微注塑成型流动中熔体壁面滑移的研究

基于宏观熔体流动的基本理论及其流动过程中壁面滑移机理的分析,针对微注塑成型模具中熔体充模流动时的壁面滑移行为,建立了微小通道中高聚物熔体流动的壁面滑移理论模型。并用数值模拟方法,对不同滑移系数时微小通道中熔体的壁面滑移对流动速度、熔体压力等的影响进行了研究。结果表明,微小通道中的壁面滑移可使壁面处熔体的流动速度增加,压力损失减小,有利于熔体的充模流动。     

片状模塑料模压流动仿真分析

本文采用有限元分步计算方法,对酚醛片状模塑料(P-SMC)在模压过程中的流动变形情况进行了计算机仿真模拟,与试验结果做了对比。编制了相应的有限元计算与后处理软件,分析了模压料在封闭模具中充满模腔的过程、在一定合模速率下的充模时间以及在一定粘度下的模压成型压力。对SMC模压时模具的设计以及优化成型工艺参数具有一定的理论指导意义。     

微注塑成型中对流换热系数对熔体充模流动的影响

在熔体流动理论的基础上,通过分析熔体的对流传热机理,并引入对流换热系数模型,对微注塑成型中对流换热系数对熔体充模流动进行了研究。在正方形截面分别为500μm、300μm和200μm的三种长方形微流道中,数值模拟了熔体充模流动,通过与已有实验数据相比较,验证了对流换热系数模型的合理性,并分析了不同的模具温度和熔体温度下,采用常数对流换热系数和对流换热系数模型得到的熔体温度分布及其随微流道特征尺度变化规律。     

蒸气辅助快速热循环注塑技术及模温响应模拟

快速热循环注塑采用动态模温控制新策略,可以彻底解决常规注塑工艺存在的短射、喷射痕、缩痕、流动痕、熔接痕、浮纤等缺陷。文中通过对快速热循环注塑工艺与常规注塑工艺的比较,深入研究了蒸气辅助快速热循环注塑工艺的原理,制定了相应的工艺流程,提出了一套新的利用蒸气加热和冷凝水冷却的动态模温控制方案。利用ANSYS模拟了快速热循环注塑工艺和常规注塑工艺的模温响应过程,分别获得了两种注塑工艺的模具加热速率和冷却速率,讨论了快速热循环注塑对塑件成型周期的影响规律。     

基于ANSYS CFX的注塑成型充填过程三维模拟

注塑成型中,熔体在模腔内的流动为非牛顿流体在复杂型腔内的非等温、非稳态流动。充填过程的三维数值模拟能更真实地模拟熔体在型腔内的三维流动状态。本文采用有限元分析软件ANSYS CFX进行二次开发,实现注塑成型充填过程的三维模拟,可求解熔体前沿、压力场、温度场等一系列模拟结果。模拟结果与注塑成型软件MOLDFLOW结果进行对比,验证了该方法的有效性。算例分析结果表明,对于薄壁制品,基于中面模型的注塑成型模拟方法是适用的,但对于非薄壁制品,采用三维模拟方法可以得到更合理更全面的信息。     

基于FEPG有限元分析系统的树脂充模过程模拟

为优化复杂预成型体结构的液体成型工艺,基于有限元法/生死节点法模拟了复合材料液体模塑成型过程树脂流动,并针对典型矩形平板、圆板结构、I型加筋壁板充模过程进行了仿真与验证。结果表明:典型矩形平板和圆板结构的充模过程模拟结果与理论解一致性较好,验证了生死节点法跟踪树脂流动前锋的有效性。含有方腔的变厚度圆柱体和正方体三维实体结构的充模过程模拟验证了有限元方法对三维结构的适用性。基于有限元法/生死节点法的液体充模过程模拟方法对于复杂求解区域具有更好适应性,可用于复杂实体结构的液体模塑成型工艺过程树脂流动规律预测、指导模具设计及工艺优化。      

塑料微流控芯片的注塑成型

有别于传统的微流控芯片压塑成型方法,本文提出注塑成型加工塑料微流控芯片的新工艺.采用UV-LIGA技术制作成型微通道的型芯,设计制造了微流控芯片注塑模具.充模试验表明,如何使微通道复制完全是微流控芯片注塑成型的主要技术难点.模拟与理论分析表明,熔体在微通道处出现滞流现象是复制不完全的主要原因;搭建了可视化装置对此加以试验验证.利用正交试验方法进行充模试验,研究各工艺参数对微通道复制度的影响.试验表明模具温度对提高微通道复制度起决定性作用;注射速度和熔体温度是次要因素,而注射压力相对其他因素影响力较差,但必须保持在一个较高的水平.依此形成塑料微流控芯片的注塑成型工艺,对于宽80μm、深50μm截面的微通道而言,可使微通道复制度由70%提高到90%,满足使用要求.     

