型芯、模具及其制造和注射成型工艺(Ⅱ)

基于我国光学塑料元件成型技术落后于技术发达国家的情况，同时考虑到塑料非球面透镜又是我国目前注射成型的难关，并可望在型芯、模具及其制造和注射成型工艺上有所突破，而塑料非球面透镜又主要采用的是模具及注射工艺，所以本刊编辑部将从１９９８年第４期开始不定期的报道国外塑料模具型芯、模具及其制造、注射成型工艺等方面的有关信息，以此能对我国从事光学塑料元件制造的工程技术人员有所帮助。不定期报道的主要内容有：塑料模具设计要点；模具涂层；流态分析；模具制造的改进；注射成型；注射成型机；成型工艺参数；熔流及工艺性；如何减少成型元件的内应力；材料的选择；注射故障的排除等等。     

型芯、模具及其制造和注射成型工艺(Ⅰ)

基于我国光学塑料元件成型技术落后于技术发达国家的情况，同时考虑到塑料非球面透镜又是我国目前注射成型的难关，并可望在型芯、模具及其制造和注射成型工艺上有所突破，而塑料非球面透镜又主要采用的是模具及注射工艺，所以本刊编辑部将从１９９８年第４期开始不定期的报道国外塑料模具型芯、模具及其制造、注射成型工艺等方面的有关信息，以此能对我国从事光学塑料元件制造的工程技术人员有所帮助。不定期报道的主要内容有：塑料模具设计要点；模具涂层；流态分析；模具制造的改进；注射成型；注射成型机；成型工艺参数；熔流及工艺性；如何减少成型元件的内应力；材料的选择；注射故障的排除等等。     

型芯、模具及其制造和注射成型工艺(Ⅲ)

基于我国光学塑料元件成型技术落后于技术发达国家的情况,同时考虑到塑料非球面透镜又是我国目前注射成型的难关,并可望在型芯、模具及其制造和注射成型工艺上有所突破,而塑料非球面透镜又主要采用的是模具及注射工艺,所以本刊编辑部将从１９９８年第４期开始不定期的报道国外塑料模具型芯、模具及其制造、注射成型工艺等方面的有关信息,以此能对我国从事光学塑料元件制造的工程技术人员有所帮助。不定期报道的主要内容有：塑料模具设计要点;模具涂层;流态分析;模具制造的改进;注射成型;注射成型机;成型工艺参数;熔流及工艺性;如何减少成型元件的内应力;材料的选择;注射故障的排除等等。     

塑料透镜的开发与生产

本文综述了塑料光学元件的开发和生产。首先介绍了光学塑料材料,塑料透镜的设计,模具的材料和加工技术,然后介绍了精密塑料透镜的注射成型工艺和光学塑料非球面的测量。     

自由曲面光学透镜注射成型误差因素研究

自由曲面光学透镜注射成型误差对其光学性能将产生直接影响。注射成型过程中，注射工艺参数组合的优劣，直接影响成型误差的大小。为了获得高精密度的光学元件，就热塑性塑料的注射温度、模具温度、注射压力、保压压力及保压时间等主要工艺参数，对注射成型误差的影响进行综合研究,并且进行了实验验证。研究结果表明：适当提高注射温度与模具温度，同时采用高压注射、高压保压以及快速保压工艺，可显著降低注塑工件的体积收缩率，显著提高面形精密度，其光学表面面形误差小于0.1μm。可为注射工艺设计提供合理的依据。     

光学塑料注射成型的状态分析

本文通过对塑料光学元件注射成型过程的分析，以光学塑料熔体的状态方程以及流变学Ｈａ－ｇｅｎ－Ｐｏｉｓｅｌｌｉｌｅ方程为出发点，讨论并给出了光学塑料零件的成型工艺及模具浇注系统的设计准则。     

光学塑料及其注射成型工艺的新进展

主要介绍光学塑料和塑料零件注射成型工艺在近几年来的新进展。其中包括：１．对ＣＲ３９的改性：共聚改性；ＣＲ３９分子内部改性；掺入无机化合物。２．ＥＡ光学塑料。３．对ＰＭＭＡ的改性。４．日本的新塑料ＡＲＴＯＮ５．光学塑料元件二次加工时所用的特殊抛光剂。６．利用注射压缩成型方法提高产品的质量。     

