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Influence of length-diameter ratio of injection screw on plastic quality

Por Cathy Lin October 8th, 2024 vistas 6
‌ The ratio of length to diameter of injection screw has a significant effect on the quality of plastic. ‌ length to diameter ratio refers to the effective length of the working part of the screw and the diameter ratio, usually between 15 and 25, but modern technology has reached 40 or even greater ‌.

Advantages of a large aspect ratio include:

  • ‌ improve plasticizing quality
‌ : large length-to-diameter ratio is conducive to the mixing and plasticizing of plastics, so that plastics in the barrel heating time is longer, more fully plasticizing, more uniform ‌.
  • ‌ enhance product performance
‌ : screw pressure is sufficient, can improve the physical and mechanical properties of the product, such as strength and toughness ‌.
  • ‌ improve production efficiency ‌
: extrusion is more stable, extrusion amount can be increased by 20%-40%, which is conducive to large-scale production ‌.
‌ to meet special requirements ‌ : is beneficial to adjust the temperature gradient along the cylinder axis, to meet the special polymer processing requirements ‌.
However, there are disadvantages to having a large aspect ratio:

  • ‌ increase power consumption ‌
: the length-diameter ratio is too large, the power consumed by the screw will increase correspondingly, increasing the energy cost ‌.
  • ‌ increases the difficulty of manufacturing ‌
: the processing and assembly difficulty of screw and barrel increases, the possibility of screw bending will increase, and the service life ‌.
  • ‌ affects heat-sensitive plastics ‌
: for heat-sensitive plastics, too large length-diameter ratio will lead to long heating time and easy decomposition of plastics, affecting plasticization and extrusion quality ‌.
Therefore, it is very important to choose the right aspect ratio. It is usually determined according to the physical properties of the processed plastic and the extrusion quality requirements of the product. For hard plastics, powdery plastics or crystalline plastics, a larger length-diameter ratio should be selected; For heat-sensitive plastics, a smaller aspect ratio ‌ should be selected.

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