Shanghai Daoqin Plastics Co., Ltd.

in plastics melt, process in, material 不断移 toward material front 端（计 amount inner ）, 且越 越 more, 逐渐形 formed pressure, screw toward rear 退. is retardant screw rear fast, ensure material uniform pressure 实, need to screw provide 一 反 direction pressure, this direction retardant screw rear pressure is back pressure.      back pressure 亦称塑化 pressure, it control is through adjustment injection 油缸之回油节流阀 achieve. 预塑化 screw injection molding machine injection rear 部都设 has back pressure 阀, adjustment screw rear injection 油缸泄油 speed degree, make maintain pressure.

1, can will inner material pressure 实, increase density, improve/increase amount, products weight and dimensions stability property.

    2, can will material inner gas 体“ extrusion ”, decrease/reduce products surface gas 花, internal bubbles, high gloss uniform property.

    3, decrease slow screw rear speed degree, make inner material separation 塑化, increase color powder, masterbatch and material mixed combined uniform degree, products mixed color phenomenon.

    4, improves back pressure, can improvement products surface sink marks and product 周边 走胶情况.

    5, can improves material temperature degree, make material quality improve/increase, improvement material 充模时 flow property, products surface cold 胶纹.

    三, back pressure low 时, easy lower issues

    1, back pressure low 时, screw rear fast, 流入炮筒 front 端 熔 material density small （ relatively dispersion ）, 夹入空 gas more.

    2, 会导致塑化 quality 差, amount unstable, product weight, products dimensions large.

    3, products surface 会出现 sink marks, gas 花, cold material 纹, gloss and other defect phenomenon.

    4, product internal easy bubbles, product and easy 走, 不满胶.

    四, high back pressure, easy lower issues

    1, front 端 熔 material pressure high, material temperature high, viscosity decline, material in screw in and material and screw 间隙 漏流 amount increase large, reduce efficiency (mono time inner material amount).

    2, for/regarding heat stabilized property plastics （如: PVC, POM and other ） or color agent, material temperature degree rise high in material in hot time growth formed hot separation understanding, or color agent color degree increase large, products surface color / gloss 变差.

    3, back pressure high, screw rear slow, 预塑回 material time long, increase cycle time, production efficiency decline.