注塑成型光学制品折射率分层模拟与实验研究

与玻璃制造光学制品相比,高分子注塑光学制品具有质量轻、易加工、抗冲击性好等优点,在航空航天、精密透镜等高端领域得到广泛应用。然而受注塑过程复杂压力场、温度场的耦合作用,注塑透明制品折射率通常呈非均匀的分布,存在角偏差、光畸变等光学缺陷。因此,开展注塑工艺对其折射行为影响的模拟与实验研究,对实现折射率可控光学制品的成型具有重要意义。基于Hele Shaw注塑理论和Lorentz Lorenz物理光学理论,构建了注塑光学制品厚度方向折射行为分层预测模型,开发了相关模拟程序,基于自主研发的注塑模软件ZMold实现了注塑过程与折射率分布的一体化模拟。以聚碳酸酯注塑平板件为例,利用Brewster法对折射率模拟结果进行了验证。该方法成功应用到神舟系列航天舱外服面窗的研制。     

注塑制品重量的闭环控制

基于注塑数值模拟技术,研究注塑工艺特性、熔体在模腔中的状态及制品质量特性之间的关系,建立了制品质量控制环和工艺控制环串联的制品质量闭环控制理论。以该控制理论为基础,应用神经网络内模控制策略,建立了注塑制品重量控制的理论和方法,并设计了制品质量控制器和工艺控制器。根据上述理论,基于注塑数值模拟技术,在Matlab平台上开发了注塑制品质量闭环控制系统,实现了制品质量闭环控制仿真。对一工业产品重量的控制表明制品质量控制环和工艺控制环串联的制品质量闭环控制具有较好的控制性能。     

分层注塑厚壁光学透镜模具设计及其模拟分析

设计一种退芯模具,用以实现光学厚壁透镜的分层注塑,并使用Moldflow进行数值模拟分析;以三棱镜作为光学厚壁透镜制品代表,聚甲基丙烯酸甲酯(PMMA)为原材料,以光的相移角度为制品质量参照,模拟分析分层注射对注塑光学厚壁透镜制品光学质量的影响规律。结果表明,不同的分层工艺方式对注塑光学厚壁透镜的光学质量有着明显差异。通过模拟实验得到在该双层注射三棱镜模型中,层与层之间5 s的间隔、外层薄内层厚、先外后内包裹注射的分层方式最佳,层厚分布在各项工艺方式中对注塑效果影响最大,通过分层注射,可以减小光学厚壁透镜的平均体积收缩率。     

非球面塑料透镜注射成型与注塑压缩成型工艺的对比分析

基于Moldflow对非球面塑料透镜注射成型与注塑压缩成型进行对比分析。结果表明,注塑压缩成型只需要较小的注射压力和锁模力;压缩过程中使融化树脂受力均匀,成型制品产生较小的气穴和熔接痕,对外观质量影响较小;在光学性能方面,注塑压缩成型的双折射率较小,满足光学镜片的使用性能,而注射成型Z方向相移和Z方向迟滞变化范围较广,会产生明显的偏振现象,严重影响光学元件的成像效果。     

基于Moldfl ow的注塑光学厚壁透镜工艺优化

利用Moldflow数值模拟分析并结合正交试验法,以光学厚壁透镜制品的光相移角度(双折射)为参照,对注塑光学厚壁透镜的工艺条件进行优化,且模拟分析了分层注射对注塑光学厚壁透镜残余内应力的影响规律。结果表明:优化注射工艺参数能够降低制品的残余内应力,减小光学透镜的双折射缺陷,其最优注射条件为:模具温度90℃、熔体温度240℃、注射时间9 s、保压压力60 MPa。此外,分层注射可以有效减小制品的残余内应力,并使其分布更加均匀,该效果与分层方式以及层厚、层数有关。     

聚苯乙烯制品熔接线区域的双折射行为分析

基于双折射实验原理,利用偏光显微镜,运用"楔形法",测定了聚苯乙烯注塑制品熔接线区域厚度面上双折射行为分布。结果表明:距离嵌件的不同位置处,由于流动行为的差异导致了完全不同的双折射行为,根据应力-光学定律,这种行为也体现了塑料制品的分子取向、残余应力的分布情形。     

南京春辉科技实业有限公司产品总汇

多组份玻璃光纤及其制品玻璃光学纤维是由高折射率的多组分玻璃作芯料和低折射率的多组分玻璃作包层所构成。当光线经折射进入光学纤维后,在芯料和皮层的界面上发生多次全反射,将光能由一端传至另一端,实现光的传导。由于光纤具有弯曲性和柔软性,其传导的光线就能随意...     

