基于ANSYS的注塑模三维温度场数值模拟

建立了注塑模具和塑件三维瞬态传热分析的数学模型并确定了边界条件和初始条件,基于ANSYS平台二次开发实现了模具和塑件温度场的耦合分析。模拟了不同冷却方式、初始模具温度和初始熔体温度下的冷却过程,分析了这3种因素对塑件温度场和塑件温度-时间曲线的影响。结果表明:同熔体温度相比,模具温度对冷却过程的影响更大;塑件温差随模具温度、熔体温度的升高而增大,其中熔体温度的影响较大;通入冷却水后,塑件温度降低速率加快、塑件温差减小,且在较高模具温度下这种效果更为明显。     

振动注射成型中模腔冷却过程的研究

研究了振动注射成型中模腔内聚合物溶体产生的振动剪切热,并研究在振动作用下模腔内物料的冷却过程。结果表明,模腔内熔体的温升速率随着振动频率、应变振幅及振动剪切速率的增加而增加,随熔体温度的增加而减少。由于振动剪切换,使振动注射成型需要更长的冷却时间。     

温度相关工艺参数对外角撑制件双料注射成型质量的影响

基于界面扩散结合理论,利用Moldflow软件研究温度相关工艺参数对外角撑制件界面结合强度和翘曲变形的影响.结果表明:提高先、后注射材料的熔体温度和后注射材料的模具温度以及缩短先注射材料的模内冷却时间均可增加制件界面结合强度;除冷却时间外,制件总体变形随材料注射温度和模具温度的提高均有不同程度的增加,但高度方向的变形却在减小.     

玻璃吹制成型熔体与模具传热耦合模拟

玻璃吹制成型过程中熔体与模具接触时间短,热交换迅速、剧烈,同时玻璃的黏度对温度极其敏感,微小的温度波动将会引起黏度的剧烈改变,并最终决定制品的厚度分布,因此熔体与模具传热的耦合求解是十分必要的。鉴于此,本文在熔体与模具接触面上引入了界面单元来处理接触面热阻区的热传递问题,建立了熔体流动与模具温度场耦合模拟的控制方程,完成了算法编制,实现了熔体流动与模具温度场的耦合模拟。算例证明,与耦合传热算法相比迭代结果不足以满足吹制成型对温度场准确性的要求;通过模拟与实验对比,在连续生产条件下模具绝大部分的温度保持稳定,但与熔体接触的型腔壁的温度却有大幅的周期性变化;模拟的最终产品壁厚较准确地反映了产品的实际壁厚分布,准确度达到88%以上。     

基于有限差分法的注塑腔体温度场建模研究

注射机腔体的温度是保证塑料制品加工质量的重要参数之一。为了得到注塑腔体的温度场分布,本研究基于有限差分法建立了模具腔体的温度分布模型,利用matlab的pdetool工具箱进行温度分布的数值仿真。仿真结果表明:在模具冷却的过程中,热量从模具腔体内侧向模具腔体外侧进行传递。在0～6 s时,模具腔体外侧温度的上升速度增加,此后上升速度逐步减小,最终趋近于熔体的温度。对于不同熔体温度的塑料,熔体的温度越高,同时间的模具外侧温度越高。不同塑料丙烯腈-丁二烯-苯乙烯共聚物(ABS)、聚氯乙烯(PVC)、聚碳酸酯(PC)和聚苯乙烯(PS)的冷却时间与模具性能相关,在同一模具下基本保持一致,分别为28、26.7、27.6和28.4 s。     

变模温注塑模瞬态温度场数值模拟与工艺优化

应用Autodesk三维有限元瞬态传热分析方法对变模温模具传热过程和模具与熔体之间的耦合传热进行了瞬态求解和数值模拟,获得了模具温度场的变化过程及分布规律。应用三维瞬态注塑模拟,结合正交试验设计,对变模温成型工艺参数进行了优化。数值模拟后获得的最优结果:热水温度150℃,熔体温度250℃,冷却时间4s,注射时间0.3s,保压时间2s,保压压力为注射压力的110%。最后对最佳工艺参数进行了数值模拟验证,获得的结果是最大翘曲变形量为0.180 mm。     

