气体辅助注射成形充模流动数值模拟的研究

基于广义Hele—Shaw流动模型,通过引入合理的简化和假设,建立了实现气体辅助注射成形充模流动模拟的数学方程、气体穿透过程的边界条件、CAD/CAE建模关键技术以及系统程序设计方法等。该研究对气体的穿透过程、压力场分布、小同时刻熔体/气体边界的移动状态以及在模壁上形成表层聚合物熔体壁厚的过程进行_了气体辅助注射成形充模流动的实例数值模拟研究。结果表明:增大气体注射压力,在其气体穿透方向所形成的表层熔体厚度比值也增人,降低熔体注射温度和非牛顿指数会增大气体穿透的壁厚值,其值接近试验测定的数值范围,也比较符合实际的气辅注射成形工艺结果。     

汽车把手件气辅成型气指缺陷影响因素分析

在气体辅助成型工艺中,常常遇到一种缺陷是“气指”,气泡穿过气道形成指状分支,严重的“气指”会降低注塑件的强度,造成气辅成型技术的失败,或者不能发挥气辅成型技术的优势。为了消除或减少这种缺陷的产生,本文采用数值模拟方法和正交试验方法对气辅成型制品“气指”缺陷进行了研究。研究了对“气指”缺陷影响最重要的6个工艺参数：熔体短射量、气体注射延迟时间、气体注射压力 、模具温度、熔体温度以及气体注射时间对气辅成型制品“气指”缺陷的影响关系。结果表明,影响“气指”最重要的工艺参数依次是气体注射延迟时间、熔体温度和气体注射压力。因此优先选择合理的延时,熔体温度和注气压力参数尤为重要,为控制气指行为建议在相同熔体温度下适当延长气体注射延迟时间。     

薄壁气体辅助注塑件气体穿透过程的研究

基于气体穿透实验技术的研究分析，针对气体辅助注射成形中气体穿透气道的复杂过程，对薄壁气辅注塑件沿圆形截面气道穿透推进并形成模壁表层熔体的充模流动过程进行了研究。通过引入合理的简化和假设，建立了反映充模流动压力梯度、材料性能、表层熔体厚度比、非牛顿指数等影响因素的计算穿透速度和时间的数学方程．对气体注射压力、熔体温度、非牛顿指数影响气体穿透充模过程进行了实例数值模拟研究。结果表明，增大气体注射压力，其气体穿透方向所形成的表层熔体厚度比值也增大，降低熔体注射温度和非牛顿指数会增大气体穿透的壁厚值，其值接近国外试验测定值，也比较符合实际的气辅注射成形工艺结果。     

气辅成型工艺参数对气指缺陷影响的试验研究

采用正交实验方法和数值模拟方法,研究气辅成型工艺参数对制品气指缺陷的影响关系.结果表明: 熔体温度与气体注射延迟时间的交互作用对"气指"影响较为严重.较长的延迟时间可以减轻气指的程度,但延时过长会造成气体穿透不足,因此选择合适的熔体温度和气体延时组合尤为重要.     

气辅成型工艺参数对气指缺陷影响的试验研究

采用正交实验方法和数值模拟方法，研究气辅成型工艺参数对制品气指缺陷的影响关系。结果表明：熔体温度与气体注射延迟时间的交互作用对“气指”影响较为严重。较长的延迟时间可以减轻气指的程度，但延时过长会造成气体穿透不足，因此选择合适的熔体温度和气体延时组合尤为重要。     

气辅成形中熔体吹穿的实验和模拟研究

以U型管气辅注塑件为例，进行了气辅成形过程中熔体吹穿的工艺实验和模拟研究。通过对7种不同牌号的PP和PC树脂的气辅注塑模拟和实验分析，发现树脂材料的非牛顿指数，温度，熔体的预注射量和粘度，对熔体吹穿有明显的影响。提出了圆管壁熔体涂层厚度的计算公式和U型管气辅注塑件预注射量的经验计算公式。     

液气射流泵扩散管内气泡尺寸的试验研究

在工作水压力小于500kPa的低压水射流情况下,通过取样法和摄像法试验研究了下喷式液气射流泵扩散管内部气泡直径范围,获得内部气液两相流动情况及气泡分布特性。在一定的孔口雷诺数下,不同气液比下扩散管中气泡直径范围约80%集中在0.6～1.3mm。测量不同孔口雷诺数下的气泡直径,在孔口雷诺数较小的情况下气泡直径变化明显,最大直径可以达到3mm左右。由试验结果可以看出,气液比的变化相对于工作压力的改变对气泡尺寸影响比较明显。液气射流泵作为气液接触、射流混合及反应的设备,用于气体的吸收和分离操作。其含气率和气泡分布以及相接触面积是内部射流混合的重要参数。研究结论和结果有利于进一步提高气液两相混合效果。     

气辅压力成型装置控制系统试验研究

分析了气辅成型装置输出的气体压力控制曲线不同压力值下的气体压力闭环控制特征。确立了气体压力稳定阶段和升降阶段对应的PID控制算式,开发出了气体压力控制程序。该控制程序已在自行研制的气辅成型装置上得到应用。     

