复杂薄壁金属零件的快速制造技术

本研究以真空差压铸造技术为基础,结合选择性激光烧结（SLS）快速原型技术和陶瓷壳型精密铸造技术,开发了一种从计算机三维模型到金属零件的快速制造工艺－快速精确铸造工艺,可以实现复杂薄壁铝合金零件的快速成形。本文着重描述了由SLS塑料原型快速制取陶瓷型壳和真空差压精确铸造技术的工艺特点,解决了新产品开发中金属零件快速制造的关键问题,为快速成形技术在铸造中的应用开辟了一个新领域。     

Manufacturing of WC–Co moulds using SLS machine

Tungsten carbide–cobalt composite is widely used as a wear-resistant material for cutting tools, molds and other applications. Its production by Selective Laser Sintering (SLS) technique promises to combine the material properties of a composite with the flexibility of a production process. The present paper deals with SLS of a powder mixture of tungsten carbide and cobalt with an aim to make functional parts using a modified Rapid Prototyping (RP) machine (100 W DTM Sinterstation 2000). The associated manufacturing problems and their solutions are discussed. Various compositions of powders have been tried before being settled to a particular composition of WC–9 wt.% Co for making final parts. Bronze infiltration is done on laser sintered parts to enhance their mechanical properties. Fretting wear test is taken as a main characterizing test which is used for estimating the wear resistance of samples.     

Selective Laser Sintering of PEEK

Polyetheretherketone (PEEK) is a good choice especially for manufacturing medical instruments or implants. These parts are typically produced by conventional manufacturing methods, like injection moulding. Selective Laser Sintering (SLS) could offer more flexibility. It enables the direct manufacturing of products with complex geometries. Although SLS of polymers like polyamide or polystyrene is a standard industrial process already, laser sintering of PEEK remains a challenge.This article will show for SLS of PEEK the necessary adaptations in systems technology and material modifications and discuss a step-by-step process implementation. Process boundaries are shown concerning temperature and energy input. The high influence of porosity, which could be varied from zero to 15%, on mechanical properties is shown.     

铸造--支持金属零件(模具)快速制造的关键使能技术

金属零件(模具)的快速制造分为直接法和间接法.由于直接快速制件在力学性能、尺寸精度等方面还存在不足,基于快速原型间接制造金属零件(模具)就成为目前切实可行的主要方法,其中,铸造技术由于具有成形、快速、成本低、性能好的特点,成为支持金属零件或模具快速制造的关键使能技术.实践和研究表明,铸造与快速成形技术的结合是成功的.给出了基于铸造技术实现金属零件快速制造的工艺路线.     

间接选择性激光烧结与选择性激光熔化对比研究

采用选择性激光烧结（Selective laser sintering，SLS）和选择性激光熔化（Selective laser melting，SLM）工艺，分别进行了铁基合金粉末的快速成形试验，对比分析了SLS与SLM成形机理、相应的工艺参数以及它们对测试件成形过程、金相组织与力学性能的影响。结果表明：由于成形机理不同，相对于SLS技术，采用SLM能够制造高致密度、组织均匀、力学性能良好的金属零件，但容易出现翘曲变形、裂纹与球化现象。通过制定合适的材料与工艺参数能够避免上述缺陷。     

On the use of SLS Tools in Sheet Metal Stamping

A few rapid tooling technologies have been recently proposed and among them Selective Laser Sintering is probably one of the most relevant and promising. In the paper, the authors report some results of a wide experimental research on the application of SLS tools in sheet metal forming. A wear test was earned out to investigate the progressive degradation of laser-sintered materials in comparison with traditional cold-work steels. In particular SLS tools were utilized in a sheet metal stamping process of S-shaped parts: their performances (in terms of tool wear and dimensional quality of the stamped part) were compared with the ones of traditional tools.     

The use of off-line part production to predict the tensile properties of parts produced by Selective Laser Sintering

Rapid Manufacturing, and specifically Selective Laser Sintering, has the potential to become one of the most useful manufacturing techniques of the future, largely as a result of the extremely high levels of geometric complexity which can be produced. As the use of these technologies becomes more widespread, so the amount, and variety, of materials available for use in these processes also increases. However, the Selective Laser Sintering process can be both expensive and time-consuming when testing new materials. A method of off-line casting has been proposed here, and the tensile properties of parts produced using this method are compared with the properties achieved in Selective Laser Sintered parts produced in the same materials. For the materials tested it has been shown that the casting method provided an acceptable correlation with the properties of the Selective Laser Sintered parts, rendering this a suitable method of assessing the properties of a Selective Laser Sintering material without the requirement to produce a full build.     

基于SLS技术对传统熔铸法模具制造工艺改进的研究

采用HB1粉末作为SLS烧结对象,在HRPS_ⅢA型SLS激光快速成型机上进行烧结。讨论了如何应用SLS技术对传统的熔模铸造工艺进行改良,使生产周期大大缩短,成本大大降低;新工艺能够处理的零件可以是任意形状的,几乎不受其外形复杂程度的限制,从而使企业能够更快对市场做出反应,确保企业在现代和未来的市场竞争中处于更有利的地位。     

Full densed alumina-glass composites by SLS and ceracon forging process

Selective Laser Sintering (SLS) process has been employed to fabricate alumina-glass composites using monoclinic HBO₂ as an inorganic binder. Subsequent post-thermal processing of green SLS parts at various temperatures yielded glass-ceramic composites. Composites with higher glass contents showed higher density and bend strength for all firing temperatures than those with lower glass contents. For a firing temperature of 900°C, the glass redistribution arising from a better viscous flow of glass gave all composites maximum density and bend strength. In addition, fully dense SLS glass-ceramic parts were obtained by employing the Ceracon forging process. Bend strength of these Ceracon forged composite parts reached as high as 70 to 110 MPa.     

