不同截面型腔的气辅共注塑成型制件质量分析

基于自行开发的UDF模型进行溢流法GACIM数值模拟,研究了气体在5种截面型腔中,穿透芯层熔体的截面形状以及芯/壳层熔体残余壁厚分布情况.模拟发现,在相同成型工艺参数条件下,气体在不同截面型腔中穿透芯层熔体的截面形状不同,截面型腔外凸尖角越少,气体穿透芯层熔体的截面形状越接近圆形.芯/壳层熔体在非圆形截面型腔的外凸尖角...     

水辅助注塑中高压水穿透过程的数值模拟

对水辅助注塑(WAIM)中高压水的穿透过程进行有限元模拟,研究熔体的充模行为,并分析其拉伸场和剪切场。结果显示,高压水推动熔体充模的过程可分为填充初期、快速填充期和填充末期3个阶段;较明显的拉伸应变速率仅出现在高压水前沿和熔体前沿区域;高压水前沿区域存在分布较宽且较为强烈的剪切速率,而高压水对已穿透区域的熔体几乎没有剪切作用。此外,模拟所得WAIM制品的穿透长度和掏空率与实验结果较吻合。     

水辅助注塑成型技术及其进展

水辅助注塑成型技术是一种新型的生产中空或者部分中空注塑制品的成型方法。介绍了这种成型技术的加工原理、成型方法、设备及其进展，并将其与气体辅助注射成型技术进行了比较。     

水辅助注射成型中水穿透行为的可视化研究

基于自主研发的注水系统,利用具有矩形变截面和弯道模腔的水辅助注塑可视化模具,采用聚苯乙烯(PS)材料,对不同水压下的水辅助熔体流动充模的过程进行了观察,着重研究了水的穿透行为。研究发现：注水喷嘴的冷却使其周围熔体黏度增大,水穿透高黏度熔体区后产生紊动射流,射流穿透长度随注水压力的增大而增长。注水压力较低时,水的穿透方向容易发生改变,注水压力越高,水道越光滑。水在弯道入口和收敛过渡区的穿透过程中前缘逐渐缩小,在弯道出口和扩散过渡区的穿透过程中前缘逐渐扩宽。     

水辅助注塑制品水穿透长度和残留壁厚的研究

介绍了自主研发的水辅助注塑设备以及一款经过大量实验后得到的新型喷嘴,并通过单因素实验法研究了短射法成型聚丙烯弯管时工艺参数对制品水穿透长度和沿水道的残留壁厚的影响。结果表明,熔体注射量对水穿透长度影响最大,当其增加13．5％时水穿透长度减小了153mm；沿水道上制品注水后充填部分比注水前充填部分的残留壁厚减小约0．5～1．0 mm；提高注水压力与增加注水延迟时间时注水后填充部分的残留壁厚略有减小。     

水辅助注塑制品残留壁厚和穿透长度影响因素的研究

为能水辅助注塑成型壁厚较小且较均匀的聚丙烯弯管,设计了一种自锁式喷嘴,既满足高流量的要求,又可防止熔体堵塞喷嘴。在相同的工艺条件下,分别使用自锁式喷嘴和孔形喷嘴,对成型的弯管壁厚进行比较,结果表明:与孔形喷嘴相比,使用自锁式喷嘴时制品的残留壁厚更小更均匀。此外,使用该自锁式喷嘴,研究了水辅助注塑中注水压力和延迟时间对制品残留壁厚和水穿透长度的影响.     

水辅助注塑技术研究进展

水辅助注塑是在气体辅助注塑基础上发展起来的一种成型中空制品的新技术,综述了水辅助注塑中熔体的流动行为、工艺参数对制品残留壁厚及穿透长度的影响、制品微观形态及力学性能和数值模拟技术的最新进展,最后对水辅助注塑技术研究前景进行展望。     

冷却水质对注塑成型的影响

良好的冷却对提高加工设备效率十分重要 ,由于这个原因 ,冷却水的质量对塑料模塑加工过程存在着极大的影响力。生产加工用水控制系统原始简单会造成许多不利后果 ,如 :　　 ( 1 )循环周期延长 ;　　 ( 2 )水和电消耗增加导致环境成本提高 ;　　 ( 3)损害模具、机器、冷却塔、骤冷器、水流管道和其它冷却装置 ;　　 ( 4 )导致员工生病而缺勤。　　冷却水管道内腐蚀作用和水垢沉积促使循环周期延长 ,水垢存在影响了模塑界面的散热速率 ,从而使模塑成型周期延长。这些相同的沉积物降低了冷却塔和骤冷器的效率 ,而反过来 ,为了达到所需冷却温度…     

