Decomposition applied to layered manufacturing using critical points

Slicing represents an important step in all rapid prototyping processes. This paper proposes the use of critical points for adaptive local slicing for strataconception in particular and rapid prototyping technologies in general. The context of using critical points in rapid prototyping to optimise usual slicing is presented. Its definition on both surfaces and triangular meshings is given and extended to other geometric entities, such as edges, facets and faces. Finally, this new slicing approach is compared with the usual one on a few models manufactured through the stratoconception process.     

Decomposition applied to layered manufacturing using critical points

Slicing represents an important step in all rapid prototyping processes. This paper proposes the use of critical points for adaptive local slicing for strataconception in particular and rapid prototyping technologies in general. The context of using critical points in rapid prototyping to optimise usual slicing is presented. Its definition on both surfaces and triangular meshings is given and extended to other geometric entities, such as edges, facets and faces. Finally, this new slicing approach is compared with the usual one on a few models manufactured through the stratoconception process.     

基于STL模型的快速成形分层技术研究

研究了快速成形STL模型的分层处理技术,对模型拓补信息的重建,基于几何特征的分类排序,基于几何连续性的分组排序、分层求交与切片轮廓的生成等关键环节的技术原理进行了讨论,指出了存在的不足及今后的研究方向。     

Rapid prototyping: from product development to medicine and beyond

This paper discusses the current status of layer-based manufacturing rapid prototyping (RP) technology and how it is currently being implemented as a tool for product development (PD). A discussion on RP for PD is given, focusing on the limitations of existing technology. The paper then goes on to discuss the specific application field of medicine, explaining how this application may influence changes in the technology. Future trends for RP development are then discussed with further consideration for software issues in future applications and how the technology is being accepted worldwide.     

Rapid prototyping: from product development to medicine and beyond

This paper discusses the current status of layer-based manufacturing rapid prototyping (RP) technology and how it is currently being implemented as a tool for product development (PD). A discussion on RP for PD is given, focusing on the limitations of existing technology. The paper then goes on to discuss the specific application field of medicine, explaining how this application may influence changes in the technology. Future trends for RP development are then discussed with further consideration for software issues in future applications and how the technology is being accepted worldwide.     

基于成形工具姿态调整的适应性积层制造技术研究

当前的积层制造技术主要采用2.5D切片。成形中台阶效应不可避免,本文提出了一种新的基于3D切片的适应性成形方法。通过增加成形工具的运动自由度,使之能根据实体的几何外形自动调整姿态,从而有效地克服了台阶效应对成形精度的影响。在保持同等成形精度的前提下。采用适应性斜切成形技术可以使用更厚的层片。提高成形效率,实现了成形精度和速度的兼得。     

基于细分曲面的快速原型制造研究

针对快速成形制造中生成实体表面光滑度不高的问题,把细分曲面造型技术应用到快速成形制造中。先定义了顶点平坦度概念,然后对蝶形细分模式进行了改进,用此方法可以直接在初始的三角网格模型上提高模型的表面光滑度而避免了由CAD造形系统重新生成的问题,由此提出了一种可以提高生成实体表面光滑度方法。从光滑度分析和大量的实验结果可以看出,该方法可有效地提高实体表面光滑度,并具有较好的稳定性。     

Measurement and characterization of porosity in aluminium selective laser melting parts using X-ray CT

ABSTRACT

Selective laser melting (SLM) is an additive manufacturing technique which has the capability to produce complex metal parts with almost 100% density and good mechanical properties. Despite the potential benefits of SLM technology, there are technical challenges relating to the qualification and certification of the manufactured parts that limits its application in safety-critical industries, such as aerospace. Material porosity in SLM parts is detrimental for aerospace applications since it compromises structural integrity and could result in premature structural failure of parts. This paper describes the application of the non-destructive X-ray computed tomography (XCT) method to characterize the internal structure to enhance the understanding of the process parameters on material porosity and thus provide quality control of the SLM AlSi10Mg parts. An efficient and reliable XCT image processing procedure that involves image enhancement and ring artefact removal prior to image segmentation is presented. The obtained porosity level is compared with the conventional Archimedes method, showing good agreement. The characteristics of pores, such as shapes and sizes, are also discussed.     

RP－based Abrading Technique for Graphite EDM Electrode

Traditional processes for machining mold cavities are lengthy and costly.EDM(electro-discharge machining)is the most commonly used technique to obtain complex mold cavities.However,some electrodes are difficult to fabricate because of the complexity.Applying RP(rapid prototyping)technology to fabricate an abrading tool which is used to abrade graphite EDM electrodes,the cost and cycle time can greatly be reduced.The paper describes the work being conducted in this area by the authors.This technique will find widespread application in rapid steel mold manufacturing.     

