排气对注射成型过程的影响与排气槽参数的选择

注射成型过程中产品上出现的缺陷原因之一是由于模具的排气不良引起的,对充模过程中模腔内气体的状态变化可看作是绝热压缩和等温压缩过程,并分别对模腔内的气体压力和温度进行了计算,通过对计算结果的分析,指出模腔内滞留气体的压力和温度升高是造成塑件缺陷的主要原因,最后给出排气槽参数设计的原则和计算方法。     

基于TRIZ理论的注射成型工艺创新设计

模具温度是重要的注射工艺参数,也是注射成型中重要的技术冲突。通过TRIZ理论的冲突解决原理,进行注射成型工艺的创新设计,并与目前先进成型技术相佐证,说明TRIZ理论在注射成型工艺应用中的有效性,为下一步的创新提供参考依据。     

Fractal phenomena in powder injection molding process

1　INTRODUCTIONGenerally ,Thefilling processofpowderinjec tionmolding(PIM )isanalyzedbyrheologicaltheory .Rheologicalmodelismadeupofbasicconservatione quations(mass ,momentum ,energyconservatione quations)thatmustbesatisfiedbymeltfeedstockinPIM ,constitutiveequationthatisusedtodescribetheprocessing parametersofmaterials ,andcorre spondingrestrictiveconditions .Itisagroupofpartialdifferentialequationsandisalsoanonlineardynamicssystemofmanyinfluentialfactors .Thevariationofmaterialthermo…     

Effect of reprocessing on shrinkage and mechanical properties of ABS and investigating the proper blend of virgin and recycled ABS in injection molding

In this research, the effect of reprocessing of acrylonitrile–butadiene–styrene (ABS) on the mechanical properties of the polymer was studied through a five-stage reprocessing. To this end, the injection mold of the standard samples was manufactured. Then, using an injection molding machine, all of the virgin material was processed. After sampling, the rest of the parts were ground and then reprocessed under the same conditions. In order to get a proper combinational ratio of virgin and recycled ABS with respect to shrinkage and mechanical properties, another experiment was designed. In order to do this, virgin material was blended with 20%, 35% and 50% of the recycled material. The blends were reprocessed and samples were obtained. Impact, tensile, flexural and shrinkage tests, selected from ASTM standard, were used to investigate the mechanical properties of the polymer as well as its shrinkage. Furthermore, viscosity test was used to investigate the changes in the structure of the polymer. As the reprocessing cycles increased, shrinkage decreased and tensile and flexural ultimate strengths increased, more in flexural strength than in tensile. While Young's modulus slightly increased, viscosity decreased and consequently molecular weight decreased too. The proper blend for the least shrinkage was 50% whereas the best mechanical properties were achievable by the 20% blend. The obtained results suggest that reprocessing causes polymer degradation which is a result of the break in the bonds of poly butadiene. Moreover, it can be concluded that reprocessing in ABS can lead to the loss of effectiveness of some additives.     

水辅助注塑工艺介绍

介绍了新型注塑技术——水辅助注塑工艺的基本工艺原理和工艺过程,介绍了利用可视化研究方法观察水辅助注塑成型过程中熔体和水流在型腔的填充过程。在实验室中用锁模力为800 kN的常规注射机配备水注射辅助单元进行试验,所用注射材料为半结晶状态的聚丙烯。为了研究水辅助注射中熔体和水的流动特征,特别设计了一个可视化的模具应用于这项研究。一台高速的摄像机用来记录模腔填充的过程,长方形型腔配置3种不同的流道几何布局:平面流道、一个平面带2个不同高度的台阶、一个平面带有对称的肋板。观察和研究了充模过程中水辅助和聚合物的相互作用以及水的推展过程。     

水辅助注射成型充模过程的数值模拟研究

基于Hele-Shaw流动模型,采用广义牛顿流体本构方程,建立了三维薄壁塑件的水辅助注射成型充模过程数学模型,采用有限元/有限差分/控制体积法数值求解。对薄壁平板塑件的水辅助注射成型充模过程进行了模拟,模拟得到的熔体前沿位置与前人实验结果吻合较好,浇口处压力变化、水的厚度分布及平均温度分布合理,验证了所建立的模型和采用的数值模拟方法的有效性。     

