熔接痕位置预测及优化技术研究进展

综述了熔接痕位置预测、优化和控制技术的研究进展,介绍了填充过程熔接痕形成的数学模型。对数值模拟技术、数值模拟技术结合数学规划理论、阀式浇注和大型注射成型制品多浇口进料顺序控制技术等3种技术的分析流程、预测方法和应用实例进行了详细介绍,其中基于数值模拟技术和数学规划理论结合的熔接痕位置确定新算法是行之有效的熔接痕位置优化技术,已成为当前研究热点。随着该技术的日趋成熟,应用范围将逐渐增大。而阀式浇注和大型注射成型制品多浇口进料顺序控制技术的实施可以成功避免注塑件熔接痕的出现,在大型零件生产中具有广阔的应用前景。     

基于Moldflow的注塑件熔接痕缺陷验证与优化

针对某制冷家电公司生产制造的移动空调前盖注塑成型过程中出现的熔接痕问题,先通过三维建模,采用Moldflow模拟分析技术,验证MPI软件制品缺陷预测的可行性;然后在此基础上采用热流道时序阀控制注塑成型技术对模具的浇注系统进行优化设计,最后运用MPI模拟分析,获得最佳优化方案,有效地消除熔接痕缺陷,从而提高制品外观质量和力学性能.     

无熔接痕液晶电视机支撑座的浇注系统优化设计

根据熔接痕形成的机理,分析了由传统浇注系统成型的液晶电视机支撑座的熔接痕形成原因。通过对浇注系统进行创新式设计,让流经两个浇口的熔体首先在二级流道中汇合,然后以扩展流的形式进行充模。利用 Mold-flow 对液晶电视机支撑座进行充模流动模拟分析,结果发现这种新型的浇注系统可以有效避免制品熔接痕的形成。     

顺序控制技术在汽车散热格栅边框注射成型中的应用

分析了采用传统热流道注射成型的大型边框制品的缺陷,针对其熔接痕问题,利用Moldflow软件,采用多浇口顺序控制技术对其填充过程进行优化,通过数值模拟研究发现,采用顺序控制注射技术控制各个浇口的开启时间,能切实有效地消除制品的熔接痕,提高制品的质量。     

注塑件熔接痕位置预测技术的研究进展

介绍了注塑件充填过程熔接痕形成的数学模型,综述了数值模拟技术、数值模拟技术结合数学规划理论、阀式浇注塑大型注塑成型制品多浇口进料顺序控制技术等3种注塑件熔接痕位置预测、优化和控制方法,介绍了该技术的分析流程、预测方法及国内外的研究进展和应用实例,熔接痕控制技术,尤其是熔接痕消除技术的完善是今后熔接痕研究的一个重要方向。     

基于阀式浇注技术的注塑件熔接痕控制

通过对注塑件熔接痕形成机理的研究,阐述阀式浇注技术对熔接痕的控制原理,以注射成型某平板为例,将其模具浇注系统的流道设计为热流道,并采用阀式浇注,采用CAE软件对充填过程进行模拟。结果表明,采用阀式浇注技术对控制熔接痕取得了较好的效果。     

基于Moldex3D的嵌件注射成型浇注系统优化分析

利用Moldex3D软件中嵌件成型模块对热敏性嵌件成型薄壁制品进行分析,针对不同浇注系统得到充模流动模拟和保压过程模拟结果。通过对成型过程熔体压力场和温度场分布结果、熔体流动前沿温度分布结果的对比分析,结合熔接痕等品质缺陷预测结果,最终得出成型稳定性较优的浇注系统设计方案。     

轿车保险杠顺序注射成型CAE分析

采用Moldflow软件对轿车后保险杠三点进浇顺序注射成型的过程进行模拟.为了分析阀浇口不同的延迟开启时间对熔接痕形成的影响,进行了两组仿真实验.结果表明,阀浇口不同的延迟开启时间可以对熔接痕的形成施行动态控制,从而影响熔接痕形成的时间、压力及熔体前沿温度的变化,这样有利于降低注塑压力、消除熔接痕或把熔接痕控制在不影响其外观质量的位置,获得最佳制品质量.     

