Processing Machinery
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PVC Screw Low Compression Ratio
Fenómeno del problema
Processing PVC with a general-purpose screw caused uneven plasticization and frequent black specks; the problem disappeared after changing the material
Análisis de la causa
The general-purpose 3:1 compression ratio screw shears too strongly, and PVC locally overheats and degrades in the compression section; the PVC-dedicated screw has a low compression ratio of 1.5-2.5:1, a long feeding section, and no mixing section, plasticizing by external heat rather than shear
Solución
①Select a PVC-dedicated low compression ratio 1.6-2.0:1 screw; ②chrome-plate the screw flights to prevent material sticking and retention; ③deep channel design to reduce shear; after adjustment, continuously sample to verify the effect, and resume mass production after confirming stability
Conclusión clave
The PVC screw is a dedicated part, not a general-purpose part; low compression ratio plus chrome-plated flights eliminate shear degradation from the hardware; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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