Dec 07,2025
Design of two-color injection and rotating mold base: process cornerstone to realize complex structure
Design of two-color injection and rotating mold base: process cornerstone to realize complex structure
Bi-color/multi-color injection molding combines two different colors or materials of plastic in one set of molds to create a functionally integrated, cool-looking product. The central director of this precision dance is a specially designed rotating die carrier.
Structure and driving mechanism of mainstream two-color mould bases
Horizontal rotary type die carrier
Structure: the moving part is installed on a central turntable which can rotate 180 ° . There are two sets of different cavity (a cavity and B cavity) on the fixed mold side, and a set of common core on the moving mold side.
Workflow:
First Injection: Molding of the first material is done in cavity A.
Open the die and rotate the moving die 180 ° .
Mold closing: the first product that has been formed enters the B cavity with the core.
Second Injection: coating a second material on the first product.
Drive mode: hydraulic motor or servo motor, the latter is more accurate, more accurate positioning, is to achieve precision dual-color mainstream choice.
Core back type die carrier
Structure: there are two or more sets of cores in the moving die, which can be driven alternately by hydraulic or mechanical pressure.
Workflow: the first shot, a core forward to participate in the molding; after opening the mold, a core back, B core forward; after the mold for the second shot.
Applicable scenario: it is suitable for the situation where the product structure is complex and can not be realized by simple rotation, but the structure is more complex and the cost is higher.
Design essence and challenge of two-color mould
Front-end collaboration in product design phase
Material Compatibility: two materials must have good adhesion (such as common chemical bond) or mechanical interlocking structure (such as Under-cut) .
Separating surface design: the dividing line between the two materials must be precisely defined at the product design stage and translated into a precise sealing surface on the mold.
Precision and rigidity of die design
Repeat positioning accuracy: rotating or switching mechanism must ensure that each positioning accuracy within ± 0.02 mm, otherwise it will produce flash or uneven wall thickness.
Thermal expansion management: two sets of mold core may be at different temperatures, the need to accurately calculate the impact of thermal expansion on positioning accuracy.
Guide post strengthening: The Guide Post and the cone positioning mechanism need to be thickened to bear the side force that may be generated when rotating the mold.
Complex layout of flow passages and cooling systems
Runner design: two independent sets of hot runner system corresponding to a, B two fixed mold cavity, layout should be compact and avoid interference.
Cooling design: due to the compact structure of the rotating die carrier and the limited design space of the cooling waterway, innovative technologies such as 3D printing conformal waterway are needed to ensure the cooling effect.
Application Development: multi-material combined with hard and soft adhesive
Soft and hard glue combination: widely used in handle, button, sealing ring. The key to design:
Hardness difference: usually hard adhesive part for ABS, PC, soft adhesive part for TPU, TPE, TPV.
Mold temperature: lower mold temperature (40-60 °C) is required for the hard part and higher mold temperature (60-80 °C) is required for the soft part to improve fluidity and adhesion. This requires the mold with zoning temperature control capability.
Conclusion:
The two-tone mould base is a perfect blend of mechanical design, materials science and control technology. Its success depends on global planning from the concept stage onwards, as well as the ultimate pursuit of rotational accuracy, thermal management and runner layout. Master the technology of the mold factory, to provide customers with unprecedented product innovation and huge market differentiation advantage.
Next: Die maintenance and life management: from“Fire-fighting maintenance” to“Preventive maintenance”
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