基于Moldflow与Fluent模拟流体对注塑模温的热响应研究

以螺纹转接头注塑模为例,通过应用Moldflow与Fluent创建不同工况下的注塑模型,模拟动态模温模具的加热和冷却,分析流体类别及流速对模具温度变化的影响,获取动态模温注塑热响应曲线。结果显示:冷却流体流速对模温的影响有明显的区间差异性;模具型腔表面温度变化幅度比成型件内大,加热介质为热水时更显著;介质流速快的平均模温比流速慢的高,其中传热油特别明显;同一介质加热温度越高,加热及冷却时的模温变化幅度越大;加热介质对模温变化影响存在滞后性,其中传热油更明显。     

DFDA-7042薄膜透光性研究

气相流化床工艺生产的线型低密度聚乙烯DFDA-7042薄膜透光性相对较差,制膜条件对薄膜的透光性有着直接的影响。研究了熔体温度、冷却线高度、吹胀比对薄膜雾度的影响,利用正交实验确定最佳制膜条件。实验表明,熔体温度和冷却线高度对透光性影响较大,吹胀比对透光性的影响相对较小,制膜最佳条件为熔体温度200℃、冷却线1.5、吹胀比3.2。     

蒸汽加热变模温注射成型数值模拟与结果分析

采用Moldflow软件对变模温注射成型过程进行数值模拟。利用蒸汽加热和冷却水冷却的变模温注塑工艺,研究不同蒸汽加热时间下注塑位置处压力以及制件冷凝层的变化规律,同时分析了制件表面和模具型腔表面的热响应规律。结果表明,相比于传统注射成型工艺过程,变模温注射成型通过提高注塑充填过程中模具温度,使得制件冷凝层出现在充填阶段之后;随着模具加热时间从10、15、25 s增加到40 s,注塑位置处最大注射压力从87.0608、84.6064、79.6863 MPa减小到74.4342 MPa,大大提高了熔体注塑充填过程中的充填能力;通过不同的蒸汽加热时间,制件表面和模具型腔表面可以获得不同的温度值,同时通过模拟获得了传热系数对制件表面温度的影响。     

工艺参数对水辅助熔体充模流动的影响

基于水辅助注塑仿真模具,采用示踪技术,对不同注水延迟时间、注水压力、熔体温度和熔体填充量下的水辅助充模的熔体流痕进行了考察,研究了工艺参数对熔体流动的影响.实验结果表明:随着注水延迟时间的增加,一次穿透中的回流区域呈向水道边靠近的趋势,随水流动的熔体减少,受强剪切作用的熔体区域在水道边变窄.熔体温度低,模壁附近的高黏度...     

Development of stress birefringence and flow patterns during mold fillin and cooling

An experimental study was carried out to investigate the development of stress birefringence patterns of molten polymer during the mold filling and cooling operation. For this study, a rectangular mold cavity with glass windows on both sides was constructed, which permitted us to record on a movie film the changes in stress birefringence patterns in the mold cavity during the molding operation, using a circular polariscope. The mold was equipped with an automatic relay system which closes the shut-off valve when the pressure in the mold cavity reaches a predetermined value. The mold was also equipped with both heating and cooling devices, so that either isothermal or non-isothermal injection molding could be carried out. The mold temperature was controlled by thermistor regulated controllers. During the entire cycle of the molding operation, the mold cavity pressure was continuously recorded on a chart recorder, using a melt pressure transducer. The present study shows how molding conditions (namely, injection pressure, melt temperature, mold temperature) influence the distribution of stress birefringence patterns in a molten polymer while it is being injected into, and cooled in, a rectangular mold cavity.     