外部气辅成型技术在高光注射成型工艺中的应用研究

以平板电视前壳上的螺柱结构为例,研究了外部气辅成型技术的密封和进气结构,获得了气辅参数对快速热循环高光泽塑件表面缩痕的影响规律,提出了消除塑件表面缩痕缺陷的有效方法。试验表明,在快速热循环注射成型技术中应用外部气辅成型工艺,通过采用有效的进气、密封结构以及合理的气辅工艺参数,能够很好地消除塑件在筋、柱部位对应表面上的缩痕缺陷,确保塑件外观平整无缩痕。     

网格生成方法对注塑流动模拟的影响

研究了注塑成型过程中CAD模型向CAE模型转换的方法和网格生成技术对注塑流动模拟的影响。给出了采用ANSYS自适应网格划分的功能，对CAD模型进行网格划分和数据重构，建立可用于C－MOLD软件分析的CAE模型，以及将CAD模型直接转换为C－MOLD可分析模型的技术方法。在同等工艺条件下，分析了两种CAE模型注塑成型模拟的结果，比较了模拟结果与实际注塑件生产的误差。验证了上述技术方法的可行性。     

The metal injection molding process comes of age

Metal injection molding is a new commercial process for producing complex component parts from steels and other ferrous alloys. The process combines the shape-making capability of plastic injection molding with high-temperature sintering technology to produce complex, high density metal parts with outstanding properties. The savings in production costs can be substantial over investment casting or expensive machining operations.     

基于Kriging模型的注塑工艺稳健优化

为降低薄壁注塑件的翘曲变形,提出了基于Kriging模型的工艺稳健优化方案。特别地,研究并提出了基于变异粒子群算法的Kriging模型建立与优化算方法,建立了注塑工艺参数和翘曲变形之间的Kriging模型。通过实验设计、CAE仿真结果数据建立起Kriging模型,并结合变异粒子群算法实现了工艺的优化设计。在此基础上,为减少工艺参数波动对注塑件质量的影响,建立了注塑成型的6 Sigma稳健优化设计方法,提高了工艺的稳健性与可靠度。以汽车出风口壳体为计算用例,结果表明,基于Kriging模型与变异粒子群算法的工艺稳健优化策略在小样本情况下能够得到较高质量的稳健优化参数组合。     

基于正交试验的注射成型工艺参数优化方法研究

结合正交试验法和注射模拟分析软件Moldflow,对注射成型工艺参数进行优化。为获取优化的注射工艺参数组合,设计了试验方案,并对Moldflow模拟试验结果进行了极差、方差分析法处理,确定了各因素及其交互作用的主次顺序、因素之间交互作用对试验指标影响的显著程度,分析了各因素与试验指标之间的关系,得出了试验因素的最优水平和试验范围内的最优组合,即注射工艺参数组合方案,并对该工艺组合方案进行模拟和实际验证。这一研究方法对注射工艺分析与模具设计具有指导意义。     

Surrogate-based process optimization for reducing warpage in injection molding

In this paper, an adaptive optimization method based on Kriging surrogate model is proposed to minimize the warpage of injection molded parts. Kriging surrogate model combining design of experiment (DOE) methods is used to build an approximate function relationship between warpage and the process parameters, replacing the expensive simulation analysis in the optimization iterations. The adaptive process is implemented by an infilling sampling criterion named expected improvement (EI). This criterion can balance local and global search and tend to find the global optimal design, even though the DOE size is small. As an example, a cellular phone cover is investigated, where mold temperature, melt temperature, injection time, packing time and packing pressure are selected to be the design variables. The results show that the proposed adaptive optimization method can effectively decrease the warpage of injection molded parts.     

基于敏感性分析的注塑成型工艺参数优化

工艺参数的选取对注塑产品质量至关重要。文章建立了无量纲形式的敏感度函数和敏感度因子的多因素敏感性分析方法,并以某监控系统设备外壳成型为例,对影响产品翘曲的工艺参数进行了敏感性分析和优化。结果表明,保压压力和模具温度是影响产品Z向翘曲的主要因素。最后,对应用优化工艺参数的制造产品进行了翘曲检测,检测结果与模拟结果基本吻合,缩短了试模周期,提高了产品质量。     

