薄壁塑件注塑成形特性的试验研究

设计制造了一可成形薄壁塑件的模具,利用正交试验方法(田口方法)进行充模试验,研究各工艺参数(注射速度、注射压力、熔体温度、注射量和模具温度等)对薄壁塑件注塑成形充模过程的影响.研究结果表明:模具温度对薄壁塑件的填充起决定性作用,注射压力和注射量是影响薄壁塑件成形的重要工艺参数,注射速度与熔体温度之间的交互作用对薄壁塑件成形的影响显著.     

薄壁塑件注塑成形特性的试验研究

设计制造了一可成形薄壁塑件的模具,利用正交试验方法(田口方法)进行充模试验,研究各工艺参数(注射速度、注射压力、熔体温度、注射量和模具温度等)对薄壁塑件注塑成形充模过程的影响。研究结果表明:模具温度对薄壁塑件的填充起决定性作用,注射压力和注射量是影响薄壁塑件成形的重要工艺参数,注射速度与熔体温度之间的交互作用对薄壁塑件成形的影响显著。     

微注塑充模流动过程熔体黏度影响规律的数值模拟

微型塑件注射成型充模流动过程中,与宏观塑件相比,塑料熔体黏度随剪切速率的变化对流动的影响有很大的不同.对比微观和宏观黏度模型,运用流体分析软件Fluent,对微注塑充模流动过程熔体黏度的影响规律进行了研究.分析了熔体黏度的分布规律,结果表明微尺度降低了熔体黏度.研究了微尺度熔体黏度模型对熔体速度场、温度场和压力场的影响规律,结果表明:微尺度黏度模型的速度相对较大,近壁面区熔体温度相对较高,对微通道中的压力分布几乎没有影响.总体而言,由于通道微尺度而造成的熔体黏度变化有利于微注塑成型.     

薄壁气体辅助注塑件气体穿透过程的研究

基于气体穿透实验技术的研究分析，针对气体辅助注射成形中气体穿透气道的复杂过程，对薄壁气辅注塑件沿圆形截面气道穿透推进并形成模壁表层熔体的充模流动过程进行了研究。通过引入合理的简化和假设，建立了反映充模流动压力梯度、材料性能、表层熔体厚度比、非牛顿指数等影响因素的计算穿透速度和时间的数学方程．对气体注射压力、熔体温度、非牛顿指数影响气体穿透充模过程进行了实例数值模拟研究。结果表明，增大气体注射压力，其气体穿透方向所形成的表层熔体厚度比值也增大，降低熔体注射温度和非牛顿指数会增大气体穿透的壁厚值，其值接近国外试验测定值，也比较符合实际的气辅注射成形工艺结果。     

微壳体塑件充模流动三维数值模拟

针对微注塑成形中熔体充模流动行为,运用流体分析软件Fluent,对微壳体塑件熔体充模流动进行了三维稳态模拟。建立了微观黏度模型和壁面滑移模型,运用VOF多相流模型,研究了熔体充满型腔时的稳态三维流场,做出切片图分析了压力场和速度场。通过对考虑和不考虑微尺度影响(微观黏度和壁面滑移)的对比和分析,可以看到考虑微尺度因素影响时充模阻力减小约19%,而速度变化不明显。分析表明微尺度黏度对熔体流动影响显著,有利于微注塑熔体充模,而壁面滑移对充模流动影响较小。     

气体辅助注射成形充模流动数值模拟的研究

基于广义Hele—Shaw流动模型,通过引入合理的简化和假设,建立了实现气体辅助注射成形充模流动模拟的数学方程、气体穿透过程的边界条件、CAD/CAE建模关键技术以及系统程序设计方法等。该研究对气体的穿透过程、压力场分布、小同时刻熔体/气体边界的移动状态以及在模壁上形成表层聚合物熔体壁厚的过程进行_了气体辅助注射成形充模流动的实例数值模拟研究。结果表明:增大气体注射压力,在其气体穿透方向所形成的表层熔体厚度比值也增人,降低熔体注射温度和非牛顿指数会增大气体穿透的壁厚值,其值接近试验测定的数值范围,也比较符合实际的气辅注射成形工艺结果。     

