Shanghai Daoqin Plastics Co., Ltd.

injection molding machine injection molding core process is 充模. plastics melt mold cavity flow type （ flow 状态）决定 made parts poly structure and table/sheet structure （如 crystallization, separation orientation, combined uniform property and other ）, most effect/influence made parts use property can.

plastics melt from gate type positive 常充模 methods is rear melt melt front 缘, expand 展, type 腔平面直至抵达 type inner 壁, 充满整 type 腔. flow non positive 常形式 is 喷射流 and 滞流充模形式. 喷射流 and performance is 充模开始时 melt relatively large can, through gate 喷射入 type 腔, separation formed melt and fine filament 状直接喷射 to gate for type 腔壁面 upper, rear 续 充模 process also expand dispersion flow that 样. 充模时发生不 positive flow flow make melt generate separation and combined, formed relatively more melt 熔接缝, to made parts property can belt/tape effect/influence.

effect/influence melt flow factors has: melt temperature degree, mold temperature degree, injection pressure, injection speed degree and mold type 腔 空间 large small, gate dimensions and 位置.

using/adopting color material injection molding method and transparent mold method, different process conditions lower melt flow 形式变化. color material injection molding method is in transparent raw materials resin in mixed different material, injection molding Sample, products upper flow marks 花纹, according to flow marks 花纹判断 is positive 常 铺展式充模 flow, also is non positive 常 充模 flow. transparent mold method is using/adopting transparent mold, 直接观察充模 flow features methods.

injection molding machine as principle : screw （ or 柱塞） 推 force, will already good melt 状态（即 viscous 流态） plastics injection combined good mold cavity inner, solid type rear products process process.

injection molding is 一 循 ring process, cycle main/primary 包括: amount add material —熔 melt 塑化—施 pressure injection —充模 cooling —启模取 parts. 取出塑 parts rear also again 闭模, lower 一 循 ring.

injection molding machine as 程序
nozzle front 进→ injection → holding pressure →预塑→倒 shrink → nozzle rear 退→ cooling → mold opening → ejection →退针→开门→关门→ clamping → nozzle front 进.

generally injection molding machine injection plant/unit, clamping plant/unit, liquid pressure system and electrical control system and other separation.
injection molding basic requirements is 塑化, injection and molding. is achieve and ensure molding products quality front 提, is meet/satisfy molding requirements, injection must ensure has pressure and speed degree. meanwhile, due to injection pressure very high, versus in mold cavity in generate very high pressure （ mold cavity inner pressure generally in 20~45MPa between ）, therefore must has large clamping force. can 见, injection plant/unit and clamping plant/unit is injection molding machine key/critical parts.

预塑动 as selection
according to add material front rear base/seat is rear 退, nozzle is 否离开 mold, injection molding machine generally has types selection.

（1） solid add material: front and rear nozzle 都始终贴进 mold, base/seat 也不移动.

（2） front add material: nozzle mold 进行预塑 add material, 预塑完毕, base/seat rear 退, nozzle mold. selection this type of methods is: 预塑时 utilizing mold injection 孔抵住 nozzle, 避免熔 material in back pressure relatively high from nozzle 流出, rear can nozzle and mold long time 接触而 generate hot amount 传递, effect/influence it 们各自 temperature degree versus for stability.

（3） rear add material: injection formed rear, base/seat rear 退, nozzle mold rear 预塑, 预塑完注 base/seat again front 进. as suitable for processing molding temperature degree especially narrow plastics, due to nozzle and mold time short, hot amount 流失, 也避免 熔 material in nozzle inner solid. injection pressure selection
injection molding machine injection pressure pressure 阀进行 adjustment, in pressure lower, through high pressure and low pressure 油路 通断, control front rear injection pressure high low.
普通 in type above injection molding machine has types pressure selection, high pressure, low pressure and high pressure rear low pressure. high pressure injection is injection 油缸通入 high pressure pressure achieve. due to pressure high, plastics from 一开始就 in high pressure, high speed lower mold cavity. high pressure injection plastics 入模迅 speed, injection pressure table/sheet upper rise very fast. low pressure injection is injection 油缸通入 low pressure pressure achieve, injection process pressure table/sheet upper rise slow, plastics in low pressure, low speed lower mold cavity. high pressure rear low pressure is according to plastics types type and mold requirements from time upper control 通入油缸 pressure pressure high low achieve.
is meet/satisfy different plastics requirements has different injection pressure, can using/adopting more different screw or methods, this meet/satisfy injection pressure, also separation machine production can force. in large type injection molding machine in tool has more injection pressure and more grade injection speed degree control function, this more can ensure products quality and degree.
injection speed degree selection
generally injection molding machine control sheet/plate upper has fast speed — slow speed use meet/satisfy injection speed degree requirements. in liquid pressure system in has large amount and small amount meanwhile 运行供油. 当油路接通 large amount 时, injection molding machine achieve fast speed clamping, fast speed injection and other, liquid pressure provide small amount 时, injection molding machine various as slow 进行.
ejection selection
injection molding machine ejection has machine ejection and liquid pressure ejection types, has also has gas ejection system, ejection 次数设 has mono and more types. ejection as can is 手动, can is 自动. ejection as is mold opening 停止限位开关 启动.
clamping control
clamping is large machine force will mold combined 紧, 以抵挡 injection molding process melt plastics high pressure injection and filling mold mold 发生 巨 large force.
injection molding machine clamping structure has full liquid pressure and machine 械连杆式. tube/pipe is that types structure 形式, most rear is 由连杆完 full 伸直 实施 clamping force. 连杆 伸直 process is active sheet/plate and sheet/plate process, is 四根拉杆受 force by tensile process.

