基于塑料微挤出成型的熔融沉积成型技术表面粗糙度研究进展

熔融沉积成型技术(FDM)是一种无模成型技术,易实现复杂模型的个性化定制,使得它在航空、汽车、医疗行业具有广泛、潜在的应用。同时FDM打印也是一种逐层打印技术,但制件表面粗糙,限制了它的应用。文中回顾了近10年来,尤其是近3年来在改进FDM表面粗糙度方面的研究现状和进展,并从制件后处理、软件控制、数学模型预测、优化工艺参数及结合其它成型技术等多方面论述了国内外关于FDM打印件表面粗糙度的改进方法及研究进展。     

CATIA曲面造型技术在小型无人机设计中的应用

探讨了利用CATIA软件完善的曲面造型功能,进行小型无人机产品设计的问题.建立了全机高品质的理论外形数字曲面,实现了重要结构件的三维参数化实体建模(如机身头锥、翼面和整流罩等),以及模具的快速设计.还介绍了将CATIA软件的一些特殊功能应用于无人机外形设计的问题,例如翼身整流罩的自动生成等.结果表明CATIA软件的应用为小型无人机结构设计和模具制造提供了良好的三维设计手段,缩短了研发周期,节省了研制成本.     

基于数控加工的熔融沉积成型精度控制

目的 为了提高零件熔融成型精度,提高零件的加工质量.方法 提出基于数控加工的熔融沉积成型精度控制方法,根据零件图纸利用计算机实现加工代码的自动编制,通过熔融沉积成型精度自学习,准确生成熔融沉积成型微调值,进而实现熔融沉积成型精度控制.结果 在相同的测试时间内,设计控制方法的控制偏度系数比对照组的低.结论 设计的控制方法...     

基于熔融沉积法的快速成形柔性丝材技术研究

目的研究柔性材料的熔融沉积(Fused Deposition Modeling,FDM)快速成形工艺。方法通过理论推导和实验研究的方法,针对柔性材料的FDM技术做了初步的探讨。结果柔性材料FDM工艺,相对于硬质材料来说,其进丝量需要更加精准的控制,进丝齿轮旋转角速度和打印速度、打印层厚呈正比关系,其比例系数取决于喷嘴直径、齿轮外径以及所使用丝材直径;同时,打印温度、打印层厚,尤其是首层打印间隙等工艺参数对于柔性打印制件的表观质量有更加重要的影响,这主要是因为熔融态柔性材料粘性较大所导致。结论现有硬质材料的FDM机器,需要作出适当的调整,才能更好地适应柔性材料打印。     

基于动态运动基元的微小型四旋翼无人机路径规划

针对微小型四旋翼无人机的路径规划问题,引入运动学习框架,提出了一种基于动态运动基元的路径规划方法。该方法通过对给定运动样本的学习提取出运动基元,并将学习结果推广到新的飞行目标,从而泛化出相应的运动轨迹。有障碍物的情况下,在已有学习基础上通过设计耦合因子规划出避障路径,然后将规划的轨迹点集提供给微小型四旋翼无人机完成路径跟踪飞行任务。该路径规划方法的可行性通过微小型四旋翼无人机不同目标点的飞行任务仿真得到了验证。仿真实验还验证了该方法在三维空间进行有效避障的性能。     

Investigating the shape memory properties of 4D printed polylactic acid (PLA) and the concept of 4D printing onto nylon fabrics for the creation of smart textiles

3D printing is an ever growing industry that provides many benefits to the advanced manufacturing and design industry. However, parts tend to be static, rigid, and lack multi-purpose use. Recently, a new technology has emerged that uses 3D printing to print parts with the ability to change shape over time when exposed to different external stimuli. This new technology has been called 4D printing. Creation of a new material that is capable of changing shape when exposed to different stimuli and possess the ability to be 3D printed can be a difficult and a long process. Due to this strenuous process, the potential of a common fused deposition modelling material, poly(lactic) acid (PLA), for use in 4D printing is investigated and the concept of combining PLA with nylon fabric for the creation of smart textiles is explored. PLA possesses thermal shape memory behaviour and maintains these abilities when combined with nylon fabric that can be thermomechanically trained into temporary shapes and return to their permanent shapes when heated.     

