注气参数对气辅成型气体穿透影响的研究

以气辅塑件为研究对象,采用气辅成型全三维数值模拟和物理试验,探讨注气参数(注气时长、注气压强)对气体穿透的影响。结果表明:注气时长和注气压强决定气体穿透程度,特别对气体再次穿透程度、气指尺度及塑件外观质量起着决定性作用;增加注气时长,能加大气体穿透程度,提升气体穿透体积比例,减轻外观不良,减少翘曲变形程度,但会增加气指缺陷。加大注气压强,会减小气体穿透程度,加重气指缺陷,而对气体穿透体积比例影响不大;另外,适当提高注气压强可以减轻外观不良,但过高的注气压强容易使制品产生发泡缺陷。     

气辅成型过程气体穿透行为

对气体辅助注射成型过程在不同工艺参数设定下的气体穿透行为进行研究,通过实验对延迟时间、熔体的注射量,以及延迟时间与注射压力间的交互作用对气体穿透长度的影响进行了讨论,并对“无进气点”进行了讨论分析。     

基于Taguchi方法优化气辅成型气体穿透深度

基于气体辅助注塑成型过程的三维数值模拟,利用Taguchi实验方法设计了L9(34)实验矩阵,采用标准方差分析方法,分析了预注射量、注射温度、气体压力和延迟时间等工艺因素对气体穿透深度的影响,预测了优化工艺组合下的气体穿透深度。研究表明:在所选择的工艺因素中,对气体穿透深度影响程度依次为预注射量(F=87.8%)、气体延迟时间(F=8.1%)、气体压力(F=3.5%)和注射温度(F=0.6%)(F为因子重要性)。在优化工艺组合下预测的气体相对穿透深度为87.1%,与模拟计算值符合较好。     

注气时间对气辅成型气体穿透影响的数值模拟和实验研究

以具有代表性结构特征的气辅塑料件为研究对象,结合气辅成型全三维数值模拟和物理实验,探讨气体辅助注气时间与气体穿透行为的关系。结果表明:注气时间对气体穿透深度(特别是二次穿透程度)、气指缺陷、制品表面质量等有着显著的影响。较长的注气时间可以加强气体穿透效果,提高气体体积百分比,减少制品表面缺陷,减小制品内应力和翘曲变形,但又会加重气指缺陷的程度。     

气体辅助注射成型中气道截面对气体穿透的影响

将各种不同气道截面等效于圆形,引入形状因子来衡量它们偏离圆形的程度。利用moldflow软件对气体在不同构型气道内的穿透过程进行了数值模拟。结果表明:形状因子越大则气体穿透深度越大,对气体辅助注射成型有利。但由于形状因子越大则气道截面偏离圆形越远,不利于形成均匀的熔体壁厚,因此在设计气道截面时,应合理选择形状因子以便获得恰当的气体穿透深度和熔体壁厚。最后还给出了气道设计的一般原则。     

气体辅助注射成型中气道布置及大小对薄壁穿透的影响

将两种不同的气道尺寸,利用Moldflow软件对气体在4种不同布置的气道内的穿透过程进行了数值模拟,结果表明:同样的气道尺寸、不同的气道布置以及相同的气道布置、不同的气道尺寸,其气体的薄壁穿透程度都是不同的。因此在气道设计中,应合理选择气道尺寸和气道布置。最后还给出了气道设计的一般原则。     

气辅成型过程气体穿透行为与工艺参数优化的试验研究

基于带平板的回形管式气体辅助成型样件对气体穿透行为和残余壁厚与气辅工艺参数的关系进行了研究分析.试验结果表明,气辅工艺参数如气体延迟时间、气体注射压力和熔体预注射量是影响气体辅助成型中气体穿透长度和残余壁厚的重要因素,而各参数间的交互作用致使气体穿透与残余壁厚的变化趋势更为复杂.     

气辅新增参数对气辅注塑成型质量的影响

气辅注塑成型新增气辅参数(注气时间、注气压力、延迟时长)直接影响了其成型质量.采用气辅注塑成型全三维数值模拟、成型实验以及正交设计法,研究各新增气辅参数与气辅注塑成型质量之间的关系.结果 表明,较长的注气时间能提高气体穿透深度,减少表面缺陷,降低内应力和翘曲变形,但是会使气指缺陷的程度增大.当注气时间过长时,会导致气辅...     

延迟时间对气辅注射成型气体穿透行为影响的数值模拟和实验研究

以一个具有气辅成型典型结构的塑料制品为研究对象,通过物理实验和全三维数值模拟结合的方法,研究了不同延迟时间时的气辅成型中气体穿透行为,对结果进行了分析和探讨。结果表明,延迟时间对气体穿透长度、气指尺度和残余壁厚等衡量气辅成型质量的关键参数有较大的影响。     

气体辅助共注成型流动分析数学模型

根据气体辅助共注成型流动过程的特点，从流体力学基本理论出发，引入合理的假设和简化，建立了描述气体辅助共注成型熔体充模和气体穿透的数学模型。     

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.     

