Injection Molding
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General-purpose polyethylene injection molded products uneven color/color difference
Problem Phenomenon
Areas with inconsistent color depth appear on the product surface, or there is a color difference from the standard color sample.
Color difference may appear between different parts of the product, different cavities or different batches, affecting product appearance consistency.
Cause Analysis
（1） Color masterbatch dispersion uneven, mixing time insufficient or mixing ratio unstable\
（2） Barrel temperature fluctuates greatly, color masterbatch coloring effect differs at different temperatures\
（3） Screw speed and back pressure set improperly, plasticization and mixing insufficient\
（4） Barrel or screw worn, dead zones produce discoloration or uneven coloring\
（5） Mold surface conditions inconsistent, gloss differences in different areas cause visual color difference
Solution
（1） Ensure the color masterbatch and raw material are fully mixed, mixing time 5-10min, use weighing equipment for accurate metering\
（2） Stabilize the barrel temperature, temperature difference of each section controlled within ±3°C （160-260°C range）\
（3） Appropriately increase back pressure to 5-10MPa, optimize screw speed to ensure uniform plasticization and mixing\
（4） Check screw and barrel wear, replace the screw tip or check ring if necessary\
（5） Regularly clean the mold cavities, ensure consistent surface conditions of all cavities
Key Takeaway
Color difference is caused by uneven colorant dispersion or process parameter fluctuations, requiring consistency assurance from three aspects: mixing, plasticization and temperature control.
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