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injection molding machine screw its 实跟 extrusion machine 一样 important, this parameters effect/influence to injection molding products quality. lower:
◆ screw has long degree 跟直径 ratio value long ratio （L/D）
☆L/D large, plastics from material to need relatively long 距离;
☆经 this 段距离 time plastics time;
☆ screw outer structure table/sheet is screw 三段 螺纹圈数:
12-6-6（20/1 L/D） screw = long ratio 20: 1
螺纹圈数喂 material 段: 12圈; pressure shrink 段: 6圈; amount 段: 6圈.
screw usually separation 三段:
喂 material 段—传送 plastics
pressure shrink 段—熔化 plastics
计 amount 段— mixed combined plastics
各段 螺纹槽 deep degree different:
喂 material 段 螺纹槽 deep degree ratio amount deep, it ratio value pressure shrink ratio.
例如, 3: 1 pressure shrink ratio screw, material 段 螺纹槽 deep degree is amount 段 三倍.
screw pressure shrink ratio and long ratio
low -1.5～2.5:1(剪切敏感 plastics ,如PVC)
in -2.5～3.0:1( generally applications plastics ,如PS)
high -3.0～5.0:1( crystallization type plastics ,如PA)
◆ long ratio （L/D） selection :
☆L/D small , plastics 熔化效果差; plastics time short;
☆L/D large ,传递扭矩 large , can amount consumption increase; plastics time long;
☆ pressure shrink ratio large ,剪切 function strong/high ,塑化 can force low ;
☆ crystallization type plastics need long material 段,无定 type plastics need long pressure shrink 段
screw function
☆塑化 rear 退--- material front plastics pressure function;
◆ screw structure and methods can to below/following 目 :
☆输送 plastics to material front 段;
☆ generate scratch and hot amount, fast speed plastics;
☆ injection front 进--- liquid pressure inner pressure function ;
☆ mixed combined plastics, provide uniform melt temperature degree and color distribution;
☆塑化转动---马达（ liquid pressure or electrical 动）起 function;
☆完 formed injection and holding pressure process.
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