3DP法三维打印金属多孔结构基本打印单元的研究

介绍了3DP法三维打印多孔结构的打印方式,开展了3DP法三维打印试验,研究供胶压力、喷头驱动电压、点胶时间、喷头温度四项喷胶参数对单道喷胶线条的影响,确定3DP法能够成形的多孔结构的单元最小极限尺寸。结果表明,在保证喷胶线条质量及线宽尽可能小的情况下,喷胶参数的合理选取范围为供胶压力18～22 kPa、喷胶驱动电压42～48 V、点胶时间1. 0～1. 6 ms、喷头温度25℃～35℃,相应得到的单道喷胶线宽约为0. 5～1. 0 mm。能够成形的多孔结构最小骨架尺寸约1. 95mm,最小孔隙尺寸约0. 75 mm。     

多元多型结构三维打印机的设计

着眼于三维打印与加工中心的相似点,将三维打印喷头、加热块、送丝机构等作为三维打印喷头模块,与加工中心的刀具进行类比,设计了多元多型结构三维打印机。通过三维打印喷头模块的自由切换,避免了人工更换喷头所引起的高度调节误差,以及多喷头蹭料等问题,可以完成除支撑材料外的多种材料交替打印,使三维打印更智能化与实用化。     

三维打印机中XJ-128喷头驱动控制设计

简要介绍了所设计的打印机控制系统。重点研究了选用的Xaar128压电式喷头及其驱动信号时序关系,阐述了驱动信号实现模块图及具体流程。在此基础上利用LPM例化的双FIFO实现喷头数据暂存和位宽处理,并阐述了在三维打印中利用电机编码器位置脉冲来直接触发喷头喷射的优点。     

基于挤出沉积技术的多喷头3D打印机研制

针对组织工程中多材质和梯度化生物制品的三维打印问题,对喷头温控功能、沉积工作台制冷功能、喷头切换方式、控制系统等方面进行了研究,提出了一种基于挤出沉积技术的多喷头生物3D打印机。使用半导体制冷片和聚酰亚胺加热膜对喷头进行了温控设计,设计了双向滚珠丝杆切换装置和外循环超低温沉积工作台结构,最后利用羧甲基纤维素钠水凝胶材料在研制完成的多喷头生物3D打印机上进行了多喷头打印测试。测试结果表明:多喷头生物3D打印机实现了多材料和梯度化复杂模型的多喷头三维打印,同时打印精度满足生物组织工程的需求,为实现高仿生三维结构的打印奠定了良好基础。     

喷蜡粉器

过去,我厂精铸车间所用的蜡料,是事先将回收处理的蜡锭,用凿子铲成碎块,供搅拌蜡膏用。这种方法,不但劳动强度大,而且效率低。后经我们班同志的反复试验和实践,终于试验成一台风压喷蜡粉器。目前操作,只须将回收处理过的液态热蜡倒入缸内,通人压缩空气,就直接喷出形状象洗衣粉的蜡粉。该喷粉器结构简单,制造方便,每小时可自动喷蜡粉50公斤,提高效率三倍,保证了蜡膏的质量。一、工作原理喷蜡粉器结构如图所示。喷嘴2是用农药喷雾器上的喷头。输蜡管5与     

喷蜡粉器

过去,我厂精铸车间所用的蜡料,是事先将回收处理的蜡锭,用凿子铲成碎块,供搅拌蜡膏用。这种方法,不但劳动强度大,而且效率低。后经我们班同志的反复试验和实践,终于试验成一台风压喷蜡粉器。目前操作,只须将回收处理过的液态热蜡倒入缸内,通入压缩空气,就直接喷出形状象洗衣粉的蜡粉。该喷粉器结构简单,制造方便,每小时可自动喷蜡粉50公斤,提高效率三倍,保证了蜡膏的质量。一、工作原理喷蜡粉器结构如图所示。喷嘴2是用农药喷雾器上的喷头。输蜡管5与     

基于MAM和PAM的多喷头3D打印系统

针对生物组织工程中多组分生物模型的三维打印问题,对电机挤出沉积式喷头、气动式微滴喷射式喷头、多材质模型路径规划及多喷头协调控制等方面进行了研究,提出了基于MAM和PAM的多喷头3D打印系统及多喷头协调控制方法,优化了PAM打印系统以提高系统打印精度,并改进了路径规划方法从而满足了多材质模型打印;最后利用多材质模型的打印实验对该系统的可行性进行了测试。研究结果表明:多喷头3D打印系统实现了多喷头之间的协调控制,实现了多材质复杂模型的打印;同时MAM和PAM喷头打印精度均满足了生物组织工程的需求,为实现高仿生结构的打印奠定了良好的基础。     

