等离子熔积直接快速制造金属原型技术

开发了等离子熔积直接快速制造金属原型技术。该技术以等离子束为热源，根据零部件计算机三维CAD模型，数字控制熔积枪或工作台运动，粉末材料在等离子体中被加热并沉积到基板表面或熔积层的熔池中，凝固并与之熔合后形成新的熔积层，直至完整的零件制作完成。所制造零件内部无孔隙，层与层之间完全冶金结合，可以用于金属原型或难熔难加工材料零件制造、表面修复等，具有重要的应用前景。     

面向等离子熔积直接制造的工控组态平台自动控制系统

分析了等离子熔积直接制造金属零件工艺的特点，开发了一种基于工控组态软件的等离子熔积直接制造自动控制系统。该系统满足多层熔积与表面光整复合成形工艺控制的要求，且开发周期短、成本低、开放性较好、易于操纵和维护。     

等离子熔积成形与铣削光整复合直接制造金属零件技术

针对国内外现有的金属直接快速制造技术中存在的制件表面质量不高的瓶颈问题,开发了在制造过程中将等离子熔积增材成形与铣削光整减材复合的金属零件直接快速制造方法。研究该复合制造工艺参数对熔积成形性和形状特性以及热态干铣削刀具和工艺的影响规律,找到合理的工艺条件并用其试制出金属零件原型,为改善快速原型表面质量提供了有效的途径。     

等离子激光复合成形中角度对弧柱形态和熔积层精度的影响

提出了等离子激光复合直接制造金属零件的新技术,介绍了等离子激光复合直接制造技术的基本原理。通过实验研究分析了激光束与等离子束复合角度对熔积层精度的影响规律。得到了在相同条件下,熔积层的宽度随复合角度的增加而增加的重要结论并分析了其原因。     

等离子激光复合熔积高温合金粉末的工艺研究

研究了等离子激光复合熔积高温合金粉末过程中激光对等离子弧柱形态、熔积时熔深和熔宽等的影响。实验结果表明，激光作用于等离子弧后，等离子弧弧柱的直径变小，挺度增加，稳定性增强，起弧容易，熔积层的熔深增大，熔宽减小。实验证明，这种方法直接快速成形高温合金或者难加工材料零件是可行的。     

等离子熔积与激光切割复合直接制造CAM软件研究

针对等离子熔积制造易产生侧表面阶梯效应,导致精度和表面质量不高的问题,提出将等离子熔积和激光轮廓切割复合以改善熔积成形件表面质量的方法。开发了等离子熔积激光切割复合直接制造CAM软件,在软件中提出了一种带法向的分层切片方式,对等离子熔积、激光轮廓切割的轨迹分别进行了规划,产生相应的NC代码,并对2个单工序NC代码进行了复合,以达到等离子熔积和激光轮廓切割工艺上复合的目的。     

等离子熔积/铣削复合直接制造高温合金双螺旋整体叶轮

采用等离子熔积与铣削复合制造技术，在等离子熔积成形过程中复合铣削精整，试制了难加工高温合金双螺旋整体叶轮样件，其组织性能和力学性能均高于采用传统工艺加工获得的叶轮。该技术解决了现有高能束熔积成形技术因无支撑和台阶效应造成的尺寸精度和表面质量不高的瓶颈问题，是难加工材料零件短流程、低成本、高质量无模精确制造的新的有效加工方法。     

大悬臂回转体金属零件的熔积增量成形技术

在具有倾角曲面或悬空特征的、复杂金属零件的直接增量制造中,无需支承的LENS与HPDM技术可省去因设立支承带来的诸多不便,在制造高性能和梯度功能材料零件方面独具优势;但尚未有效解决大悬臂复杂形状零件成形过程中的流淌问题。为此,本文提出基于骨架特征的变方向无支承制造技术,以改善制造效果。采用高效低成本的电弧熔积五轴直接成形制造系统,完成了大悬臂零件的直接成形制造。试验结果表明,该技术可用于此类零件的增量成形,为无支承增量成形技术在复杂悬臂结构零件的精确数字化熔积制造中的应用提供了有效途径。     

等离子熔积高温合金件表面激光气化光整研究

针对高温合金零件机械加工周期长、刀具损耗大的难点,开发采用高功率调Q激光对高温合金零件进行表面光整的方法.通过系统研究分析激光表面去除加工的激光功率、调Q频率、扫描速度、保护气体气压等主要工艺参数对高温合金零件表面光整加工质量的影响,获得适于高温合金件的表面光整条件,采用此条件光整加工得到表面质量好的高温合金零件,为等离子熔积成形快速直接制造高温合金零件提供技术基础.     