模具设计中常用的排气方法

在设计注塑模、压铸模、吹塑模及拉延模等成形模具时必须考虑排气的问题。如果注塑模型腔内的气体不能顺利排出,将使制品产生气泡、疏松、充填不满、熔接不牢、制件表面发乌,或在注塑时由于气体被压缩所产生的高温使制件底部碳化烧焦。而且型腔内气体被压缩产生的反压力会降低充模速度,影响注射周期和产品质量(特别是高速注射时)。     

微流控芯片注塑成型缺陷的成因与对策

微流控芯片是应用于生物、化学和生物医学等领域的芯片型微全分析系统,是一种表面具有微通道的薄壁塑件,微通道主要用于样本的分离.与热压成型相比,微流控芯片注塑成型效率更高,更适合大批量生产,但其成型质量控制更为复杂.试验发现,微通道复制不完全和表面缩痕是其主要成型缺陷,其对后续的芯片键合以及取样液体的电泳分离都会造成不利的影响.模拟与理论分析以及可视化试验表明,熔体在微通道处出现滞流现象和芯片各部分收缩方向不一致是上述缺陷产生的主要原因.利用正交试验方法进行充模试验,研究各工艺参数(模具温度、注射速度、注射压力和熔体温度等)对微通道复制度的影响.研究结果表明模具温度对提高微通道复制度起决定性作用;注射速度和熔体温度是次要因素,而注射压力相对其他因素影响力较差,但必须保持在一个较高的水平.     

全三维注塑成形流动模拟有限元模型的研究

注塑制品往往具有复杂的几何形状，存在着壁厚的差异。三维流动模型比二维模型能更准确地模拟出熔体充模流动的情况。提出了一种基于全三维模型的注塑成形流动模拟的数学模型和数值实现方法，把速度和压力同次插值的方法成功地应用到三维注塑模拟的计算中，采用三维控制体积追踪塑料熔体的流动前沿，在温度场计算中，全面考虑了对流项在各个方向的影响，使模型的适用范围更广，结果更准确。在此基础上开发了相应的软件，可以计算熔体充模过程中的压力场、速度场和温度场等。实验验证和算例分析说明了三维流动模型的有效性。     

基于Taguchi技术的注射模工艺参数优化设计

将Taguchi技术和注射模CAE相结合,通过两次正交设计实验,研究了成型工艺参数对塑件翘曲量的影响,并以塑件翘曲量作为考察结果对成型工艺参数进行了优化。对所选参数,熔体温度和保压压力对塑件翘曲量影响高度显著,注射时间显著,其它参数影响甚微,且在实验范围内,塑件翘曲量随着熔体温度和保压压力的升高而减小。     

Influence of molding conditions on the shrinkage and roundness of injection molded parts

During the plastic injection molding process, one of the biggest challenges is shrinkage which deteriorates the quality of produced parts. To control and reduce this defect, the essential way is to perfectly determine the variables like molding parameters. In this study, the effects of molding parameters including packing pressure, melt temperature, and cooling time on shrinkage and roundness have been investigated experimentally. Also, the relationship among initial molding parameters, the cavity pressure, and mold temperature was investigated. The results of this experimental study and analysis fulfill various requirements of plastic injection molding and clarify the relationship between molding conditions and the overall quality of produced parts. This study illustrated that packing pressure and melt temperature are dominant factors which determine the quality of parts.     

基于Taguchi试验设计的储箱箱盖注射工艺参数研究

注射成型受众多因素影响,在制件结构和模具结构确定的条件下,通过合理的注射工艺参数,可消除或减少塑件成型中出现的缺陷。针对某企业在试生产一种储物箱箱盖时产生翘曲变形的问题,采用Taguchi试验方法,应用Moldflow对注射过程进行模拟,获得了塑件在熔料温度、模具温度、注射时间和保压压力四因素三水平下成型的翘曲变形量。采用极差分析,比较了不同工艺参数对翘曲变形量的影响程度,得到了优化的工艺参数组合。经试验验证,其效果良好,产品的翘曲变形得到了一定的改善。     

