How to Improve the Precision of Thin-Wall Injection Molding
Cavity and core precision control: Use high-precision equipment such as five-axis machining centers and precision grinders. Ensure key cavity dimension tolerances are within ±0.005mm and surface roughness Ra ≤0.02μm via fine polishing, reducing melt flow resistance and demolding friction. Calculate the core-cavity fit gap (0.01–0.02mm) based on material shrinkage to avoid flash and sticking issues.
Cooling system uniformity design: Adopt conformal cooling channels with a 15–20mm distance from the cavity surface and 8–12mm diameter. Use high-precision temperature controllers to keep mold temperature differences ≤1℃. Add local cooling inserts or 3D-printed conformal channels for complex structures to prevent defects from uneven cooling.
Gating system optimization: Prioritize hot runner or multi-point balanced gates to shorten melt flow paths. Match gate diameter to 0.8–1.2 times the product wall thickness to avoid jetting or insufficient holding pressure. Set exhaust grooves (0.01–0.02mm deep, 5–10mm wide) at melt flow ends and corners to eliminate gas marks and scorching.
Injection speed and pressure matching: Adopt high-speed injection (100–200mm/s) to ensure full cavity filling before melt solidification, avoiding short shots. Adjust injection pressure to 150–200MPa based on material fluidity and product complexity. Use segmented pressure control: low pressure initially to prevent splashing, and gradual pressure increase later to avoid flash or incomplete filling.
Temperature field control: Apply segmented barrel temperature control with fluctuations ≤±2℃ for uniform plasticization. Set nozzle temperature 5–10℃ lower than the maximum barrel temperature to avoid cold material blockage or drooling. Match mold temperature to materials—80–120℃ for PC to enhance fluidity, 20–40℃ for PP to reduce shrinkage deformation, and minimize internal stress.
Holding pressure and cooling optimization: Set holding pressure at 60%–80% of injection pressure with fluctuations ≤±5%. Use segmented holding pressure to compensate for shrinkage and reduce internal stress. Adjust cooling time to 20–60 seconds based on wall thickness and thermal conductivity, ensuring full solidification before demolding. Adopt multi-point uniform ejection to prevent deformation.
High-precision equipment selection: Choose injection molding machines with injection volume error ≤±0.1% and clamping force fluctuation ≤±1%, and screw length-diameter ratio of 18–25:1 for uniform plasticization. Equip with servo drive systems and high-precision sensors for closed-loop control of speed, pressure and temperature (response accuracy: 0.01mm/s, 0.1MPa). Ensure guide mechanism coaxiality and parallelism to reduce vibration.
Adaptive material selection: Prioritize high-fluidity materials with MFR ≥10g/10min to lower filling resistance. Select materials by application: PC/ABS alloys for 3C products, ISO 13485-certified PP for medical devices, and PEEK for high-temperature conditions. Control material shrinkage fluctuation ≤±0.2% to avoid precision deviations.
Online testing application: Integrate high-precision vision inspection systems with industrial cameras to monitor key dimensions in real time (detection accuracy ±0.003mm), identifying flash, short shots and deformation promptly. Implement 100% full inspection of key dimensions and use SPC to analyze data trends, issuing early warnings for abnormal fluctuations. Calibrate testing equipment regularly.
Intelligent control system construction: Apply digital twin technology to simulate molding processes, optimizing parameters and reducing trial mold times. Use AI algorithms to analyze sensor data (temperature, pressure, speed) and adjust parameters automatically (response time ≤0.1s) for adaptive control. Maintain and calibrate molds, cooling systems and hydraulic systems regularly for long-term stability.
