Shanghai Daoqin Plastics Co., Ltd.

         in extrusion process in, need from material in gas 体, this gas 体如不 can 排出, products surface or internal can can 会出现孔隙, bubbles and surface dark and other defect, heavy can effect/influence to products material mechanical properties, chemical property can and electrical property can. in material and machine between 设置 1 ～ 2 排 gas can remove melt extrusion material material in water separation and other 挥发份. 但钢筒开口常常会出现一, most Common issues is from gas material, a small amount of material effect/influence 挥发份 排出, make product quality to effect/influence; a large amount of material 就会堵塞排 gas 口, 甚至导致停 machine.

        冒 material generally has causes, is screw design combined 理, 导致排 gas material material 倒流; is gas design combined 理, in melt material material through gas by “挂住”. causes from gas screw in material material is 否倒流, in large more gas extrusion machine in, can to screw in toward front melt. generally lower, 螺槽充满 material material degree ultra- 50 %, if ultra-, not only effect/influence gas 效果, also can can 引起排 gas 口 冒 material; small 于 50 % 时, screw can positive as. material can can is due to gas or separation parts design combined 理引起.

         effect/influence material factors and solutions

        1. screw factors

        排 gas screw more using/adopting more design, design advantages in gas is pressure, material material 不致流出. has 一 排 gas extrusion machine requirements has 2 阶 screw, has 2 排 gas need 3 阶 screw. 每 1 阶 has pressure 段, pressure shrink and amount 段, 第 1 阶起始段 is pressure add material 段, 第 2 阶 is pressure gas 段, is gas in 位置. for/regarding gas extrusion machine screw design has 2 main/primary issues: 第一, in to gas 段时, material material must full melt, 以排出挥发份; 第二, 第 2 阶 screw material amount must large 于第 1 阶 screw, make 第 2 阶起始处螺槽未充满, this can make gas maintain pressure. 当第 1 阶 screw material amount ratio 第 2 阶 screw large 时, extrusion machine in melt 就会发生倒流. need understanding 此决此 issues, decrease/reduce 第 1 阶 送 material amount or increase 第 2 阶 送 material amount.

        2.   process conditions

         solution material most fast speed methods is process conditions. drop temperature, increase large 沿钢筒 or screw scratch and 剪切应 force and increase large 沿钢筒 surface scratch or viscosity increase material amount.

        第 1 阶 送 material amount can through below/following types methods reduce:(1) rise high 钢筒 2 区 and 3 区 temperature degree. (2) cooling 第一阶 screw. (3) using/adopting method material. (4) adjustment material temperature degree (需反复实验). increase 第 2 阶 送 material amount can using/adopting lower methods:(1) reduce 第 2 阶钢筒 temperature degree. (2) rise high 第 2 阶 screw temperature degree. (3) rise high machine temperature degree. (4) increase large machine 头间隙 or decrease/reduce machine retardant force. (5) decrease/reduce 滤网 数 amount. (6) use relatively large 滤网.

         if processing conditions still can solution issues, using/adopting other methods, heavy new design screw, reduce machine retardant force, add long screw and or in extrusion machine and machine between 安装一 gears 泵. gears can solution material issues, it ratio new screw cost more high.

        3.排 gas 口

         if gas screw separation 充满, gas still material, that gas design in issues. gas 口应该 ratio material need wide, ensure gas by melt 堵塞. meanwhile, gas 口 开 degree 也不应太 large, this can decrease/reduce melt time and material 流 膨胀 time. in positive as lower, semi 充满, this gas is pressure, upper 滚动熔 material in still has pressure, pressure is 0.21 ～ 0.35MPa or more high, make gas 口 处 熔 material 膨胀. this gas in design 时就应考虑 to material material positive viscous elastic property 膨胀, 否则, separation material 流就会 by “挂住”, in separation parts 处. melt material 流膨胀 how much it through gas time 决定. time long, large. time also screw speed and gas large small control, improve/increase screw speed can decrease/reduce time. this is low speed extrusion ratio high speed extrusion material heavy causes. 不, gas degree large, time long. melt in gas 口堆积时, it will 堵塞排 gas 口, solution method is 改变排 gas 口 开 degree meet/satisfy melt in gas positive 常膨胀. if material 流膨胀 5 ～ 10mm, gas 口 开 deep degree less is 5 ～ 10mm.

        4. gas separation parts

        举一 现实生 active in 例子, use 150mm rigid abrasion belt/tape gas mono screw extrusion machine extrusion sheet/slice 材时严 heavy material, method production combined product. as 工想检查一 lower gas 口处螺槽 in material 情况, 但根本无 method to screw, this 就说明 separation parts design in very large issues, as 工不 不取 lower separation parts 检查螺槽 充满程 degree. rear 发现螺槽仅充满 40 %, screw design is combined 理.

         that fault/failure 焦点便集 in in separation parts upper. tube/pipe this is 一家著名 extrusion machine manufacturing 商, its separation parts design in heavy defect. in separation parts 时, 发现排 gas not only in upper has can make material material positive 常膨胀 底切口, but also in lower 阶同样设 has 此口. upper screw full has necessary design 底切口, but also 设置此切口 is is 不利, is it increase in gas 口处 停留 time but also make 熔池膨胀 more more, increase gas melt pressure 累积. another issues is 平口形 and 矩形排 gas 口, this ratio 直口形 more difficult 清洁.

         if separation parts design combined 理, gas and semi versus 垂直. through above analysis, separation parts can using/adopting below/following types methods 进行修补: 第一, will upper 阶底切口填满 metal; 第二, 矩形开口改 formed toward, can make as to screw in material 情况. upper methods 改进, solution material issues, production excellent product.

        结论

        排 gas screw is material, and extrusion process, plastics property can and screw and gas design has 直接 关系, therefore production in use gas extrusion machine production processing 时, need for processing process, resin features and equipment property can as understanding, can make gas extrusion machine positive stability 运行.