快速成型技术在工业设计中的应用

先进的技术必将推动工业设计的发展.该文分析了快速成型技术在工业设计中应用的必要性以及工业设计与快速成型技术的互动性.     

规格说明语言ChiSL

ＣｈｉＳＬ是一种作用式可执行的功能规格说明语言，它是以数据抽象为核心的将代数规格说明和面向模型的规格说明两种技术有机地结合起来的模块化语言，具有良好的数据性质和可读性，能比较方便地书写大型规格说明?由于该语言是可执行的，因此ＣｈｉＳＬ规格说明可作为所要开发的软件系统的一个原型在该语言的支撑系统上执行。本文后面介绍了使用ＣｈｉＳＬ语言及其支撑系统开发软件原型的一些应用实例。     

Composites by rapid prototyping technology

The use of rapid prototyping (RP) technology for rapid tooling and rapid manufacturing has given rise to the development of application-oriented composites. The present paper furnishes succinct notes of the composites formed using main rapid prototyping processes such as Selective Laser Sintering/Melting, Laser Engineered Net Shaping, Laminated Object Manufacturing, Stereolithography, Fused Deposition Modeling, Three Dimensional Printing and Ultrasonic Consolidation. The emphasis of the present work is on the methodology of composite formation and the reporting of various materials used.     

Extending the product portfolio with ‘devolved manufacturing’: methodology and case studies

Current research by the developers of rapid prototyping systems is generally focused on improvements in cost, speed and materials to create truly economic and practical economic rapid manufacturing (RM) machines. In addition to being potentially smarter/faster/cheaper replacements for existing manufacturing technologies, the next generation of these machines will provide opportunities not only for the design and fabrication of products without traditional constraints but also for organizing manufacturing activities in new, innovative and previously undreamt of ways. This paper outlines a novel devolved manufacturing (DM) ‘factory-less’ approach to e-manufacturing, which integrates mass customization (MC) concepts, RM technologies and the communication opportunities of the Internet/World Wide Web, describes two case studies of different DM implementations and discusses the limitations and appropriateness of each, and, finally, draws some conclusions about the technical, manufacturing and business challenges involved.     

Fabrication of 3D chitosan–hydroxyapatite scaffolds using a robotic dispensing system

A new robotic desktop rapid prototyping (RP) system was designed to fabricate scaffolds for tissue engineering applications. The experimental setup consists of a computer-guided desktop robot and a one-component pneumatic dispenser. The dispensing material (chitosan and chitosan–hydroxyapatite (HA) dissolved in acetic acid) was stored in a 30-ml barrel and forced out through a small Teflon-lined nozzle into a dispensing medium (sodium hydroxide–ethanol in ratio of 7:3). Layer-by-layer, the chitosan was fabricated with a preprogramed lay-down pattern. Neutralization of the chitosan forms a gel-like precipitate, and the hydrostatic pressure in the sodium hydroxide (NaOH) solution keeps the cuboid scaffold in shape. Comparison of the freeze-dried scaffold to the wet one showed linear and volumetric shrinkage of about 31% and 62%, respectively. A good attachment between layers allowed the chitosan matrix to form a fully interconnected channel architecture. Results of in vitro cell culture studies revealed the scaffold biocompatibility. The results of this preliminary study using the rapid prototyping robotic dispensing (RPBOD) system demonstrated its potential in fabricating three-dimensional (3D) scaffolds with regular and reproducible macropore architecture.     

Integrated methodology for board assignment and component allocation in printed circuit board assembly

An approach to minimize makespan for assigning boards to production lines is described. Because of sequence-dependent set-up times, board assignment and component allocation have to be performed concurrently. An integrated methodology is developed to obtain a solution to these two problems. The methodology consists of seven phases: printed circuit board grouping, family decomposition, subfamily sequencing, Keep Tool Needed Soonest (KTNS) procedure, component set-up determination, component allocation and board assignment. Application of the methodology to industrial problems demonstrates that it can solve large-scale problems efficiently. In addition, the effect of two key parameters, feeder capacity and threshold value, on the performance of the solution procedure was examined. The results indicate that feeder capacity has an impact on total workload imbalance but not on the global makespan. Threshold value, a measure of effectiveness of joining a component type to a component group for a printed circuit board family, has a significant effect on the global makespan. The interactions of threshold value, and variations in printed circuit board requirement and component usage also affect global makespan.