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 闻都设 has back pressure 阀, adjustment screw rear injection 油缸泄油 speed degree, make maintain pressure （如 lower 图 示）; full electrical machine screw rear speed degree （ retardant force ） is, 由AC伺服阀 control.

　　适当调校 back pressure benefits:

　　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 speed 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 wet degree, make material quality improve/increase, improvement material 充模时 flow property, products surface cold 胶纹.

　　 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.

　　4, back pressure high, material pressure high, rear nozzle easy 发生熔胶流涎 phenomenon, lower 次射胶时, water runner inner cold material 会堵塞 water or products in cold material 斑.

　　5, in process in, 常会因 back pressure large, nozzle 出现漏胶 phenomenon, raw materials 并导致射嘴附近 发 hot bad.

　　6, machine and screw machine abrasion loss increase large.

　　 back pressure low 时, easy lower issues:

　　1, back pressure low 时, screw rear fast, 流入迷炮筒 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.

　　 back pressure 调校:

　　 injection molding back pressure 调校应视 raw materials property can, drying 情况, product structure and quality 状况而定, back pressure generally in 3-15kg/cm3. product surface has less gas 花, mixed color, sink marks and product dimensions, weight large 时, can increase back pressure. 当射嘴出现漏胶, 流涎, material hot separation understanding, product color and material slow can 考虑适当 decrease low back pressure.

　　 back pressure is injection molding process in control material quality and product quality important parameters 之一, combined back pressure for/regarding improve/increase product quality has important function, can overlook!

if is machine, has can adjustment back pressure 阀, back pressure table/sheet in as 侧, right lower upper.

back pressure pressure and screw speed  

1.      screw speed degree and setting
in 此节 讨论 screw speed degree and setting is in process utilizing screw plastics toward material front 面, about/regarding screw toward front speed degree （ injection speed degree ）则 in relatively rear 章节论 and.

1.1 screw speed degree
soft 化 塑 material hot can, 部份 自 screw 转动, 转动愈 fast, temperature degree high, although screw speed degree can to very high value, this table/sheet 示 我们应该 use this high speed degree. relatively good method is according to plastics and types type and production cycle long short adjustment screw speed degree.
1.1.1 screw speed degree selection
screw speed degree effect/influence injection molding process stability degree and function has plastics upper hot amount. screw high speed 旋转时, to plastics abrasion scratch （剪切） can amount improve/increase efficiency, meanwhile increase material temperature degree uniform degree. this for production stability requirements is 极不受欢迎, is it can can make material local hot phenomenon. but also using/adopting high screw speed make can 源（ electrical can ） 消 consumption increase large, versus screw speed degree low, material temperature degree uniform property good, causes is has local hot phenomenon; but also from 经济角 degree 考虑, product manufacturing can relatively less, can need in to certain injection molding process production can force 规定, positive screw speed degree selection is and other important, this by setting value must can and production conditions parameters 天然变化.
当我们提 and screw speed degree 时, its most important parameters is screw performance speed degree. different 塑材 容许 is most large screw surface speed degree is 一样（请参看 table/sheet 6.2） this speed degree mono is mm ／秒 (mm/s), or is 肥尺／秒(m/s) or is made 尺／秒(ft/s), due to screw speed degree (rpm) and it surface speed degree property 关系, therefore different 塑材, it 们 容许 most large speed degree is versus and other.
1.1.2 screw speed degree 计算
large type injection molding machine screw speed degree relatively small type injection molding machine is less, causes is in and other speed degree large screw generate hot can ratio small screw high very more, in upper can below/following 列公式 table/sheet screw surface speed degree and screw and screw separation 钟 转 speed 关系;

screw surface speed degree (mm/s)= screw 直径(mm)× screw speed (rpm)×0.0524（ this 里0.0524 is about/regarding mm and rpm 转换常数）. plastics most and most large screw surface speed degree table/sheet 1.1.
table/sheet inner most large value can injection molding in production issues is 否源自 screw speed. upper very more injection molding in injection molding machine 调校时 using/adopting high screw speed degree 而不自觉, plastics thermal degradation phenomenon 才醒觉 need low screw speed degree （ plastics thermal degradation phenomenon can from parts disadvantages 知）, screw speed is 洽当时, material temperature degree relatively is stability, injection molding machine screw and material plant/unit abrasion loss degree relatively light micro.
1.2 screw 复位
screw is injection molding cycle process rear, screw toward rear 移动至原先未 injection 时 位置, screw rear 时 旋转 speed degree is 一预先 setting value, meanwhile has 一预先 setting back pressure pressure function in screw upper, screw therefore can stability rear is due to material inner plastics by toward front speed degree is stability, meanwhile material in material front 部不断 increase lower generate pressure function in screw upper, make it toward rear 移动至原先 位置.
1.2.1 screw 精确复位 important property
screw cycle 复位精确 degree is non important. this 位置决定 in lower cycle screw need toward front 推动 实际距离（ screw 行程）以便 mold cavity can in holding pressure front can to filling, this effect/influence its rear injection time, filament material long degree and parts weight －－ especially is holding pressure 转换 模式 is 行程决定 or is time 决定时, therefore screw 复位 精 degree 愈不准确, production process unstable property large. screw 复位变化 usually is 由 于 screw in rear setting amount （计 amount 位置）; screw rear 时应停 in setting amount 位置. can is screw 往往退 rear 一点引致 in screw front 端 熔 material 容积发生变化. screw 直径愈 large, screw 越位程 degree more add need control, good injection molding is make scope/range control in 0.4mm(0.16in) inner, most good is control in 0.2mm(0.008in) inner.

