基于全区域连通型随形介质槽的注塑模具

针对无痕注塑成型,提出一种全区域连通型随形槽结构,在定模型腔近距离位置、塑件外壳对应区域加工与外壳表面一致的随形槽.模具结构中不但需要有贴近型腔的定模随形介质通道,而且需要在其近距离增加隔热层,从而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,这样同一侧模芯内部不需要热冷介质的对冲切换,可避免大量能耗.     

局部薄壁塑件的高光无痕注塑成型

针对局部薄壁塑件的无痕注塑成型,在定、动模型腔近距离位置和塑件外壳对应区域分别加工与外壳表面一致的随形槽.模具结构中不但需要有贴近型腔的随形介质通道,而且需要在其背面近距离位置增加隔热层,从而实现滑模具型腔表而均匀传热,减少模具传热体积.本文进一步提出塑件模外快速冷却的成型工艺,以克服凹痕的产生,并且使外壳表面光亮度保持一致.     

螺旋槽纹管管内单相油传热及流阻的实验研究

以单相机油为介质 ,研究了普通螺旋槽纹管、开发出的W形螺旋槽纹管的管内传热及流动阻力性能 ,并与圆形光滑管进行了比较 ,整理出了相应的传热及流动阻力关联式。该研究结果为以油为介质的换热器的设计及改造提供了理论依据     

注塑模具随形冷却水道的设计方法与分析

随着3D打印技术的发展,注塑模具的冷却水道设计由传统的直线型设计优化为随形水道设计.对国内外随形冷却水道的设计方法和发展现状进行了综述,并对随形冷却水道的设计原则、截面形状变化、布局以及优化技术进行了详细的阐述,并做了归纳总结.注塑模具采用随形水道设计,可使冷却介质与型腔表面距离一致,能提高冷却效率、成型效率和模具型腔表面温度分布的均匀性,从而使成型制品的质量和性能得到较大改善和提高.     

螺旋槽管内氟利昂113沸腾传热强化和阻力研究[摘要]

以R—113为介质,进行水平螺旋槽管内氟利昂沸腾传热和阻力的实验研究。得出螺旋槽管内给热系数比光滑管提高54～132％。结合实验数据分析了螺旋槽管强化管内沸腾传热的性能。根据传热和阻力     

注塑模具随形冷却水道冷却效能分析

设计了汽车仪表盘注塑模具,采用无冷却水道、传统冷却水道和随形冷却水道3种冷却系统。利用ANSYS软件对模具进行热分析,模拟了无冷却水道、传统冷却水道和随形冷却水道模具的温度场,分析在不同冷却水道的塑件达到脱模温度的时间、冷却性能、冷却均匀性。结果表明,随形冷却水道模具达到顶出时间仅需要29 s,与无冷却水道达到顶出时间相比,缩短了371 s,与传统冷却水道相比,缩短了10 s;当随形冷却水道模具达到开模时刻(29 s),无冷却水道模具型腔表面的平均温度约为132.36℃,传统冷却水道模具型腔表面的平均温度约为62.56℃,随形冷却水道模具型腔表面的平均温度约为47.20℃,随形冷却水道模具型腔表面的平均温度与同时刻无冷却水道模具相比降低了85.16℃,与传统冷却水道相比,降低了15.36℃,冷却性能分别提升了64.34%和24.54%;随形冷却模具型腔表面的冷却均匀性最佳,方差仅为3.32,与无冷却系统模具相比,减小了5.32,与传统冷却系统相比,减小了10.93。因此,注塑模具采用随形冷却水道,在缩短生产周期的同时,还能提高产品的生产质量。     

基于3D打印的随形冷却注塑模具传热因素研究

对比了传统冷却技术与随形冷却技术在注塑模具冷却过程的差异性,详细分析了模具冷却过程的传热,对熔体的冷却时间、模具型腔壁面温度和温度均匀性的影响。得出了冷却水道直径、冷却水道中心距模具壁面的距离、两相邻冷却水道距离这三个因素对于模具冷却起到主要影响。最后通过Moldflow软件对简化模型进行模拟实验,确定了三个影响因素对模具型腔壁面温度的影响。     

横纹槽管结构优化的正交数值模拟试验研究

运用正交试验法设计了横纹槽管结构优化的试验,试验运用数值模拟方法进行,采用标准K-ε方程湍流模型和速度分布两层模型进行模拟计算,研究了横纹槽管结构参数e/d,p/d, a/e和流动Reynolds数对热阻力性能的影响.试验结果表明：在试验参数范围内,影响横纹槽管综合传热性能的主要结构参数为肋节距p/d和肋形a/e,而肋高e/d影响较小,并且传热综合因子随流动Reynolds数增大而迅速降低.通过分析正交试验结果,提出了较佳横纹槽管管型.     

