高光注塑成型模具热响应研究

高光无痕注射成型技术是一种新兴的注射技术,能够消除塑件表面熔接痕等缺陷,表面可以达到镜面效果,免去二次喷涂。本文通过建立模具的二维几何模型,利用ANSYS模拟了加热、冷却过程,获得了模具表面及熔体中心层的热响应和温度分布情况。同时对比分析了常规注塑与高光注塑成型两种成型工艺,通过加热、冷却时间及温度分布等结果的对比,验证了高光注塑的优越性。     

蒸汽加热模具及模具变温辅助控制装置的研制

对高光无痕注射成型工艺的成型装置和辅助控制系统进行了研究和开发,介绍了蒸汽加热注射成型工艺原理。通过辅助系统来控制蒸汽加热模具的型腔温度,特殊的水道设计使模具型腔的温度能够迅速升至熔体的热变形温度以上,进而获得高光表面制品。同时指出了蒸汽加热模具在模具材料的选择、测温点的分布等方面的设计思想,阐述了辅助控制装置的组成部分及控制原理。结果表明,蒸汽加热模具可加工高表面光洁度、无熔接痕、无流痕的塑料制品,可免除后续喷涂工艺,降低了生产成本,成型周期由120 s 缩短到43 s。     

蒸汽直接加热模腔的高光注塑技术研究

提出了蒸汽直接加热模具型腔表面的高光注塑新方法,研制了蒸汽直接加热模具型腔的高光注塑模具及模具温度控制机.该装置将高温蒸汽直接通入模腔,使模腔表面达到所需的温度,然后通入高温干空气,吹除模腔内残留的冷凝水,再注射、保压、冷却、开模,完成一个注塑周期.该方法使动定模模面得到均匀加热,熔融科前锋温度和速度高,且只加热模面以...     

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。     

双色高光注塑成型技术及发展

介绍双色高光注塑技术的特点,通过比较双色高光注射成型与单色高光注塑成型、普通注射成型,深入分析了双色高光注塑成型塑件结构与黏合设计及模具结构设计要点。阐述了国内外双色高光注塑技术的应用现状及发展。讨论并指出了将双色高光注塑成型技术进一步推广有待解决的关键技术问题。     

节能型无痕注塑模具及工艺

本文针对目前高光无痕注塑成型技术能耗高的问题提出了一种节能型模具结构,它不但需要有贴近定模型腔的随形介质槽,而且需要在随形介质槽近距离处增加隔热层,从而可以实现沿模具型腔表面均匀传热,减少模具传热体积,仅需要在定模进行加热,而动模进行冷却,这样不需要热冷介质的对冲切换,可避免大量能耗。     

基于Moldflow的高光无痕电视前壳注射模具设计

以液晶电视机前壳为例,结合制品的精度要求和模具结构特点,详尽分析高光无痕注塑模具流道系统、温度控制系统和复杂抽芯机构的设计方法,给出整套模具其它结构的设计要点。利用Moldflow软件,采用变模温工艺技术,对高光无痕注射成型工艺进行模拟分析,验证了流道系统和温度控制系统的控制效果。     

间隙对电热变模温高光注塑模具加热效率的影响

采用电热方式的高光注塑模具可以有效消除传统注塑成型过程中塑件的熔接痕、浮纤、银纹等缺陷。高光注塑成型技术要求对模具温度的快速动态控制,然而在电加热高光注塑成型中,电加热棒与模具安装孔之间不可避免地存在间隙,间隙层内的空气大大阻碍热量向模具传递。研究了电加热棒与模具安装孔之间的间隙对电热变模温加热效率的影响,构建了电加热高光注塑模具的三维热响应分析模型,利用有限元分析软件ANSYS进行了三维瞬态传热分析,得到了在不同间隙下的模具表面和电加热棒内部的热响应曲线,并通过大量实验证明了理论分析和模拟方法的正确性。结果表明,加热相同时间,间隙量越小,模具表面温度越高,电加热棒内部温度越低,加热效率越高,相较于间隙在0.32 mm,间隙在0.05 mm加热到60 s的模具表面温度至少高出50%,电加热棒内部的温度至少低55%。隙量对模具加热效率的影响并非成线性关系,而是间隙量在越小的区间,加热效率对间隙更加敏感,研究结果为电热变模温高光模具结构设计和电加热棒的选用提供依据。     