复杂制品注塑成型模拟分析

应用CAE软件MoldflowPlasticsInsight4.1的充模、保压、冷却、翘曲等分析模块,对汽车尾门饰件注塑成型过程进行CAE分析,研究了浇口位置、工艺参数等对制品性能的影响。最后,基于模拟结果分析了制品翘曲的主要原因,为模具设计及注塑工艺的确定提供参考。     

液晶显示器前壳变模温注塑数值模拟与结果分析

介绍了变模温注塑的成型原理,分析了变模温注塑的成型特点,对液晶显示器前壳注塑模具进行计算机辅助工程建模,并分别针对常规注塑和变模温注塑过程进行了填充模拟和冷却翘曲模拟。结果表明,与常规注塑相比变模温注塑能降低模内应力、减小翘曲量、减少甚至消除制品表面熔接痕、提高熔接强度等,明显提高了制品的质量。     

注塑成型熔接线截面熔接过程数值模拟

在多浇口和带嵌件注塑制品的成型过程中必然存在熔体的熔接过程,从而形成熔接线。熔接线沿厚度方向的熔接过程是影响该区域的力学强度以及纤维取向等制品性能的重要因素。本文采用有限元法针对注塑制品的典型截面建立数学模型,采用T6P3单元(速度二次插值,压力线性插值),数值模拟了注塑制品熔接线的截面熔接过程。通过等厚度截面和非等厚度截面两个算例,给出了两股熔体熔接过程中的截面速度场和压力场分布。讨论了熔接线区域的壁厚均匀程度对熔接过程的影响。该计算结果可以为制品力学性能以及纤维取向等数值模拟提供数据支持。     

Study of birefringence character of injection- and compression-molded polycarbonate and its interpretation

Birefringence development in molded polycarbonate is of great importance in the manufacture of optical discs. It is important in characterizing birefringence to realize that we are dealing not with a scalar but with the anisotropy of the refractive index tensor–and with the orientation and shape of the refractive index ellipsoid. This usually varies heterogeneously; i.e., point-to-point through the thickness of molded parts. We present here an experimental study of the shapes and orientations of refractive index ellipsoids in injection- and compression-molded polycarbonate parts. We consider the variations in ellipsoid character as a function of molding conditions such as injection rate and quench. In injection-molded parts, the refractive index ellipsoid is coaxial with the flow direction in the center of the parts, but varies with position in the direction of the mold walls. In some cases, the extinction angle reaches a maximum at the mold wall and in other cases, there is an intermediate maximum. In the central “flow-thickness” direction plane, the transverse axis of the refractive index ellipsoid is perpendicular to this plane. The birefringence (in principal axis coordinates) in the flow-thickness direction plane exhibits an intermediate maximum whose position and magnitude vary with molding conditions. In some cases, multiple maxima exist. In compression-molded parts, a principal axis is normal to the mold wall. The results are interpreted in terms of the Rheo-Optical Law using flow-induced orientation and residual stress mechanisms. If the contribution of the residual stress to the birefringence can be subtracted, we may compute biaxial orientation factors. We do this for a case that has low residual quench stresses.     

Effect of packing pressure on fiber orientation in injection molding of fiber‐reinforced thermoplastics

Injection molding of fiber‐reinforced polymeric composites is increasing with demands of geometrically complex products possessing superior mechanical properties of high specific strength, high specific stiffness, and high impact resistance. Complex state of fiber orientation exists in injection molding of short fiber reinforced polymers. The orientation of fibers vary significantly across the thickness of injection‐molded part and can become a key feature of the finished product. Improving the mechanical properties of molded parts by managing the orientation of fibers during the process of injection molding is the basic motivation of this study. As a first step in this direction, the present results reveal the importance of packing pressure in orienting the fibers. In this study, the effects of pressure distribution and viscosity of a compressible polymeric composite melt on the state of fiber orientation after complete filling of a cavity is considered experimentally and compared with the simulation results of Moldflow analysis. POLYM. COMPOS. 28:214–223, 2007. © 2007 Society of Plastics Engineers     

普通注塑机上实现电视机面壳双层双色注射成型

介绍了一种在普通单色注塑机上增加辅助螺杆和特殊模具设计实现电视机面壳零件双色注射成型的技术方案。该方案使用型芯下沉式模具结构,通过特殊的顶针板设计,解决了双色彩电面壳内部众多不等高螺丝柱注射成型难的问题,并且不会在制品表层透明材料的表面上产生光学缺陷。目前,采用这种设计的模具已经实现工程量产,塑件成型效果良好。     

薄壁塑件注射压缩成型工艺的模拟分析

基于正交分析法和单因素分析法,用Moldflow软件数值模拟注射压缩成型中不同工艺条件对薄壁制品残余应力的影响.计算的残余应力沿厚度方向的分布表明:薄壁制品残余应力主要为流动诱导残余应力.模具温度与压缩距离对制品残余应力影响显著,模具温度越高,压缩距离越大,制品残余应力越小;其他工艺参数对残余应力均有不同程度的影响.     

