Extrusion Freeforming of Millimeter-Wave Electromagnetic Bandgap (EBG) Photonic Crystals

Extrusion freeforming can be used for the rapid prototyping of millimeter-wave electromagnetic bandgap (EBG) structures. In this work, an alumina-polymer paste with a relatively high volatility solvent (propanol) was used and the characteristics of the ceramic paste, particularly the rheological features are described. The advantage of high volatility solvent is that the viscosity and elastic modulus of the paste are increased sharply as the solvent evaporates. Thus, the rigidity of the extruded filament is quickly increased as a small amount of solvent evaporates. Finally, by employing this procedure, different EBG structures such as 2-D, 3-D woodpile and aperiodic structures were fabricated and their bandgaps were measured. The experimental results show that extrusion freeforming is a relatively simple and easy method to fabricate these woodpile structures with a bandgap in the 90-110 GHz region.

Generation and Suppression of Pendant Droplet Oscillation in Electron Beam Directed Energy Deposition

Electron beam–directed energy deposition(EB–DED)has emerged as a promising wire-based metal additive manufacturing technique.However,the effects of EBs on pendant droplets at wire tips have not yet been determined.The aim of this study is to enhance the understanding of this action by analyzing the mechanism of droplet oscillation.The pendant droplet oscillation phenomenon hinders the stable transfer of droplets to the molten pool and limits the feasibility of manufacturing complex lattice structures by EB–DED.Hence,another aim of this study is to create an oscillation suppression method.An escalating asymmetric amplitude is the main characteristic of droplet oscillation.The primary oscillationinducing force is the recoil force generated from the EB-acted local surface of the droplet.The physical mechanism of this force is the rapid increase and uneven distribution of the local surface temperature caused by the partial action of the EB.The prerequisites for droplet oscillation include vacuum conditions,high power densities,and bypass wire feeding processes.The proposed EB–dynamic surrounding melting(DSM)method can be applied to conveniently and effectively suppress oscillations,enable the accurate transfer of droplets to the molten pool,and achieve stable processes for preparing the strut elements of lattice structures.Lowering the temperature and improving the uniformity of its distribution are the mechanisms of oscillation suppression in EB–DSM.In this study,the physical basis for interpreting the mechanism by which EBs act on droplets and the technical basis for using EB–DED to prepare complex lattice structure parts are provided.

Surface form inspection with contact coordinate measurement:a review

Parts with high-quality freeform surfaces have been widely used in industries,which require strict quality control during the manufacturing process.Among all the industrial inspection methods,contact measurement with coordinate measuring machines or computer numerical control machine tool is a fundamental technique due to its high accuracy,robustness,and universality.In this paper,the existing research in the contact measurement field is systematically reviewed.First,different configurations of the measuring machines are introduced in detail,which may have influence on the corresponding sampling and inspection path generation criteria.Then,the entire inspection pipeline is divided into two stages,namely the pre-inspection and post-inspection stages.The typical methods of each sub-stage are systematically overviewed and classified,including sampling,accessibility analysis,inspection path generation,probe tip radius compensation,surface reconstruction,and uncertainty analysis.Apart from those classical research,the applications of the emerging deep learning technique in some specific tasks of measurement are introduced.Furthermore,some potential and promising trends are provided for future investigation.

3D bioprinting of complex biological structures with tunable elastic modulus and porosity using freeform reversible embedding of suspended hydrogels

Three-dimensional(3D)bioprinting has been used widely for the construction of hard tissues such as bone and cartilage.However,constructing soft tissues with complex structures remains a challenge.In this study,complex structures characterized by both tunable elastic modulus and porosity were printed using freeform reversible embedding of suspended hydrogels(FRESHs)printing methods.A mixture of alginate and gelatin was used as the main functional component of the bioink.Rheological analysis showed that this bioink possesses shear thinning and shear recovery properties,supporting both cryogenic and FRESH printing methods.Potential printing capabilities and limitations of cryogenic and FRESH printing were then analyzed by printability tests.A series of complex structures were printed by FRESH printing methods which could not be realized using conventional approaches.Mechanical tests and scanning electron microscopy analysis showed that the printed structure is of excellent flexibility and could be applied in various conditions by adjusting its mechanical modulus and porosity.L929 fibroblast cells maintained cell viability in cell-laden-printed structures,and the addition of collagen further improved the hydrogels’biocompatibility.Overall,all results provided useful insight into the building of human soft tissue organ blocks.

