飞秒激光切割与微细电阻滑焊组合制备三维金属微结构

提出了一种采用飞秒激光切割结合微细电阻滑焊制备3D金属微结构的工艺方法(微型化双工位金属箔叠层制造法,(Micro-DLOM)),并通过制备具有复杂形状的3D微型腔模具验证了该工艺方法的可行性。首先,以厚度为10μm的0Cr18Ni9不锈钢箔为基材,在110mW的飞秒激光功率、100μm/s的切割速度和0.75μm的切割补偿量下获得二维微结构,并分析了激光功率和切割速度对切割精度的影响;然后,利用微细电阻滑焊对多层二维微结构进行热扩散焊接,通过多层二维微结构的叠加拟合形成具有曲面特征的微型腔,并对焊接区进行了X射线衍射(XRD)分析。分析发现:微细电阻滑焊所产生的热量仅使焊接区主要物相的相对含量发生了变化,而没有使该区域产生新的物相。与UV-LIGA工艺相比,本工艺可以加工具有自由曲面特征的三维微结构,并且单层钢箔越薄,成形精度越高;与飞秒激光分层平面扫描烧蚀工艺相比,本工艺仅需切割每层二维结构的轮廓,提高了成形效率;与微细电火花加工工艺相比,虽然所成形的微型腔表面粗糙度相对较差,但却省去了制备微电极的工艺步骤,并且不存在微电极工作过程中的损耗问题,所以可以加工深宽比不受限制的微模具。     

逐层微细电阻滑焊工艺制备三维微结构

采用飞秒激光切割和微细电阻滑焊组合的方法制备了高深宽比的三维微结构。为了提高每层二维微结构的叠加精度和连接强度,用逐层微细电阻滑焊对每层二维微结构进行滑焊以获得较好的工艺参数。对上述工艺参数所制备的微结构进行了抗剪切能力测试,测试结果显示:随着滑焊放电次数的增加,微结构的极限剪切力由8.04N逐渐增加至65.97N。而后,通过能量分散光谱仪(EDS)对电极的沉积效应进行了研究。最后,在120mW的飞秒激光,50μm/s的切割速度,0.21V的焊接电压,0.2MPa的焊接压强,100ms的预压时间,10ms的焊接时间以及160次的滑焊放电次数等工艺参数下制备了基本尺寸为50μm×50μm的微方孔阵列以及微齿轮结构。实验结果表明:通过逐层微细电阻滑焊制备的微结构表面质量良好,各层微结构之间叠加较好,显示逐层微细电阻滑焊可以较好地保证三维微结构中各层二维微结构的连接强度和叠层精度。     

Fabrication of 3D metal micro-structure based on fs laser cutting and micro electric resistance slip welding

提出了一种采用飞秒激光切割结合微细电阻滑焊制备3D金属微结构的工艺方法(微型化双工位金属箔叠层制造法,(Micro-DLOM)),并通过制备具有复杂形状的3D微型腔模具验证了该工艺方法的可行性.首先,以厚度为10 μm的0Crl8Ni9不锈钢箔为基材,在110 mW的飞秒激光功率、100 μm/s的切割速度和0.75 μm的切割补偿量下获得二维微结构,并分析了激光功率和切割速度对切割精度的影响;然后,利用微细电阻滑焊对多层二维微结构进行热扩散焊接,通过多层二维微结构的叠加拟合形成具有曲面特征的微型腔,并对焊接区进行了X射线衍射( XRD)分析.分析发现:微细电阻滑焊所产生的热量仅使焊接区主要物相的相对含量发生了变化,而没有使该区域产生新的物相.与UV-LIGA工艺相比,本工艺可以加工具有自由曲面特征的三维微结构,并且单层钢箔越薄,成形精度越高;与飞秒激光分层平面扫描烧蚀工艺相比,本工艺仅需切割每层二维结构的轮廓,提高了成形效率;与微细电火花加工工艺相比,虽然所成形的微型腔表面粗糙度相对较差,但却省去了制备微电极的工艺步骤,并且不存在微电极工作过程中的损耗问题,所以可以加工深宽比不受限制的微模具.     

