Shrinkage and warpage prediction of injection‐molded thin‐wall parts using artificial neural networks

This study demonstrates the successful use of back‐propagation artificial neural networks (BPANNs) in predicting the shrinkage and warpage of injection‐molded thin‐wall parts. The effects of structural parameters of a BPANN on the predictionaccuracy and the capability of a BPANN in determining the optimal process condition are also discussed. The training and testing data are obtained experimentally based on a Taguchi L₂₇ (3¹³) test schedule. The results show that the trained BPANN can successfully predict the shrinkage and warpage of injection‐molded thin‐wall parts. Comparing the prediction accuracies of the trained BPANN and C‐Mold software, it is noted that the trained BPANN predicts more accurately. In terms of determining the optimal process condition for minimizing the shrinkage and warpage of injected thin‐wall parts, the trained BPANN is also shown to give a better optimal process condition than Taguchi's method. Polym. Eng. Sci. 44:2029–2040, 2004. © 2004 Society of Plastics Engineers.     

注射成型薄壁制品收缩与翘曲因素

介绍了薄壁注射成型的充填、保压、冷却和残余应力的数值模型,并将集成的模拟程序对收缩翘曲问题进行定量地模拟分析.采用Taguchi 实验优化设计理论,用L₂₇（3¹³）正交表设计实验并进行了统计分析.研究了因素如熔体温度、模具温度、保压时间、保压压力、浇口尺寸和注射速率对收缩与翘曲的影响的显著性.得出优化工艺参数如熔体温度、模具温度、保压时间和压力能减少残余热应力;保压压力和熔体温度是影响收缩与翘曲的最显著因素.     

Optimization and numerical simulation analysis for molded thin‐walled parts fabricated using wood‐filled polypropylene composites via plastic injection molding

Plastic injection molding is discontinuous and a complicated process involving the interaction of several variables for control the quality of the molded parts. The goal of this research was to investigate the optimal parameter selection, the significant parameters, and the effect of the injection‐molding parameters during the post‐filling stage (packing pressure, packing time, mold temperature, and cooling time) with respect to in‐cavity residual stresses, volumetric shrinkage and warpage properties. The PP + 60 wt% wood material is not suitable for molded thin‐walled parts. In contrast, the PP + 50 wt% material was found to be the preferred type of lignocellulosic polymer composite for molded thin‐walled parts. The results showed the lower residual stresses approximately at 20.10 MPa and have minimum overpacking in the ranges of ?0.709% to ?0.174% with the volumetric shrinkage spread better over the part surface. The research found that the packing pressure and mold temperature are important parameters for the reduction of residual stresses and volumetric shrinkage, while for the reduction of warpage, the important processing parameters are the packing pressure, packing time, and cooling time for molded thin‐walled parts that are fabricated using lignocellulosic polymer composites. POLYM. ENG. SCI., 55:1082–1095, 2015. © 2014 Society of Plastics Engineers     

采用RFR-GA算法的薄壁注塑件质量多目标优化

汽车内饰件可由注塑加工获得,但成型过程中塑件产生的翘曲、体积收缩较大,针对该问题,以某汽车薄壁注塑件为例,研究了其注塑工艺参数的优化方法.通过以注塑过程中的最小翘曲和最小体积收缩率为目标函数,以注塑温度、模具温度、注射压力、保压压力、保压时间以及冷却时间等参数作为设计变量,构建了多目标全局优化模型.利用Moldflow...     

基于CAE的薄壁注塑件翘曲变形研究

对于薄壁注塑件,翘曲变形是影响其质量最主要的问题之一。以碎纸机进纸口薄壁件为例,采用Moldflow软件对制品的注塑工艺进行了数值模拟。通过采用正交试验,获得了不同工艺条件下的翘曲变形值,从而寻找出影响翘曲变形的关键因素和最优的工艺参数组合。     

Review on the Effects of Process Parameters on Strength,Shrinkage, and Warpage of Injection Molding Plastic Component

Injection molding process causes differences between designed shape and real parts, all of them associated to shrinkage and warpage phenomena. Temperature, pressure distribution, and other injection parameters during molding process originate local shrinkage and the internal stresses depending on the relative stiffness of each part area. The aim of this work is to review and report the influence of injection molding process parameters on the postmolded strength, shrinkage, and warpage of injection molded parts. It is also to investigate the influence of injection molding process parameters on the postmolding shrinkage and warping of parts made of polypropylenes.     

