The manufacturing of multi-color injection molds for consumer products is primarily used for high-appearance daily items (such as toothbrushes, handles, keyboard keycaps, cosmetic casings, toys, home appliance panels, etc.). Its core goal is to achieve two-color injection molding / multi-color injection molding / multi-component injection molding effects, producing attractive products with clear color separation in a single molding process, without the need for secondary painting.
The manufacturing process of multi-color injection molds is similar to that of ordinary molds, but it imposes significantly higher requirements on parting line design, runner layout, positioning accuracy, and transfer mechanisms (or multi-nozzle systems).
- Product Structure Analysis and Process Selection
- Analyze the location of color separation lines on the consumer product appearance, the volume ratio of different color areas, and material compatibility (most commonly ABS, PC, PP, or soft-hard combinations like TPE/TPU with the same material series but different color masterbatches).
- Decide whether to use rotary (turntable) type, core-rotating type, slide transfer type, or independent multi-color molds (multi-component parallel injection).
- 3D Mold Design (the most critical stage)
- Design two (or more) sets of cavities: the first-color substrate cavity + the second/third-color overmold or splice cavity.
- Precisely control the position of the color joint line (weld line / color separation line) to avoid flash, misalignment, or burrs.
- Design a hot runner system (typically with independent hot nozzles for each color) to prevent color bleeding or cross-contamination.
- Incorporate high-precision locating pins and guide pillars to ensure the turntable’s 180° rotation repeatability error is less than 0.01 mm.
- Reserve sufficient cooling circuits, as different colored materials have varying cooling shrinkage rates and require independent temperature control.
- Mold Materials and Machining
- Core and cavity commonly use imported steels such as 738H, NAK80, S136 (S136H or H13 for high mirror-finish requirements).
- Employ high-speed CNC machining + electrode EDM + slow wire cutting to ensure parting surface fit and sharp color separation lines.
- The turntable/rotary shaft components require nitriding or special heat treatment to withstand hundreds of thousands of rotations without loosening.
- Mold Trial and Color Tuning Phase
- First, perform single-color trials to confirm substrate dimensions, shrinkage, and warpage.
- Then conduct two-color combined trials, optimizing injection sequence, pressure, turntable dwell time, and temperature profiles.
- Common issue corrections: color line burrs → improve mold precision + adjust holding pressure; color turbidity → optimize color masterbatch compatibility + reduce shear heat.
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Manufacturing a multi-color injection mold for consumer products involves overlaying the precision of two ordinary molds and adding a high-repeatability transfer/rotation mechanism. It tests the comprehensive strength of design experience, machining equipment, and mold trial processes. When done well, it enables products to leave the factory with high aesthetics, significantly reducing post-processing costs and defect rates.