顺序阀技术在轿车后保险杠熔接痕控制中的应用

轿车后保险杠由于其面积大、内孔多,采用传统的注射成型方法,往往会出现熔接痕数目多,造成保险杠表面色差明显,机械强度低等问题。根据广义Hele-Shaw流动模型原理,将顺序阀技术用于控制料流方向,从而将熔接痕移至分型面边缘,以此来减少熔接痕的数目。并以轿车后保险杠为例,采用数值模拟技术对其进行顺序控制模拟分析,通过多种方案分析对比,获得了合理的热流道浇注系统和工艺参数,经试模,制品表面无明显熔接痕。采用顺序阀技术对提高轿车保险杠注射成型有着实际意义。     

基于熔接痕处应力值的浇口位置优化设计

针对熔接痕性能评价和模具浇口设计问题,结合注射成型数值模拟和结构分析数值模拟,研究了实际工作条件下制品熔接痕处的应力值,并利用熔接痕处应力值评价浇口位置设计的优劣。结果表明,通过熔接痕性能的数值模拟分析,可为模具浇口位置设计提供有效的途径和可靠的指导。     

Enhancement of weld line mechanical strength using a novel ejector‐pins compression system

This study proposes a novel ejector‐pins compression system (EPCS) to improve the mechanical strength of weld lines that are formed in the injection molding process. Weld lines are significant defects that affect injection molding quality, causing the poor appearance and low mechanical strength of injection‐molded parts. In this experiment, several ejector pins are placed intentionally near the weld lines appearing, and are initially sunken beneath the cavity surface to form a reflow trap such that some of the molten plastics are allowed to flow into it during the filling process. These molten plastics are then compressed by the arisen ejector pins. Accordingly, the compressed molten plastics reflow through the weld lines, disordering the molecular orientation. Experimental verification revealed that the use of an EPCS can efficiently eliminate the orientation of the molecules parallel to the weld line. The specimens' impact strength of using EPCS can increase to between one and two times than that of conventionally injection‐molded. Therefore, this simple and novel method is feasible for greatly improving the mechanical strength of weld lines. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013     

注塑件成型缺陷分析与解决方案

针对耳罩圈注塑件填充不足和熔接痕的缺陷问题,本文从注塑模具浇注系统分析入手,找出存在的问题,制订出改正措施,并最终解决了这些缺陷问题;在针对使用一模六腔模具成型的护盖注塑件存在缩痕缺陷的问题,通过采用了控制流入模具型腔熔体量平衡的方法,最终达到了消除注塑件缺陷的目的;针对薄壁壳体注塑件变形等缺陷的问题,则采用了脱件板方...     

Effect of supercritical nitrogen content on the weld lines and mechanical properties of microcellular injection molded double gate PP/Al parts

Injection molding products made of aluminum flakes and polymer blends exhibit a distinctive esthetic effect. However, during the filling process, the melt flows in different directions converge and collide, resulting in the flop effect of the aluminum flake and consequent weld line formation. Herein, microcellular injection molding (MIM) was employed to fabricate polypropylene/aluminum flakes (PP/Al) composite foamed parts with distinct weld lines using supercritical nitrogen (scN₂) as the physical blowing agent. The scN₂ content has a significant effect on cell diameter and cell density. When the scN₂ content was 0.6%, the weld line width of the foamed part was 13.03 μm, while it was 30.41 μm for the solid counterpart due to the expansion and rupture of cells in the flow front during filling. Moreover, the orientation of Al flakes was mostly along the flow direction for the foamed parts, while it was generally aligned perpendicular to the flow direction for solid parts in the weld line region. In addition, the flexural modulus of foamed parts was increased by 29% compared with the solid parts, although the tensile strength was reduced by 18% due to the alignment of Al flakes and the stress concentration on the cell walls. Therefore, this work provides insight into the improvement of flexural property and the mitigation of weld lines for injection molded composite parts using MIM.     

