Injection Molding
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Nozzle clogging in random copolymer polypropylene '2079851475616104452
Problem Phenomenon
During injection, the melt cannot be ejected normally from the nozzle or the ejection volume decreases, and injection pressure rises abnormally.
Nozzle clogging causes short shot or complete inability to produce, usually caused by cold material or impurities clogging the nozzle hole.
Cause Analysis
(1) Nozzle temperature is on the low side; the melt cools and solidifies at the nozzle
(2) Improper design of the mold sprue cold slug well; cold material flows back into the nozzle
(3) The raw material contains impurities that clog the nozzle hole
(4) The nozzle hole diameter is too small or the nozzle internal structure is unreasonable
(5) The nozzle and mold sprue are poorly aligned, and eccentricity produces flash and stuck material
Solution
(1) Increase nozzle temperature to a reasonable value within the 190-260°C range, 5-10°C lower than the front barrel temperature
(2) Check the mold sprue cold slug well to ensure its size is sufficient
(3) Check raw material cleanliness, and install a magnetic rack and screen on the hopper
(4) Select a nozzle with a suitable hole diameter, generally 0.5-1mm smaller than the small end of the sprue
(5) Correct the alignment of the nozzle and the mold, ensuring coaxiality within 0.05mm
Key Takeaway
Nozzle clogging 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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