熔积和铣削复合精密无模快速制造金属零件

运用熔积和铣削复合快速制造金属零件的先进制造工艺,并结合ABAQUS有限元软件,模拟分析了复合制造中温度场分布及铣削力,在模拟和试验结果指导下,成功实现了多特征金属阻力片的制造。经蔡斯双管显微镜检测,零件尺寸精度控制在±0.03mm以内,表面粗糙度Ra≤0.869μm,满足产品设计要求。实验结果证明,该工艺可无模精密直接制造出满密度的复杂形状金属零件,大幅度缩短研制周期,降低成本。     

基于氩弧焊的柴油机冷却式针阀偶件的研制

冷却式针阀偶件的针阀体在普通的机械加工生产条件下是很难加工制造出来的.课题基于氩弧焊焊接加工工艺方法,从对针阀体进行分离设计、制造,然后装配、焊接入手,研究了冷却式针阀体冷却腔的结构设计及布置、焊缝的强度控制、过热影响区对二次机械加工的影响等难题.摸索出了一套冷却式针阀偶件的制造加工方法,解决了为改善柴油机经济性而使用重油后,带来的喷孔周围结胶、积碳问题.     

Effect of deposition orientations on dimensional and mechanical properties of the thin-walled structure fabricated by tungsten inert gas (TIG) welding-based additive manufacturing process

Welding-based additive manufacturing can potentially produce a cost-effective process for the production of dense metallic parts. Tungsten inert gas (TIG) welding-based additive manufacturing process uses wire as a filler material and offers a high deposition rate with low spattering. In this study, different orientations of wire feeding nozzle and TIG welding torch, such as front wire feeding (FWF), back wire feeding (BWF), and side wire feeding (SWF), were investigated for thin-walled metal deposition with enhanced dimensional accuracy and mechanical properties. The dimensional accuracy of thin-walls deposited at four different orientations were investigated in terms of deposition height and deposition width. The FWF orientation with higher wire feeding angle and SWF orientation produced poor dimensional accuracy in the deposition. FWF orientation with normal wire feeding angle and BWF orientation provided a decent dimensional accuracy and surface appearance. The deposited samples exhibited a similar trend for Vickers microhardness, residual stress, and microstructure for the four different wire feeding orientations.     

Development of a cold wire-feed additive layer manufacturing system using shaped metal deposition method

Shaped metal deposition (SMD) method would be an alternative way to traditional manufacturing methods, especially for complex featured and large scale solid parts and it is particularly used for aerospace structural components, manufacturing and repairing of die/molds and middle-sized dense parts. This method is implemented by depositing continuous cold or hot-water melted via welding arc plasma heat. This paper presents the designing, constructing, and controlling of an additive manufacturing system using TIG plus wire based Shaped metal deposition (TW-SMD) method. The aim of the current study is to design and develop an integrated system which is able to reduce time consuming and boring task of deposition process. The developed additive system is capable of producing near net shaped components of sizes not exceed 400 mm in 3 directions directly from CAD drawing. The results showed that the developed system succeeded to produce near net geometries and error-free depositions for various features of SS308LSi components. Additionally, workshop tests have been conducted in order to verify the capability and reliability of the developed AM system.     

Effects of the nozzle design on the properties of plasma jet and formation of YSZ coatings under low pressure conditions

How to control the quality of the coatings has become a major problem during the plasma spraying. Because nozzle contour has a great influence on the characteristic of the plasma jet, two kinds of plasma torches equipped with a standard cylindrical nozzle and a converging-diverging nozzle are designed for low pressure plasma spraying(LPPS) and very low pressure plasma spraying(VLPPS). Yttria stabilized zirconia(YSZ) coatings are obtained in the reducing pressure environment. The properties of the plasma jet without or with powder injection are analyzed by optical emission spectroscopy, and the electron temperature is calculated based on the ratio of the relative intensity of two ArⅠspectral lines. The results show that some of the YSZ powder can be vaporized in the low pressure enlarged plasma jet, and the long anode nozzle may improve the characteristics of the plasma jet. The coatings deposited by LPPS are mainly composed of the equiaxed grains and while the unmelted powder particles and large scalar pores appear in the coatings made by VLPPS. The long anode nozzle could improve the melting of the powders and deposition efficiency, and enhance the coatings' hardness. At the same time, the long anode nozzle could lead to a decrease in the overspray phenomenon. Through the comparison of the two different size's nozzle, the long anode is much more suitable for making the YSZ coatings.     

Numerical simulation of powder flow field on coaxial powder nozzle in laser metal direct manufacturing

In the laser metal direct manufacturing, gas–solid two-phase flow theory is adopted to simulate the flow field of powders in coaxial nozzle to fabricate complex parts of compact structure. The separate model in FLUENT is used to evaluate the concentration distribution rule and the focusing characteristics of the powder flow field. The results indicate that the focal concentrations of the coaxial powder nozzle in radial direction and axial direction are approximately obeyed by the Gaussian distribution. When the cone angle of coaxial nozzle is invariable, the cone ring gap is smaller, the focal point concentration in the powder flow field is bigger; the focus radius is smaller, the focal distance is also smaller, and the gathering characteristic is better. When the cone ring gap of the coaxial powder nozzle is invariable, the cone angle getting too big or too small is harmful for powder gathering. When other conditions are invariable, extreme protective gas velocity (too large or too small) is harmful for powder gathering. When the protective gas velocity approaches to 6 m/s, the gathering characteristic of the coaxial nozzle achieves its best performance.     