基于薄片叠层连接的金属零件三维成型技术探索研究

为了制备具有复杂内腔的零件,近年来出现了通过不同焊接方法进行薄片叠层连接的技术工艺,如:热扩散焊接、电阻焊等。该工艺主要是通过线切割等机加工工艺获得金属薄片,再通过电阻焊或真空热扩散焊接等不同的焊接工艺焊接在一起。研究中,利用激光加工0.1 mm厚度的不锈钢片,从而获得单层二维图形结构,然后通过激光扫描焊接和热扩散焊接的方式来焊接经过叠加和固定的薄层,进而直接制造金属零件。通过研究激光加工与真空热扩散焊接两种工艺对薄片叠层后零件的外型轮廓以及片层间距的影响,探索薄片叠层连接技术对于复杂内腔零件制造的可行性。实验结果表明,进行薄片叠层时,真空热扩散焊接比激光焊接的零件成型效果更好,片层间间隙基本消失,贴合更加紧密,内腔层片状现象基本消失。因此真空热扩散焊接更适合于薄片叠层制造具有复杂内腔和精度要求较高的零件。     

微结构与微型零件的微注射成形

设计并制作了微注射成形模具，采用光刻、离子蚀刻工艺相结合在硅片上制得了微零件型腔、流道及浇口。利用该模具在微型注射机上进行了聚丙烯微注射成形实验，注射成形了微结构零件及独立的微型零件，其中最小微结构部分是直径50μm的微圆柱，最小独立的微型零件是直径300μm、厚300μm的微圆片。分析了模具温度、注射压力及保压时间对微注射成形的影响，其中模具温度影响最大，注射压力、保压时间的影响次之。     

微注射成形制品质量影响因素分析

在不同工艺条件下进行聚合物和粉末微注射成形试验,制得微米级的聚丙烯和二氧化锆陶瓷微结构,微型腔采用感应耦合等离子深槽刻蚀技术在硅模具镶块上加工。分析微注射成形工艺及硅模具对微结构的填充、尺寸精度及表面质量的影响。不合理的工艺参数容易导致微结构出现填充不足、表面粗糙、气孔等缺陷,提高模具温度和注射压力以及注射前模具抽真空有利于微型腔的填充,模具抽真空还可以改善微结构件的表面质量。深槽刻蚀后的硅模具表面粗糙度为0.31 μm,填充完好的聚丙烯微结构及陶瓷微结构素坯表面粗糙度不再受注射工艺参数的影响,其值近似于刻蚀后的硅模具,亚微米级粉末的使用可以明显改善烧结后陶瓷微结构的表面粗糙度。     

微齿轮真空铸型的实验研究

利用自行设计制作的微齿轮硅胶模具,探讨了微齿轮真空铸型的可行性。采用正交实验方法进行实验,研究了微齿轮真空铸型过程中模具温度、树脂温度、真空脱泡时间和固化温度对微齿轮外形尺寸的影响作用。研究结果表明,利用硅胶模进行微齿轮真空铸型可批量获得精度较高的成形件,真空脱泡时间对微齿轮成形件的外形尺寸影响最大。     

石墨烯微结构的电喷射按需打印研究

采用电喷射按需打印工艺,以石墨烯悬浮液为打印材料,打印制备了石墨烯微结构,研究了高压脉冲电压幅值和脉冲频率参数对打印石墨烯微结构的影响。结果表明,过高或者过低的脉冲幅值都不利于打印的稳定性;脉冲频率则会直接影响到石墨烯微结构的尺度。最终,利用电喷射按需打印工艺,打印出线宽约为40μm的石墨烯微结构图案。     

UV-LIGA和微细电火花加工技术组合制作三维金属微结构的研究

研究了UV-LIGA和微细电火花加工技术组合制作三维金属微结构的工艺方法。首先通过UV-LIGA制作二维金属微结构,再对该微结构进行微细电火花加工得到三维金属微结构。该方法具有加工精度高、可实现自由曲面三维金属微结构制作的优点。制作出了局部为梯形凸台和锥形凹槽三维微结构的镍模具。分析了微细电火花加工中放电参数对表面粗糙度的影响,通过减小放电电压和电容的方法降低了表面粗糙度。     

UV-LIGA技术制作微型螺旋形加速度开关

微型加速度开关是用于空间飞行体中感受加速度并完成致动的重要惯性器件。本文采用UV-LIGA技术,结合SU-8厚胶工艺、微电铸工艺以及牺牲层技术,制作了微型螺旋形加速度开关。研究了牺牲层工艺、SU-8光刻技术以及螺旋形弹簧形变控制等微细加工的工艺细节;分析了多种牺牲层材料的特性,优选了与工艺相适应的Zn牺牲层体系,解决了微结构易脱落的工艺问题。通过优化微电铸工艺来减小金属膜层的内应力,优化牺牲层释放工艺来避免腐蚀过程对弹簧膜结构的冲击。实验结果表明,通过工艺优化可得到平整的微型螺旋形弹簧—质量块结构,螺旋弹簧厚度为20μm,质量块厚度达200μm,本文的工作可为大批量、低成本地研制微型加速度开关提供工艺基础。     

