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J. Zhao R. H. Mayes Ge Chen Hong Xie Poh Sing Chan 《Polymer Engineering and Science》2003,43(9):1542-1554
The trend towards miniaturization has brought about strong demand for increasingly smaller precision‐molded plastic components. In order to control metering accuracy and homogeneity of the very small quantities of melt in the micro molding process, new micro molding machines that use an injection system comprising a screw extruder and a plunger injection unit have been developed. By use of such injection systems, standard plastic granules can be handled by the screw extruder and melt accuracy can be achieved by the electrically driven injection plunger. The objective of this work is to investigate the effects of the process parameters on the micro molding process and part quality. A series of micro gears were molded using a polyoxymethylene resin in a set of statistically designed experiments. Micro component inspection, characterization, and data analysis work was carried out to study the molded gears. It was found that metering size and holding pressure time are the process parameters that have the most significant effects on part quality, and that the process is also significantly affected by the interaction of these two parameters. There is an optimum metering size range in which the hold pressure can act together with the metering size to properly fill micro mold cavities. 相似文献
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针对某异型出风罩注塑成型工艺,以聚碳酸酯/丙烯腈-丁二烯-苯乙烯共聚物(PC/ABS)工程塑料合金为填料,运用Moldflow软件对其注塑过程进行模流分析,通过田口实验设计研究了熔体温度、保压时间、保压压力、注射时间和模具温度对塑件收缩率和翘曲变形量的影响,得到它们对塑件收缩率的影响次序为:保压时间>熔体温度>保压压力>注射时间>模具温度,对翘曲变形量的影响次序为:保压压力>注射时间>熔体温度>保压时间>模具温度。基于灰色关联分析,获得了最优组合工艺参数,即:熔体温度280℃、模具温度为65℃、注塑时间2.1 s、保压时间11 s、保压压力21 MPa。优化后的仿真结果表明,塑件的体积收缩率为6.523%、翘曲变形量为0.80 mm,比灰色关联次序中位组合的样本数据分别降低6.9%和15.8%,并获得最大注射压力为20.34 MPa、最大锁模力为3.25×10^5 N,为后期模具的设计和注塑参数设定提供了有力的参考,缩短了模具开发周期。 相似文献
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分析了注塑制品的收缩机理及收缩过程,并讨论了聚酰胺(PA)注射成型过程中模腔平均压力、熔体温度、模温、充模速率、成型时间等工艺条件对其收缩率的影响及制品后收缩率的因素,给出了减小制品收缩率,提高制品尺寸稳定性的方法。 相似文献
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Some engineering thermoplastics cannot be easily processed by injection molding because of their high viscosity. This is the case for Ultra-High Molecular Weight Polyethylene (UHMWPE). Parts are either compression molded or machined from extruded shapes. Over the years, forging has been increasingly used to produce more or less complicated parts. Forging is a process in which a preform is subjected to bulk deformation in constraining dies, by applying heat and pressure, but with the polymer remaining in the solid (semi-crystalline) phase. To fabricate acceptable mechanical components such as gears and sprockets, a close control of the operating conditions and a good prediction of shrinkage are necessary, For a better understanding, a study has been conducted on forged UHMWPE disks and gears. Parameters such as material and mold temperatures, dwell time, speed of forging and dwell pressure were investigated. Results show that material and mold temperatures are the most important parameters. For gears, optimization of processing conditions led to a shrinkage of ~0.2 percent, measured on pitch diameter. The effect of post-annealing at various temperatures is also reported. 相似文献
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以轿车左右外后视镜三角护罩为例,在详细分析护罩塑件结构、成型材料性能和塑件壁厚的基础上,采用MFI2015对其浇口位置进行了仿真分析。在综合"最佳浇口位置"、塑件结构和成对注塑的基础上,确定了模具采用热流道的牛角形潜伏浇口浇注系统和近型冷却系统方案;在对塑料成型工艺分析中,对影响产品质量的填充时间、流动前沿温度、速度压力切换时的压力、冻结层因子、气穴、锁模力、缩痕、体积收缩率、总变形量等进行了分析。运用UG软件对型腔、型芯结构,导向与塑件精度保证机构、顶出机构和各六套的侧向滑块分型、侧向斜顶抽芯机构,及其复位机构与模具的整体等进行了分析设计,完成了一次注射成型配对护罩塑件的模具设计。同时,运用由导柱导套+锥槽定位+楔紧镶块调节+厚薄调节垫组成的"四位一体"精度保证与保持系统,使塑件精度更高。 相似文献
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Nanyang Zhao Junfeng Liu Mingcheng Bi Zhongbin Xu Jing Zhou Jisong Ding Qiong Wu 《应用聚合物科学杂志》2024,141(9):e55018
Online viscosity information on processing lines can reflect the material flow resistance and offer valuable guidance for manufacturing across various industries. Considering the accuracy, devices, and processes involved in injection molding, characterizing the melt's flow state during material processing poses a significant challenge. To reduce investment in viscometers, avoid influencing the components' surface aesthetics due to the installation of sensors, and make the flow state detect online in mold, this study designs a rheometric mold with cylindrical runners for identifying the in situ viscosity of molten resin during injection molding. The detection conditions of injection speed and cavity pressure variations, the entrance effect, and the viscous dissipation for Polycarbonate are analyzed under various conditions. The in situ viscosity is identified and compared with the standard cross-WLF model. The result shows that the melt velocity and cavity pressure variations during the filling process create a stable environment for in situ rheological characterization and the detected viscosity is related to the shear rate, melt temperature, and channel dimension in injection molding. The designed mold with cylindrical runners for determining the in situ thermal-rheological behavior of polymer is distinguished successfully and exhibits prospects for the development of low-cost, nondestructive, and inner-mold measurement in manufacturing applications. 相似文献