工艺参数对聚丙烯/聚酰胺6共混物水辅助共注塑管件壁厚及性能的影响

基于自行搭建的水辅助共注塑实验平台,通过正交实验制备了系列水辅助共注塑管件,探究工艺参数对各层壁厚、拉伸性能及各相结晶的影响。结果表明,外层壁厚随着外层熔体温度、注水压力、内层熔体注射压力、模具温度增大而逐渐减小,随着熔体注射切换延迟时间、注水延迟时间增大而逐渐增大;内层壁厚随着注水延迟时间、内层熔体注射压力增大而逐渐增大,随着注水压力、模具温度增大而逐渐减小;管件拉伸强度随着外层熔体温度增大而逐渐减小,随着熔体注射切换延迟时间、注水延迟时间增大而逐渐增大;工艺参数会影响到成型壁厚及冷却进程,进而影响各相结晶度,最终影响管件性能。     

非对称温度场下微孔发泡模内表面装饰复合成型工艺的翘曲变形

以拉伸试验样条为研究对象,采用正交试验设计与流动仿真计算,对非对称温度场下微孔发泡模内表面装饰复合成型工艺（MIM/IMD）中制品翘曲的影响因素进行分析,获取翘曲变形最小的最佳工艺参数组合。并对4种注射成型工艺（MID/IMD、IMD、MID、CIM）分别在X、Y、Z方向的翘曲变形仿真结果进行对比,分析不同成型工艺的翘曲变形在不同方向上的变化、泡孔半径及密度,探究微孔结构及分布对翘曲变形的影响规律。结果表明,熔体温度210 °C、注射速率55 cm³/s、充填体积98 %、超临界N₂浓度0.2 %（质量分数）、冷却时间40 s时,翘曲最小,翘曲变形最大减少3.414 mm;采用发泡工艺对制品的翘曲有一定的抑制作用;非对称温度场导致覆膜侧的泡孔尺寸及密度大于非覆膜侧,且温度较非覆膜侧高,使样条覆膜侧收缩变形慢于非覆膜侧,从而导致样条两侧产生具有向非覆膜侧内凹卷曲趋势的不均衡翘曲变形。     

Studies on structural foam processing II. Bubble dynamics in foam injection molding

An experimental study was carried out to gain a better understanding of the dynamic behavior of gas bubbles during the structural foam injection molding operation. For the study, a rectangular mold cavity with glass windows on both sides was constructed, which permitted us to record on a movie film the dynamic behavior of gas bubbles in the mold cavity as a molten polymer containing inert gas was injected into it. The mold was designed so that either isothermal or nonisothermal injection molding could be carried out. Materials used were polystyrene, high-density polyethylene, and polycarbonate. As chemical blowing agents, sodium bicarbonate (which generates carbon dioxide), a proprietary hydrazide and 5-phenyl tetrazole, both generating nitrogen, were used. Injection pressure, injection melt temperature, and mold temperature were varied to investigate the kinetics of bubble growth (and collapse) during the foam injection molding operation. It was found that the processing variables (e.g., the mold temperature, the injection pressure, the concentration of blowing agent) have a profound influence on the nucleation and growth rates of gas bubbles during mold filling. Some specific observations made from the present study are as follows: an increase in melt temperature, blowing agent concentration, and mold temperature brings about an increase in bubble growth but more non-uniform cell size and its distribution, whereas an increase in injection pressure (and hence injection speed) brings about a decrease in bubble growth but more uniform cell size and its distribution. Whereas almost all the theoretical studies published in the literature deal with the growth (or collapse) of a stationary single spherical gas bubble under isothermal conditions, in structural foam injection molding the shape of the bubble is not spherical because the fluid is in motion during mold filling. Moreover, a temperature gradient exists in the mold cavity and the cooling subsequent to mold filling influences bubble growth significantly. It is suggested that theoretical study be carried out on bubble growth in an imposed shear field under nonisothermal conditions.     