Three-dimensional numerical simulation for plastic injection-compression molding

Compared with conventional injection molding, injection-compression molding can mold optical parts with higher precision and lower flow residual stress. However, the melt flow process in a closed cavity becomes more complex because of the moving cavity boundary during compression and the nonlinear problems caused by non-Newtonian polymer melt. In this study, a 3D simulation method was developed for injection-compression molding. In this method, arbitrary Lagrangian- Eulerian was introduced to model the moving-boundary flow problem in the compression stage. The non-Newtonian characteristics and compressibility of the polymer melt were considered. The melt flow and pressure distribution in the cavity were investigated by using the proposed simulation method and compared with those of injection molding. Results reveal that the fountain flow effect becomes significant when the cavity thickness increases during compression. The back flow also plays an important role in the flow pattern and redistribution of cavity pressure. The discrepancy in pressures at different points along the flow path is complicated rather than monotonically decreased in injection molding.     

Mold design and forming process parameters optimization for passenger vehicle front wing plate

The main objective of the present article is to solve the problems of poor molding quality, large warpage, inadequate cooling effect and unsuitable selection of process parameters, in the injection molding process for passenger vehicle front-end plastic wing plate. The thickness and parting surface of the vehicle front-end fender were determined, the injection mold and its cooling system were designed. The relevant process parameters, affecting the product molding quality, were tested, according to orthogonal experimental approach, while their influence on the warpage was obtained, by analyzing the data. Finally, the BP neural network of warpage model was established and globally optimized using genetic algorithm. The optimal parameter combination of the injection molding process was derived as: melt temperature 236 °C, mold temperature 51 °C, cooling time 32 s, packing pressure 97 MPa and packing time 16 s.

     

A study on compound contents for plastic injection molding products of metallic resin pigment

Injection molding process is widely used for producing most plastic products. In order to make a metal-colored plastic product especially in modern luxury home alliances, metallic pigments which are mixed to a basic resin material for injection molding are available. However, the process control for the metal-colored plastic product is extremely difficult due to non-uniform melt flow of the metallic resin pigments. To improve the process efficiency, a rapid mold cooling method by a compressed cryogenic fluid and electricity mold are also proposed to decrease undesired compound contents within a molded plastic product. In this study, a quality of the metal-colored plastic product is evaluated with process parameters; injection speed, injection pressure, and pigment contents, and an influence of the rapid cooling and heating system is demonstrated.

     

汽车把手件气辅成型气指缺陷影响因素分析

在气体辅助成型工艺中,常常遇到一种缺陷是“气指”,气泡穿过气道形成指状分支,严重的“气指”会降低注塑件的强度,造成气辅成型技术的失败,或者不能发挥气辅成型技术的优势。为了消除或减少这种缺陷的产生,本文采用数值模拟方法和正交试验方法对气辅成型制品“气指”缺陷进行了研究。研究了对“气指”缺陷影响最重要的6个工艺参数：熔体短射量、气体注射延迟时间、气体注射压力 、模具温度、熔体温度以及气体注射时间对气辅成型制品“气指”缺陷的影响关系。结果表明,影响“气指”最重要的工艺参数依次是气体注射延迟时间、熔体温度和气体注射压力。因此优先选择合理的延时,熔体温度和注气压力参数尤为重要,为控制气指行为建议在相同熔体温度下适当延长气体注射延迟时间。     

Optimization of injection molding process parameters using integrated artificial neural network model and expected improvement function method

In this study, an adaptive optimization method based on artificial neural network model is proposed to optimize the injection molding process. The optimization process aims at minimizing the warpage of the injection molding parts in which process parameters are design variables. Moldflow Plastic Insight software is used to analyze the warpage of the injection molding parts. The mold temperature, melt temperature, injection time, packing pressure, packing time, and cooling time are regarded as process parameters. A combination of artificial neural network and design of experiment (DOE) method 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 expected improvement which is an infilling sampling criterion. Although the DOE size is small, this criterion can balance local and global search and tend to the global optimal solution. As examples, a cellular phone cover and a scanner are investigated. The results show that the proposed adaptive optimization method can effectively reduce the warpage of the injection molding parts.