The influence of slicing parameters on the multi-material adhesion mechanisms of FDM printed parts: an exploratory study

ABSTRACT

The potentiality of the Fused Deposition Modeling (FDM) process for multi-material printing has not yet been thoroughly explored in the literature. That is a limitation considering the wide diffusion of dual extruders printers and the possibility of increasing the number of these extruders. An exploratory study, based on tensile tests and performed on double-material butt-joined bars, was thus conceived; the aim was to explore how the adhesion strength between 3 pairs of filaments (TPU-PLA, PLA-CPE, CPE-TPU) is influenced by the material printing order, the type of slicing pattern used for the layers at the interface, and the infill density of the layers below the interface. Results confirm the effectiveness of mechanical interlocking strategies in increasing the adhesion strength even when thermodynamic and diffusion mechanisms of adhesion are not robust enough. Besides, thermal aspects also demonstrated to play a relevant role in influencing the performance of the interface.     

化学气相沉积聚合制备聚溴代对亚苯基二亚甲基及其性能的研究

用化学气相沉积(CVD)聚合法制备了聚溴代对亚苯基二亚甲基(PPX-B r)膜,采用FT-IR和元素分析的方法证实了其化学结构。对膜溶解性和抗化学氧化性能的研究表明,聚溴代对亚苯基二亚甲基膜具有优异的耐溶剂性和抗化学氧化性能。对其热性能的研究表明,溴的引入使得膜的玻璃化转变温度降低,室温柔性增强,热降解性能与聚氯代对亚苯基二亚甲基(PPX-C)相似。与PPX膜相比,溴的引入对膜的亲水性能影响不大,而水汽渗透率明显降低,具有更好的防潮性。     

聚对苯(撑)二甲基膜的化学气相沉积(CVD)聚合

采用化学气相沉积(CVD)聚合工艺制备的对苯撑二甲基聚合物可广泛应用在航天、航空、军工、电子、生物医学工程、控制系统、文物保护、纳米材料和磁性材料等诸多领域.综述了聚对苯(撑)二甲基系列膜的化学气相沉积聚合工艺和原理,介绍了底物温度和沉积舱压力等主要因素对膜沉积率的影响和膜的一些主要性能,并讨论了典型的Parylene N膜的光氧降解性能.     

Si(111) 衬底上3C-SiC的超低压低温外延生长

研究了发展一种Si衬底上低温外延生长3C－SiC的方法。采用LPCVD生长系统,以SiH4和C2H4为气源,在超低压（30Pa) ,低温（900℃）的条件下,在Si(111衬底上外延生长出高质量的3C－SiC薄膜材料。采用俄歇能谱（AES）,X射线衍射（XRD）和原子力显微镜（AFM）等分析手段研究了SiC薄膜的外延层组分,晶体结构及其表面形貌。AES结果表明薄膜中的Si/C的原子比例符合SiC的理想化学计量比,XRD结果显示了3C－SiC外延薄膜的良好晶体结构,AFM揭示了3C－SiC薄膜的良好的表面形貌。     

a-C:H(N)薄膜的制备及性能

采用射频－直流等离子化学气相沉积法用Ｃ２Ｈ２、Ｎ２和Ａｒ组成的混合气体制备ａ－Ｃ：Ｈ（Ｎ）薄膜,研究了薄膜的制备工艺、结构及直流导电特性。实验结果表明,ａ－Ｃ：：Ｈ（Ｎ）薄膜的沉积速率随混合气体中Ｃ２Ｈ２含量的增加而增大,当混合气体中Ｎ２含量增加到７５％时,薄膜的含氮量增大到９．０９％。薄膜中Ｃ、Ｎ原子以Ｃ≡Ｎ和Ｃ－Ｎ键的形式存在,结合进薄膜中的氮大大降低薄膜的直流电阻率。     

Using Structural Equation Modeling (SEM) for the Study of Impurity Profiles of Drug Substances

The impurity profile is one of the most important quality characteristics of a drug substance. Although it is always desirable to determine the chemical structure of all impurities forming the impurity profile, unfortunately this is not always economically and technically feasible because of the extremely low concentrations at which some impurities may be found in the drug substance. Therefore, alternative approaches to the chemical analysis are needed for trying to determine the origin of the unidentified impurities.