应用CAD/CAM与快速成形技术重建颌面器官

目前,国内医院对治疗半侧颌面萎缩类疾病中的耳、眼缺失仍然采用技师手工翻制蜡模的方法。本文从医工结合的角度,采用患者CT数据或激光扫描数据,将CAD/CAM技术与快速成形技术(Rapid prototyping,RP)结合用于患者半侧耳及眼缺失治疗,可通过RP模型直接生成硅橡胶赝复体。临床结果表明该方法成功地提高了赝复体的外形精度,并可使之与病人的缺损面周围组织完美衔接,对医工结合领域的发展具有重要的意义。

虚拟油泥技术FreeForm在产品曲面造型设计中的应用

归纳了产品曲面造型、工艺品的曲面造型、角色动漫的曲面造型及其其他特殊的产品曲面造型设计,将其划分为有规律的曲面造型和无规律的曲面造型、具象的形态造型和抽象的形态造型、规整式(折线型、直线圆弧型)的曲面造型和不规整式的曲面造型。结合了实例,详述了其建模方式,对于提升设计速度、丰富表达效果(曲面造型)、优化设计流程具有快速和方便的应用价值。最后,通过了其在各个领域的应用及其详细的作图步骤,得出了该技术有利于产品的概念设计、灵活多变的设计流程,有利于快速、高效的进行批量化生产。同时,也有利于发挥设计的设计智慧、兼顾经济和社会效益,其造型易于满足消费者对于新颖和夸张的需求,并有利于明确的市场需求、良好的商品造型化及其产业化前景。

基于FreeForm的青瓷原型快速成型研究

通过研究与分析传统工业设计产品开发过程,运用基于FreeForm的快速成型技术,实现快速设计与制造开发模式。通过对龙泉青瓷的快速建模,实现青瓷快速设计、快速成型和快速制造,改变传统青瓷复杂设计与制作工艺,结合3D打印技术,提高青瓷产业制造效率,促进丽水地方的特色产业的快速发展。

工业造型设计中的建模技术研究

分析了建模技术的发展变化,详细分析了目前常用的各种通用建模技术的优缺点,指出在其建模过程中只涉及视觉和听觉信息是不完整的,真正高效的建模系统还应包含触觉信息的交互与反馈。在此基础上,基于力反馈技术介绍了自由雕塑建模系统,分析了自由雕塑的体系结构,介绍了它的实现形式——FreeForm系统,并通过实例分析了它在工业造型设计中的优越性。

FreeForm虚拟造型系统在家具设计复杂曲面的应用研究

研究了一种以Free Form虚拟造型设计系统为中心接口,结合3D打印等技术的家具复杂曲面设计与实现的方法。首先,对Free Form自由造型系统及设计平台的原理进行了分析。在此基础上,提出了基于Free Form虚拟造型系统为中心接口的复杂曲面设计与实现的思想。然后,对欧式家具复杂曲面设计与实现的案例进行展示与研究。最后,通过对比传统方法,总结出此方法具有设计快速、数据转换方便、人机交互性优等六大优势。

FreeForm在虚拟产品设计中的应用研究

在虚拟产品设计中，自由曲面的建模应用广泛，且建模过程困难。FreeForm是基于力反馈技术的建模系统，文中介绍了该系统的架构和核心技术，提出了基于FreeFortn的建模方法。通过实例建模，验证了基于FreeFoma的虚拟产品设计可以大大缩短产品开发周期。

基于FreeForm和快速原型的快速产品开发研究

通过分析FreeForm和快速原型技术在产品开发中的作用,提出了基于FreeForm和快速原型的快速产品开发模式。通过某人物玩具开发的实际应用,表明该模式可以快速地制造出产品的样件,可实现产品开发的快速设计、快速定型、快速营销和快速制造,产品能很好地再现设计模型,加快了产品的开发速度,开发成本和风险大大降低,加速新产品的开发速度和成功率,提高企业的竞争优势。

虚拟油泥技术Freeform在文物快速复原中的应用研究

通过研究与分析传统文物的复原过程,运用基于虚拟油泥技术Freeform的快速成型技术,快速构建文物缺失部分,实现文物快速复原。借助三维扫描仪和三维建模工具,快速构建残缺文物的三维模型,运用虚拟油泥技术复原残缺文物缺失部分,改进传统文物复原过程的复杂工艺,结合3D打印技术,提高文物复原效率,为文物保护事业提供数字化思路。

虚拟触觉设计Freeform在产品开发设计中的应用研究

分析了现代软件在产品设计过程中的重要作用,研究了Freeform与曲面设计相结合进行产品开发的方法,重点讨论了"虚拟油泥"、"虚拟设计"以及"力的反馈"等技术的运用,通过实例证明该技术对不同的设计可以根据不同的需求自由地添加泥土和减少泥土,为复杂软件用于产品开发设计提供了一种切实有效的方法.

