Extrusion & Post
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PE Film Thickness Deviation
Fenómeno del problema
PE film shows periodic machine-direction (MD) thickness fluctuations or transverse-direction (TD) one-side thick one-side thin, resulting in uneven strength and heat sealing after bag making.
Análisis de la causa
MD deviation mostly comes from extrusion output pulsation or haul-off speed fluctuation; TD deviation mostly comes from uneven die lip gap, transverse die temperature unevenness, asymmetric air ring/cooling or off-center bubble.
Solución
①MD direction: stabilize the extrusion and haul-off, and monitor the screen pack pressure differential; ②TD direction: adjust the die lip bolts, calibrate the temperature of each die zone, cool uniformly and center the bubble; ③configure online thickness measurement with closed-loop control; ④establish thickness SPC monitoring.
Conclusión clave
PE film thickness is managed by direction: for MD check the stability of extrusion and haul-off, for TD check the symmetry of the die lip and temperature/air ring; closed-loop thickness measurement is standard, and adjusting the die lip by hand feel has long been unable to keep up with the quality requirements.
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