国外光学塑料透镜成型工艺及其模具制造

本文主要介绍了国外光学塑料透镜的成型工艺及其模具制造。其中包括光学塑料零件的离心旋转成型法、高压高速注射成型法、二次加压注射成型法、固态注射成型法,用此方法,可大大缩短试制周期,提高了产品质量。     

改善塑料光学零件成型质量的几个问题

从改进注射成型技术和模具制造技术的角度介绍了提高塑料光学零件的质量所采取的措施。在抑制变形的成型技术中所采用的注射压缩成型方法中，用机械的方法对熔融塑料均匀加压以减小塑件的变形及残余应力。也可采用适当的补偿方法修正模具以补偿塑件的变形。在模具制造中可以在模芯表面镀一层非电镀镍，然后用金刚石车削机床加工，而获得很好的表面粗糙度和表面面形精度。     

塑料光学元件的清洗、镀膜和胶合

各种塑料光学元件在光学系统中的应用越来越广泛。作为光学元件,必然涉及清洗、镀膜和胶合等工艺技术问题。本文就塑料光学元件的这三个技术作一介绍。     

Biaxially Self-Reinforced High-Density Polyethylene Prepared by Vibration-Assisted Injection Molding. I. Processing Conditions and Physical Properties

A pulse pressure was imposed on the melt in the injection molding cavity during the injection and holding pressure stages, called vibration-assisted injection molding (VAIM) technology. With the VAIM technology, biaxially self-reinforced high-density polyethylene (HDPE) samples were prepared and the physical properties affected by the vibration processing conditions were studied. The tensile properties can be improved in both the machine direction (MD) and the transverse direction (TD) by changing the vibration frequency and vibration pressure amplitude, respectively. The elongation at break increased with increasing the vibration frequency for the VAIM sample processed at constant low vibration pressure amplitude; the yield strength increased with increasing the vibration pressure amplitude for the VAIM sample prepared at constant low vibration frequency. The softening point temperature for the VAIM sample increased by 8°C compared with a conventional injection-molded (CIM) sample.     

Melt Vibration Improved Melt Flow Behavior and Mechanical Properties of High Density Polyethylene

A pulse pressure was superimposed on the melt flow resulting in melt vibration. With application of the melt vibration technology, the melt flow behavior and mechanical properties of high‐density polyethylene were studied. For vibration‐assisted extrusion (VAE) at constant vibration pressure amplitude, the viscosity decreases sharply with increasing vibration frequency, and also does so when increasing vibration pressure amplitude for VAE at constant vibration frequency. The effect of vibration field on melt rheological behavior is also related to the melt temperature; a large decease in viscosity is obtained at low melt temperature. Compared with the mechanical properties obtained by conventional injection molding (CIM), the mechanical properties for vibration‐assisted injection molding (VAIM) samples were improved by changing the vibration frequency and vibration pressure amplitude. Injected at constant low vibration pressure amplitude, the VAIM sample prepared at high vibration frequency shows large elongation at break; injected at constant low vibration frequency, the VAIM sample prepared at high vibration pressure amplitude shows greatly improved yield strength. The above two VAIM processing routes produce different VAIM samples with different fracture behaviors; a distinct layered structure for VAIM samples was observed by SEM.     

Simulation of injection-compression molding for thin and large battery housing

Injection compression molding (ICM) is an advantageous processing method for producing thin and large polymeric parts in a robust manner. In the current study, we employed the ICM process for an energy-related application, i.e., thin and large polymeric battery case. A mold for manufacturing the battery case was fabricated using injection molding. The filling behavior of molten polymer in the mold cavity was investigated experimentally. To provide an in-depth understanding of the ICM process, ICM and normal injection molding processes were compared numerically. It was found that the ICM had a relatively low filling pressure, which resulted in reduced shrinkage and warpage of the final products. Effect of the parting line gap on the ICM characteristics, such as filling pressure, clamping force, filling time, volumetric shrinkage, and warpage, was analyzed via numerical simulation. The smaller gap in the ICM parting line led to the better dimensional stability in the finished product. The ICM sample using a 0.1 mm gap showed a 76% reduction in the dimensional deflection compared with the normal injection molded part.     

