Two-color injection molding is a core technology for integrated multi-material molding. Through the coordination of a set of molds and special equipment, it can complete the molding of plastic parts with two different materials or colors in a single production cycle. Compared with the traditional secondary assembly process, it significantly improves product structural stability and production efficiency. The technical process must strictly follow the core logic of material compatibility, mold coordination and parameter matching, with all links closely connected to ensure the quality of the final finished product.
Determine the combination of two injection materials according to product functional requirements, prioritizing pairs with good compatibility. The combination of rigid ABS and soft TPE is a common industry solution, meeting the soft-hard bonding needs of products such as handles and seals. Materials must undergo drying to remove moisture and avoid defects like bubbles and silver streaks during molding. Drying temperature and time should comply with technical specifications provided by material suppliers.
Based on material characteristics and product structure, preset key process parameters in the control system of the two-color injection molding machine. Mold temperature is generally required to be higher than that of single-color injection molding to ensure the interfacial bonding strength of the two materials, a widely recognized technical point in the industry. Meanwhile, initially set parameters such as injection temperature, injection pressure and holding time for both materials to provide a basis for subsequent debugging.
Two-color injection molds adopt a rotating core or double-injection unit structure. During installation, the mold must be accurately fixed on the moving and fixed mold plates of the injection molding machine to ensure full fit between the mold locating ring and the injection machine locating hole. For rotating core molds, check the connection accuracy of the core rotation mechanism to ensure smooth and non-jamming rotation.
The core of debugging lies in calibrating the core rotation angle and cavity clearance. The industry-recognized alignment error of core rotation should be controlled within 0.05 millimeters to avoid product dimension deviation or material mixing caused by misalignment. Meanwhile, check the operation status of the mold cooling system and ejection system to ensure coordinated movement of all components.
The first injection unit of the molding machine injects the first material into the first mold cavity according to preset parameters. After the holding and cooling stages, the first material solidifies to form the base part. At this time, the moving mold part moves with the injection machine's moving template, driving the base part to move together.
The rotating core mechanism drives the core to rotate 180 degrees, accurately transferring the core with the base part to the second cavity position, completing the mold cavity switching in preparation for the injection of the second material.
The second injection unit injects the second material into the second cavity. In the molten state, the second material fully contacts the surface of the base part, achieving tight bonding through mechanical interlocking and intermolecular forces. After subsequent holding and cooling, the two materials solidify together to form a complete two-color plastic part.
The mold ejection system ejects the two-color plastic part from the cavity. Operators or automated equipment remove the gate and flash of the plastic part. Some products require surface cleaning to remove residual debris and oil stains.
Inspection items include dimensional accuracy detection, bonding strength detection of the two materials and appearance quality inspection. Bonding strength must meet relevant industry standards and be verified by peel tests. Appearance inspection focuses on checking for defects such as delamination and uneven color mixing at the bonding interface. Under current technological trends, visual inspection equipment and intelligent detection systems are gradually applied in the inspection link to achieve rapid defect identification and classification.
After completing the production batch, clean and maintain the injection molding machine and mold, remove residual materials in the barrel, and check the surface condition of the mold cavity. Record the process parameters and quality data of this production batch to provide an optimization basis for subsequent production of similar products. With the development of intelligent manufacturing technology, the two-color injection molding process is gradually upgrading towards real-time parameter monitoring and adaptive adjustment, further improving production stability and product qualification rate.