mold opening control
当熔 melt plastics injection mold cavity inner and cooling formed rear, 随 便 is mold opening as, products. mold opening process separation stage/phase. stage/phase slow speed mold opening, anti made parts in mold cavity inner 撕裂. stage/phase fast speed mold opening, shrink short mold opening time. stage/phase slow speed mold opening, decrease low mold opening property formed impact and 振动.
 

injection molding process conditions control   

injection speed degree control
injection speed degree control is will screw injection separation is 3~4 stage/phase, in stage/phase in separation use 各自适当 injection speed degree. in melt plastics rigid through gate decrease slow injection speed degree, in process in using/adopting high speed injection, in 充模结束时 decrease slow speed degree. using/adopting this methods, can anti material, remove flow marks and decrease/reduce products residual stress and other.
low speed 充模时流 speed 平稳, products dimensions comparison stability, relatively small, products internal stress low, products inner outer toward force 趋于一致（例如 will certain poly carbon acid made parts 浸入四 chlorine carbon in, use high speed injection molding made parts has cracking toward, low speed cracking ）. in relatively is slow conditions lower, material temperature 差, especially is gate front rear material temperature large, has 助于避免 shrink and 凹陷 发生. due to time relatively long easy make made parts delamination and combined defect 熔接痕, effect/influence appearance, but also make machine strong/high degree large large reduce.
high speed injection 时, material speed degree fast, high speed 充模顺利时, material very fast type 腔, material temperature decline less, degree decline less, can using/adopting relatively low injection pressure, is types hot material 充模态势. high speed can made parts gloss degree and slip degree, remove 接缝线 phenomenon and delamination phenomenon, shrinkage small, color uniform 一致, for made parts relatively large separation can ensure 丰满. easy generate products 发胖起泡 or made parts 发黄, 甚至烧伤变焦, or formed demolding difficult, or 出现充模不均 phenomenon. for/regarding high degree plastics has can can melt 破裂, make made parts surface generate 云雾斑.
lower 列情况 can using/adopting high speed high pressure injection: （1） plastics degree high, cooling speed degree fast, long process/workflow made parts using/adopting low pressure slow speed can full type 腔各 角落; （2）壁 thick thin made parts, material to thin easy cold 凝而滞留, must using/adopting one-time high speed injection, make material can amount a large amount of consumption front 立即进入 type 腔; （3） use glass fiber reinforcement plastics, or has relatively a large amount of filling material plastics, flow property 差, is to surface light slip uniform made parts, must using/adopting high speed high pressure injection.
for high grade precision products, thick made parts, thick large and tool has relatively thick and made parts, most good using/adopting more grade injection, grade, grade, grade 甚至五 grade.
injection pressure control
usually will injection pressure control separation formed is one-time injection pressure, injection pressure （ holding pressure ） or above injection pressure control. pressure 切换时 machine is 否适当, for/regarding anti inner pressure high, anti material or material and other is non important. products ratio 容取决于 holding pressure stage/phase gate 封闭时 熔 material pressure and temperature degree. if from holding pressure to products cooling stage/phase pressure and temperature degree 一致, that products ratio 容就不会发生改变. in 恒定 模塑 temperature degree lower, products dimensions most important parameters is holding pressure pressure, effect/influence products dimensions most important amount is holding pressure pressure and temperature degree.

screw back pressure and speed control
high back pressure can make material obtain strong/high 剪切, low speed make plastics in machine inner to relatively long time. currently relatively more use for back pressure and speed meanwhile 进行程序 design control. 例如: in screw amount full 行程先 high speed, low back pressure, again to relatively low speed, relatively high back pressure, rear formed high back pressure, low speed, most rear in low back pressure, low speed lower 进行塑化, this 样, screw front material pressure to large separation 释放, decrease/reduce screw 转动惯 amount, from improve/increase screw amount 精确程 degree. high back pressure 往往造 formed color agent color degree increase large; machine and machine screw machine abrasion loss increase large; cycle long, production efficiency decline; nozzle easy 发生流涎, recycled material amount increase; make using/adopting 自锁式 nozzle, if back pressure high design elastic 簧闭锁 pressure, 亦会造 formed fatigue bad. therefore, back pressure pressure need 调 恰当.
随 technology 进步, will small type machine nano injection molding machine control system, using/adopting machine control injection molding process already formed is can can.

