Power bank shells are mainly made of ABS and PC/ABS alloy materials, with strict requirements on surface finish, assembly dimensional precision and flatness. Mass production often faces defects such as flow marks, obvious gate marks, lengthwise and transverse warpage, shrinkage depressions at buckle positions and coarse mold joint lines. Systematic full-process optimization can improve product yield, reduce defects and mold modification costs, and realize stable and efficient mass production.
Raw Material Preprocessing OptimizationABS and PC/ABS materials are highly hygroscopic, with excessive moisture causing silver lines, foggy surfaces and internal bubbles during molding, seriously affecting appearance and structural strength. Dehumidifying dryers must be used before production: pure ABS is dried at 80℃ for 3-4 hours, while PC/ABS alloy is dried at 95-105℃ for 4-5 hours, controlling moisture content below 0.02%. Sealed thermal insulation storage is conducted after drying to prevent secondary moisture absorption in humid workshops. The recycled material mixing ratio is limited to 12% for appearance shells, with crushed materials requiring screening, dust removal and secondary drying to avoid impurity mixing affecting molding quality.
Mold Structure Targeted Optimization
Optimize gate form, preferring fan gates, flat side gates and submarine gates with enlarged runner cross-sections to reduce melt shear velocity and eliminate jet flow marks and gate marks. Dense exhaust grooves (0.015-0.03mm deep) are set at parting surfaces, shell corners and dense rib positions to discharge high-temperature gas rapidly, avoiding scorching black spots and deepened welding lines. Cooling water channels are arranged evenly following product profiles, 10-14mm from cavity surfaces to ensure consistent cooling speed of all parts of the shell, improving warpage caused by unbalanced heat dissipation. Independent conformal cooling pipelines are arranged at internal reinforcing rib positions to eliminate surface shrinkage depressions. Optimize ejection layout by combining ejector pins and ejector blocks to disperse ejection force, preventing ejection marks, surface scratches and deformation pulling.
Injection Temperature System Optimization and AdjustmentSet barrel temperatures according to material characteristics: for ABS, feeding section is 200-215℃, melting section 215-230℃, metering section 225-235℃, nozzle temperature 220-230℃. PC/ABS alloy temperature is increased by 15-25℃ appropriately. Avoid long-term high-temperature material storage to prevent decomposition and yellowing, while insufficient temperature leads to poor fluidity, insufficient filling and prominent bonding lines. Use low rotating speed and low back pressure for plasticization: screw speed 45-80rpm, back pressure 0.3-0.7MPa, reducing shear heat to make the shell surface delicate and color difference uniform.
Injection Speed and Pressure Segmented OptimizationAdopt multi-stage injection filling: low speed through runners to avoid ripple marks, medium speed filling main shell surfaces smoothly, low speed filling corners, buckles and thin-walled positions to prevent air trapping and material shortage, and ultra-low speed buffer glue stopping to weaken terminal welding lines. Injection pressure is 80-110MPa, adjusted according to wall thickness: increased for thin-walled shells, reduced for thick rib positions to relieve shrinkage. Packing is regulated in two stages: high primary pressure for rapid shrinkage compensation, gradually decreased secondary pressure to avoid excessive internal stress and post-molding warpage. Packing duration is set based on wall thickness, 1.8-2.5 seconds per millimeter, balancing forming quality and production cycle.
Mold Temperature and Cooling Time AdjustmentMold temperature is controlled at 65-90℃; increasing mold temperature improves melt fluidity, weakens surface lines and welding lines, and enhances gloss. Alternating high and low mold temperature debugging can be used: high-temperature molding for high-gloss shells, medium/low temperature for matte shells to improve efficiency. Basic cooling time is not less than 18 seconds, extended to 22-28 seconds for shells with dense internal ribs to ensure complete shaping before ejection, reducing rebound deformation, shell bending and surface unevenness.
Post-molding Treatment and Defect Improvement Optimization
Newly demolded products are placed flat on pallets for natural cooling without stacking, as high-temperature shells are prone to deformation. Simple constant-temperature stress relief treatment can stabilize assembly gaps for shells with slight internal stress. Targeted adjustments solve common defects: reduce injection speed and increase mold temperature to eliminate flow marks; extend packing time to improve rib shrinkage; balance cooling water temperature difference to correct warpage; optimize exhaust structure and raise material/mold temperature to fade welding lines; adjust ejection positions and lower ejection speed/force to improve ejection marks. Standardize workshop environment to reduce external interference on molding quality.
Process Optimization SummaryPower bank shell injection molding process optimization focuses on raw material management, mold structure improvement, precise temperature/pressure/speed matching and balanced cooling shaping. Refined segmented injection replaces extensive traditional methods, solving mass production defects, shortening molding cycles, reducing waste and defective rates, and meeting stable production demands for various fast charging and portable power bank shells.
