How to ensure that the shell of a traffic light shell injection molding machine does not fade or deform over long-term use?
Publish Time: 2025-11-21
Traffic lights, as core facilities for urban road traffic management, require shells with excellent structural strength and sealing performance. They must withstand harsh environmental conditions such as intense sunlight, wind and rain, high and low temperature cycles, and ultraviolet radiation during 5-10 years or even longer of outdoor service. Fading, yellowing, warping, or cracking of traffic light shell injection molding not only affects aesthetics but may also weaken light transmittance, reduce protection levels, and even endanger the safety of internal electronic components.1. Prioritize high-weather-resistant engineering plastics to solidify the foundation for fade resistance.Traffic light shell injection molding machines commonly use polycarbonate or PC/ABS alloys as the base material. These materials themselves have excellent impact resistance and thermal stability, but the key lies in the addition of a highly efficient anti-aging additive system. Among them, ultraviolet absorbers and hindered amine light stabilizers work synergistically: UVA absorbs harmful UV rays and converts them into harmless heat energy, while HALS removes free radicals generated during photo-oxidation, blocking chain degradation reactions. Furthermore, inorganic metal oxides are used as pigments instead of organic dyes because their chemical structure is stable and they are less prone to decomposition and discoloration under light.2. Precision mold design ensures structural stability and prevents deformationShell deformation often stems from uneven cooling or residual internal stress. To address this, the mold employs a conformal cooling channel design, allowing the cooling medium to flow closely along the complex curved surfaces of the cavity, significantly shortening cooling time and improving temperature uniformity. Simultaneously, the ejection system is symmetrically laid out to avoid excessive localized stress leading to warping; the clearance between the parting surface and the slider is controlled at the micrometer level, eliminating flash that could affect assembly flatness. For large-sized lamp housings, the mold also has a pre-set anti-deformation compensation amount—based on the shrinkage trend predicted by CAE mold flow analysis, the geometry is pre-adjusted during mold core machining to offset natural shrinkage after molding, ensuring accurate final product dimensions and a crisp profile.3. Optimized injection molding process parameters eliminate potential internal stress risksEven with excellent materials and molds, improper injection molding processes can introduce residual stress, becoming a cause of later deformation or cracking. During production, four key parameters are strictly controlled: melt temperature, injection speed, holding pressure, and cooling time. For example, a multi-stage injection strategy is employed: initial low-speed filling avoids jetting marks, mid-stage high-speed filling improves fluidity, and final deceleration reduces molecular orientation. During the holding pressure stage, precise shrinkage compensation is achieved through pressure-time curves to prevent indentations or stress concentration caused by uneven shrinkage. After demolding, some high-end products undergo low-temperature annealing to further release residual stress and improve long-term dimensional stability.4. Surface Treatment and Structural Reinforcement Synergistically Enhance DurabilityTo enhance outdoor adaptability, the shell surface is often coated with UV-resistant paint or co-extruded protective layers, forming a double protective barrier. Simultaneously, the structure incorporates reinforcing ribs, curved transitions, and appropriate wall thickness, reducing weight while increasing rigidity, effectively resisting deformation caused by wind loads and thermal expansion and contraction. Connecting parts such as clips and studs use rounded transitions and localized thickening to avoid stress concentration and cracking.The "fading-proof and deformation-proof" performance of traffic light shell injection molding is not accidental, but rather the result of a three-pronged approach combining materials science, mold engineering, and process control. With high weather-resistant resin as its framework, precision molds as its form, and intelligent injection molding as its core, it silently safeguards the order and safety of urban traffic day after day, exposed to wind and sun. It is this extreme pursuit of detail that allows each traffic light to consistently and firmly emit that trustworthy red, yellow, and green light over the long years.