基于FreeForm的CAD模型细节添加与修改

分析了FreeForm造型的特点及优势,并针对FreeForm在造型过程中的细节添加与修改功能进行了详细论述,将传统CAD建模与触觉交互造型有机结合起来,提出了一种基于FreeForm的CAD模型细节添加与修改方法,并给出了应用实例。

基于FreeForm的玩具模型设计

自由曲面的建模是工业设计领域应用非常广泛,但建模过程困难的问题。FreeForm触觉式设计系统是应用触觉进行建模的软件,文中概述了FreeForm系统的系统结构和核心技术,通过实例详细介绍了基于FreeForm的玩具模型设计过程,总结了FreeForm系统在自由曲面建模中的优势和不足,指出将FreeForm系统和其他CAD软件结合使用可以缩短产品开发周期。

飘动的旗帜

本例用After Effects来做一面飘动的旗帜,这类效果往往是在三维软件里才能做到,而且要有Cloth插件(模拟布的效果的插件)。这里笔者告诉大家一个办法,在After Effects里用Freeform2.0插件做一面飘动的旗帜,而且不亚于在三维软件里做到的效果。如图1所示。

增强现实环境下的FreeForm空间遥操作研究

人类在复杂环境中执行操作任务时,往往存在很多危险。空间遥操作技术实现让操作人员操控异地的设备,远离危险,在安全的环境中完成各种操作。然而,空间遥操作技术存在通讯时延,为了解决这一问题,通常使用增强现实技术对遥操作系统构建虚拟预测环境。目前,一般的增强现实技术只能对人的视觉系统进行影像增强或视野扩张,无法对触觉进行有效地模拟或仿真。本文提出将FreeForm触觉式设计系统与增强现实技术结合的方法,弥补这一缺陷。

基于Freeform的逆向工程数据修复

介绍了基于力反馈技术的Freeform触觉式设计系统在逆向工程测量数据修复方面强大的功能。利用非接触式光栅扫描仪测量飞机模型的表面数据点云,通过Freeform的分割黏土、膨胀、镜像、平滑等功能,成功地恢复了飞机模型完整的表面数据。

Topology Recovery Technique for Complex Freeform Surface Model after Local Geometry Repair

Intersections and discontinuities commonly arise in surface modeling and cause problems in downstream operations. Local geometry repair, such as cover holes or replace bad surfaces by adding new surface patches for dealing with inconsistencies among the confluent region, where multiple surfaces meet, is a common technique used in CAD model repair and reverse engineering. However, local geometry repair destroys the topology of original CAD model and increases the number of surface patches needed for freeform surface shape modeling. Consequently, a topology recovery technique dealing with complex freeform surface model after local geometry repair is proposed. Firstly, construct the curve network which freeform surface model; secondly, apply freeform surface fitting method determine the geometry and topology properties of recovery to create B-spline surface patches to recover the topology of trimmed ones. Corresponding to the two levels of enforcing boundary conditions on a B-spline surface, two solution schemes are presented respectively. In the first solution scheme, non-constrained B-spline surface fitting method is utilized to piecewise recover trimmed confluent surface patches and then employs global beautification technique to smoothly stitch the recovery surface patches. In the other solution scheme, constrained B-spline surface fitting technique based on discretization of boundary conditions is directly applied to recover topology of surface model after local geometry repair while achieving G~ continuity simultaneously. The presented two different schemes are applied to the consistent surface model, which consists of five trimmed confluent surface patches and a local consistent surface patch, and a machine cover model, respectively. The application results show that our topology recovery technique meets shape-preserving and Gt continuity requirements in reverse engineering. This research converts the problem of topology recovery for consistent surface model to the problem of constructing G1 patches from a given curve network, and provides a new idea to model repairing study.

Advances in the design and manufacturing of novel freeform optics

Freeform optics has become the most prominent element of the optics industry. Advanced freeform optical designs supplementary to ultra-precision manufacturing and metrology techniques have upgraded the lifestyle, thinking, and observing power of existing humans.Imaginations related to space explorations, portability, accessibility have also witnessed sensible in today’s time with freeform optics. Present-day design methods and fabrications techniques applicable in the development of freeform optics and the market requirements are focussed and explained with the help of traditional and non-traditional optical applications. Over the years,significant research is performed in the emerging field of freeform optics, but no standards are established yet in terms of tolerances and definitions. We critically review the optical design methods for freeform optics considering the image forming and non-image forming applications. Numerous subtractive manufacturing technologies including figure correction methods and metrology have been developed to fabricate extreme modern freeform optics to satisfy the demands of various applications such as space, astronomy, earth science, defence,biomedical, material processing, surveillance, and many more. We described a variety of advanced technologies in manufacturing and metrology for novel freeform optics. Next, we also covered the manufacturing-oriented design scheme for advanced optics. We conclude this review with an outlook on the future of freeform optics design, manufacturing and metrology.