用MPI分析注射成型工艺确定浇口数量

运用MPI模拟塑料的整个注射成型过程,在不同浇口设置的条件下,从中提取填充、保压和冷却的特征过程与参数,分析对工艺造成的影响。通过填充过程工艺参数、浇口压力曲线、螺杆速度曲线,产品重量,熔接痕,翘曲变形量等对比分析,确定了产品设置1个浇口比2个浇口更合适,达到注射过程工艺参数合理和产品质量高的目的。     

Numerical simulation of tungsten alloy in powder injection molding process

The flow behavior of feedstock for the tungsten alloy powder in the mold cavity was approximately described using Hele-Shaw flow model. The math model consisting of momentum equation, consecutive equation and thermo-conduction equation for describing the injection process was established. The equations are solved by the finite element/finite difference hybrid method that means dispersing the feedstock model with finite element method, resolving the model along the depth with finite difference methgd, and tracking the movable boundary with control volume method, then the pressure equation and energy equation can be resolved in turn. The numerical simulation of the injection process and the identification of the process parameters were realized by the Moldflow software. The results indicate that there is low temperature gradient in the cavity while the pressure and shear rate gradient are high at high flow rate. The selection of the flow rate is affected by the structure of the gate. The shear rate and the pressure near the gate can be decreased by properly widening the dimension of the gate. There is a good agreement between the process parameters obtained by the numerical simulation and the actual ones.     

Effect of shear heating during injection molding on the morphology of PC/LCP blends

Fiber relaxation of liquid crystalline polymer (LCP) in the mold during injection molding was investigated. A blend of LCP and polycarbonate was used. The LCP used, namely LC5000, is a thermotropic LCP consisting of 80% and 20% of hydroxybenzoic acid and ethylene terephthalate, respectively. The filling of the mold and the temperature profile of the melt in the mold, after the mold has been completely filled, were computed using the finite element/finite difference method (FE/FDM). The morphology of the fibers was greatly influenced by the temperature of the different layers in the sample. This was confirmed by scanning electron microscopy (SEM) examination of the injection-molded specimen. When shear heating caused the temperature of the melt to increase above 280 °C, relaxation of the fibers was rapid. This resulted in a final morphology where the LCP existed in short fibers or ellipsoids. It was concluded that the high shear rate, which is needed for fiber deformation, must be accompanied by fast cooling to minimize the effects of shear heating, so that the fibers formed could be retained.     

基于Moldflow的基座注射成型工艺与注射模设计

采用Moldflow软件对精密微型电连接器件中的基座进行了浇口位置和注射成型工艺优化。通过对熔体充填型腔的过程分析,确定了塑件成型的最佳浇口位置和熔体充填时间,针对塑件成型后的体积收缩率分析得出了注射成型的最佳熔体温度,分析了模具温度对制件收缩率和最大注射压力的影响。结合模拟分析的结果进行了模具与注射工艺参数优化设计,从而获得了高质量的塑件,降低了生产成本,缩短了产品开发周期。     

基于正交试验的气辅成型工艺优化

以加强筋为研究对象,对气辅成型中的熔体温度、熔体预注射量、气体注射压力、气体注射延迟时间、气体注射时间等影响气辅成型质量的主要参数进行数值模拟,并对影响塑件成型质量的相关工艺参数进行正交试验。先通过初步的五因素四水平L16(45)正交试验获得工艺参数的大致范围,然后在该基础上再进行改进的四因素三水平L9(34)正交试验,最终获得较好的工艺条件。     

塑件结构对气辅注射成型的影响

以转角结构作为研究对象,通过改变塑件几何结构尺寸,利用Moldflow软件对塑件成型工艺过程进行模拟。在相同的成型工艺参数下,研究了手指效应、气道穿透长度、熔接痕等气辅成型质量主要参考指标受塑件结构影响的规律,发现通过改变基板的厚度使气道两侧基板中熔体的流动平衡,可以减少气体的薄壁穿透,缩短熔接痕的长度,改善了塑件的成型质量。     

气体辅助注射成型工艺参数对成型结果的影响

利用Moldflow软件对FM全新卡车内饰顶棚把手的气体辅助注射成型工艺进行了分析,应用正交试验设计的数学方法定量分析了熔体的预注射量、气体注射压力、熔体/气体延迟时间及熔体温度对成型结果的影响程度,同时还考察了单个参数对成型结果的影响趋势。