EMI Shielded Enclosures

Co-injection processing enables unique functional material combinations impossible with single-shot molding. Electronic housings incorporate a carbon-filled conductive core inside a cosmetic PC/ABS outer skin, providing built-in EMI/RFI shielding without secondary conductive painting. Industrial transport pallets and structural panels encapsulate low-cost post-consumer recycled resin inside a weather-resistant virgin PP outer shell. Multi-layer encapsulation satisfies strict environmental sustainability criteria while lowering total part manufacturing expenses.

Key industry co-injection advantages include:

• Raw material cost reduction—Encapsulating up to 50% recycled or regrind core material reduces overall resin expenditure.
• Built-in conductive shielding—Enclosing conductive carbon black cores delivers internal EMI attenuation without secondary painting.
• Pristine surface appearance—Hiding discolored or heavily filled core resins behind a virgin skin maintains A-class cosmetic standards.

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