光学微透镜阵列模压成形研究进展与展望

光学微透镜阵列在光学系统中的应用广泛,需求量大,而玻璃模压成形技术是最高效的微透镜阵列量产加工方法,具有精度高,一致性好,生产成本低等特点,有重要的应用研究价值。本文介绍了光学微透镜阵列的设计原理,模具制造技术,模压成形技术及相应检测技术;重点介绍了微透镜阵列模压成形试验与有限元仿真研究的最新进展;最后对微透镜模压成形发展前景进行了展望,包括微透镜阵列模压材料,模具表面镀层技术及超声复合加工技术在微透镜阵列模压成形中的应用等。     

Self-Reinforced High-Density Polyethylene Prepared by Low-Frequency,Vibration-Assisted Injection Molding. 1. Processing Conditions and Physical Properties

Using a low-frequency, vibration-assisted injection molding (VAIM) device, the effects of vibration variables (frequency and amplitude) on mechanical properties and thermal softening temperature of high-density polyethylene (HDPE) injection moldings were investigated. For VAIM-processed samples, the mechanical properties can be improved by changing vibration frequency and vibration pressure amplitude. Injected at a constant vibration pressure amplitude, a low range of frequency (below 0.7 Hz) was favorable for increasing yield strength; in the high range of frequency (0.7 Hz < f < 2.33 Hz) the yield strength remained at a plateau. Injected at a constant frequency (0.7 Hz) the yield strength increased sharply with decreased elongation when applying large vibration pressure amplitude. The maximal yield strength and Young's modulus were 60.6 MPa and 2.1 GPa for a VAIM sample compared with 39.8 MPa and 1.0 GPa for a conventional injection-molded (CIM) sample, respectively; there was also a 10°C increase in Vicat softening point temperature.     

Dimensional variation in production of high-aspect-ratio micro-pillars array by micro powder injection molding

Micro powder injection molding (μPIM) is one of the potential processes for the mass production of metallic microstructures and micro components. Here, μPIM is the miniaturization of conventional PIM, which involves four processing steps: mixing, injection molding, debinding and sintering. This paper looks into the feasibility and effectiveness of μPIM as a key mass production process for the fabrication of metallic micro components. For it to be an effective re-production process, it is imperative to examine how well parts can be duplicated/fabricated from a master mold. In this work, the dimensional variation of high-aspect-ratio micro-pillars arrays, in particular the dimensional shrinkage, global warpage, and surface roughness at each stage of the μPIM process for a range of molding pressures, are quantified and compared in detail. The sensitivity of the dimensional variation of the microstructures to the packing pressure is reported. The mechanism behind the dimensional variation is analyzed. PACS 81.20.Ev; 81.20.Hy; 81.70.Fy; 07.60.Ly; 81.05.-t     

Prediction of Heat Conduction with Phase-change Effects during Cooling Stage of Injection Molding of High-density Polyethylene: Approximate Integral Approach

Phase-change problems, also known as the “Stefan problems” or “moving-boundary problems,” are practically significant in modern technological and engineering fields. Injection molding, one of the most widely used polymer processing techniques, can be divided into three stages: filling, packing, and cooling. The cooling stage, which accounts for over three fourths of total molding cycles, greatly affects both productivity and quality of the molded articles. In this work, an approximate integral method was adopted to predict the transient heat conduction with phase-change effects during the cooling stage of injection molding of crystalline polymers. Experiments were conducted to compare with the calculated results, and reasonable agreement was obtained. It was concluded that the present modeling makes good predictions for the cooling stage of injection molding of crystalline polymers, which may be applicable to further studies on the microstructure evolutions during injection molding process as well as the optimal designs in industrial applications.     

INTERNAL STRUCTURE OF CO-INJECTION MOLDED PP/PP SPECIMEN

An overview of the microstructural characteristics of co-injection molded isotactic polypropylene products is given. Polarized light optical microscopy is used for comparison of traditional injection molded and co-injection molded products' microstructure. It is shown that a transcrystalline layer occurs on the boundary of the skin and the core components when a nucleation agent was added to either of the components; this proves that this surface layer is not shear induced cylindritic structure. Also shown is a method for preparing β-phase transcrystalline structure capitalizing on the advantages of the co-injection molding technology.