微齿轮注塑成型正交优化及数值模拟

介绍了采用高聚物成型微齿轮的主要成型方法--微注射成型.比较了不同种类的注射原料ABS、聚丙烯(PP)、聚碳酸酯(PC)的成型工艺,并就影响微注射成型中影响微制件质量的主要工艺过程:充模压力、熔体温度、模具温度和充填时间等进行数值模拟研究,采用正交优化方法对成型方案进行优化,获得优化的成型参数.为微齿轮成型模具的结构设计、成型工艺参数的合理化等等提供理论依据.通过对微齿轮成型过程的数值模拟优化,得到微注射成型的模具温度升高、注射压力增大、注射温度升高都会缩短充模时间;结果显示,聚合物材料对微注塑齿轮的适用性依次为:ABS＞PP＞PC.     

采用紫外光刻电铸技术的微型腔注塑成型

针对复杂微型腔制作的难点,基于紫外光刻电铸(UV-LIGA)技术和掩膜腐蚀的方法加工了细胞皿微型腔。以聚丙烯(PP)进行单因素充模流动工艺试验,通过极差分析,研究了注射速率、模具温度、熔体温度、保压压力和保压时间对微制品成型质量的影响规律。注射速率对提高充填率起主要作用,模具温度和熔体温度是次要因素,而保压压力和保压时间相对其它因素对充填质量影响较差,但必须保持在一个较高的水平。在获取优化工艺参数后,获得合格的制品。因此基于UV-LIGA技术和掩膜腐蚀的方法制作复杂结构微型腔对于微注塑成型是可行的。     

树脂膜熔渗工艺充模过程的模拟与分析

树脂膜熔渗工艺(RFI)是一种新型的复合材料成型工艺.为了更深入了解树脂膜熔渗工艺过程中充模阶段的控制参数对制品质量的影响,避免制品出现空斑、充模不完全等问题,针对该工艺过程中树脂在复杂形状预制件中的流动行为进行了分析,在达西定律基础上建立了二维等温流动控制方程,利用有限元/控制体方法建立了数值分析模型,编制了FORTRAN程序进行模拟运算,并讨论了流动过程中施加的压力对充模时间的影响.由计算实例可见,所编制程序能够很好地预测树脂膜熔渗工艺过程中充模时间、各个时刻树脂的流动前沿位置及模腔中的压力分布.     

Analysis of thermal cycling efficiency and optimal design of heating/cooling systems for rapid heat cycle injection molding process

Rapid heat cycle molding (RHCM) is a molding process that the mold cavity is rapidly heated to a high temperature before plastic melt injection, and then cooled quickly once the cavity is completely filled. Heating/cooling efficiency and temperature uniformity of the RHCM system are two key technical parameters to ensure a high productivity and high-quality products. In this study, a numerical model to analyze the heat transfer in heating and cooling phases of RHCM was built. The effect of heating/cooling medium, layout and structure of the heating/cooling channels, mold structure, etc., on heating/cooling efficiency and temperature uniformity was studied and discussed by analyzing the thermal responses of the molding system in RHCM process. Based on the simulation results, the optimization design of the RHCM mold with hot-fluid heating was performed. Then, a new RHCM mold structure with a floating mold cavity was proposed to improve the heating/cooling efficiency and temperature uniformity. The effectiveness of this new mold structure was also verified by numerical experiments. At last, a RHCM production line with steam heating and water cooling was constructed for a thin-wall plastic part. In testing production, the molding systems can be heated and cooled rapidly with a molding cycle time of about 72 s. The production results show that the aesthetics of the molded parts was greatly enhanced and the weld mark on the plastic part’s surface was completely eliminated.     

陶瓷产品数字化设计与模具精确成型方法研究

目的 传统陶瓷依靠手工直接制坯与石膏模具成型,但会存在尺寸精度不足与不便修整等问题。应用数字化技术完成陶瓷产品特征建模与子模模具设计,应用3D打印技术实施模具精确制造,使用直接或间接成型方法制得造型多样的陶瓷产品。方法 根据制定陶瓷3D打印精确成型技术路线,并以“跑车水杯”为例说明陶瓷产品精确成型过程,包括数据采集、逆向设计、3D打印子模模具、制造石膏子模、注浆成型等步骤。结论 基于数字化设计与模具精确成型技术,验证了定制的陶瓷产品精确成型方法,总结出陶瓷造型数字化设计流程及技术化科学研究进路,使生产效率提高的同时,还能制造多样化造型的陶瓷产品。     