基于Mori⁃Tanaka方法的短纤维复合材料开孔板分析

基于Mori?Tanaka均匀化方法，对短纤维复合材料开孔板力学性能进行研究。首先，使用Mori?Tanaka方法预测单向和二维2种分布形式的短纤维复合材料应力?应变曲线曲线。其次，通过试验方法分析不同区域纤维取向对开孔板力学性能的影响。最后，使用多尺度方法研究不同注塑位置和不同开孔方式对开孔板力学性能的影响，该部分在宏观有限元分析中耦合了注塑模拟的纤维方向分布以及Mori?Tanaka均匀化方法得到的复合材料参数。结果表明，短边注塑开孔板综合力学性能更好；孔周围纤维分布是影响应力集中的主要因素；整体的纤维取向分布影响开孔板的刚度；单向纤维材料的角度对材料性能的影响不是单调的。     

普通注塑机上实现电视机面壳双色注射成型

介绍了一种在普通单色注塑机上增加辅助螺杆和特殊模具设计实现电视机面壳零件双色注射成型的技术方案。该方案使用型芯下沉式模具结构,通过特殊的顶针板设计,解决了双色彩电面壳内部众多不等高螺丝柱注射成型难的问题,并且不会在制品表层透明材料的表面上产生光学缺陷。目前,采用这种设计的模具已经实现工程量产,塑件成型效果良好。     

Effect of gas channel design on the molding window of gas‐assisted‐injection‐molded polystyrene parts

Gas channel design plays a dominant role in determining the successful application of gas‐assisted injection molding. Although empirical guidelines for gas channel design have been proposed by the various equipment suppliers, quantitative criteria based on well‐designed experiments have not been reported yet. In this study, transparent polystyrene plates designed with semicircular gas channels of different radii and with rectangular gas channels of different width‐to‐height ratios were gas‐assisted‐injection‐molded to investigate the geometrical effects on gas penetration with various plate thicknesses. Plate parts designed with gas channels having four different types of cross sections but with the same section area were also examined. Molding windows and criteria for gas penetration were properly chosen so that the design rule could be defined quantitatively. The moldability index was also classified into five levels (excellent, good, fair, poor, and bad) based on the relative areas of the molding windows. From a plot of the moldability index versus the ratio of the equivalent gas channel radius to the plate thickness, we found that the ratio should be approximately greater than 2 for an appropriate molding window (fair moldability index) to be obtained. The dimensional ratio of the width to the height for rectangular gas channels also affected the moldability index under the same equivalent radius. Meanwhile, for four gas channel designs, both gas channel designs attached to the top rib provided better moldability than the other designs. This investigation offers part designers preliminary quantitative design and molding guidelines for choosing an effective gas channel design that allows the parts to be molded under an appropriate molding window so that the uncertainty in both simulation and process control can be overcame. Furthermore, this study provides a methodology for the establishment of quantitative gas channel design guidelines. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2979–2986, 2003     

Integrated simulation to predict warpage of injection molded parts

Injection molding analysis programs were developed for CAE (Computer Aided Engineering) in injection molding of thermoplastics. The programs consist of mold cooling, polymer filling-packing-cooling, fiber orientation, material properties and stress analyses. These programs are integrated to predict warpage of molded parts by using a common geometric model of three dimensional thinwalled molded parts. The warpage is predicted from temperature difference between upper and lower surfaces, temperature distribution, flow induced shear stress, shrinkage, and anisotropic mechanical properties caused by fiber orientation in the integrated simulation. The integrated simulation was applied to predicting warpage of a 4-ribbed square plate of glass fiber reinforced polypropylene for examination of its validity. Predicted saddle-like warpage was in good agreement with experimental one.     

注射成型大尺寸透明平板的应力、翘曲及收缩分析

根据透明平板注射成型的特点,建立了残余应力计算模型和翘曲计算模型,采用HsCAE软件的相应模块对大尺寸透明平板注射过程中的残余应力、翘曲变形及收缩进行了分析。结果表明,平板边缘的残余应力和厚向收缩率较大;而中间区域的残余应力和厚向收缩率小且比较均匀;平板中间区域的翘曲变形量最大,且沿平板平面向四周均匀递减。同时进行了平板的注射成型试验,通过实测平板的外形尺寸进一步验证了模拟结果。