背壓 形 formed, function 與調校
 

day 期: 2009-02-11
 

一,    back pressure formed

    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; full electrical machine screw rear speed degree （ retardant force ） is AC伺服阀 control.

二,    适当调校 back pressure benefits

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,熔 material in screw in and material and screw 间隙 漏流 amount increase large,会 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.

4, back pressure high, material pressure high, rear nozzle easy 发生 熔胶流涎 phenomenon, lower 次射胶时, water runner inner cold material 会堵塞 water or products in cold material 斑.

5, in process in, 常会因 back pressure large, nozzle 出现漏胶 phenomenon, raw materials 并导致射嘴附近 发 hot bad.

6, machine and screw machine abrasion loss increase large.

五, back pressure 调校    

   injection molding back pressure 调校应视 raw materials property can, drying 情况, product structure and quality 状况而定, back pressure generally in 3-15kg/cm product surface has less gas 花, mixed color, sink marks and product dimensions, weight large 时, can increase back pressure. 当射嘴出现漏胶, 流涎, material hot separation understanding, product color and material slow can 考虑适当 decrease low back pressure.
 

brief overview back pressure

一, back pressure formed     
     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 （我不会 upper sheet/slice, need has sheet/slice comparison 清楚）; full electrical machine screw rear speed degree （ retardant force ） is AC伺服阀 control.  
二, 适当调校 back pressure benefits
   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. 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.
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,熔 material in screw in and material and screw 间隙 漏流 amount increase large,会 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.
4, back pressure high, material pressure high, rear nozzle easy 发生 熔胶流涎 phenomenon, lower 次射胶时, water runner inner cold material 会堵塞 water or products in cold material 斑.
5, in process in, 常会因 back pressure large, nozzle 出现 漏胶 phenomenon, raw materials 并导致射嘴附近 发 hot bad.
6, machine and screw machine abrasion loss increase large.

五, back pressure 调校    
  
   injection molding back pressure 调校应视 raw materials property can, drying 情况, product structure and quality 状况而定, back pressure generally in 3-15kg/cm 3. product surface has less gas 花, mixed color, sink marks and product dimensions, weight large 时, can increase back pressure. 当射嘴出现漏胶, 流涎, material hot separation understanding, product color and material slow can 考虑适当 decrease low back pressure.   
   back pressure is injection molding process in control material quality and product quality important parameters 之一, combined back pressure for/regarding improve/increase product quality has important function, can overlook!

back pressure liquid pressure is back pressure force (即 back pressure,也叫回油 pressure). from upper 讲, liquid pressure 缸运动时, liquid pressure 油流出 that 腔都叫 back pressure 腔, or 回泊腔. usually back pressure or 回油腔却 is liquid pressure front 进, especially is 工进时 back pressure or 回油腔. back pressure force (即 back pressure) direction and 进油腔 liquid pressure versus 反,消 consumption separation rate,但却 increase 运动 平稳- property, especially in outer negative 载突然变 small decrease is 零时, can for system 起缓冲 function. back pressure is is back pressure 腔建立 back pressure use, make from 回油腔流回油箱 油 liquid formed retardant force back pressure force. back pressure force easy large,否则功 rate loss large, efficiency reduce; easy small,否则不起 function.
      back pressure can 知, can back pressure has:节流阀, speed 阀, 溢流阀, 顺序阀, mono toward and other. its in,溢流阀做 back pressure most good, can maintain back pressure 恒定; mono toward back pressure 阀时,因 its elastic rigid degree soft,故应 will mono toward upper relatively hard elastic 簧, make its pressure to 0.2Mpa~0.6Mpa
for machine 构而言 back pressure is liquid from machine to or 油泵吸油口时,执行 machine 构回油处 pressure.
for system back pressure is toward 阀T口 pressure. formed: tube/pipe 路 沿程 loss 失, through 各阀（包括滤油 device / cooling device and other ） pressure loss 失.