Injection Molding
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Nozzle blockage in low density polyethylene '2079851475616104452
Problem Phenomenon
During injection, the melt cannot be normally injected from the nozzle or the injection amount decreases, and the injection pressure rises abnormally.
Nozzle blockage causes short shots or complete inability to produce, usually caused by cold material or impurities blocking the nozzle hole.
Cause Analysis
(1) Nozzle temperature too low, the melt cools and solidifies at the nozzle
(2) Improper design of the cold slug well of the mold sprue, cold material flows back into the nozzle
(3) Impurities in the raw material block the nozzle hole
(4) Nozzle hole diameter too small or unreasonable internal structure of the nozzle
(5) Poor alignment between the nozzle and the mold sprue, eccentricity causes flash and material jamming
Solution
(1) Increase nozzle temperature to a reasonable value within the 160-220°C range, 5-10°C lower than the front barrel temperature
(2) Check the cold slug well of the mold sprue to ensure the cold slug well is large enough
(3) Check raw material cleanliness, install magnetic grate and filter screen on the hopper
(4) Select a nozzle with appropriate hole diameter; generally the nozzle hole diameter is 0.5-1mm smaller than the small end of the sprue
(5) Correct the alignment of the nozzle and the mold to ensure coaxiality within 0.05mm
Key Takeaway
Nozzle blockage is caused by cold material solidification or impurities, and needs to be solved from nozzle temperature, cold slug well design, and raw material cleanliness.
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