异形钢管蒸发式冷凝器的传热与能耗性能

提出了弹形管和扭曲管对蒸发式冷凝器强化传热,测试了冷却水喷淋密度和风速对其传热与能耗性能的影响,并与圆管进行了对比.研究结果表明,传热系数和能耗均随冷却水喷淋密度和风速的增大而增大,但冷却水喷淋密度增大到一定值后,传热系数基本不变甚至略有减小;弹形管和扭曲管比圆管的传热系数分别高9.2%～19.0%和18.0%～33.1%,总能耗分别低2.6%～4.9%和高2.6%～4.9%,综合性能比分别高11.1%～23.0%和16.7%～23.7%.     

三维槽道的周期性层流流动与传热

应用数值模拟方法分析了以周期性方式布置不同节距比(PR=L/H)、倾角为45°挡板槽道的流动特性与传热特性。挡板在槽道上下壁面对齐布置高度比(BR=b/H)为0.2,以便在槽道内部形成一对沿流向的反向旋涡。数值模拟计算Reynolds数范围为100~1000,流体介质为空气。计算结果表明:布置斜置挡板后,在槽道内诱导产生了沿流向的旋涡流,且在测试段中旋涡流冲击槽道上下壁面和槽道一侧壁面,结果使得传热效率提高;分析了范围内平均Nusselt数比Nu/Nu₀、摩擦系数比f/f₀及传热增强系数η随节距比PR和Reynolds数的变化关系,并建立了相应的准则关系式;当挡板间节距比为0.5时,传热增强系数可达最大值3.0。     

Optimal thermal design of compression molds for chopped-fiber composites

Because heat is convected by the motion of material in the cavity of a compression mold, the time-averaged heating load on the cavity surface is nonuniform. In rapid production of large, thin parts, this can lead to large variations in cavity surface temperature when the mold is heated by the usual uniform distribution of heating lines. In this paper, a new method is developed for optimizing the mold heating design so that this nonuniform heating requirement can be satisfied with a minimum variation in cavity surface temperature. Oil heating is considered specifically, but the method can also be used for stream or electric heat. The optimal position and power supply for each heating line in the mold is determined by combining mathematical programming techniques with an analysis of the steady temperature field in the mold. The nonuniform heating load on the cavity surface is represented by a time-averaged steady heat transfer coefficient calculated from the transient temperature distribution in a polyester sheet molding compound as it fills the mold cavity. The design method is applied to an example mold for a large flat panel. At a one-minute cycle, the optimal heating design dramatically reduces nonuniformity in cavity surface temperature compared with a conventional distribution of heating lines. The optimal design is remarkably simple, uses only conventional equipment, and involves only half the customary number of heating lines. Nevertheless, it still has sufficient flexibility to adjust for changes in cycle time without sacrificing uniformity in cavity surface temperature.     

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。     

Experimental investigation of infrared rapid surface heating for injection molding

A low cost and practical infrared rapid surface heating system for injection molding is designed and investigated. The system was designed to assemble on the mold and a control system was used to operate the motion of the lamp holder. Four infrared halogen lamps (1 kW each) were used as the radiative source to heat the surface of mold insert. The temperature increase is verified on the mold plate with a thermal video system. Two types of specular reflectors combined with different bulb configurations were applied to study the heating ability of radiation heating. A modified spiral flow mold was used to test the enhancing filling ability of the rapid surface heating system. Three resins, PP, PMMA and PC were molded in the spiral flow injection molding experiments. If spherical reflector and centralized lamp configuration are used, the temperature at the center of the mold surface is the highest. The temperature of mold center surface is raised from 83°C to 188°C with 15 s of infrared heating. Because the surface temperature of the mold insert is higher than the glass transition temperature of resins before filling, the flow distance of resins in the modified spiral flow mold will be increased. The location effect of the infrared surface heating system on a thin‐long cavity was studied to demonstrate the possibility of using smaller infrared heating area on a large mold surface. A microprobe cavity also demonstrated that with the assistance of infrared heating technology the formability of a microprobe can be greatly improved. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3704–3713, 2006     

Optimal thermal design of injection molds for filled thermosets

Since the cure rate of injection molded thermosets is usually very sensitive to cavity surface temperature, spatial variations in these temperatures can lengthen the necessary cure time for the entire part and cause distortion and residual stress in the molded article. This problem is addressed in the present paper by combining an optimization algorithm with a quasi-steady heat conduction analysis in the mold to determine the heating line positions and operating temperatures that minimize the spatial variation in cavity surface temperature. The method is applied to an example mold for a flat panel of uniform thickness, using two different gate locations. At a one-minute cycle, the optimal designs for each gate location dramatically reduce the variation in cavity surface temperature compared with corresponding results using a conventional heating system. These results are made more significant by the fact that the optimal designs use considerably fewer heating lines. In spite of their simplicity, the optimal designs still have enough flexibility to adjust to a changing cycle without sacrificing uniformity in cavity surface temperature.     

