Injection Molding
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Large weight fluctuation of random copolymer polypropylene injection molded products
Problem Phenomenon
The weight of products continuously produced from the same mold is unstable, fluctuating more than ±2%.
Weight fluctuation reflects process instability and directly affects dimensional accuracy and mechanical property consistency, which is especially critical in precision '2079851475616104452.
Cause Analysis
(1) The screw check ring is worn or damaged, making each shot volume inconsistent
(2) Plasticizing back pressure is unstable, and melt density fluctuates
(3) Barrel temperature fluctuates greatly, and melt density changes with temperature
(4) Injection speed is unstable, and hydraulic system pressure fluctuates
(5) Raw material supply is discontinuous, with bridging at the feed opening or unstable material level
Solution
(1) Check the screw check ring; replace if wear exceeds 0.1mm to ensure consistent shot volume each time
(2) Stabilize back pressure at 5-8MPa, with back pressure fluctuation not exceeding ±0.5MPa
(3) Stabilize barrel temperature, with fluctuation of each section controlled within ±3°C (190-260°C range)
(4) Check hydraulic system pressure stability, and repair the hydraulic pump and valves if necessary
(5) Ensure smooth feeding; install a magnetic rack on the hopper to prevent metal impurities and avoid bridging
Key Takeaway
Weight fluctuation is caused by unstable plasticizing and metering and needs to be solved from the screw check ring, temperature control and hydraulic system stability.
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