陶瓷微注射成型技术的研究与进展

本文介绍了陶瓷微注射成型工艺过程的新特点和新技术;探讨了陶瓷微注射成型充模流动模拟所采用的理论模型及其应用研究现状;最终指出微注射成型技术研究应该着重于陶瓷微注射模拟新方法、微尺寸型腔内的流动机理、微型零件的质量控制方法、微注射成型工艺和设备研制上.     

高分子材料先进制造的微积分思想

为了解决现代制造业发展进程中,高分子制品微型精密化和大型复杂化所遇到的瓶颈问题,提出了高分子材料先进制造的微积分思想。基于这一思想,在高分子材料注射成型、挤出成型、静电纺丝、纳米复合材料制备和制品结构创新等先进制造技术领域开展了比较系统的原理探索和方法研究,发明了一系列加工成型新方法、新装备和制品应用新技术。通过部分工业化应用的实践检验,证明高分子材料先进制造的微积分思想对于突破传统制造模式的束缚、发展加工成型新方法和制品应用新技术具有一定的指导意义。     

精密陶瓷原位凝固制备技术的研究

七十年代末，世界范围内伴随着陶瓷热机部件的热潮，精密陶瓷受到了各国政府、研究部门及产业界的充分重视。进入九十年代后，精密陶瓷的发展遇到了许多问题，其中形状复杂结构部件的成型工艺是制造高性能陶瓷材料最为关键的环节之一。本文综合分析了近年来精密陶瓷成型工艺的研究进展，着重强调指出砂位凝固成型技术是保证坯体均匀性和解决高性能陶瓷可靠性的重要环节，同时，指出成型工艺今后需要加强和解决的几个关键技术。     

陶瓷注射成型的研究

注射成型是可批量制备形状复杂陶瓷部件的一种先进技术,本工作研究了陶瓷注射成型悬浮体的流变特性,考察了不同注射工艺参数对成型过程和坯体质量的影响,对脱脂过程中有机物的热分解和热失重特性进行了分析,研究了脱脂机理及陶瓷部件的实际脱脂过程,制备了完好的大尺寸陶瓷涡轮转子和叶片。     

陶瓷注射成型研究进展

陶瓷注射成型是一种近净尺寸陶瓷可塑成型方法，是当今国际上发展最快、应用最广的陶瓷零部件精密制造技术。清华大学新型陶瓷与精细工艺国家重点实验室近十年一直致力于陶瓷注射成型的研究，本文将介绍我们在这一领域取得的进展。     

陶瓷的制备新技术──直接原位凝固成型

陶瓷的制备新技术──直接原位凝固成型据《国内外陶瓷信息》报道：目前精密结构陶瓷的可靠性低，制造成本高，阻碍了其工业化应用。其根本原因是制备技术落后，特别是异形复杂部件的成型工艺。为此，目前研究发展了陶瓷直接原位凝固成型技术，具有如下特点：（１）净尺寸...     

氮化硅陶瓷注射成型体脱脂过程的研究

陶瓷注射成型是制备复杂形状陶瓷部件的一种有效方法。在这一陶瓷制备技术中,注射成型体的脱脂过程是关键一环。本文针对尺寸较大、形状复杂的陶瓷涡轮转子、研究了坯体中有机物排出的脱脂过程。结果表明:在低温段(RT～300℃左右),埋粉性质对脱脂速率和坯体质量影响显著,而高温段有机物的排除主要以裂解形式,脱脂气氛和压力起着重要作用;对于尺寸较大,形状复杂的陶瓷注射坯体在氮气中加压脱脂更为有利。     

陶瓷注射成型技术及其新进展

详细阐述了陶瓷注射成型技术的关键因素,全面介绍了国内外的新进展和动态,重点介绍了粉末共注成型、低压注射成型和微粉末注射成型等新技术。在此基础上评价和展望了该技术的发展前景。     

陶瓷基微反应器制备的研究进展

微反应器中亚毫米级的流体通道具有高效的传质传热效应,使其能够强化反应过程。随着微细加工技术的发展,制备出了耐高温耐腐蚀的陶瓷基微反应器,适用于更严苛的反应条件,然而陶瓷基微反应器的制备存在微结构成型工艺复杂、密封难度较大等问题。本文主要介绍不同陶瓷材料微反应器的制备工艺,重点论述陶瓷基微反应器制备过程中常规微加工技术的优化和新型微加工技术的引入,对比这些技术对微结构成型的改善效果。列举常用的陶瓷微通道密封连接方法,概述其特点和适用范围。并提出在陶瓷基微反应器制备的后续研究过程中,应注重陶瓷基微反应器制备的成功率和新技术的开发,完善陶瓷基微反应器的性能,将陶瓷基微反应器引入到更广泛的应用体系中。     