气体辅助注塑成型技术

介绍一种新的塑料加工技术——气体辅助注塑成型技术的工艺过程和设备配置，分析了其成型特点和典型应用。根据气辅成型的不同工艺过程，可分为标准成型法、副腔成型法、熔体回流法和活动型芯法四种。气辅成型所用设备包括注塑机、气辅装置、进气喷嘴等。其特点是所需注射压力小、制品翘曲变形小、可消除缩痕，提高表面质量、适用于成型壁厚差异较大的制品、在不增加制品重量的情况下可增加制品的刚度和强度、对一般制品可通过气体的穿透，减轻重量，缩短成型周期。典型的应用是制作刷柄、扶手、方向盘等棒形或管形件，汽车仪表盘等大的板形件，厚薄不均的各种家电外壳和塑料家具等。     

熔体温度对水穿透行为影响的可视化研究

利用水辅助注塑可视化模具和自主研发的注水系统,以聚苯乙烯(PS)为原料,对不同熔体温度下的水辅助熔体流动充模的过程进行了观察,并研究了水的穿透行为。结果表明：熔体温度低,水前缘熔体的惯性力增大,产生"折线"水道,水在后半模腔熔体的穿透中,水前缘速度与水前缘熔体速度相近;熔体黏度高,水前缘速度大于水前缘熔体速度;熔体温度越高,射流穿透的时间越长,水在前半模腔穿透用时越少。     

方管短玻璃纤维增强聚丙烯高压水穿透行为研究

采用方形截面管件,以短玻璃纤维增强聚丙烯为原料,通过溢流法水辅助注射成型实验探究了熔体注射温度、注水延迟时间和注水压力等工艺参数对制件宏观现象的影响机理,并分析了高压水在方形管道中的穿透行为。结果表明,当熔体温度升高时,方管的直角边和斜边残余壁厚都呈减小趋势,但温度过高时会出现管件收缩现象,管件截面中空面积增大且截面形状与高压水的穿透前沿形状一致,偏圆形,但截面的圆率逐渐减小;当注水压力增加时,管件残余壁厚减小,截面中空面积增大,其截面形状随着注水压力的增加逐渐与型腔结构一致,偏方形;当注水延迟时间增加时,管件残余壁厚增大,中空截面减小且管件截面形状也与高压水前穿透前沿一致,偏圆形,但相较另外两个参数,注水延迟时间对方管件的影响程度更小,因而对截面的圆率影响不大。     

Formation mechanism of high-pressure water penetration induced fiber orientation in overflow water-assisted injection molded short glass fiber-reinforced polypropylene

Recently, there has been growing interest in water-assisted injection molding (WAIM) not only for its advantages over gas-assisted molding (GAIM) and conventional injection molding (CIM), but also for its great potential advantages in industrial applications. To understand the formation mechanism of water penetration induced fiber orientation in overflow water-assisted injection molding (OWAIM) parts of short glass fiber-reinforced polypropylene (SGF/PP), in this work, the external fields and water penetration process within the mold cavity were investigated by experiments and numerical simulations. The results showed that the difference of fiber orientation distribution in thickness direction between WAIM moldings and CIM moldings was mainly ascribed to the great external fields generated by water penetration. Besides, fiber orientation depended on the position both across the part thickness and along the flow direction. Especially in the radial direction, fiber orientation varied considerably. The results also showed that the melt temperature is the principal parameter affecting the fiber orientation along the flow direction, and a higher melt temperature significantly facilitated more fibers to be oriented along the flow direction, which is quite different from the results as previously reported in short-shot water-assisted injection molding (SSWAIM). A higher water pressure, shorter water injection delay time, and higher melt temperature significantly induced more fibers to be orderly oriented in OWAIM moldings, which may improve their mechanical performances and broaden their application scope.     