FDM工艺的螺纹式双喷头创新设计

介绍了FDM工艺的3D打印双喷头工作原理。双喷头是FDM工艺的工业级3D打印装备的核心部件,重点分析了现有双喷头的关键部件存在的主要问题:送丝机构和切换机构。在此基础上,首次提出了螺纹式送丝机构,螺纹和丝料接触均匀,不会损伤丝料,降低了对驱动电机的要求,以较小驱动力实现丝料稳定挤出;同时创新性的设计了纯机械式、免驱动的高精度切换机构方案,减少了双喷头的重量和体积。在实际的生产应用中取得了较好的效果,证明了创新设计方案是可行的,为FDM工艺的双喷头设计提供了参考,具有较高的工程应用价值。     

FDM型三轴并联桌面3D打印机研究

FDM型3D打印技术是对STL格式数据模型进行切片,把可黏合的塑料耗材进行叠层堆积来打印实体模型的。FDM型三轴并联桌面3D打印机的控制器是单片机,采用步进电动机驱动同步带运行,打印喷头的轨迹行进是用滑块进行控制的,挤出机也是采用步进电动机进行驱动,辅助喷头进行打印。喷头在X、Y、Z三个坐标轴上的运动速度大于185mm/s;喷头响应速度不小于0.1 m/s,喷头加热温度可控制在190~380℃,实现数字温控。     

FDM三维成型样品缺陷的工艺分析与研究

基于熔融沉积成型的技术原理,利用桌面式三维打印机,研究了喷头温度、分层层厚、打印速度和成型方向对样品质量的影响,分析了翘曲、鼓泡、拉丝等打印缺陷产生的工艺原因,并进一步通过优化参数设置,改进了样品的成型精度和质量。以此在低成本制造的基础上充分发挥三维成型的优势,为促进桌面级3D打印技术的推广应用提供支持。     

Bubble growth and ink ejection process of a thermal ink jet printhead

The present study investigated bubble growth and the ink ejection process of a thermal ink jet (TIJ) printhead with a thin-film heater on the bottom-wall of the ink nozzle. Numerical predictions are presented for bubble volume, temperature, and pressure, and ink jet ejection length under various heating conditions. An inexpensive optical system was set up to visualize the transient ink ejection process. Experimental results to show the effect of the heating pulse conditions on the ejected droplet volume and ejected ink length are also presented. The experimental and numerical results agree well on both the ejected ink length for shorter time history (< 6 μs) and the threshold operating voltage for the ink ejection.     

Fatigue test of MEMS device : a monolithic inkjet print

A testing system was developed to improve the reliability of printhead and several printheads were tested. We developed a thermally driven monolithic inkjet printhead comprising dome-shaped ink chambers, thin film nozzle guides, and omega-shaped heaters integrated on the top surface of each chamber. To perform a fatigue test of an inkjet printhead, the testing system automatically detects a heating failure using a Wheatstone bridge circuit. Various models were designed and tested to develop a more reliable printhead. Two design parameters of the width of reinforcing layer and heater were investigated in the test. Specially, the reinforcing layer was introduced to improve the fatigue life of printhead. The life-span of heater with a reinforcing layer was longer than that without a reinforcing layer. The wider the heater was, the longer the life of printhead was.     

Jetting stability of molten caprolactam in an additive inkjet manufacturing process

This paper proposes a novel additive manufacturing concept which uses inkjet technology to manufacture parts in nylon 6. The methodology involved a series of experiments to investigate whether caprolactam, the monomer of nylon 6, could be jetted in the molten state. Once this was established, further experiments were undertaken to determine the possible boundaries for the process parameters. The main parameters were the vacuum level at which the melt could be controlled for stable jetting, the jetting voltage amplitude and frequency which were investigated against the jet array stability by monitoring the printhead’s nozzle plate. The jet(s) instability behaviour were characterised in different sets of experiments in order to optimise the jetting conditions for the molten caprolactam. The jetting voltage and vacuum level were found to have a significant effect whereas the jetting frequency did not. Instabilities occurred in the form of individual deviating jet trajectory and also jet array failures. These were found to be initiated by air motion when using inappropriate jetting voltage resulting in incorrect jet trajectory. A combination of incorrect jetting voltage and vacuum level led to air bubble entrapment during jetting and, therefore, rapid failure of the jets. Analysis of jet array instability led to a stable process window for further stages of the research on the additive inkjet manufacturing process development.     