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The injection molding of reprocessed plastics with a preplastication plunger injection‐molding machine was investigated with a focus on the processing conditions. The process of the filling of the resin into the mold is much better controlled with preplastication than with processing in a conventional injection‐molding machine. Reprocessing of the resin leads to a reduction in molecular weight due to drastic changes in the resin morphology, thereby causing a reduction in melt viscosity. Direct experimental evidence for reduced viscosity was obtained from measurements of the filling pressure recorded on the machine and also with a melt‐flow indexer. The results of this study provide a practical solution for reducing the resin temperature when reprocessed resin is used in the injection molding of plastics. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1455–1461, 2001 相似文献
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通过对一种用于减速的斜齿双圆柱塑料齿轮进行结构特点及注塑成型工艺分析,完成了该塑件注塑成型模具的总装结构设计。介绍了推杆、推管和向心推力球轴承相结合使齿形型腔旋转推出塑件的方式,有效解决了两齿轮型腔镶块在转动中的"先、后"差异及"同步"问题,阐述了采用弹簧定距拉杆和定距拉板三次顺序定距分型结构来实现自动脱模的模具工作过程。 相似文献
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This study of injection molding of glass fiber reinforced phenolic molding compounds examines fiber breakage and fiber orientation with key material and processing variables, such as injection speed, fiber volume fraction, and the extent of resin pre-cure. The fiber orientation, forming discrete skin-core arrangements, is related to the divergent gate to mold geometrical transition, the extent of pre-cure and injection speed functions of the melt viscosity. Transient modifications to the melt viscosity during mold filling produce variations in skin/core structure along the flow path, which are correlated to the mechanical properties of injection moldings. The melting characteristics of the phenolic resin during plasticization impose a severe environment of mechanical attrition on the glass fibers, which is sequentially monitored along the screw, and during subsequent flow through runners and gates of various sizes. Differences found between the processing characteristics of thermosets and thermoplastics raise questions concerning the applicability of thermoplastic injection molding concepts for thermosets. 相似文献
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基于Moldflow软件,采用正交试验和响应曲面法,对高铁橡胶外风挡注射成型的模拟方案优化设计,并对注射成型工艺参数进行研究。结果表明:模具温度是影响橡胶外风挡顶出时的体积收缩率和缩痕指数的最显著工艺因素,其次分别是熔体(胶料)温度、保压时间、保压压力、注射时间;优化的注射工艺参数为:模具温度185℃,熔体温度65℃,注射时间160 s,保压时间14 s,保压压力110 MPa。在此工艺参数下的橡胶外风挡顶出时的体积收缩率最大值为4.165%,缩痕指数最大值为5.103%。 相似文献
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结合注塑模拟分析软件Moldflow和正交试验法,对不同工艺条件下的塑件成型过程进行模拟分析,确定塑件制品品质评价指标为制品体积收缩率、表面缩痕指数和最大翘曲量,运用模糊数学中的综合评判法,建立主要成型工艺影响因素的多指标综合评价数学模型;通过对综合目标值的极差分析,确定熔体温度、模具温度、注射时间、保压压力、保压时间等工艺参数对综合目标值的影响程度的大小,绘制因素水平影响趋势图,分析得出最优的工艺参数组合方案,并对该工艺组合方案进行模拟验证。 相似文献
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Heating mold and resin have been widely used in resin transfer molding (RTM) to improve injection and manufacturing efficiency. The unreasonable mold/resin temperatures sometimes lead to excessive viscosity of resin and premature curing, which will result in failure of the filling process. Selection of optimal mold and resin temperature has become a source of concern in the polymer industry. This article presents an optimization method to select mold and injection resin temperatures by using numerical simulation based on chemorheological and exothermal reaction of the RTM process. The results show that the optimization method has high computational efficiency for three-dimensional parts with different shapes. The selected mold/resin temperature ensures the smooth filling process, which provides a powerful tool for parameter design in polymer industry. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48245. 相似文献
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Cycle times in resin transfer molding (RTM) of an unsaturated polyester have been reduced significantly using an in-line microwave resin preheating system. Microwave preheating lowers the resin viscosity during injection and modifies the thermal age of the resin, potentially influencing the quality of RTM laminates. The tensile properties of RTM laminates have been measured with regard to improved fiber wet-out by the lower viscosity resin. Degree of cure measurements have been included to establish the effect of microwave preheating on resin conversion within the laminate. Local pressure that develops within the mold during the cure phase can lead to mold deflections. Variations in the laminate thickness associated with these deflections are presented, and the use of microwave resin preheating to reduce these variations is discussed. 相似文献
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Metal and plastic can be bonded in a single molding process by metal insert molding, in which a metal is inserted into a mold and a plastic resin is then injected. However, the adhesive strength at the interface between the metal and plastic is weakened by the difference in the shrinkage ratio and inherent differences between the materials in the metal insert molding. This study reports the treatment of a metal surface that is followed by inserting the metal into a mold to increase the adhesive strength between the metal and glass fiber (GF)‐filled acrylonitrile butadiene styrene (ABS). A laser process was used for an engraving surface treatment and a plating process was performed for an embossed surface treatment of the metal. In addition, the adhesive strength between the metal and GF‐filled ABS was evaluated after the insert molding process was completed. Particles such as glass beads, ceramic beads, artificial diamonds, and aluminum oxides were employed in the plating process. The adhesive strength varied depending on the surface treatment of the metal. In particular, the adhesive strength significantly increased when an undercut shape was formed at the metal surface. The best adhesive strength with GF‐filled ABS was found in the metal specimen plated using aluminum oxide particles. POLYM. ENG. SCI., 59:E93–E100, 2019. © 2018 Society of Plastics Engineers 相似文献