灌水器管材模具机头的改进

本文主要介绍灌水器管材机头模具设计装置的改进,为了增强管材的密度和消除分流器支架上的分流筋产生的结合线,对机头的结构特点进行了优化设计。     

带阻流装置的管材机头设计

介绍一种带阻流装置的塑料管材机头模具设计,为了增强管材的密实度和消除分流器支架上的分流筋产生的结合线,对机头的结构特点进行了优化设计。结果表明:与普通挤出管材机头对比,物料密实度得到增加,加工性能和挤出稳定性得到显著提高。     

带阻流装置的管材机头设计

介绍一种带阻流装置的塑料管材机头模具设计,为了增强管材的密实度和消除分流器支架上的分流筋产生的结合线,对机头的结构特点进行了优化设计。结果表明:与普通挤出管材机头对比,物料密实度得到增加,加工性能和挤出稳定性得到显著提高。     

钢丝挤出覆胶机头

本实用新型为一种用于子午胎的钢丝帘线覆胶的挤出机机头，至少包括左、右机头，左、右机头连接成机头本体，机头本体一端设有胶料进口；机头本体一侧设有钢丝进口．另一侧设有钢丝和胶料出口，在钢丝和胶料出口上下2侧的左、右机头之间沿机头纵向设有连通于胶料进口和出口的覆胶流道，     

对平左拉工艺线的探讨

在连续玻璃纤维拉丝生产中,漏板、集束轮、机头之间具有一定的相对位置,一般称为拉丝工艺线布置或拉丝工艺位置。根据机头与漏板相对位置的不同,工艺线布置可以分成右拉或左拉两种形式。一般机头位于漏板右下方称为“右拉”,机头位于漏板左下方称为“左拉”。使用双机头自动换筒拉丝机生产时,则有三种形式,即     

巨型工程机械子午线轮胎钢丝帘线挤出机液压式机头的优化设计

对巨型工程机械子午线轮胎钢丝帘线挤出机传统的旋转、拆卸式机头进行重新设计与优化,改为以导轨形式液压前后水平移动及液压插销式锁紧的机头.采用新结构机头后:钢丝帘线挤出上下覆胶均匀;口型板和穿线板采用卡槽式设计,更换钢丝帘线规格时,操作时间缩短,设备产能提升;采用液压式插销和滚珠丝杠,装卸操作简化,节约时间,降低劳动强度;...     

挤出吹塑薄膜流道线产生的原因及解决方案

对螺旋机头在塑料薄膜挤出吹塑过程中容易产生白色流道线和透明流道线的原因进行了分析,研究了从加工工艺和模头设计两种不同的途径解决白色流道线和透明流道线的具体方法,通过流变学理论进行建模并针对有关塑料进行仿真模拟分析,进一步完善螺旋机头的设计,根除或减少流道线的产生,以满足生产和试验的更高要求。     

结构参数对轿车子午线轮胎滚动阻力的影响

针对不同规格的轿车子午线轮胎,采用单变量分析方法,研究结构参数（成型机头宽度、带束层结构、冠带层结构等）对轮胎滚动阻力的影响。结果表明,通过合理增大成型机头宽度、选取合适的带束层钢丝帘线规格、增大带束层钢丝帘线压延密度、减小带束层钢丝帘线角度和冠带层帘线压延密度等方法均可以降低轮胎滚动阻力。     

半鼓式成型机头引起钢丝圈上抽的原因浅析

分析影响钢丝圈上抽的几个主要因素：帘线假定伸张值、成型机头宽度、成型机头肩部曲线、帘线成型伸张值、帘布层间级差、钢丝圈直径、帘布裁断角度，并提出相应的解决措施。     

压延工艺对轮胎质量的影响

锦纶帘布张力压延后长度比压延前增大0．5％～1.5％。在轮胎结构设计时，锦纶66帘线的假定伸张值取1.02～1.04，锦纶6帘线取1.01～1.04，并适当增大成型机机头宽度(已投产的轮胎可适当减小裁断角度，不改变机头宽度)，以减小压延后帘线定负荷伸长率变化对轮胎质量的影响。     