In a previous study conducted by our group, based on exploratory (principal component and hierarchical cluster) analysis, we were able to suggest a hypothesis for explaining the origin of the unidentified impurities of a drug substance. However, there was still a concern that alternative hypotheses might explain the same phenomenon equally well. This article explores the application of recent developments in structural equation modeling for the systematic generation and selection of hypotheses (models) worthy of being confirmed by chemical research.     

Initiated Chemical Vapor Deposition: A Versatile Tool for Various Device Applications

Advances in device technology have been accompanied by the development of new types of materials and device fabrication methods. Considering device design, initiated chemical vapor deposition (iCVD) inspires innovation as a platform technology that extends the application range of a material or device. iCVD serves as a versatile tool for surface modification using functional thin film. The building of polymeric thin films from vapor phase monomers is highly desirable for the surface modification of thermally sensitive substrates. The precise control of thin film thicknesses can be achieved using iCVD, creating a conformal coating on nano‐, and micro‐structured substrates such as membranes and microfluidics. iCVD allows for the deposition of polymer thin films of high chemical functionality, and thus, substrate surfaces can be functionalized directly from the iCVD polymer film or can selectively gain functionality through chemical reactions between functional groups on the substrate and other reactive molecules. These beneficial aspects of iCVD can spur breakthroughs in device fabrication based on the deposition of robust and functional polymer thin films. This review describes significant implications of and recent progress made in iCVD‐based technologies in three fields: electronic devices, surface engineering, and biomedical applications.

     

Combinatorial initiated chemical vapor deposition (iCVD) for polymer thin film discovery

Initiated chemical vapor deposition (iCVD) is a technique used to synthesize polymer thin films and coatings from the vapor phase in situ on solid substrates via free-radical mechanisms. It is a solventless, low-temperature process capable of forming very thin conformal layers on complex architectures. By implementing a combinatorial approach that examines five initiation temperatures simultaneously, we have realized at least a five-fold increase in efficiency. The combinatorial films were compared to a series of blanket films deposited over the same conditions to ensure the combinatorial system provided the same information. Direct synthesis from the vapor phase allows for in situ control of film morphology, molecular weight and crosslinking, and the combinatorial system decreases the time required to find the relationship between these interrelated properties. Some coatings were tested for antimicrobial performance against E. coli and B. subtilis.     

脉冲激光沉积法在Si(111)衬底上生长高c轴取向LiNbO3薄膜

在氧压20Pa,衬底温度600℃,靶材与衬底距离4cm的最优化条件下,利用脉冲激光沉积(PLD)技术首次在无诱导电压和任何缓冲层的情况下,在单晶Si(111)衬底上生长具有优良结晶品质和高c轴取向的LiNbO3晶体薄膜.利用X射线衍射(XRD)、扫描电子显微镜(SEM)和原子力显微镜(AFM)对LiNbO3薄膜的结晶品质,择优取向性以及表面形貌进行了系统的分析.结果表明生长出了具有优异晶体质量的c轴取向LiNbO3薄膜,表面光滑平整且无裂纹产生,表面粗糙度约4.8nm,有利于硅基光电子器件的制备和利用.     

A methodology for design and reconfiguration of reconfigurable bending press machines (RBPMs)

Customer requirements have become very dynamic and unprecedented. A manufacturing paradigm called reconfigurable manufacturing system was initiated to adjust the physical machine entities. The main enabler of a machine structure’s reconfigurability is a modular design approach. The paper explains a function-driven object-oriented methodology for the design and reconfiguration of RBPMs. The complete method aims to optimise initial design of RBPMs, followed by subsequent design of RPBM modules which are stored in a module library so as to enable full-automatic reconfiguration of the RBPMs. The methodology is implemented on a pilot project to design a 145 ton bending capacity RBPM, with a maximum reconfigured length of 5?m and total height of 3?m. In order to deduce the design for the reconfigurable bending press machine, the reconfigurability needs were identified first, followed by the construction of a function tree for the machine. The function tree identifies the primary function for the RBPM, which is to bend sheet metal. The primary function is further decomposed to lower level functions until terminal functions are arrived at. The terminal functions are then used to identify the modules for the machine. The modules implement specific brunches of the machine functions.