Improving surface quality of microcellular injection molded parts through mold surface temperature manipulation with thin film insulation

Microcellular injection molding offers many advantages such as material and energy savings, reduced cycle times, and excellent dimensional stability. However, typical surface characteristics of microcellular injection molded parts—such as gas flow and swirl marks and a lack of smoothness—have precluded the process from being used for applications where surface appearance is important. This article presents an insulator‐assisted method that has been shown to improve the surface quality of microcellular injection molded parts significantly. By incorporating a thin film (75–225 μm) of polytetrafluoroethylene (PTFE) insulator on the mold surface, the polymer melt–insulator interfacial temperature can be manipulated and can be kept high enough during mold filling to reduce or eliminate swirl marks on the surface. The experimental results in terms of surface roughness and surface profile of conventional and microcellular injection molded parts with and without the insulator film are discussed. Thermal analyses of the corresponding microcellular injection molding experiments were performed to elucidate the correlation between film thickness, interfacial temperature, and the surface quality. The effect of insulator on the cooling time increase is also analyzed and presented. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

基于微注射成型的微连接器工艺实验研究

基于正交实验设计方法,对微连接器在不同的微注射成型工艺参数下的充填情况进行研究,选择制品的质量作为实验指标,确定模具温度、熔体温度、注射速度、保压压力、保压时间、冷却时间等6个工艺参数为实验因素,通过对实验数据进行极差分析,得到了各因素对指标值的影响的主次顺序。实验结果表明,模具温度是影响制品质量精度的主要工艺参数因素,而冷却时间的影响最小。通过因素水平影响趋势图分析,得出了微连接器的最优工艺参数组合方案为模具温度80 ℃、熔体温度335 ℃、注射速度100 mm/s、保压压力20 MPa、保压时间1.5 s、冷却时间3.0 s,为微型器件生产中的工艺设计提供了理论依据和实际指导。     

The effect of injection molding process parameters on mechanical and fracture behavior of polycarbonate polymer

In this work, the mechanical and failure behavior of injection molded aviation standard optical grade polycarbonate (PC) was investigated through uniaxial tensile testing. The effect of different injection molding process parameters including injection velocity, packing pressure, cooling time, mold temperature, and melt temperature were determined to observe their effect on yield and postyield behavior of PC. Out of these examined parameters, the mold and melt temperature show significant effect on mechanical behavior of studied polymer. The yield and flow stresses in polymer increase with the increase in mold and melt temperature during injection molding. However, other process parameters i.e., packing pressure, injection velocity, and cooling time showed little effect on mechanical performance of the polymer. The molded specimens were annealed at different temperatures and residence time to evaluate its effect on mechanical behavior and fracture morphology. The yield stress increases gradually with the increase in annealing temperature and time. The annealing treatment also changed the failure mode of PC specimens from ductile to brittle. In addition to process parameters, the effect of increased loading rate was also undertaken which shows substantial effect on mechanical and failure behavior of PC. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44474.     

一模两腔不对称薄壁塑件工艺参数对收缩的影响研究

以降低塑件收缩率为目标,运用模流分析技术和正交试验法,通过方差分析,研究了工艺参数对塑件收缩率的影响程度。结果表明,使用最优工艺参数组合得到的塑件收缩率值为4.3117 %,该值远小于25次正交试验得到的实验值;对于丙烯腈-丁二烯-苯乙烯共聚物(ABS)材料而言,各工艺参数对收缩率的影响程度排序为：注射时间>熔体温度>保压时间>模具温度>冷却时间>保压压力。     

Coupled Part and Mold Temperature Simulation for Injection Molding Based on Solid Geometry

This paper presents a coupled method that determines the interface temperatures by filling and cooling analyses simultaneously to simulate the mold and part temperature distributions for injection molding. The mold temperature is assumed to be changing and is calculated with melt together at the filling stage instead of keeping constants as is usually done in conventional methods. The mold temperature is first determined with a 3-D finite element method by specifying the heat-flow rate at the interface between mold and part. Then the finite difference approach is employed to solve the melt thermal problem to get melt temperature distributions inside the cavity and the heat-flow rate at the interface. The under-relax scheme is used to correct the boundary condition and to resolve both mold and melt thermal problems until the solutions are convergent. This method can simulate transient and multicycle problems with more complex process conditions. The simulated results agree with experimental data.