Modeling and experiment of surface error for large-aperture aspheric SiC mirror based on residual height and wheel wear

Shaped metal deposition method using gas tungsten arc welding is a novel manufacturing technology that can be used for fabricating solid dense parts in layered manufacturing. This paper reports for the first time using the pulsed current shaped metal deposition technique for fabricating components using cold wire of AISI 308LSi stainless steel. The aim of this work was to investigate and compare the effect of pulse frequency and other deposition process parameters on the morphology aspects and microstructure characteristics of the manufactured components using pulsed and continuous current processes. The obtained results reveal that the structure of the deposited specimens produced via pulsed arc current is generally having finer grains, high residual ferrite, and absence of columnar grains. Pulse frequency and current ratio have a significant influence on the surface morphology and microstructure of the manufactured parts. Good metallurgical bonding with no sensitization effects can be seen in all tested specimens. The presented additive layered manufacturing method can be recommended for near net-shaped processing of austenitic stainless steel components, and it can be used as an alternative manufacturing method for fabricating metal components with free defects, higher corrosion resistance, and superior mechanical properties.     

声辐射力驱动角形金属粉末微输送特性

为解决载气式、超声振动和惯性力等现有微输送方法在较宽输送速率范围内难以克服的角形金属粉体堵塞难题,本文研究以超声驻波场声辐射力为驱动力,通过悬浮分散微喷嘴内密集态粉末颗粒,实现金属粉末的稳定微输送。以激光熔覆技术中常用且易堵塞的100目、200目和300目角形铬粉和200目角形钛合金粉为对象,进行脉冲式和连续式两种模式的微输送精度和稳定性实验研究。实验显示,300目角形铬粉单脉冲输送质量可控范围为0.4~16mg且连续输送速率可控范围为6.0~65mg/s;脉冲微输送质量的变异系数随微喷嘴内径的增大而大幅降低(小于2%)、连续输送速率的变异系数均低于6%。实验结果表明,声辐射力驱动微米级角形金属粉末具有较大的输送速率可控范围、输送精度、稳定性和多种角形金属粉末的普适性,可从根本上解决角形粉末喷嘴微输送的堵塞问题。本文研究结果也可为其它尺度金属粉末和非金属粉末的微输送提供参考。     

直接金属成形喷射技术

分析了现有典型直接金属成形同轴喷射喷头系统的专利,结合试验提出了喷头系统的设计准则。在此基础上设计开发了单喷点同轴喷射系统。试验证明该喷头使成形工艺控制更加灵活,提高了成形零件的质量。     

A novel technique to produce metallic microdrops for additive manufacturing

In additive manufacturing (AM), three-dimen sional objects are built layer by layer by joining each layer to the previous one. Those layers can be formed from the direct deposition of metallic drops resulting from the breakage of a micrometer jet. The jet is produced by ejecting through a nozzle/orifice a metal melted in a crucible. In this paper, we propose a novel technique to produce a continuous droplet stream of a low-melting-point alloy for additive manufacturing. Our technique does not make use of a crucible. Instead, the tip of a metal wire is melted by an induction heating system as it is introduced in the nozzle. If the values of the control parameters are chosen appropriately, a quasi-steady jetting regime is established. This method is much more energetically efficient than its counterparts because it consumes just the energy necessary to melt the demanded material at any times.     

Self-Adaptive Control System for Additive Manufacturing Using Double Electrode Micro Plasma Arc Welding

Wire arc additive manufacturing(WAAM)has been investigated to deposit large-scale metal parts due to its high deposition efficiency and low material cost.However,in the process of automatically manufacturing the high-quality metal parts by WAAM,several problems about the heat build-up,the deposit-path optimization,and the stability of the process parameters need to be well addressed.To overcome these issues,a new WAAM method based on the double electrode micro plasma arc welding(DE-MPAW)was designed.The circuit principles of different metal-transfer models in the DE-MPAW deposition process were analyzed theoretically.The effects between the parameters,wire feed rate and torch stand-off distance,in the process of WAAM were investigated experimentally.In addition,a real-time DE-MPAW control system was developed to optimize and stabilize the deposition process by self-adaptively changing the wire feed rate and torch stand-off distance.Finally,a series of tests were performed to evaluate the con-trol system's performance.The results show that the capability against interferences in the process of WAAM has been enhanced by this self-adaptive adjustment system.Further,the deposition paths about the metal part's layer heights in WAAM are simplified.Finally,the appearance of the WAAM-deposited metal layers is also improved with the use of the control system.