基于ANSYS的LED电视面壳高光模具方案设计

基于高光成型工艺原理,为实现LED电视面壳的高光效果,提出采用油加热、油冷却方式对其型腔表面进行变模温控制。构建基于多种不同模具材料和结构变模温注塑工艺分析模型,利用ANSYS对其加热响应、冷却过程进行数值模拟。最终采用以AMPCOLOY 972作为模具材料且带隔热方式的高光模具结构方案。     

浅析高光无痕注塑工艺技术

采用高光无痕注塑工艺后,良好的外观效果提升了产品档次,并且在环保、低成本化、产品变革等多方面具有积极的意义。随着高光无痕注塑工艺在产品上的应用越来越多,为了加强认识、了解,学习以及推广该技术,本文就目前使用蒸汽(或高温水)成型之高光无痕注塑工艺在平板电视产品应用的模具、材料以及塑压工艺方面予以探讨。     

Research on a New Variotherm Injection Molding Technology and its Application on the Molding of a Large LCD Panel

The polymer injection products produced by using the current injection molding method usually have many defects, such as short shot, jetting, sink mark, flow mark, weld mark, and floating fibers. These defects have to be eliminated by using post-processing processes such as spraying and coating, which will cause environment pollution and waste in time, materials, energy and labor. These problems can be solved effectively by using a new injection method, named as variotherm injection molding or rapid heat cycle molding (RHCM). In this paper, a new type of dynamic mold temperature control system using steam as heating medium and cooling water as coolant was developed for variotherm injection molding. The injection mold is heated to a temperature higher than the glass transition temperature of the resin, and keeps this temperature in the polymer melt filling stage. To evaluate the efficiency of steam heating and coolant cooling, the mold surface temperature response during the heating stage and the polymer melt temperature response during the cooling stage were investigated by numerical thermal analysis. During heating, the mold surface temperature can be raised up rapidly with an average heating speed of 5.4°C/s and finally reaches an equilibrium temperature after an effective heating time of 40 s. It takes about 34.5 s to cool down the shaped polymer melt to the ejection temperature for demolding. The effect of main parameters such as mold structure, material of mold insert on heating/cooling efficiency and surface temperature uniformity were also discussed based on simulation results. Finally, a variotherm injection production line for 46-inch LCD panel was constructed. The test production results demonstrate that the mold temperature control system developed in this study can dynamically and efficiently control mold surface temperature without increasing molding cycle time. With this new variotherm injection molding technology, the defects on LCD panel surface occurring in conventional injection molding process, such as short shot, jetting, sink mark, flow mark, weld mark, and floating fibers were eliminated effectively. The surface gloss of the panel was improved and the secondary operations, such as sanding and coating, are not needed anymore.     

Analysis of the effects of internal heating and cooling during the rotational molding of plastics

In rotational molding, shortening the cycle time is one of the most important requirements for increasing production rates and reducing product cost. A characteristic feature of the process is that the mold and plastic powder are heated from room temperature to the melting temperature of the plastic and then back to room temperature. In addition, in the vast majority of cases the heat input and subsequent heat extraction occur at the outside surface. In order to improve the heat transfer, this paper considers the effects of internal heating and cooling. A mathematical model has been developed in which an internal heating term can be incorporated. The experiments with rotomolding powders show that the predictions made by the model are accurate. In particular, it is found that the introduction of internal heating is very effective in shortening the cycle time and that the introduction of internal cooling in rotational molding provides a more uniform structure and less likelihood of warpage.     

Development of rapid heating and cooling systems for injection molding applications

The injection molding process has several inherent problems associated with the constant temperature mold. A basic solution is the rapid thermal response molding process that facilitates rapid temperature change at the mold surface thereby improving quality of molded parts without increasing cycle time. Rapid heating and cooling systems consisting of one metallic heating layer and one oxide insulation layer were investigated in this paper. Design issues towards developing a mold capable of raising temperature from 25°C to 250°C in 2 seconds and cooling to 50°C within 10 seconds were discussed. To reduce thermal stresses in the layers during heating and cooling, materials with closely matched low thermal expansion coefficient were used for both layers. Effects of various design parameters, such as layer thickness, power density and material properties, on the performance of the insert were studied in detail with the aid of heat transfer simulation and thermal stress simulation. Several rapid thermal response mold inserts were constructed on the basis of the simulation results. The experimental heating and cooling response agrees with the simulation and also satisfies the target heating and cooling requirement.     