Relationship between the crystallization behavior and the warpage of film‐insert‐molded parts

The dimensional variation of an injection‐molded, semicrystalline polymer part is larger than the variation of an amorphous polymer part because the shrinkage of a crystalline polymer is generally greater than the shrinkage of an amorphous one. We investigated the warpage of film‐insert‐molded (FIM) specimens to determine the effect of the crystallization behavior on the deformation of FIM parts. More perfect crystalline structures and higher crystallinity developed in the core region of the FIM specimens versus other regions. Relatively imperfect crystalline structures and low crystallinity developed in the adjacent regions of the inserted films, whereas a thin, amorphous skin layer developed in the adjacent regions of the metallic mold wall. The crystallizable substrate in the FIM specimens caused very large warpage because nonuniform shrinkage occurred in the thickness direction of the specimens. Therefore, the warpage of an experimentally prepared FIM poly(butylene terephthalate) specimen was greater than that predicted numerically because of its complex crystallization behavior. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

基于灰色关联分析的注塑工艺多目标优化及PSO–SVM预测模型的建立

针对某电器活动上盖翘曲变形及体积收缩问题,对相关注塑工艺参数进行正交实验设计,在Moldflow中模拟分析,并对翘曲变形量及体积收缩率进行信噪比优化处理。利用灰色关联分析法得到翘曲变形量和体积收缩率的灰色关联度,通过对灰色关联度进行极差分析得到各注塑工艺参数对塑件综合目标(翘曲变形量及体积收缩率同时较小)的影响程度为:保压时间>注塑时间>模具温度>熔体温度>保压压力>冷却时间,同时由灰色关联度极差分析结果得出最优工艺参数组合,在最优工艺参数组合下的翘曲变形量相对于正交实验水平下最小翘曲变形量降低了11.8%,体积收缩率相对于正交实验水平下最小体积收缩率降低了5.9%。最后采用粒子群优化算法(PSO)优化后的支持向量机(SVM)神经网络模型对该塑件翘曲变形量及体积收缩率进行预测,通过与不优化的SVM神经网络及BP神经网络预测模型相比发现,PSO–SVM神经网络模型预测精度及稳定性都优于SVM及BP神经网络,可以用于塑件翘曲变形量和体积收缩率的协同优化,解决塑件实际翘曲变形及体积收缩问题。     

薄壁塑件注射成型工艺参数优化

在注射成型过程中将计算机模拟技术和实验优化设计相结合,以相机外壳为例利用MoldFlow对各工艺参数进行注射成型过程的模拟.通过分析塑件体收缩变形和翘曲变形的原因,得出熔体温度是影响塑件体收缩变形的主要因素,而保压压力对翘曲变形起主导作用力.并在正交试验的指导下优化工艺参数,使收缩率和翘曲变形分别降为原来的75.9%和87.0%.     

注射成型工艺对制品收缩与翘曲的不同影响

以PP盒形制品为例,设计了一种测量方案使得收缩与翘曲可以独立度量,分别考察了这两者在不同工艺水平下的变化。使用单因素方差分析表确定熔体温度、保压压力等注射成型工艺参数对收缩与翘曲的影响程度,并以置信区间图示出各参数对收缩与翘曲的影响规律。通过对实验数据的总结发现,保压压力对收缩影响最为显著,而模具温度对翘曲影响最显著。制品收缩与翘曲随工艺参数变化呈3种不同特征：收缩与翘曲呈相反的变化趋势,提高注射速率或熔体温度,制品收缩率减小而翘曲增大;随保压压力升高收缩率单调减少而翘曲呈“U”形曲线变化;调整其他工艺参数,收缩与翘曲有相同的变化趋势。这些影响规律的总结为减小注射成型中塑料制品的收缩与翘曲提供依据。     

基于CAE的注塑件翘曲变形优化研究

运用Moldflow软件进行某后盖产品的翘曲变形分析,结合Moldflow软件的翘曲变形分析理论,将影响注塑件的翘曲变形因素分为3类:冷却不均、收缩不均及取向因素。然后针对翘曲变形不同的影响因素提出冷却优化、结构优化、保压优化及反变形设计等优化方案。分析结果表明:提出的这几种优化方案能极大地改善注塑件的翘曲变形,为注塑制品企业在控制产品尺寸、满足装配质量要求、改善翘曲变形等方面提供优化思路及工艺参考。     

塑料盖注塑成型方案分析及翘曲变形参数优化

以塑料盖作为研究对象,获得最优成型方案,预测塑件成型后的翘曲变形程度以提高塑件质量。初步提出两种注塑工艺方案加工塑料盖,使用Moldflow软件对两种方案注塑过程进行模拟对比分析,对产生翘曲缺陷的原因进行研究;利用五因素四水平的正交试验,以减小翘曲变形程度作为优化目标,优化工艺参数。模拟结果表明:方案二为最优方案,且翘曲变形主要是由收缩不均匀以及取向不均匀而造成的,翘曲变形程度最小的工艺参数组合为熔体温度250℃、模具温度60℃、保压时间12 s、冷却时间12 s、填充时间0.9 s,优化后比优化前翘曲变形程度降低9.4%左右,熔料熔接和材料性能也有所改善,塑料盖整体质量提高。实验可有效地缩短塑料盖的研发周期,降低生产成本,提高塑料盖的研发成功率。     

