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《Polymer-Plastics Technology and Engineering》2013,52(5):971-982
Abstract The dimensions quality of the injection‐molded parts is the result of a complex combination of material, part, and mold designs and process conditions. In this article, warpage prediction relies on the calculation of residual stresses developed during the molding process. The solidification of a molten thermoplastic between cooled parallel plates is used to model the mechanics of part warp in the injection‐molding process. Flow effects are neglected, and a thermorheologically simple thermoviscoelastic material model is assumed. The warp and residual stresses numerical simulation with finite element method (FEM) is time dependent. At each time step, the material properties can be temperature and pressure dependent. Mold temperature or mold‐cooling rate effects on part warp have been numerically predicted and compared with experimental results. By showing the mold‐cooling effects, it was concluded that mold cooling has a significant effect on part warpage, and mold‐cooling parameters, such as mold temperature, resin temperature, cooling channels, etc., should be set carefully. 相似文献
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Seong Yun Kim Sung Ho Kim Hwa Jin Oh Seung Hwan Lee Soo Jin Baek Jae Ryoun Youn Sung Hee Lee Sun‐Woo Kim 《应用聚合物科学杂志》2009,111(2):642-650
Virgin injection‐molded tensile specimens without any inserted film and four kinds of film insert molded (FIM) tensile specimens were prepared. They were annealed at 80°C to investigate the effect of residual stresses and thermal shrinkage of the inserted film on thermal deformation of tensile specimens. The FIM specimens with the unannealed film were bent after ejection in such a way that the film side was protruded and the warpage was reversed gradually during annealing and the film side was intruded. Warpage of the FIM specimen with the film annealed at 80°C for 20 days was not reversed during annealing. Processing of the FIM specimens have been modeled numerically to predict thermoviscoelastic deformation of the part and to understand the warpage reversal phenomenon (WRP). Nonisothermal three‐dimensional flow analysis was carried out for filling, packing, and cooling stages. The flow analysis results were transported to a finite element stress analysis program for prediction of deformation of the FIM part. The WRP was caused by the combined effect of thermal shrinkage of the inserted film and relaxation of residual stresses in the FIM specimen during annealing. It is expected that this study will contribute towards the improvement of the FIM product quality and prevention of large viscoelastic deformation of the molded part. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
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Optimization and numerical simulation analysis for molded thin‐walled parts fabricated using wood‐filled polypropylene composites via plastic injection molding
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M.D. Azaman S.M. Sapuan S. Sulaiman E.S. Zainudin A. Khalina 《Polymer Engineering and Science》2015,55(5):1082-1095
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 相似文献
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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。 相似文献
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In injection molding simulation the phase change from melt to solid state is usually simplified by using a so called transition temperature. In the present work, the transition temperatures of several amorphous and semicrystalline polymers were determined using DSC‐runs at different cooling rates. The transition temperature was described as a function of cooling rate. The obtained transition temperatures of the semicrystalline polymers were used in injection molding simulations with the commercial software package Autodesk Moldflow Insight 2010 to calculate the shrinkage and warpage of box‐shaped test parts. The simulation results were compared with the experimental values of optically measured injection‐molded boxes. The results showed a strong influence of the transition temperatures on the simulation results of a 3D model and a very low influence for a 2.5D model. Transition temperatures obtained at higher cooling rates improved the 3D simulation results for several dimensions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
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王鑫;杜林芳;李海梅 《中国塑料》2010,24(12):77-79
针对某座椅塑件的开裂问题,通过Moldflow软件模拟分析,发现塑件在原始工艺条件下呈现一定的向下挠度翘曲,最大可达1.6 mm,又经量化得出塑件厚侧边的磨砂皮纹对塑件的摩擦力可大于14 kN,推知工艺条件和模具结构是导致塑件开裂的原因,并通过优化工艺参数和改变原始模具结构,使问题得到解决。 相似文献
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Yung-Hsiang Chang Tzu-Hsiang Wei Shia-Chung Chen Ying-Fan Lou 《Polymer Engineering and Science》2020,60(11):2895-2907
Injection molding is one of the commonly used processes for plastic part production due to numerous advantages, such as rapid production, complex shape modability, and material selectivity. However, highly experience-based conventional production restrains the industry development. Company know-how loses with the experienced operator's left. On the other hand, molded part quality was only based on the operator check. There is without an effective solution to maintain its stability and defect-free adjustment. How to establish a scientific injection molding setup and quality control method is an urgent topic. This study established a practical method for quality monitoring based on the pressure-volume-temperature (PVT) property. The PVT processing path control for scientific molding parameter setup was investigated. This is not only the method for parameter optimization but also the molded part quality control. Three major qualities were discussed in this study, including product weight, shrinkage, and warpage. By the molding condition optimization, three qualities improved up to 1%, 41.9%, and 9.2%, respectively. 相似文献