Prediction of process parameters of water-assisted injection molding based on inverse radial basis function neural network

Because of the introduction of new processing parameters in water-assisted injection molding (WAIM), processes control has become more difficult. First, design of experiment (DOE) was carried out by using optimized Latin hypercubes (Opt LHS). On the basis of this, computational fluid dynamics (CFD) method was used to simulate and calculate hollowed core ratios and wall thickness differences of cooling water pipe at different positions. Then inverse radial basis function (RBF) neural network model reflecting the fitting relationship between processing parameters and molding quality was established, and accuracy of the model was detected by cross validation. Finally, expected molding quality was applied to predict processing parameters, and the obtained molding quality under the predicted processing parameters was verified by computer aided engineering (CAE) simulation and experimental methods. The results showed that mean relative precisions of processing parameters such as melt temperature, delay time, short shot size, water pressure, and mold temperature for inverse RBF model were 98.6%, 93.6%, 98.5%, 93.9%, and 97.9%, respectively, which met the accuracy requirements. Furthermore, compared with expected values of hollowed core ratios and wall thickness differences, the average errors of CAE and experiment were 2.3% and 4.9%, respectively.     

Gas-assisted powder injection molding: A study on the effect of processing variables on gas penetration

Parts of polypropylene and of a stainless steel powder feedstock were molded by means of gas-assisted injection molding in epoxy cavities made by stereolithography. The design of the experiment method using the Taguchi L₉ array was implemented to test the effect of gas pressure, gas delay time, shot size and melt temperature on gas penetration depth and residual wall thickness. Simulations were conducted and compared with direct experimentation. Simulation predicted that the shot size was the only significant factor when processing polypropylene and the powder metal feedstock. The experiment showed that shot size and gas delay time were significant when processing polypropylene; and shot size, gas pressure, and melt temperature were significant factors when processing the powder metal feedstock. The residual wall thickness could not be controlled by the processing variables used in this study as the S/N ratios calculated were very small.     

注塑充模流动过程灵敏度数值分析

从注塑模充模过程控制方程出发,建立了注塑成型充模过程物理场对设计参数瞬态连续灵敏度分析理论,得到了充模过程压力场、温度场、速度场等物理场对设计参数的灵敏度控制方程.数值分析沿用了注塑模流动分析的基本思想,压力灵敏度采用有限元法、通过对时间和厚度方向的差分求解温度灵敏度,借助于控制体积的概念得到运动边界灵敏度分析.数值算例分析了注射压力对注射流率、熔体温度的设计灵敏度,与数值实验吻合良好.     

气体辅助注射成型关键技术研究

介绍了气体辅助注射成型原理、成型周期和技术优势,说明了气体辅助注射成型生产工艺和制品设计特点。     

正交试验优选气辅成型工艺参数

为优化气辅成型工艺参数,采用单因素法考察工艺参数对气辅成型质量的影响,以熔体预注射量、熔体温度、模具温度、注气压力、延迟时间、注气时间为因素,气体穿透深度、最大气指幅度为评价指标,采用L25(56)正交试验设计优选气辅成型工艺参数为:熔体预注射量85％,熔体温度240?℃,模具温度40?℃,延迟时间4?s,注气压力3?...     

Computer simulation of the filling process in gas‐assisted injection molding based on gas‐penetration modeling

Gas‐assisted injection molding can effectively produce parts free of sink marks in thick sections and free of warpage in long plates. This article concerns the numerical simulation of melt flow and gas penetration during the filling stage in gas‐assisted injection molding. By taking the influence of gas penetration on the melt flow as boundary conditions of the melt‐filling region, a hybrid finite‐element/finite‐difference method similar to conventional‐injection molding simulation was used in the gas‐assisted injection molding‐filling simulation. For gas penetration within the gas channel, an analytical formulation of the gas‐penetration thickness ratio was deduced based on the matching asymptotic expansion method. Finally, an experiment was employed to verify this proposed simulation scheme and gas‐penetration model, by comparing the results of the experiment with the simulation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2377–2384, 2003     

UV光固化注射成型工艺实验研究

在传统注射成型工艺的基础上,对模内“光化学制造”工艺参数进行实验研究,分析得到UV材料温度、保压压力对制品精度的影响。其中,利用成型制品平均质量评价UV光固化制品整体成型质量精度。此外,采用横截面图形比较法对制品微结构形态质量进行评价。结果表明,UV光固化注射成型具有替代热塑性材料注射成型方面的可行性。