基于CAE的注塑模浇口与保压优化设计

通过Moldflow软件，对平板形塑料件注塑过程中的流动、翘曲情况进行数值模拟。通过设置不同的浇口数量、位置和保压压力、保压时间，分析了注塑压力、熔接线分布、翘曲变形量和缩水缺陷等情况，优化了浇口数量、位置和保压压力、保压时间以减少注塑缺陷和塑料件变形；并结合分析结果指导模具设计及注塑过程工艺参数的设定。     

A study on the distinguishing responses of shrinkage and warpage to processing conditions in injection molding

A challenging task in injection molding industry is to minimize shrinkage and warpage (S&W) through optimal setting of molding conditions. In determining the relationship between molding conditions and product dimension, most existing literature considered S&W as a whole entity or focused on only one of them. The intention of this study was to distinguish these two terms, and perform a thorough analysis on the effect of operative conditions on S&W during injection molding process through a combination of experimental and numerical methods. Six process parameters with five levels were examined on a box-shaped product, and the single factor analysis of variance (ANOVA) was adopted in identifying the significance of each variable in the experiment. Results indicated that the effect of processing conditions on shrinkage is different from that on warpage. Specifically, packing pressure affects shrinkage most while packing time is the dominant factor in determining warpage. The reaction of shrinkage to packing pressure is monotonic, whereas the plot of warpage shows a U-shaped variation. A differential treatment of S&W can therefore help to enhance product quality. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

基于灰色关联度的车灯装饰框注塑工艺优化

以汽车前大灯装饰框为研究目标,在正交试验基础上,采用了信噪比和灰色关联分析法,针对注塑成型过程中各工艺参数对翘曲变形量和体积收缩率的影响进行分析,从而得到最优工艺参数组合。结果表明,使用信噪比和灰色关联度法,得到的翘曲值和体积收缩率分别比Moldflow系统推荐参数模拟结果减少31.3%和4.4%;该方法能有效降低注塑过程中的缺陷,提高塑件产品质量。     

基于二阶响应面模型车灯灯体注塑工艺优化

以车灯灯体注塑为例,采用计算机辅助工程(CAE)分析和正交试验研究了工艺参数对翘曲变形的影响规律,确定了保压压力和熔体温度是影响灯体注塑质量的关键因素。采用响应面法建立了翘曲变形和顶出时体积收缩与注射压力和熔体温度的二阶相应面模型,获得了优化的工艺参数和优化结果,且通过模拟试验验证了模型的正确性。     

基于翘曲分析的注塑模工艺参数的优化

结合CAE及Taguchi DOE技术,研究工艺参数对注塑制品翘曲量的影响。采用了有交互作用的L16(215)正交表设计实验以及没有交互作用的L9(34)正交表设计实验,研究了因素如熔体温度、模具温度、保压压力、保压时间和注塑时间对翘曲影响的显著性。对所选参数,保压压力和熔体温度对注塑制品的翘曲量影响最大。通过两次正交设计实验,使手机上壳制品的翘曲量减少了34.23 %,提高了制品品质。     

Quantitative study of shrinkage and warpage behavior for microcellular and conventional injection molding

This research investigated the effects of processing conditions on the shrinkage and warpage (S&W) behavior of a box‐shaped, polypropylene part using conventional and microcellular injection molding. Two sets of 2^6‐1 fractional factorial design of experiments (DOE) were employed to perform the experiments and proper statistical theory was used to analyze the data. After the injection molding process reached steady state, molded samples were collected and measured using an optical coordinate measuring machine (OCMM), which had been evaluated using a proper R&R (repeatability and reproducibility) measurement study. By analyzing the statistically significant main and two‐factor interaction effects, the results show that the supercritical fluid (SCF) content (nitrogen in this case, in terms of SCF dosage time) and the injection speed affect the S&W of microcellular injection molded parts the most, whereas pack/hold pressure and pack/hold time have the most significant effect on the S&W of conventional injection molded parts. Also, this study quantitatively showed that, within the processing range studied, a reduction in the S&W could be achieved with the microcellular injection molding process. POLYM. ENG. SCI., 45:1408–1418, 2005. © 2005 Society of Plastics Engineers     

微孔塑料注射成型制品体积收缩与翘曲变形数值分析

采用Moldflow软件，通过微孔注射成型过程的数值模拟，系统研究了熔体注射温度、模具温度对其体积收缩、翘曲变形和残余应力的影响规律，并基于流变学理论，揭示了其影响机理。研究结果表明，随着熔体注射温度和模具温度增加，微孔注射制品翘曲变形和残余应力均增加，成型制品的体积收缩随着熔体注射温度升高而增加，而随着模具温度升高而减小。本研究为微孔注射成型工艺和模具的设计提供理论指导。     

基于CAE和DOE技术的注射成型工艺优化

以打印机上盖为例,以体积收缩率、翘曲量和沉降斑指数为考察指标,结合CAE和DOE技术研究了模具温度、熔体温度、注射时间、保压压力和保压时间五个工艺参数对考察指标的影响,用DOE软件回归拟合得到体积收缩率、翘曲和沉降斑指数的预测模型,并运用该模型求解最佳的工艺参数,通过试验验证了该方法的可行性.