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In rotational molding, polymer powders are subjected to heating, melting, cooling, and subsequent crystallization processes. Because of the asymmetrical cooling condition, thermally induced residual stresses are created inside molded parts leading to part warpage. A detailed theoretical heat transfer model is presented for the entire rotational molding process including the consideration of endothermic and exothermic transitions. At the same time, the development of residual stress inside the molded parts is simulated with thermoelastic model. The warpage values are calculated under different processing cases, and the generated numerical results are in good agreement with data reported in the literature. Our results show that both crystallinity and temperature gradients developing within the polymer during the cooling process greatly affect the dimensional stability of ethylene copolymers typically processed in rotational molding. The latter is found to be the determining factor in evaluating the effect of cooling conditions on the warpage generated in a molded product. Our results also demonstrate the importance of the crystallization kinetics, the material stiffness, and its evolution during the solidification process on the dimensional stability of the molded products. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers 相似文献
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首先采用CAE软件Moldflow MPI 6.0和正交试验,对异形透盖塑件在不同注射成型工艺参数下的翘曲变形量进行了模拟,然后利用BP人工神经网络建立了主要工艺参数和塑件翘曲变形量之间的数学模型,并通过模型对塑件翘曲变形量进行了预测,结果表明,所建立的模型具有较高的预测精度。 相似文献
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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。 相似文献
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以家用空调遥控器前壳注塑件为例,在应用CAE模流分析确定塑件浇注系统和冷却系统的基础上,选取模具温度、熔体温度、注塑时间、保压时间和保压压力为设计变量,通过集成有限元模拟、Taguchi正交试验、BP神经网络(BPNN)以及粒子群优化算法(PSO)等来实现对薄壁塑件翘曲变形量的优化。优化后的工艺参数使得塑件翘曲变形量较优化前减少了37%,并应用Moldflow对优化工艺参数可靠性进行了模拟验证,结果显示,验证值和优化结果吻合度高,仅相差0.015 mm,表明所采用的薄壁塑件翘曲变形优化方法能显著减少注塑工艺参数调控过程对操作人员的经验依赖,具有较高的工程应用价值。 相似文献
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利用Moldflow软件对某厚壁塑料制件的注射成型过程进行分析,选取反映制品收缩与翘曲的多个评价指标,结合正交实验法,优化充填时间、熔体温度、保压时间、保压压力、冷却时间等工艺参数,通过均值分析与极差分析研究各因素对各评价指标的影响,并通过综合评分法得到一组最佳的工艺参数。结果表明,增加保压时间与保压压力能减小产品的收缩和翘曲,且得出的最佳工艺组合为注射时间为2.5 s,熔体温度为280 ℃,保压时间为130 s,保压压力为110 MPa,冷却时间为40 s,该工艺下产品的质量疏松度、体积收缩率、平面误差、翘曲分别降低了6.66 %、7.90 %、12.5 %、20.83 %,产品整体成型品质得到有效提高。 相似文献
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The dimensional stability of ethylene copolymers in rotational molding was studied by comparing the warpage observed for a series of conventional and single‐site catalyzed ethylene copolymers. Bench‐scale molding trials were carried out under controlled molding conditions. The rapid cooling of the mold using a water spray resulted in greater warpage. Under such conditions, molded parts made using the single‐site resins showed less warpage compared to the Ziegler‐catalyzed copolymers with otherwise comparable densities. The Ziegler‐catalyzed copolymers were characterized by a faster crystallization rate, and were shown to generate larger crystallinity gradients through the part thickness during the cooling process. Second to temperature gradients, crystallinity gradients are a leading cause for the development of residual stresses and causing warpage. Differences in the crystallization rates between single‐site and Ziegler‐catalyzed copolymers are discussed based on their intermolecular comonomer distributions. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers 相似文献
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Takaaki Matsuoka Jun-Ichi Takabatake Akihiko Koiwai Yoshinori Inoue Satoru Yamamoto Hideroh Takahashi 《Polymer Engineering and Science》1991,31(14):1043-1050
Injection molding analysis programs were developed for CAE (Computer Aided Engineering) in injection molding of thermoplastics. The programs consist of mold cooling, polymer filling-packing-cooling, fiber orientation, material properties and stress analyses. These programs are integrated to predict warpage of molded parts by using a common geometric model of three dimensional thinwalled molded parts. The warpage is predicted from temperature difference between upper and lower surfaces, temperature distribution, flow induced shear stress, shrinkage, and anisotropic mechanical properties caused by fiber orientation in the integrated simulation. The integrated simulation was applied to predicting warpage of a 4-ribbed square plate of glass fiber reinforced polypropylene for examination of its validity. Predicted saddle-like warpage was in good agreement with experimental one. 相似文献
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Rectangular plates of the size of 1800 × 600 × 12 mm3 and 1200 × 600 × 12 mm3 were selected for injection molding and injection compression molding, respectively, in order to investigate warpage characteristics of the large‐sized polymer plates with orthogonal stiffener. To determine the mold system and to reduce warpage of the specimen, numerical analyses for injection molding and injection compression molding were performed by using a commercial simulation code. Experiments were performed to verify the suggested mold system and warpage of the specimen. Relatively large warpage of the injection molded product was observed and small warpage of the injection compression molded product was generated. Compression force of the injection compression molding was only 6% of the clamp force of the injection molding. Warpage of the product was reduced significantly by using the injection compression molding. The injection compression molding will be used to substitute expensive and disused wood forms with inexpensive and recyclable polymer plates for concrete casting. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献