Shanghai Daoqin Plastics Co., Ltd.

当 melt in high speed, high pressure conditions lower 注入容积 relatively large type 腔时, easy generate melt phenomenon, 此时, melt surface 出现横 toward fracture, fracture is coarse 糙 夹杂 in parts table/sheet formed 糊斑. especially is a small amount of material 直接注入容 easy large type 腔时, melt more is heavy, 呈现 糊斑也就越 large.

melt essence is due to high poly material material elastic property is generate, material in material in flow 时, material 筒附近 熔 material to abrasion scratch, force relatively large, material flow speed degree relatively small, material from nozzle 注出, tube/pipe function force 消失, material in 部 熔 material speed high, 筒壁处 熔 material by in 心处 熔 material belt/tape accelerated, due to material flow is versus for 连续, inner outer material flow speed degree will heavy new 排列, 趋于平均 speed degree.

in process in, material will 发生急剧 应 force will generate 应变, injection speed degree fast, to force especially large, large material can force, melt 破裂.

if material in runner in has 突然 形状变化, 如直径 shrinkage, expand large and 出现死角 and other, material in 死角处停留 and ring, it and positive material force different, 剪切形变 relatively large, its mixed positive material in 注出时, due to 两者 形变恢复不一致, can combined, 若悬殊 very large, 则发生 fracture 破裂, its performance 形式也 is melt 破裂.

1. attention/notes remove runner in 死角, make runner amount 流线化;

2. 适当 improve/increase material temperature, decrease/reduce material time, make its 形变容 easy and combined;

3. in raw materials in add low separation material, is material molecular weight low, distribution wide, has decrease light elastic property 效应;

4. 适当 control injection speed degree and screw speed;

5. is combined 理设置 gate and selection positive gate 形式, this versus important, table/sheet 明, using/adopting expand large type gate, gate (隧道 gate) relatively is 理想. gate most good selection in material 先注入 渡腔 rear again relatively large 容腔, need make material 直接进入 relatively large 容腔.

this is 导致塑 parts surface generate and important causes, especially is injection speed degree large small for its effect/influence very large, material slow speed type 腔时, material flow is 层流;当 injection speed degree upper rise to value 时, flow 状态逐渐变 is 紊流.

generally lower, 层流形 formed parts surface relatively is light 亮平整, conditions lower formed parts not only surface easy 出现糊斑, but also parts internal easy generate gas 孔. therefore, injection speed degree can high, will material control in 层流状态 lower 充模.

if material temperature degree high, easy 引起熔 material separation understanding 焦化, 导致塑 parts surface generate 糊斑. generally injection molding machine screw 转数应 small 于90r/min, back pressure small 于2mpa, this can material generate amount scratch hot.

if molding process in due to screw 退回时 旋转 time long generate amount abrasion scratch hot, can through increase screw speed, long molding cycle, reduce screw back pressure, improve/increase material material temperature degree and using/adopting lubricated property raw materials and other methods 予以克服.

injection process in, material 沿螺槽回流太 more and ring has resin 滞留, 都会导致熔 material drop poly separation understanding. for 此, selection viscosity relatively high resin, reduce injection pressure, use long comparison large injection molding machine. injection molding machine commonly used ring comparison easy 引起滞留, make its separation understanding color, separation understanding color understanding material type rear, formed color or black 焦点. for 此, 应定期清理以 nozzle is in screw system.

if mold gas by demolding agent and raw materials solid material retardant 塞, mold gas 设置不够 or 位置不 positive 确, and speed degree fast, mold inner and 排出 空 gas hot pressure shrink generate high temperature gas 体都会 make resin separation understanding 焦化. for 此, remove retardant material, reduce clamping force, improvement mold gas defect.

mold gate and 位置 确定也 versus important, in design 时应充 separation 考虑熔 material flow and mold gas property can.

in addition, demolding agent use amount can more, type surface need maintain relatively high light degree.

if raw materials in water separation and easy material content high, melt flow index large, lubricant use amount 都会引起烧焦 and fault/failure.

for 此, use material drying device or its it drying methods raw materials, use melt relatively small resin and decrease/reduce lubricant use amount.