Modification to weld lines in extruded thermoplastic pipe using a rotating die system

When a polymer melt flows around the cross head or past the fins of a torpedo in a pipe die, a weld line is produced where the separated melt streams rejoin. This weld line may result in an area of weakness in the extruded pipe, although in the case of unfilled materials the effect can be reduced by using a compression section in the die. However, With fiber reinforced polymers it is unlikely that fibers will cross the weld line, and a reduction in strength is inevitable. It is shown theoretically that by rotating the core of the extrusion die the weld line can be modified to form a spiral around the pipe wall, with a large-surface area for improved strength. Experimental investigations, which employ photographs of thin sections of pipe containing carbon black particles, support these conclusions.     

Effect of a separator in a sheet die on the anisotropy of tear strength of extruded medium density polyethylene

Sheets of medium density polyethylene (MDPE) were extruded through a slit die containing an internal separator. Thus, the melt stream was momentarily split before emerging from the die. A line of separation was evident in the extruded sheets. It is attributed to incomplete welding or healing. Measurements of tear energy G_c revealed that the extruded sheets were anisotropic and that the weld line was extremely weak after extrusion start-up, only about 1/5 of the strength elsewhere. As extrusion continued, the strength of the weld line increased to reach that of the bulk material after about 10 min. This is attributed to an increasing temperature of the melt in the die region, aiding interdiffusion. A sample containing 30% by weight of short glass fibers showed less initial weld-line weakness but the weld line remained weak in this case, even after long extrusion times.     

A numerical and experimental study on weld lines formation and strength in extrusion

In this work, we present a study on numerical and experimental approaches aiming to improve our understanding about the relation between the flow conditions and the strength of weld lines in extruded profiles. For this purpose, a prototype extrusion die that comprises a movable spider leg is used to produce tapes under different flow conditions, by varying the location of the spider leg and the flow rate. The same case studies are numerically studied, considering a viscoelastic Giesekus constitutive model. The numerical results are then investigated to identify potential relationships between the flow conditions, in which the weld lines are formed, with the strength of the weld line experimentally characterized. The results obtained allow identifying a clear correlation between the flow conditions and the weld‐line strength. POLYM. ENG. SCI., 58:249–260, 2018. © 2017 Society of Plastics Engineers     

注塑成型熔接痕缺陷研究进展

根据国内外对熔接痕的各项研究,介绍了熔接痕的分类、形成过程、熔接痕的特点、数学模型及预测模型、影响熔接痕的各种因素等内容;并介绍了控制熔接痕的措施,对于全面了解熔接痕缺陷及研究进展将会有一定帮助.     

注射模浇注系统对成型工艺和塑件质量影响研究

通过筒形结构的塑件CAE模拟分析,设置不同的分流道的形状,浇口形状、位置和数目,研究对于流动、填充时间、最大注射压力、最大锁模力和熔接痕等成型工艺和塑件质量的影响。     

Weld line studies on transfer-molded thermosetting composite materials

Multiple gating and the presence of inserts make weld lines (also known as knit lines) almost unavoidable in commercially produced moldings. These weld regions may be significantly weaker in strength than the bulk material away from the weld line. Hence, a molded section containing a weld line will only be as strong as the weld line, no matter how strong the surrounding bulk material. The influence of processing history on weld line performance is essential to optimally designed transfer-molded composite products with discontinuous-fiber-reinforced molding materials. This study has therefore been directed toward experimentally characterizing the weld line strength of a bulk molding compund (BMC) and a thick molding compound (TMC) as a function of the mold temperature, fill time/fill rate, and the postbake operation.     