微分注射成型微型齿轮的实验

介绍了现有微注射成型机的特点,基于高分子材料微积分方法研制成功全电动微分注塑机,利用该微分注塑机成功注射成型平均质量仅为0.0116 g的精密微型齿轮。同时设计了正交试验探究不同工艺参数对制品成型质量的影响权重,研究成果为进一步提高微注射成型效果提供了一定理论基础。     

Powder-binder separation in injection moulded green parts

For powder injection moulding (PIM) the ceramic powder is mixed with a thermoplastic binder system to achieve an injectable feedstock. In contrast to injection moulding of polymeric components, the binder must be removed after the shaping step before sintering the ceramic part to full density. During the mould filling process shear forces act on the blend that might cause separations of powder particles and binder. In this case polymer films form at the mould surface and at internal interfaces which induce microstructural defects in the debinded part. In particular for multi-component parts this effect is critical since binder films in the joining zone weaken the bonding strength between the two components that might even lead to delamination.For detecting binder separations within the injection moulded bulk material and at joining zones of two-component parts the microstructure of green samples has been studied. Since conventional machining techniques like grinding and polishing modify the original structure, e.g. when particles are pulled out of the matrix and binder smears onto the surface, a special ceramographic method for the preparation of cross-sections was applied. This approach bases on broad ion beam techniques and enables the simultaneous polishing of hard ceramic particles and soft polymer molecules without destroying the structure or producing a relief at the surface. In the analysed samples binder accumulations were found along flow lines, at weld lines, at boundaries of so-called dead water regions and at the interface of two-component parts.     

Processing technologies for the injection moulding of hybrid microstructures

For the production of hybrid microsystems, appropriate joining methods (for plastics parts as well as for other materials) are required. Furthermore, for their industrial realization, special handling systems and feasible process control items are necessary. These topics are objectives of a research program involving several institutes of Aachen University of Technology (RWTH). Based on the micro injection moulding process, which has been investigated at the IKV for several years, a process called micro assembly injection moulding is developed and investigated. It combines the joining of hybrid elements with the generation of functional structures. Micro assembly injection moulding is a quite diverse process with many influencing parameters. For basic studies of this process, a special mould technology with maximum flexibility and precision is developed. The mould concept includes a special system for the positioning of inlay parts and complex sensor equipment (pressure, temperature, endoscopical devices) for controlling and analyzing the process. First test structures are two‐component micro hinges, fluidic hollow structures and optical structures. The high potential of the injection moulding process (high integration rate, large scale production, wide variety of geometries and materials) is thereby transferred to the economic and efficient production of microsystems.     

Net shape CMC components produced by composite flow moulding,pyrolysis and reactive silicon infiltration

This paper describes a novel technique to produce net shape ceramic matrix composites (CMC) artefacts by a modified injection moulding technique called composite flow moulding, (CFM) followed by pyrolysis and reactive silicon infiltration. The peculiarity of the produced components stands in their microstructure which is characterized by fibres crossing the part without interruption. This new method will open the use of CMCs to complex geometries for structural applications because they can be produced to net shape without machining and thus interrupting the fibres.A net shape CMC screw was manufactured, but other shapes, such as: bolts, nuts, rivets, springs and even turbine blades can be easily produced.     

利用外加剂改善陶瓷用石膏模性能的研究

本文研究了促凝剂、缓凝剂、表面增强剂、保水剂、高效减水剂等石膏外加剂对陶瓷母模石膏粉和工作模用石膏粉性能的提升作用.试验表明,加入一定的外加剂可提高石膏的表面强度,降低膨胀率,提高吸水速率,对提高陶瓷产品质量和降低生产成本具有重要意义.     

