Extrusion & Post
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Pressure fluctuation
Problem Phenomenon
Die head pressure is unstable, swinging over a large range.
When this defect appears in extrusion molded products, it is usually closely related to process links such as die design, screw plastication state, cooling and sizing system, or haul-off stability.
Persistence of the defect will lead to out-of-tolerance product dimensions, unqualified appearance, or decreased mechanical properties, increasing scrap rate and rework costs.
Timely diagnosis and troubleshooting from both extrusion process parameters and equipment status are basic requirements for ensuring stable continuous production.
Cause Analysis
1.
Operational factors: Uneven feeding or material interruption.
2.
Process parameter factors: Unstable screw rotation speed.
3.
Material/formulation factors: Melt temperature fluctuations cause viscosity changes.
4.
Comprehensive factors: Changes in the degree of screen clogging.
5.
Mold/tooling factors: Local blockage inside the die.
Solution
1.
Process parameter optimization and adjustment: Ensure stable and uniform feeding of the feed system.
2.
Mold/tooling improvement and maintenance: Check the screw drive system and motor.
3.
Equipment inspection and system maintenance: Improve temperature control accuracy and stability.
4.
Material/formulation optimization: Replace screens at regular intervals.
5.
Operating specifications and preventive measures: Clean the die.
Key Takeaway
This problem is a typical manifestation of pressure fluctuation in extrusion molding.
The core of the solution lies in eliminating the root cause of the defect through systematic optimization of process parameters (temperature, speed, pressure) and precision correction of the die/sizing system.
It is recommended to start with parameter adjustment and gradually go deeper into the equipment and tooling levels.
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