Process Development and Product Quality of Micro-Metal Powder Injection Molding

Injection molding has been found to be an efficient and cost-effective manufacturing technique for the production of a wide variety of parts and components at both macro- and microscale. This is attributed to the application of robust design and process development. However, every manufacturing technique is challenged by quality issues and part defects, but tackled by continuous improvement framework(s). This systematic monitoring and control approach of dimensional accuracy, mechanical properties, and surface quality of the finished part strongly depend on process conditions at different production stage. Therefore, the aim of this study is to review process development of micro-metal injection molding; focusing on critical factors influencing part quality and optimization of process parameters. The critical factors that influenced the finished part quality are part design, mold design, material selection, machine, and process conditions. Optimizing mold temperature, melt temperature, injection speed, injection pressure, cooling time, packing, and holding parameters improve the quality of the molded part. This trend of process development of injection molding gave rise to a broad scope of applications with brighter future potentials for the next decades, particularly for medical and electronics applications.     

电脑主机风扇底座注射成形流动仿真及模具设计

目的 设计一种造型美观、结构稳固、形状复杂的3层电脑风扇底座塑料制品。方法 采用Moldflow软件对电脑主机风扇底座的注射成形工艺流动过程进行了有限元仿真,对充填过程中的充填时间、气穴位置、熔接痕进行了分析。结果 确定了气穴和熔接痕的位置,提出了改进方法,分析了最大变形量的发生位置,最后对其注射成形模具进行了设计,主要对主型芯和斜导柱侧抽芯机构进行了设计,分析了模具的主要机构组成及工作原理。结论 将仿真技术与3D模具设计技术应用在新型电脑风扇底座模型及模具开发中,能够较为准确地分析制品充填过程中的充填时间、气孔、熔接痕和变形量等参数,从而指导模具设计过程。     

笔记本电脑电池盖进浇方案MOLDflow分析

为了减少笔记本电脑电池盖产品的注塑缺陷和提高一次试模的成功率,提出在模具设计阶段改善产品成型质量的模具结构优化方案.应用MOLDFlow软件对电池盖产品的进浇方案进行仿真分析,分析了浇口尺寸、模具温度和成型工艺参数对填充时间、熔接线、气穴位置的影响,证实了所提改善方案的正确性,并得到优化的成型工艺参数,从而解决了电池盖的注塑缺陷问题,提升了生产效率,为模具设计人员进行模具设计以及注塑工艺人员进行工艺参数的调整提供依据.     

基于移动最小二乘的注塑模浇注系统稳健设计

注塑模浇注系统设计是模具设计中较为重要的一环,因此对浇注系统的优化设计研究开展得较早,但在已有的研究中,均没有考虑随机因素波动对成型质量的影响。针对该问题,选取最大翘曲变形量为成型质量指标,提出了基于可拓关联变量筛选、移动最小二乘及蚁群优化的浇注系统稳健设计方法,通过数值模拟及实例验证,表明该方法减小了响应的方差,并有效地提高了塑件的尺寸公差。     

气体辅助注塑成型制件开发工艺研究

对塑料家俱制件进行了气辅注塑工艺开发与研究,考察了塑料转奇扶手的气辅加工中气嘴位置,熔体注入量,熔体注射温度,延迟时间、气休注射压力等对充模过程的影响,应用气辅注射模拟软件Ｃ－Ｍｏｌｄ对该制件的气辅助才不同工艺条件对气辅制件的影响做了模拟,并和生产实际进行了比较。     

Inverse thermal mold design for injection molds

The thermal mold design and the identification of a proper cooling channel design for injection molds becomes more and more complex. To find a suitable cooling channel system with objective rules based on the local cooling demand of the part a new methodology for the thermal mold design based on an inverse heat transfer problem was introduced. Based on a quality function regarding production efficiency as well as part quality, additional aspects to model the injection molding process are discussed. Aim of those extensions is the improvement of the inverse optimization of the problem.     

Three-dimensional process cycle simulation of composite parts manufactured by resin transfer molding

A process cycle of resin transfer molding (RTM) consists of two sequential stages, i.e. filling and curing stages. These two stages are interrelated in non-isothermal processes so that the curing stage is dominated by the resin flow as well as temperature and conversion distributions during the filling stage. Therefore, it is necessary to take into account both filling and curing stages to analyze the process cycle accurately. In this paper, a full three-dimensional process cycle simulation of RTM is performed. Full three-dimensional analysis is necessary for thick parts or parts having complex shape. A computer code is developed based on the control volume/finite element method (CV/FEM). The resulting computer code can provide information regarding flow progression and pressure field during mold filling; and temperature distribution and degree of cure distribution for a process cycle. The computer code can also be used for process cycle simulation of composite structures with complex geometry and with various molding strategies including switching injection strategy, multiple gate injection strategy and variable mold wall temperature. Numerical examples provided in the present work show the capabilities of the computer code in analyzing the process cycle.