Laminated fabrication of 3D queue micro-electrode and its application in micro-EDM

3D micro-electrode used in micro electrical discharge machining (micro-EDM) is difficult to be fabricated. Based on laminated object manufacturing (LOM) process, this paper superimposed multilayer 2D micro-structures together to fit out 3D micro-electrode and applied it in micro-EDM to process 3D micro-cavity mold. Firstly, 100-μm-thick Cu foils were cut by wire-electrical discharge machining (WEDM) to obtain multilayer 2D micro-structures, and then these 2D micro-structures were connected together to fit out 3D micro-electrode through vacuum pressure thermal diffusion welding. Secondly, under the effect of 80-V voltage, 0.2-MHz pulse frequency, 800-ns pulse width, and 4200-ns pulse interval, the 3D micro-electrode was applied in micro-EDM and 3D micro-cavity mold with high surface quality was obtained. Thirdly, in order to reduce the adverse impact of electrode wear on machining precision of 3D micro-cavity mold, 3D queue micro-electrode was used to process the same 3D micro-cavity mold, in which the first electrode is for rough machining and the others for fine machining. Finally, based on the above studies, two kinds of 3D queue micro-electrodes were fabricated, and the 3D micro-cavity molds with surface roughness Ra?=?0.48 μm were obtained through micro-EDM. Compared with the scanning 3D micro-EDM process, the 3D micro-cavity mold can be obtained through up and down reciprocating method of the 3D queue micro-electrode, featuring simple machining process and high efficiency.     

Study on tungsten electrode deposition effect of 3D metal micro-mold during laminated slip welding

3D metal micro-mold fabricated through the micro double-staged laminated object manufacturing process is formed via stacking and fitting of multi-layer 2D micro structures. In this paper, it is suggested that micro-electric resistance slip welding technology be adopted to optimize the connection of micro structures in 3D metal micro-mold. Moreover, the deposition effect of tungsten electrode which was formed on the micro-mold surface and produced during micro-electric resistance slip welding is also studied. Firstly, the temperature field of electric resistance slip welding was simulated by ANSYS software and the maximum temperature in the slip welding area is 1,219 °C when the number of slip welding discharge is 160, which is far lower than the melting point of tungsten electrode material (3,410 °C). Hence, bulk tungsten will not shed during slip welding; however, the wear of the tungsten electrode will be deposited on the surface of the micro-mold in micro-particle shape. Secondly, the influence of slip welding discharge and surface roughness of tungsten electrode on tungsten deposition effect is studied and the study shows that: the content of tungsten within the slip welding area increases gradually as the number of slip welding discharge increases, and decreases gradually as surface roughness of tungsten electrodes increases. Finally, under 160 time’s slip welding discharge and using tungsten electrodes (0.5-mm diameter and 0.12-μm surface roughness), the 3D metal micro-molds which contains 0.4 % tungsten in slip welding area and has a good quality surface was obtained.     

恒温式微热板电阻真空传感器的研究

微热板(MHP)作为一种微结构广泛运用在各种微传感器中。本文通过对微热板的传热分析,从理论上分析了恒温模式下工作温度和结构尺寸对微热板电阻真空传感器工作特性的影响;设计了一种边长为93μm、四臂支撑的方形微热板结构的电阻真空传感器,支撑桥长65μm、宽21μm,微热板与衬底之间的气隙高度为0.5μm;采用表面微机械加工技术成功实现了该传感器的加工。测试结果显示,该微热板真空传感器气压测量范围约2Pa～105Pa,且响应特性与理论计算结果相符。     

Mg/Al合金爆炸焊连接及其界面接合机制

采用爆炸焊接技术制备以AZ31B镁合金为基板,以6061铝合金为覆板的AZ31B/6061合金的层状复合板。对复合板界面的宏观形貌、微观组织、界面元素扩散行为及界面接合性能进行测试、分析。结果表明:AZ31B/6061合金爆炸复合板接合界面呈波状接合;靠近接合界面处的塑性变形程度最大,以孪晶和再结晶形式为主;在AZ31B一侧靠近界面处出现与界面呈45°的绝热剪切带组织,带内为动态再结晶形成的细晶粒组织;接合界面两侧的显微硬度分布为:随着距离接合界面的增大,AZ31B和6061侧的显微硬度值递减趋势;复合板的拉-剪试验结果表明,界面接合强度达193.3 MPa;复合板界面接合机制为压力焊、扩散焊及局部熔化焊综合作用的结果。     

