基于选择性激光烧结PS原型的 快速铸造工艺研究

针对传统熔模精密铸造工艺中熔模制作过程复杂的问题,以某典型零件为研究对象,开展了基于选择性激光烧结技术的熔模精密铸造工艺研究。首先采用SolidWorks建立了零件的三维模型,将模型导入激光烧结设备中,调整并优化了烧结设备的工艺参数,以PS(聚苯乙烯)粉末为原材料进行了激光烧结成型,制得了零件的PS原型;然后,以该PS原型与蜡浇注系统结合后的整体模型作为熔模替代了传统压制蜡模,进行了熔模精密铸造,制得了目标零件的精密铸件;最后,测量并分析了铸件的尺寸精度和表面质量。研究结果表明:通过该快速铸造工艺制得的铸件质量较好,尺寸精度可达CT6级,表面粗糙度可达Ra6.3μm。     

快速成型技术原理及成型精度分析

介绍了快速成型技术的基本原理;对立体光固化（SLA）、熔融沉积（FDM）、选择性激光烧结（SLS）和分层实体制造（LOM）这四种成型方法的工作原理、材料选择和精度影响因素进行了分析;介绍了快速成型的应用情况;在此基础上指出了快速成型技术的发展趋势。     

基于激光快速成型的快捷制造技术

介绍了几种可以大幅度缩短产品制造周期的快捷制造技术。论述了激光快速成型技术的原理和方法,重点介绍了光固化成型SLA、选择性激光烧结SLS、熔化沉积成型FDM、逐层物体制造技术LOM、固体基础固化SGC方法。对利用激光快速成型技术为基础发展起来并已成熟的快速模具工装制造技术、快速精铸技术、快速金属粉末烧结技术的原理和技术途径进行了说明。     

汽车发动机零件的快速制造

介绍了最适用于发动机零件制作的选区激光烧结(简称SLS)方法,并将快速成型技术与传统的铸造技术进行有效的结合形成快速铸造技术--熔模快速铸造和快速砂型铸造,以快速制造复杂金属零件.     

薄材叠层、粉末烧结快速成形技术的应用

基于快速成形的快速模具制造技术提供了一种方便快捷、成本低廉、新的制模方法。薄材叠层、粉末烧结快速成形技术与传统铸造工艺相结合,在小批量生产塑料件、用LOM原型件代替铸造用木模、SLS蜡件用做精密铸造熔模等方面取得了广泛的应用,可极大提高传统行业的市场竞争力。     

选择性激光烧结技术的研究现状与展望

选择性激光加工是20世纪80年代末出现的一种新的快速成型工艺,它利用激光束烧结粉末材料制造原型,具有原料广泛、制作工艺简单、周期短等特点,在诸多领域得到了广泛的应用.介绍了选择性激光烧结技术的原理、特点及实际应用,综述了选择性激光烧结技术发展状况、存在的问题及研究热点.     

快速成型技术在熔模精密铸造中的应用

快速成型技术是具有高柔性的先进制造技术,无需任何专用工具,由零件的CAD模型直接完成零件或零件原型的成型制造。将快速成型技术与铸造技术结合起来,采用快速成型技术制造铸型或铸模,可极大提高铸造的柔性和生产效率,满足新品试制和小批量生产的需求,这也是快速成型技术的一个主要发展方向。本文通过几种快速成型模在熔模精密铸造中的实际应用和试验得出,采用SLA法制作的蜂窝结构快速成型模在尺寸波动方面满足精铸需要,并能实现铸件的快速制造。     

基于快速原型的钢模具无余量消失模铸造工艺研究

由机械科学研究院完成的“基于快速原型的钢模具无余量消失模铸造工艺研究”课题，以快速原型技术（Rapid Prototyping简称RP）为基础即基于离散／堆积成型原理，直接采用计算机数字模型控制激光加工系统，使材料一层层堆积成型。通过快速原型与消失模精密铸造技术相结合，分析工艺过程中的尺寸精度影响因素，可将工艺过程中的误差数据以及金属凝固过程中尺寸精度变化反馈到CAD模型设计中。     

基于选择性激光烧结成型的无模具快速精铸工艺

论述了基于选择性激光烧结(SLS)成型无模具快速精铸工艺。该工艺将CAD、SLS壳型铸造与传统的砂型铸造相结合，特别适宜具有复杂形状铸件的单件、小批量铸件工艺的设计和生产，并使传统的分散、多工序的铸造工艺设计和生产过程实现了集成化和自动化．     

激光绕结成型及其在精铸中的应用

本文介绍了增材制造技术及其分类，着重阐述了激光烧结成型技术的原理和方法，汇报了开展激光烧结成型技术研究的试验结果，并分析了该技术在零件精密铸造中的应用。     

The two-dimension hollowing algorithm for rapid prototyping technology

The hollowing process plays an important role in some rapid prototyping technologies such as stereo lithography apparatus (SLA), fused deposition modelling (FDM) and select laser sintering (SLS). This paper introduces an efficient two-dimensional hollowing algorithm. The principles of algorithm and implementation are presented. In addition, a detailed analysis is used to study the effect of the scanning path and online character in the actual fabricating process.     