压电膜片式微喷的多场耦合仿真模型及其应用

基于自行设计制造的压电驱动膜片式微喷装置的实际结构,建立了一个多场耦合的数值模型,用来研究压电驱动的膜片式微滴喷射过程中的参数作用和变化规律。在模型的建立过程中,对流体部分的湍流判定和表面力作用的关键技术问题进行了分析研究。该模型能较好地模拟微喷装置工作过程。利用该模型研究了驱动波形对液滴属性的决定关系,以及液体腔中一个工作周期内压力的变化规律等问题。     

Experimental study on synthetic jet array for aerodynamic drag reduction of a simplified car

This paper describes an experimental parametric study of synthetic jet array actuation to reduce the aerodynamic drag of a threedimensional simplified car. By using two configurations of an Ahmed body with 25° and 35° slant angles, we performed wind tunnel tests under different conditions of synthetic jet array. Several parameters, namely, jet location, jet direction, jet momentum coefficient, jet driving frequency, and number and position of activated jets within the actuator array, were considered. The total aerodynamic drag coefficients were compared, and the rear wake flows were studied by using the data obtained from rear surface pressure distribution and flow visualization tests. Results of the parametric study show that the aerodynamic drag exhibits different behavior depending on the location of the jet for each slanted model. Jet direction, jet momentum coefficient, and jet driving frequency affect only the amount of change in the aerodynamic drag. The distribution of the activated jets also affects jet efficiency.     

Pressure response and droplet ejection of a piezoelectric inkjet printhead

The present study aims to investigate the pressure rise in the ink flow channel and the ink droplet formation process of a piezoelectric printhead after an electrical pulse is applied to the printhead. The ink flow channel is modeled as a straight circular pipe followed by a convergent nozzle. Both numerical analysis and experimental observations are performed in this study. In the numerical analysis, a characteristic method is used to solve the one-dimensional wave equation to obtain the transient pressure and velocity variations in the flow channel of the printhead. In this analysis, the channel is assumed to have a non-uniform cross section. In addition, a flow visualization system was set up to observe the ink droplet injection process. After the piezoelectric material is driven by the input electric pulse, the ink droplet images are immediately captured by a charge-couple device (CCD) camera converted to a digital image via a frame grabber, and stored in a computer. The results obtained from the experimental observations are also compared with the numerical prediction. The effects of electric pulse shape and voltage on the ink injection length and the ejected droplet weight are also presented.     

基于超磁致伸缩致动器的脉冲喷射开关阀建模与仿真

利用超磁致伸缩致动器(Giant magnetostrictive actuator, GMA)应变率大、响应频率高的优点和脉冲喷射装置的结构特点设计了基于GMA的脉冲喷射开关阀,分别分析GMA和脉冲喷射开关阀本体在动态工作条件下的系统传递函数,综合分析后建立阀的流量、喷射速度与驱动电流之间的系统方框图和传递函数。Simulink的开关阀动态仿真结果显示,基于GMA的脉冲喷射开关阀的工作频带宽度大于400 Hz,可满足大部分喷射装置的工作要求。GMA位移扫频试验结果表明,该模型在低频范围内可正确反映开关阀的动态特性,高频范围内需考虑温度和磁滞的影响。     

气液活塞式脉冲液体射流泵装置性能的理论研究

运用流体动力学理论,导出气液活塞式脉冲液体射流泵装置性能方程,分析了反吸与压力两个不同工作过程中的主要因素对装置性能方程的影响,并与恒定流液体射流泵装置性能方程对比,阐明了二者之间的关系。     

压电薄膜喷流泵研究

将压电流体驱动技术和仿生技术、喷流推进技术结合,提出了一种新型的压电喷水推进装置,并对该装置的核心部件—压电喷流泵进行了研究。详细分析和介绍了泵的结构及工作原理,设计制作了实验用样机,并进行了性能测试。实验测试表明,该泵工作性能稳定,喷流量大,在正弦信号激励下,电压为190 V,工作频率为140 Hz时,最大喷流量可达到714 ml/min。     

无针注射器数值模拟和工作特性分析

采用CFD Fluent软件对无针注射器的工作全过程进行数值模拟,得到了注射管内药液驱动压强和药液射流速度的变化规律。模拟了药液射流在空气中的演化过程,以及射流穿透皮肤,在皮肤层和皮下组织层扩散的全过程。数值结果与实验定性结果一致。