Film insert molding as a novel weld‐line inhibition and strengthening technique

Specimens with weld lines were produced via conventional and film insert molding techniques using two types of materials as the substrate resin, i.e. a polycarbonate/acrylonitrile‐butadiene‐styrene (PC/ABS) blend and glass fiber‐filled polycarbonate (PC‐gf). The formation and morphology of the weld line region was assessed with and without the presence of 0.5‐mm‐thick PC film inserts. The weld line formation and characteristics were found to be dependent on the extent of interaction between the injected resin and the mold surface or the film insert. Better interfacial interaction between the substrate and film led to the distortion of the weld line orientation, which significantly enhanced the mechanical properties of the weld line. The incorporation of glass fibers into the substrate resin would usually reduce the resistance of the weld line towards tensile, flexural and impact loadings. However, with the attachment of film inserts, the mechanical properties of the weld line region have significantly improved, even with the presence of rigid fibers. Upon examination of tensile and impact fracture surfaces of film insert specimens, a unique orientation of fibers across the weld line (parallel to the flow direction and perpendicular to the weld line) could be observed at regions directly under the film. The combination of favorable properties from the unique fiber orientation and distortion of the weld line, as well as the ability of the film to effectively dissipate forces towards a larger area, have synergistically contributed towards the mechanical property enhancement of the weld line region in film insert moldings. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

A new approach to increase weld line strength of incompatible polymer blend composites: selective filler addition

A ternary blend composite composed of two immiscible organic phases, polypropylene (PP) and polyamide-6 (PA), and talc as inorganic filler is studied in terms of weld line properties and morphology. Effects of different filler levels as well as compatibilizer on weld line strength under tensile loading condition of each polymeric phase are investigated. Special attention is paid to relate the nature of dispersed domains especially in weld line regions with final performance. It is observed from scanning electron microscopy (SEM) studies that addition of talc filler which is selectively wetted by dispersed PA phase dramatically reduces the elongated domain size in the weld line region and causes to much more homogeneous microstructure. The selective wetting of talc particles by PA phase, therefore, seems to be beneficial in increasing weld line strength via increasing the viscosity of the PA dispersed phase and consequently decreasing the elongated domains at weld line region. Compared to uncompatibilized blend composites, compatibilized ones represent much higher weld line strength for all levels of talc loading.     

基于Kriging和NSGA-Ⅱ的辅以困气改善的熔接痕优化策略

从熔接痕的成型机理出发,考虑了困气状况和熔合温度对熔接痕熔合质量的影响,提出一种以困气改善辅助提升熔接痕熔合质量的方法,建立了以“气穴面积”和“熔接痕处流动前沿温度”为熔接痕熔合质量指标的多目标评价体系,并构建了一种基于Kriging模型和非支配排序遗传算法（NSGA-Ⅱ）的多目标寻优策略,以实现工艺参数的择优选择。以多孔板熔接痕优化为例,选用拉丁超立方抽样（LHS）设计实验,建立并检验反映工艺参数和优化目标之间影响规律的Kriging模型,采用NSGA-Ⅱ确定多目标优化问题的Pareto前沿及其最优解。仿真及生产实验结果表明所建立的多目标优化策略能有效实现熔接痕的多目标优化,同时以困气改善辅助提升熔接痕熔合质量的方法效果显著。     

Effect of processing on weld line strength in five thermoplastics

Weld line strength has been measured in five engineering thermoplastics. The effect of processing parameters was studied using experimental design. Four parameters–holding pressure, injection velocity, melt temperature, and mold temperature–were varied in two levels. For each parameter setting the weld line strength was measured and compared with the bulk strength via a weld line factor (WL-factor), defined as: strength of specimens with weld line/strength of specimens without weld line. Results from flexural tests on both filled and unfilled materials showed that the weld line factors for cold weld lines varied between 0.25 and 0.98 depending on material and parameter setting. Highest WL-factors were obtained for unfilled materials and using high melt temperature, high holding pressure, and low mold temperature. Results from instrumented falling weight impact tests on weld lines sometimes showed a WL-factor higher than 1.0. There was generally a poor correlation between results from impact tests and results from flexural tests.