双层型腔的包装盒注塑模具设计

介绍了双层注塑结构及工作原理,指出了该模具的设计要点。该模具采用热流道技术,缩短了开模行程和成型周期;在成型面积和锁模力不变的情况下,一次注射两层制品,使生产效率提高近１倍;产品加工费用降低了４０％～５０％;节约主机投资,提高设备利用率     

Process–property–structure relationship in miniaturized injection moulded polyoxymethylene samples

Micro‐injection moulding is one of the key manufacturing technologies for thermoplastic polymeric materials for the mass production of high value miniaturized components. However, this process is not just a straightforward down scaling of the conventional injection moulding technique. Indeed, during the micro‐injection the polymer melt is forced to flow at high strain rates through very small channels in nonisothermal conditions; this can lead to complex microstructures and to parts with unexpected performances. In this work, the relationships among the processing conditions, the mechanical properties and the microstructural characteristics of polyoxymethylene miniaturized specimens obtained by injection moulding were investigated. The attention was focused on the influence of the process temperatures on the mechanical behavior, examined by uniaxial tensile tests, and on the microstructural characteristics of the specimens, examined by differential scanning calorimetry, wide‐angle X‐ray diffraction, polarized light microscopy, and dynamic‐mechanical thermal analysis. The results highlighted that material ductility in the miniaturized specimens is significantly affected by the mould temperature, because of the sample microstructure. Different degrees of orientation of polymer crystallites and different morphologies of the skin/core transition region were observed in dependence on the process temperatures. POLYM. ENG. SCI., 54:512–521, 2014. © 2013 Society of Plastics Engineers     

可熔型芯注射模塑新工艺

阐述了用可熔型芯注射成型热固性塑料的工艺过程和原理、工艺控制要点。用低熔点合金制成可熔型芯替代注射模具中的抽芯部件,在升温固化制件的同时熔化可熔型芯,用熔芯代替抽芯取出制件。通过合理控制成型过程各阶段的温度和时间,将制件的热固化过程、可熔型芯的熔化与再浇铸过程结合在一起同时进行,既实现了无法抽芯的中空异形制件的整体成型,又简化了模具结构,同时充分利用了热能、降低了成本、提高了生产效率。     

高压陶瓷电容器凝胶注模成型研究

凝胶注模成型是九十年代初发明的一种新型成型技术.它是传统陶瓷工艺和高分子化学结合的产物.这种方法具有素坯密度高、密度均匀、强度大,可成型复杂形状近净尺寸的大型陶瓷制品等特点,应用前景十分广阔.本文报告了高压陶瓷电容器凝胶注模成型研究结果.     

Rotary moulding of ceramic hollow wares

A novel processing method for the fast and economic production of hollow ceramic components has been developed by combining in situ coagulation moulding with a modified version of the technique of rotary moulding[Binner, J. G. P., Al-Dawery, I. A., Tari, G. and Yan, Y., Rotary casting technique. UK Patent application No. 0506349.0, March 2005], the latter being adapted from the polymer industry. The process was found to require a high solids content suspension, hence development work was performed in this direction though in the end a new, commercial suspension was utilised. Of the three forming routes of gel casting, direct coagulation casting and in situ coagulation moulding, the latter was found to be the most promising for the new process of rotary moulding of ceramics. Due to the low value of clay-based ceramics, a new low cost coagulant was identified and the effect of lactone concentration and temperature on setting time determined.Following substantial optimisation work, it was found that a two-speed approach to multi-axial rotation was the most successful; medium sized cream jugs could be produced in just 7 min. With respect to mould materials, the porous resin normally used for pressure casting of sanitary ware was found to be the best option, though since this is quite expensive conventional plaster-of-paris moulds were found to be a suitable material to enable companies, particularly SMEs, to become familiar with the technology whilst avoiding high costs for trials. The processed articles could be successfully fired and glazed using gas-fired kilns with no sign of any black cores.Major advantages of the process include the ability to precisely calculate the amount of ceramic slip required, eliminating either slip wastage or the need to pour used slip back into the virgin material as currently happens with slip casting. In addition, since the precursor suspension has a very high solids content, the time and energy required to dry the green product and associated moulds has been considerably reduced.     

Quantifying part irregularities and subsequent morphology manipulation in stereolithography plastic injection moulding

Abstract

The direct use of moulds produced by stereolithography (SL) provides a rapid tooling technique which allows low volume production by plastic injection moulding. The greatest advantage of the process is that it provides parts that are the same as those that would be produced by metal tooling in a fraction of the time and cost. However, work by the authors demonstrates that the parts possess different characteristics to those produced by metal tooling. This knowledge defies the greatest advantages of the SL injection moulding tooling process – the moulded parts do not replicate parts that would be produced by metal tooling. This work specifically demonstrates that a different rate of part shrinkage is experienced and subsequently investigates the mechanisms in SL tooling that induce these different part properties. The work culminates in different approaches to modifying the moulding process which allow the production of parts whose key morphological characteristics are closer to those that have been produced from metal moulds.