Comparative study of conventional and micro WEDM based on machining of meso/micro Sized Spur Gear

This paper discusses the comparison of micro machining process using conventional and micro wire electrical discharge machining (WEDM) for fabrication of miniaturized components. Seventeen toothed miniaturized spur gear of 3.5 and 1.2 mm outside diameter were fabricated by conventional and micro WEDM respectively. The process parameters for both conventional and micro WEDM were optimized by preliminary experiments and analysis. The gears were investigated for the quality of surface finish and dimensional accuracy which were used as the criteria for the process evaluation. An average surface roughness (R_a) of 50 nm and dimensional accuracy of 0.1–1 μm were achieved in micro WEDM. Whenever applied conventional WEDM for meso/micro fabrication, a R_a surface roughness of 1.8 μm and dimensional accuracy of 2–3 μm were achieved. However, this level of surface roughness and dimensional accuracy are acceptable in many applications of micro engineering. A window of conventional WEDM consisting of low energy discharge parameters is identified for micromachining.     

Tool fabrication system for micro/nano milling—function analysis and design of a six-axis Wire EDM machine

The dies or molds used for the fabrication of micro products usually are made of ultra-hard materials such as tungsten carbide or silicon carbide and have sophisticated three-dimensional geometries. Such kind of dies or molds can only be fabricated by milling operations instead of grinding processes with ultra-hard milling tools made of PCD or CBN. Electrical discharge machining (EDM) is a good choice for the fabrication of such ultra-hard tools. In this paper, a function analysis and design of a six-axis Wire EDM (WEDM) machine is introduced. Based on the typical micro/nano cutting tool geometry features, a mathematical model between the cutting tool and the electrode wire is built. Then, the mathematical model is analyzed and it turns out that six axes are needed for cutting such complicated tool geometries. According to the WEDM features, first the axes are allocated to the workpiece side and the electrode wire side. The workpiece is assigned three linear motions and one rotary motion around its center line and the wire has two rotary motions. Second, the axis sequences are defined. At last, the best concept of the mechanical structure for the six-axis WEDM machine is selected.     

Fabrication of 3D metal micro-mold based on femtosecond laser cutting and micro-electric resistance slip welding

This paper proposes a novel fabrication process based on femtosecond laser cutting and micro-electric resistance slip welding to address the bottleneck presented by ultraviolet–Lithographie, Galvanoformung, Abformung combined with micro-electroforming, in which micro-molds are usually fabricated with vertical wall structures. At first, 10-μm thick 0Cr18Ni9 stainless steel foils were cut by femtosecond laser to obtain several single-layer graphics which were then joined by micro-electric resistance slip welding. The slip welding process formed a 3D micro-structure and the weld zone of micro-structure was tested by the X-ray diffraction (XRD). The XRD results show that the phases of weld zone remain unchanged, but that the phase content slightly changes. Finally, a 3D metal micro-structure mold was processed under 110 mW femtosecond laser power, 0.1 mm/s cutting speed, 0.21 V welding voltage, 10 ms welding time, 0.2 MPa welding pressure, 0.5 mm bar electrode diameter, 160 time’s slip welding discharge, which proves that the forming process could be a useful method for the production of 3D micro-molds.     

STUDY ON JOINING PROCESS FOR LAMINATED OBJECT MANUFACTURING USING METALAS MODELING MATERIALS

In order to solve some key problems associated with the rapid manufacturing of metallic functional part, a new technique using vacuum solid-state pressure diffusion welding process to join the metallic slice sheets is put forward. The following results can be drawn from the experiments: only 1% shrinkage happened in the stack direction and it came from the regular system error. The atoms diffuse between joint interfaces clearly and new grains formed meanwhile. The average shear strength of welding zone is more than 100 MPa and micro hardness of welding zone is almost the same as that of matrix. It is shown from above results that the vacuum solid-state pressure diffusion welding process is an available technique to join metal slice sheets for the rapid manufacturing of metallic functional parts.     

A method for the fabrication of thin-foil apertures for electron microscopy

A method is described for making thin foil apertures by piercing a plastic film with a heated microneedle and subsequently metallizing the plastic film by vacuum evaporation. Apertures can be made with diameters from 5 μm to 100 μm. They are round and very sharp-edged and can be made in various patterns and combinations of sizes.