A new shell casting process based on expendable pattern with vacuum and low-pressure casting for aluminum and magnesium alloys

A new shell casting process, with the adoption of the foam pattern of lost foam casting (LFC) as prototype and the combination of the thin shell fabrication technology of investment casting and vacuum and low-pressure casting process, was proposed for manufacturing complicated and thin-walled aluminum and magnesium alloy precision castings. Loose-sand uniting vacuum was used in the new process to further reinforce the thin shell, and the new process proves to be a process with simple process, low cost, and high thin shell strength. Because the molten metal filling and solidification are completed under air pressure and vacuum level, the filling capability and feeding capacity of the molten metal are greatly improved, and the castings become denser. This paper mainly investigated the fabrication technology of thin shell based on foam pattern prototype, the removing foam and roasting shell process and vacuum and low-pressure casting process. The few-layer compound thin shell of silica sol–sodium silicate was adopted for the new process. Removing foam pattern was carried out at 250°C for 30 min, and the shell was roasted at 800°C for 1 h. Combined with the vacuum and low-pressure casting process, this new shell casting process has successfully produced thin wall and complex aluminum and magnesium alloy parts with high quality. In addition, comparisons in terms of filling ability, microstructure, mechanical properties, porosity, and surface roughness among this new shell casting, gravity casting, and LFC were also made to show the characterization of this new shell casting process.     

FDM成形件精度预测模型的建立

熔融沉积成形(FDM)是快速成型(RP)最有发展前途的工艺之一,掌握提高成形件精度的控制方法是推广其应用的重要途径。在分析FDM成形件精度影响因素的基础上,提出应用误差反向传播(BP)神经网络建立预测精度模型的方法。将主要影响因素作为BP神经网络模型的输入参数,并根据最小预测误差选择输入层和中间层的维数,确定了BP模型结构。利用多组实验数据进行模型训练,建立了BP神经网络模型。模型预测与实验测量的对比结果表明,模型的预测误差在6%以内,具有很高的预测精度,可以指导实际应用。     

新的激光快速成形方法及应用

针对目前主要激光快速成形方法的优缺点,提出一种基于三维实体边界分割的激光快速成形新方法.该方法将叠层实体制造(LOM)法主要进行激光二维轮廓线扫描和选择性激光烧结(SLS)法能够加工多种覆膜粉末材料的优点有机结合,能够克服SLS法加工效率低,成形件致密度、硬度、精度和表面粗糙度等性能较低的缺点.利用自主开发的快速成形系统,采用热像仪测温与Ansys模拟激光能量输入模型相结合的方法对工艺参数进行确定,对基于三维实体边界分割激光快速成形方法进行应用研究,实现三维实体的快速成形及金属零件的快速铸造,并通过无模具快速铸造的手段获得金属齿轮铸件.     

基于SLA成形的EDM电极加工工艺

介绍基于立体光成形(SLA)EDM电极的加工工艺。该工艺将CAD、SAL壳形铸造与真空离心铸造相结合,特别 适宜具有微形复杂形状EDM电极的单件、小批量生产,并使传统分散、多工序的EDM电极加工工艺实现了集成化和自 动化。     

Analytical modeling of ductile-regime machining of tungsten carbide by endmilling

The aim of the present research was to compare the efficacy of two powder based 3D printing technologies for rapid casting of light alloys. The technologies of ZCast process and investment casting were employed to cast aluminium A356 alloy and zinc ZA-12 alloy. The split pattern shells were printed in ZCast501 powder and used directly as mould with outside sand support in case of ZCast process. Two commercially available powders starch-based ZP14 and plaster-based ZP100 were infiltrated with two infiltrants acrylate and wax resulting in four different material systems for making investment casting patterns. A standard method was premeditated by identifying and designing the benchmark component. The proposed concept was presented in physical form by fabricating prototypes to appraise the impact of technology used on dimensional accuracy. The dimensional accuracy was acceded by assigning tolerance grades as per UNI EN 20286-1 ISO. In addition, the working suitability of castings was analysed by comparing important mechanical properties, and further, the results were supported by radiography and microstructure analysis. The feasibility of decreasing shell wall thickness for ZCast process was also checked so as to make the process more economical and fast.     

控制FDM成型制件误差的方法研究

快速制模是快速成型的主要应用之一,但成型件的精度难以达到快速制模对原型或型芯尺寸精度和表面精度的要求.系统分析了熔融堆积成型( FDM)工艺成型精度的影响因素,分析产生误差的根源及作用机理.针对FDM产生的误差,通过定性和定量分析,提出减小误差的途径和方法,并通过实例验证了解决翘曲变形和尺寸精度问题的方法,提高了原型的精度,对熔融堆积成型工艺精度的提高具有实际的参考价值.     

Novel technologies for the lost foam casting process

Lost foam casting (LFC) is a green precision casting process categorized as a near net forming technology. Yet, despite its popularity, it still suffers from some technological problems, such as poor filling ability of the castings, coarse and non-dense microstructure, low mechanical properties for the Al and Mg LFC processes, and defective carburization for the low carbon steel LFC process. These drawbacks restrict the development and widespread application of the LFC process. To solve these problems, the present study developed several novel LFC technologies, namely, LFC technologies under vacuum and low pressure, vibration solidification, and pressure solidification conditions; expendable shell casting technology; and preparation technology of bimetallic castings based on the LFC process. The results showed that the LFC under vacuum and low pressure evidently improved the filling ability and solved the oxidization problem of the alloys, which is suitable for producing complex and thinwall castings. The vibration and pressure solidifications increased the compactness of the castings and refined the microstructure, significantly improving the mechanical properties of the castings. The expendable shell casting technology could solve the pore, carburization, and inclusion defects of the traditional LFC method, obtaining castings with acceptable surface quality. Moreover, the Al/Mg and Al/Al bimetallic castings with acceptable metallurgical bonding were successfully fabricated using the LFC process. These proposed novel LFC technologies can solve the current technological issues and promote the technological progress of the LFC process.