injection molding front 准备工 as
molding front 准备工 as can can inner very more, 如: material material processing properties 检验（测定 plastics flow property, water separation content and other ）; raw materials processing front color and 选粒; material preheating and drying; parts and preheating; mold trial and material 筒清洗 and other.
raw materials 预处理
according to plastics features and material 情况, generally in molding front for raw materials appearance and process property can testing. if use plastics is powder 状, 如: polyvinyl chloride (PVC), also 应进行配 material and dry mixed; if products has color requirements, can add amount color agent or masterbatch material; supply material 往往含 has different degree water separation, solvent agent and its it easy low separation material, especially is tool has wet toward plastics water amount is ultra- processing 允许 限 degree. therefore, in processing front must drying 处理, 并测定含 water amount.

嵌 parts preheating
injection molding products is assembly and strong/high degree requirements, need in products in metal parts. injection molding 时, in mold cavity in cold metal parts and hot plastics melt cooling 时, due to metal and plastics shrinkage rate significantly different, make parts generate very large internal stress （ especially is polystyrene (PS) and other rigid property high poly material more more significantly ）. this type of internal stress in make parts 周围出现 cracks, products use property can large large reduce. this can through selection thermal expansion coefficient large metal （ aluminum, and other ） as parts, and will parts （ especially is large metal parts ） preheating. meanwhile, design products in parts 周围安排 relatively large thick and other measures.

machine 筒 清洗
new injection molding machine use front, or in production in need product, more raw materials, color or plastics in has separation understanding phenomenon 时, need for injection molding machine machine 筒进行清洗 or 拆洗.
demolding agent selection
demolding agent is can make plastics products easy demolding material 质. hard acid zinc suitable for remove polyamide (PA) outer generally plastics; liquid wax used for polyamide (PA) type plastics relatively good; silicon price 昂贵, use 麻烦, relatively less use.
use demolding agent control amount, amount less use or use. spray coating amount effect/influence products appearance, for products color 饰也会 generate defect effect/influence.
injection molding products generate defect causes and its methods
in injection molding processing process in can can due to raw materials 处理不 good, products or mold design combined 理, * as has combined process * as conditions, or machine 械方面 causes, make products generate 注不满, 凹陷, flash, bubbles, cracks, warpage deformation, dimensions and other defect.
for plastics products evaluation main/primary has 三 方面, is appearance quality, 包括完整 property, color, gloss and other; is dimensions and versus for 位置间 准确 property; is and applications versus mechanical properties, chemical property can, electrical property can and other. this quality requirements also according to products use combined different, requirements degree different.

screw can force is back pressure is 零, screw speed most large mono time inner can provide material amount.

evaluation screw design water 平, can through testing its can force and screw speed, back pressure and rate consumption and other for can force effect/influence 敏感程 degree. in design screw 时, screw can can can small, screw can 承受 转 speed can can high, from to can force high, quality good.

injection molding machine can force injection molding machine production can force and production efficiency. according to injection screw mechanism, due to screw property as and 塑化时 screw toward 移动以 and injection 时螺槽 inner material material and other function, formed plastics in inner melt process is non process, performance material toward temperature large, screw can force and rate consumption unstable.

screw 塑化时, back pressure for can force effect/influence is significantly, in screw process in, increase large injection 油缸 回泄 retardant force （ back pressure increase large ）时, increase large screw 均化段 front material pressure, make toward amount increase, can force versus reduce.

back pressure increase large, screw 驱动功 rate will increase large, screw speed and can force formed positive ratio, screw 驱动功 rate also positive ratio 于塑化 can force, therefore screw 驱动功 rate and screw speed formed positive ratio.
mold temperature degree uniform, improve/increase mold temperature 时, for injection molding process and products property can has lower effect/influence:

has melt flow, pressure micro reduce;

cooling time long, holding pressure time long, molding cycle long;

products demolding difficult, crystallization property polymer crystallization degree increase high （ products density improve/increase ）, rear shrinkage decrease/reduce, products shrinkage rate increase large;

products surface light degree improve/increase, products inner large separation toward degree decrease/reduce, internal stress reduce;
impact strong/high degree decline mold temperature degree non-uniform: products shrinkage non-uniform, from formed products generate internal stress, warpage deformation and force cracking. mold temperature low melt flow property reduce, 充模不满 or generate 熔接痕 strong/high degree low. products inner in relatively large internal stress easy generate warpage deformation or force cracking.