气体辅助注射成型设备的构建

为促进气体辅助注射成型设备的国产比，介绍了在传统注射成型设备基础上构建该设备的关键技术，提出了气体辅助注射成型设备注气系统的组建及对注射机和注射模的要求，突破了传统注射成型的技术限制，可节约大量因引进进口设备所花费的资金。     

Investigation of gas-assisted injection molding. Part III: Effect of gas channel design on part bending strength

Numerical simulation and experimental measurements were carried out to investigate the effect of gas channel design on the bending performance of gas-assisted injection molded parts. Plate parts designed with various channel geometries were gas-assisted injection molded. Part flexible strength were measured via bending tests. It was found that part stiffness basically increases linearly with the inertia moment of the plate. The gas channel introduces an additional moment of inertia, the amount of which is determined by the shape and the dimension of the channel section as well as the hollowed core geometry. An analysis algorithm based on DKT/VRT elements superimposed with beam elements representing gas channels of various section geometries was developed to evaluate part bending behavior. An equivalent diameter was assigned to the beam element so that both the original gas channel and the circular beam have the same moment of inertia. The analyzed results from this model of 2 1/2-D characteristics were also verified with both 3-D and 2 1/2-D analyses using ANSYS. The present simulations show reasonable accuracy as compared with experimental measurements and predictions from ANSYS. This investigation also indicates that it may be feasible to use the same CAE finite element model implemented for process simulation of gas-assisted injection when performing part structural analysis as well as warpage calculation, resulting in great computational efficiency for industrial application.     

Effect of gas channel design on the molding window of gas‐assisted‐injection‐molded polystyrene parts

Gas channel design plays a dominant role in determining the successful application of gas‐assisted injection molding. Although empirical guidelines for gas channel design have been proposed by the various equipment suppliers, quantitative criteria based on well‐designed experiments have not been reported yet. In this study, transparent polystyrene plates designed with semicircular gas channels of different radii and with rectangular gas channels of different width‐to‐height ratios were gas‐assisted‐injection‐molded to investigate the geometrical effects on gas penetration with various plate thicknesses. Plate parts designed with gas channels having four different types of cross sections but with the same section area were also examined. Molding windows and criteria for gas penetration were properly chosen so that the design rule could be defined quantitatively. The moldability index was also classified into five levels (excellent, good, fair, poor, and bad) based on the relative areas of the molding windows. From a plot of the moldability index versus the ratio of the equivalent gas channel radius to the plate thickness, we found that the ratio should be approximately greater than 2 for an appropriate molding window (fair moldability index) to be obtained. The dimensional ratio of the width to the height for rectangular gas channels also affected the moldability index under the same equivalent radius. Meanwhile, for four gas channel designs, both gas channel designs attached to the top rib provided better moldability than the other designs. This investigation offers part designers preliminary quantitative design and molding guidelines for choosing an effective gas channel design that allows the parts to be molded under an appropriate molding window so that the uncertainty in both simulation and process control can be overcame. Furthermore, this study provides a methodology for the establishment of quantitative gas channel design guidelines. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2979–2986, 2003     

Effect of thrust on supersonic gas jet penetration in gas-solid fluidized beds

Most of the jet penetration studies in gas-solid fluidized beds are for subsonic gas jets, for which many correlations can be found in the literature. In this work, horizontal supersonic gas jets, produced by convergent-divergent nozzles, have been studied, and the intent was to investigate the relationship between the thrust produced by supersonic nozzles and the jet penetration. Different nozzle geometries were used, with three gases having different characteristics (air, helium and carbon dioxide) and at different pressures. All the experimental runs were performed with silica sand particles with the same particle size distribution, and the fluidization velocity was set at a constant value of 0.09 m/s.Jet penetration was measured with a set of triboelectric probes, and it was found that the correlation proposed by Merry, although originally developed for subsonic gas jets, fits really well the experimental results. It was also confirmed that jet penetration displays a strong correlation with the thrust produced by the convergent-divergent nozzles.A correlation originally proposed by Benjelloun's has been modified and the corrected correlation gives the best predictions for gas jet penetration     

气辅成型工艺的研究

介绍了气体辅助注射成型技术工艺参数的确定和成型材料的选择原则,讨论了成型过程中出现的主要缺陷及其原因和解决方法。     

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。     

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。     

Primary and secondary gas penetration during gas‐assisted injection molding. Part II: Simulation and experiment

Simulation and experimental studies have been carried out on the transient gas‐liquid interface development and gas penetration behavior during the cavity filling and gas packing stage in the gas‐assisted injection molding of a spiral tube cavity. The evolution of the gas/melt interface and the distribution of the residual wall thickness of skin melt along with the advancement of gas/melt front were investigated. Numerical simulations were implemented on a fixed mesh covering the entire cavity. The residual thickness of a polymer layer and the length of gas penetration in the moldings were calculated using both the simulation and model developed in Part I of this study and commercial software (C‐Mold). Extensive molding experiments were performed on polystyrene at different processing conditions. The obtained results on the gas bubble dynamics and penetration behaviors were compared with those predicted by the present simulation and C‐Mold, indicating the good predictive capability of the proposed model. Polym. Eng. Sci. 44:992–1002, 2004. © 2004 Society of Plastics Engineers.