Mechanical properties of polypropylene-low density polyethylene blends

Blends of polypropylene (PP) and low density polyethylene (LDPE) were prepared by both batch mixing followed by compression molding and extruder compounding followed by injection molding. Compression molded PP-LDPE blends were found to have very poor toughness, whereas extruded blends, injection molded without weld lines, were quite tough. Injection molded blend specimens with weld lines were found to be weaker and failed at very low elongations at break. A simple adhesion analysis is presented which explains well the weakness at the weld line expected for incompatible blends. Addition of an ethylene-propylene polymer with residual ethylene crystallinity was found to be a more effective “compatibilizer” for blends deficient in toughness than a related copolymer with less crystallinity. This effect is attributed to the more block-like character of the former which permits it to play more nearly the interfacial role required of the ideal blend compatibilizing agent.     

工艺参数对熔接线注塑件应力的影响分析

本文利用有限元方法,将Moldflow软件分析的注射成型结果导入到Ansys软件进行结构力学分析,发现注塑件在外载荷和边界条件等均相同的条件下,随模具温度、保压时间和保压压力的增加最大von Mises应力下降,且幅度各不相同;而随着熔体温度的增加,最大von Mises应力也增加;同时,熔接线使注塑件的von Mises应力明显高于同等条件下没有熔接线的注塑件,而且熔接线还影响工艺参数对注塑件最大von Mises应力的变化规律。     

Effect of process conditions on the weld‐line strength and microstructure of microcellular injection molded parts

This study was aimed at understanding how the process conditions affect the weld‐line strength and microstructure of injection molded microcellular parts. A design of experiments (DOE) was performed and polycarbonate tensile test specimens were produced for tensile tests and microscopic analysis. Injection molding trials were performed by systematically adjusting four process parameters (i.e., melt temperature, shot size, supercritical fluid (SCF) level, and injection speed). For comparison, conventional solid specimens were also produced. The tensile strength was measured at the weld line and away from the weld line. The weld‐line strength of injecton molded microcellular parts was lower than that of its solid counterparts. It increased with increasing shot size, melt temperature, and injection speed, and was weakly dependent on the supercritical fluid level. The microstructure of the molded specimens at various cross sections were examined using scanning electron microscope (SEM) and a light microscope to study the variation of cell size and density with different process conditions.     

注塑件熔接痕的研究进展

介绍了注塑件熔接痕的形成机理,分析了影响熔接痕强度的各种因素,从注塑工艺参数设定、模具结构设计等方面给出了消除熔接痕或提高熔接痕强度的措施。     

Evaluation of healing models to predict the weld line strength of the amorphous thermoplastic polystyrene by injection molding simulation

In many injection molded parts weld lines are often unavoidable. These cause optical defects and a reduction of the mechanical properties of the part. Therefore, the predictability of the weld line strength at an early stage of development would provide a significant advantage by avoiding costly iterations of the mold and increases the understanding of the correlation between process history of the melt and weld line strength. For this purpose, a calculation routine has been developed to predict the weld line strength based on injection molding simulation. Different models to calculate the healing of a weld line are compared and analyzed. By adding a factor to consider the shear rate in addition to the temperature and the pressure and after calibration to one design of experiment setting of the experimental data, the prediction of the weld line strength shows good agreement for all examined process setpoints of the experimental data for polystyrene.     

基于Moldflow及时序进胶技术的熔接痕缺陷改善

诸如空调扫风百叶此类板条状注塑产品,在常规成型中多点进胶时不可避免的会产生熔接痕缺陷,影响外观质量和机械强度。通过建立分析模型,应用Moldflow软件对常规成型过程进行模拟,对熔接痕缺陷产生的原因进行了分析;同时为了改善熔接痕,提出了采用时序进胶控制技术,并通过Moldflow对比分析了采用该技术前后熔接痕、锁模力、注射压力的状态。结果表明,采用时序进胶控制技术控制各浇口处熔胶逐步推进,不仅有效地消除了熔接痕,而且改善了成型条件。     

基于Moldflow的插座面板注塑成型分析与优化

以插座面板的注塑成型设计为例,借助Moldflow软件对其充模时间,注射压力、气穴、熔接痕和翘曲变形等进行模拟分析,根据结果有针对性地优化成型设计方案,从而可以提高制品质量,缩短模具设计制造和产品开发周期。