Shanghai Daoqin Plastics Co., Ltd.

熔接痕(Weld Lines), in injection molding products more defect in, 熔接痕 is most is 普遍, remove less 数几何形状 non simple injection molding parts outer, in large more injection molding parts upper （形状 usually is strip/profile or V形槽）, especially is need use more gate mold and parts large type complex product.

熔接痕 not only make parts appearance quality to effect/influence, but also make parts force property can, impact strong/high degree, tensile strength, fracture elongation and other, to different degree effect/influence. in addition, 熔接痕 also to products design and parts lifespan belt/tape heavy effect/influence, therefore, can can 予以避免 or improvement.

熔接痕 generate main/primary causes is: melt plastics in type in to parts, 孔洞, speed 不连贯 区域 or material in 断 区域时, more melt combined; gate 喷射充模时, material material can full melt combined.

low temperature material separation combined property can relatively 差, easy formed 熔接痕. if parts inner outer surface in 同一部位 generate fine 纹时, is due to material temperature low 引起 熔接 defect. for 此, can improve/increase material and nozzle temperature degree or long injection cycle, make material temperature upper rise. meanwhile, made mold inner cooling water through amount, improve/increase mold temperature degree.

generally lower, parts 熔接痕处 strong/high degree relatively 差, if for mold in generate 熔接痕 versus 应部位进行 local add hot, improve/increase molding parts 熔接部位 local temperature degree, can improve/increase parts 熔接处 strong/high degree.

if due to need, must using/adopting low temperature molding process 时, can improve/increase injection speed degree increase injection pressure, from improvement material combined property can. can in raw materials formulation in increase use a small amount of lubricant, improve/increase material flow property can.

2.  mold defect

mold system structure parameters for material 熔接状况 has very large effect/influence, is defect main/primary generate material separation combined. therefore, amount using/adopting separation less gate 形式并 combined selection gate 位置, amount 避免充模 speed rate 不一致 and material in 断. in can can conditions lower, selection 一点式 gate, is this type of gate generate more material 流, material from direction combined, easy 避免熔接痕.

if mold system in, gate more or small, more gate 定位不 positive or gate to material 熔接处 间距太 large, system runner Imported and separation runner runner 截面太 small, material retardant force large 都会引起熔接 defect, make parts surface generate relatively 明现 熔接痕. for 此, can can decrease/reduce gate 数, combined 理设置 gate 位置, add large gate 截面, 设置辅助 runner, expand large runner and separation runner 直径.

is anti low temperature material mold cavity generate 熔接痕, in improve/increase mold temperature degree meanwhile in mold inner cold material 穴.

in addition, parts 熔接痕 generate 部位经常 due to high pressure 充模而 generate flash, but also generate this category of flash rear 熔接痕不会 generate shrink 孔, therefore this category of flash 往往不 as is fault/failure troubleshooting, is in mold upper generate flash 部位开一 very shallow small 沟槽, will parts upper 熔接痕转移 to add flash small upper, parts molding rear again will small remove, this is troubleshooting 熔接痕 fault/failure commonly used types methods.

3.  mold gas defect

当熔 material weld lines and mold clamping or heavy combined 时, mold cavity inner more material pressure gas can from clamping or 嵌缝处排出;

但当 weld lines and clamping or 嵌缝不 heavy combined, gas 孔设置不当时, mold cavity inner by material pressure 残留空 gas method 排出, bubbles in high pressure lower by strong/high force pressure, 体渐渐变 small, most by pressure shrink formed 一点, due to by pressure shrink gas separation can in high pressure lower is hot can, 因而导致熔 material material temperature degree rise high, its temperature degree and other or high raw materials separation understanding temperature degree 时, 熔接点处便出现黄点, its temperature degree high raw materials separation understanding temperature degree 时, 熔接点处便出现 black spots.

generally lower, parts surface 熔接痕附近出现 this category of 斑点总 is in 同一位置反复出现, but also 出现 部位总 is property in material 点处, in as process in, need will this category of 斑点误认 is 杂质斑点. generate this category of main/primary causes is due to mold gas defect, it is material high temperature separation understanding rear formed carbon 化点.

出现 this category of fault/failure rear, 首先应检查 mold gas is by material solid material or other material retardant 塞, gate has material. if retardant material remove rear still carbon 化点, in mold material increase gas 孔. can through heavy new gate or reduce combined force, increase large gas accelerated material combined 流. in process as 方面, can reduce material temperature and mold temperature degree, shrink short high pressure injection time, reduce injection pressure and other measures.

4.  demolding agent use 不当

demolding agent use amount more or selection product types positive 确都会引起塑 parts surface generate 熔接痕. in injection molding in, generally in and other easy demolding 部位才 uniform coating use a small amount of demolding agent, upper amount decrease/reduce demolding agent use amount.

for/regarding various demolding agent selection, must according to molding conditions, parts outer and raw materials product types and other conditions 确定. 例如, pure hard acid zinc can used for remove polyamide (PA) and transparent plastics outer various plastics, and mixed combined rear can used for polyamide (PA) and transparent plastics. also silicon 油甲苯 solvent liquid can used for various plastics, but also coating one-time can use very 久, its coating rear add hot dry, use method comparison complex.

5.  plastics structure design combined 理

if parts thick design thin can thick thin 悬殊以 and parts more, 都会引起熔接 defect. thin parts molding 时, due to material solid fast, easy generate defect, but also material in process in is in thin 壁处汇 combined formed 熔接痕, thin generate 熔接痕, 就会导致塑 parts strong/high degree reduce, effect/influence use property can.

therefore, in design parts structure 时, ensure parts most thin 部位必 must large molding 时允许 most small thick. in addition, amount decrease/reduce parts use thick can can 趋于一致.

6.  other causes

当 use raw materials water separation or easy material content high, mold in 油渍末清洗 dry 净, mold cavity in has cold material or material inner fiber filler distribution defect, mold cooling system design combined 理, material solid fast, parts temperature degree low, nozzle small, injection molding machine can force 不够, injection molding machine material in pressure loss large, 都会导致 different degree defect.

for 此, in as process in, for different 情况, separation 别采取 raw materials drying, 定期清理 mold, mold cooling water 道设置, control cooling water amount, improve/increase parts temperature degree, use relatively large nozzle, use relatively large specifications injection molding machine and other measures solution.