粉末烧结激光快速成形数字化制模技术及应用

快速成形技术是将三维CAD模型直接转化成为铸造用模的新技术。介绍了粉末烧结激光快速成形数字化制模的原理，探讨了在产品开发设计、精密铸造用蜡模、精密铸造用砂型、直接烧结金属零件和模具等方面的应用。与传统制模方法相比，具有速度快、精度高、价格便宜等优点。     

Rapid casting technology based on selective laser sintering

Selective laser sintering (SLS), as a kind of additive manufacturing technology, which uses a laser beam to scan and heat powder material layer by layer to form parts (models), is widely used in the field of casting, mainly for preparing casting coated sand cores, investment casting patterns, etc. The SLS technique facilitates rapid casting and shortens the casting production periods by eliminating mold preparation. In this study, we reached conclusions for the basic principles and characteristics of SLS methods, and focused on the research status, key technology and development trend of SLS in the fields of forming coated sand-casting molds and investment casting patterns.     

小功率激光烧结金属粉末直接成型工艺实验研究

在小功率(50W)激光快速成型机上,选择铁粉和石墨粉末按一定比例混合,在不添加粘结剂的情况下进行了金属粉末直接成型工艺实验,获得了典型的较为致密、形状和尺寸精度较高的金属烧结原型件。经二次高温烧结后显微组织表明,金属件由铁素体和珠光体组成。分析了主要工艺参数对成型的影响,研究了二次高温烧结工艺对烧结件微观组织的影响及存在的一些问题。     

激光选区烧结聚苯乙烯的试验研究

激光选区烧结是快速成形方法的一种。该文对聚苯乙烯塑料的激光选区烧结进行了大量的工艺分析，探讨了激光烧结工艺参数对烧结制品致密度的影响，并对烧结制品的结构组织进行了研究。     

基于选择性激光烧结方法的金属零件快速制造技术研究

主要研究了通过选择性激光烧结高分子原型件制造金属零件的工艺。通过采用真空压差铸造工艺。结合铸造型壳的制造，成功制造出金属零件。对基于SLS技术的精密铸造过程中的精度控制进行了研究分析，并提出了解决办法。     

Coalescence Behaviour of Two Metallic Particles as Base Mechanism of Selective Laser Sintering

In many R&D places, the process of Selective Laser Sintering (SLS) of high performance metals is subject of investigations. An observation often made in SLS of metals is, that certain materials show a proper bonding behaviour while others tend to form welding pearls («balling» effect). This paper aims to identify and explain process mechanisms related to this effect. The dominating physical mechanisms are investigated. In addition, it is described which material properties mainly affect the results. The attained insights are transferred to the conditions of SLS in a powder bed layer by process modelling and experimental testing.     

提高SLS覆膜砂铸型(芯)强度的措施

分析了影响覆膜砂铸型（芯）烧结强度的因素，详细地讨论了提高选择性激光烧结（ＳＬＳ）覆膜砂铸型（芯）烧结强度的各种措施。从烧结方式上探讨了如何既提高ＳＬＳ制件强度、又保证制件的成形速度和精度的问题。     

Forming Simulation and Experimental Verification of Combined Formation of Selective Laser Sintering and Cold Isostatic Pressing

Selective laser sintering (SLS) could manufacture complex parts rapidly which, however, have high porosity and low intensity. While the parts made by cold isostatic pressing have advantages of uniform structure without composition segregation, high-dimension precision and high density. However, it could not form high complex parts because of the difficulties in manufacturing bag. A combination of SLS and cold isostatic pressing is expected to use the advantages of the two methods and is an efficient way to make complicated parts rapidly. After SLS and cold isostatic pressing, dimensions of parts decrease and relative density increases. To predict final dimensions and density, the finite element simulations are performed for cold isostatic pressing. The results show the parts made from ball shape powder contract symmetrically. The simulation results agree with the achieved geometries within 4%. Comparisons are made with that parts made from irregular powder. The SEM pictures after SLS are also showed. This has an important indication to process of SLS and cold isostatic pressing forming.     

金属粉末选区激光熔化技术的研究现状及其发展趋势

选区激光熔化(SLM)技术是近年来出现的一种新型的快速成型(RP)技术。该技术的优点是:工艺简单、成型件尺寸精度高、表面粗糙度好、致密度几乎能达到100%、力学性能优良、应用前景广阔。本文描述了该技术的基本原理;详细介绍了国内外选区激光熔化技术相关设备、工艺以及成型用金属粉末材料等的研究成果;并进一步讨论了选区激光熔化技术的应用及其发展方向。     

分段沉积/雕铣成型工艺及其在快速模具制造中的应用

快速成型技术可以由三维CAD模型直接制造出具有复杂结构的零件。分段沉积/雕铣成型是一种传统快速成型和CNC雕铣加工相结合的复合成型工艺。介绍了分段沉积/雕铣成型工艺的原理、装置和软件,探讨了该工艺在快速模具制造中的应用。     

复杂结构薄壁件电弧增材制造离线编程技术

将增材制造技术和弧焊机器人技术相结合,对复杂薄壁件进行电弧增材制造技术研究. 首先在传统的分层方法的基础上,对成形过程中高度变化的几何模型进行预测并分析,再通过机器人的离线编程与轨迹规划技术,实现成形轨迹的自动提取. 进一步利用圆弧离散局部逼近算法,对复杂薄壁件的切片截面进行微分,计算出四元数矩阵,实现焊枪位姿自动调整;并对焊接工艺进行改良,保证成形质量. 最后通过焊制部分薄壁件进行试验验证. 结果表明,薄壁件成形质量良好,预测尺寸与实际成形尺寸误差不超过1 mm.