The effect of flow on cavity surface temperatures in thermoset and thermoplastic injection molding

In the Injection molding process, nonuniform heat transfer between the polymer and the mold caused by flow during the cavity filling stage can lead to spatial variations in the cavity surface temperature. This can result in an increase in cycle time or poor part quality. An investigation of the flow-induced, nonuniform, cavity surface temperature is reported here. A flow model for a thin, rectangular, end-gated cavity and a model for the steady-state temperature distribution in a simple mold are developed. These are applied to some thermosetting and thermoplastic systems. For both filled and unfilled thermosets, it is found that a simple plug flow model gives a good approximation for the heat transfer during flow. For thermoplastics, however, the full flow solution must be used. For the cases considered in this study, the steady-state temperature variation along the cavity surface is less for the thermoplastics than for the thermosets.     

Experimental verification of an optimal thermal design in a compression mold

A production sheet molding compound (SMC) mold for an automotive hood outer panel was instrumented with 64 thermocouples to measure cavity surface temperatures along two cross-sections in each mold half and regulate the supply of steam to each heating line. The positions and temperatures of each heating line in the mold were optimized using an in-house computer program to produce a minimum spatial variation in cavity surface temperature during steady cyclic molding. Provision was also made to heat the mold conventionally so that optimal and conventional heating could be directly compared in the same mold. While maintaining a 78 s overall molding cycle, the conventional heating system eventually produced a 10°C temperature variation on the cavity surface. This, in turn, led to serious resin undercure and severe difficulties in removing the part from the mold. When the optimal heating design was substituted in place of the conventional system, the surface temperature variation was reduced to less than 3°C and the problems experienced with conventional heating disappeared. For the most part, the measured temperatures in these experiments agreed with the results of the computer analysis to within 1°C.     

Cavity temperature—an important parameter in the injection molding process

The paper stresses the importance of cavity temperature in the injection molding process of thermoplastics. From the study of the temperature field in the mold, it follows that there is no such thing as a uniform mold temperature. The heat balance equation for the injection mold is discussed in detail. It shows that the sum of the heat exchanges during the cycle equals zero. There is an extensive explanation of the heat transfer from the melt to the mold, the heat exchange with the environment, and between the heat exchange medium and the mold. New criteria are given for the cavity material selections. The cavity temperature is a complex function of static and dynamic parameters and should be kept constant in the equal parts of the cycle. This demands a new way of regulating the temperature.     

注塑模典型截面温度场的数值分析

通过二维典型截面简化模具的三维结构,建立了注塑模典型截面温度场的边界积分方程,并进行数值求解。将模具温度分为稳态和波动两部分,稳态部分是采用循环平均假设,推导出求解模具典型截面二维稳态温度场的边界积分方程。然后利用边界元法,分别对动模和定模进行传热分析,根据分型面边界相容性条件进行耦合;波动部分是在给出温度波动的微分方程后,利用有限差分法结合传热学对型腔表面温度波动进行数值求解。最后通过实例验证了文中算法的正确性与有效性。     

皇冠轿车前保险杠注塑模设计和熔体动态充模研究

就日本丰田皇冠轿车前保险杠注塑模的总设计方案及所用原料进行了分析和确定；对型腔压力、熔体温度及动模垫板的形变选用了微机监控；对模具结构，包括浇注系统、成型零件和导向装置、侧向分型抽芯机构、模温控制装置等的设计进行了介绍；对浇注系统的冷热流道及浇口的开设采用Ｃ－ｍｏｌｄ软件进行了熔体充模流动的动态模拟分析。由模拟分析的结果表明，采用计算机Ｃ－ｍｏｌｄ软件对浇口充模进行动态模拟，可直观地了解皇冠前保险杠制品所需充模的最大压力和锁模力的真实情况，并能确知熔融前锋料流速度和熔接痕的牢度，它为指导大型注塑模具浇口的开设和最终尺寸的确定提供了科学依据，有极高的应用和研究价值。