微注射成型中变模温控制技术

阐述了变模温控制在微注射成型中的重要性，介绍、比较了当前出现的电热水冷、感应加热、薄膜电阻式加热、复合模壁绝热-加热、复合模壁绝热-压缩热空气加热几种变模温控制实现方法，展望了未来微注射成型中变模温控制的发展趋势。     

Thermal response of an electric heating rapid heat cycle molding mold and its effect on surface appearance and tensile strength of the molded part

Rapid heat cycle molding (RHCM) is a newly developed injection molding technology in recent years. In this article, a new electric heating RHCM mold is developed for rapid heating and cooling of the cavity surface. A data acquisition system is constructed to evaluate thermal response of the cavity surfaces of the electric heating RHCM mold. Thermal cycling experiments are implemented to investigate cavity surface temperature responses with different heating time and cooling time. According to the experimental results, a mathematical model is developed by regression analysis to predict the highest temperature and the lowest temperature of the cavity surface during thermal cycling of the electric heating RHCM mold. The verification experiments show that the proposed model is very effective for accurate control of the cavity surface temperature. For a more comprehensive analysis of the thermal response and temperature distribution of the cavity surfaces, the numerical‐method‐based finite element analysis (FEA) is used to simulate thermal response of the electric heating RHCM mold during thermal cycling process. The simulated cavity surface temperature response shows a good agreement with the experimental results. Based on simulations, the influence of the power density of the cartridge heaters and the temperature of the cooling water on thermal response of the cavity surface is obtained. Finally, the effect of RHCM process on surface appearance and tensile strength of the part is studied. The results show that the high‐cavity surface temperature during filling stage in RHCM can significantly improve the surface appearance by greatly improving the surface gloss and completely eliminating the weld line and jetting mark. RHCM process can also eliminate the exposing fibers on the part surface for the fiber‐reinforced plastics. For the high‐gloss acrylonitrile butadiene styrene/polymethyl methacrylate (ABS/PMMA) alloy, RHCM process reduces the tensile strength of the part either with or without weld mark. For the fiber‐reinforced plastics of polypropylene (PP) + 20% glass fiber, RHCM process reduces the tensile strength of the part without weld mark but slightly increases the tensile strength of the part with weld mark. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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.     

基于ANSYS Workbench的注胚模腔疲劳寿命研究

注胚模具成型聚对苯二甲酸乙二醇酯(PET)瓶坯的一个成型周期分为注塑、保压、冷却阶段,模具受循环载荷影响,其关键零件模腔易出现疲劳破坏。应用ANSYS Workbench(AWB)建立模腔有限元模型,运用传热学理论,完成模腔一个工作周期的温度场,位移场及热应力场的仿真模拟,获得疲劳寿命云图,为注塑模具零件优化设计提供依据。     

Injection Molding Nanoscale Features with the Aid of Induction Heating

During injection molding of micron or submicron scale features, incomplete filling frequently occurs, resulting from premature freezing of the polymer melt in contact with a cold mold. In order to overcome the filling difficulty without increasing the total cycle time, the mold surface temperature was raised rapidly by induction heating. A prototype mold insert with cooling channels was fabricated and integrated with a nickel stamp having nanoscale-grating structures. The nickel stamp surface was successfully heated from 25 to 258°C in 2.7 sec. Four different mold surface temperatures, 100, 150, 200 and 250°C, were tested to determine if the nanograting structures can be replicated with an optical quality cyclic olefin copolymer. Experimental results indicate that the nanocavities were successfully filled when the surface temperature reached 250°C, but mold release caused drag damages on the nanogratings. Further, coupled thermoelectromagnetic analyses were carried out to simulate the induction heating process of the nanostructured mold insert. The predicted surface temperature responses in general agree with the experimental ones and the simulation model can be used in the further development of process control and mold design in micro/nano molding.