我国气辅注塑技术研发获得突破

气体辅助注塑成型技术研究及气辅注塑成型机研制项目，在南昌通过江西省科技厅主持的验收。该项目的研制成功，为推动我国注塑成型技术进步，为塑料制品企业改进气辅注塑工艺，奠定了扎实的理论和实验基础。     

聚合物气体辅助挤出中气体流动对熔体截面的影响

将聚合物熔体和低速热空气均视作不可压流体,针对一聚苯乙烯（PS）片材的全气体辅助挤出,建立了描述其气体-熔体两相分层流动的三维有限元模型,采用黏弹应力分离法（EVSS）和非协调流线迎风法（SU）等有限元方法,利用PolyFlow求解器对气体辅助流道中气体和熔体流动进行了计算,分析了熔体截面变化的规律及原因。研究结果表明：气体辅助流道内,气体对熔体有拖曳作用;沿挤出方向,熔体速度逐渐增大,而截面积逐渐减小,都在口模出口面上达到极值,同时截面形状有微小改变;口模出口面上熔体沿挤出方向的速度随入口气体体积流率的增大而近似线性增大,熔体截面积则近似线性减小。     

Computing gas/melt free interface of gas-assisted injection molding

A solution was put forward to predicate the flow pattern of gas penetration in gas-assisted injection molding. The differential equations that governed the flow field and gas/melt free-interface evolution were analyzed and discretized by Galerkin finite element method, and the free interface was located by the volume of fluid method. The gas was assumed as a fluid phase of constant density and viscosity instead of being simply treated as boundary conditions. The non-Newtonian property of polymer melt was characterized by Carreau model with four parameters. As a case study, different kinds of gas channel were modeled. The gas/melt free interface was captured. The gas front velocity and the pressure of gas/melt front were also computed. The edge shape of gas channel was discussed, which are helpful for the design of gas-assisted injection molding.     

Simulations of gas penetration in thin plates designed with a semicircular gas channel during gas-assisted injection molding

Numerical simulations and experimental studies concerning gas and melt flows during gas-assisted injection molding of a thin plate designed with a gas channel of semicircular cross section were conducted. Distribution of the skin melt thickness along the gas penetration path was measured. Melt and gas flows in a gas channel of semicircular cross section were approximated by a model which uses a circular pipe of equivalent diameter superimposed on the thin plate. An algorithm based on the control-volume/finite-element method combined with a particle-tracing scheme using a dual-filling-parameter technique was utilized to predict both melt front and gas front advancements during the mold filling process. Simulated distribution of gas penetration shows reasonably good coincidence with the experimental observations.     

气体辅助注射成型数值模拟技术研究概述与展望

在介绍气体辅助注射成型数值模拟技术及其重要性的基础上,对气体辅助注射成型数值模拟技术的国内外研究现状进行了概述,并且对气体辅助注射成型数值模拟技术研究发展方向进行了展望。     

Intelligent control of gas-assisted injection molding control systems

This study described the design and construction of gas-assisted injection molding systems incorporating a traditional injection molding machine. This combined system is called a gas-assisted injection molding control system (GAIMCS). The mathematical model of GAIMCS with nonlinear dynamics is difficult to establish accurately. Therefore, model-free intelligent control strategies were developed to control this system and evaluate its control performances. This work presents two intelligent control strategies: (1) traditional fuzzy controller (TFC), and (2) grey prediction fuzzy controller (GPFC). The GAIMCS was controlled by the GPFC, which was compared to a TFC to evaluate the system control performance. The GPFC achieves better control performances in accelerating rise time, and it reduces the system steady-state error better than the TFC for high-pressure gas control in GAIMCS, based on the verified experimental results.     

气辅注气控制系统中的多模态智能PID调节器

气体辅助注射成型机的注气控制系统是一小延迟、小惯性系统。为使之能满足气体辅助注射成型工艺对气体压力的高精度控制要求，设计了一种多模态智能PID调节器。该调节器将PID控制方法和智能控制技术相结合，采用了改良型的位置式PID控制算法和归一参数在线自整定方法对控制规律和参数进行实时修正。实验证明，该PID调节器具有波动小、超调小、对环境及控制参数不敏感等优点。     

Mold surface roughness effects on cavity filling of polymer melt in micro injection molding

Micro injection molding presents many challenges in the injection-molding community. When the dimensions of the part (and thus the cavity of the mold) are small, micro-scale factors such as mold surface roughness may play an important role in the filling of polymer melt. This paper investigates the effects of mold surface roughness on cavity filling of polymer melt in micro injection molding. A disk insert, which has two halves with different surface roughness but with the same roughness mean lines, was used in the investigations. The ratio of flow area of the rougher half with the total flow area of the molded part is used to evaluate the significance of surface roughness effect. The experimental results revealed that mold surface roughness does resist the cavity filling of polymer melt in micro injection molding. For the limited range of injection rate investigated, it is not significant on the surface roughness effects. The increase of mold temperature will decrease surface roughness effects. The change of melt temperature within the range allowed by the process is insignificant for surface roughness effects.