Rapid Manufacture of Metal Tooling by Rapid Prototyping

As the race to launch a product successfully into the market increases in speed, the drive to reduce metal tooling lead time will become more important. Time reduction for fabricating metal tools depends on fast, efficient, and flexible manufacturing processes that dramatically reduce lead times while not sacrificing mechanical properties. A novel process of rapid tooling, non-baking of ceramic moulding, was studied. It uses a casting mould made from ceramic slurry and rapid prototyping to form a metal tool. It provides a quick, accurate, and relatively cost-effective route for producing metal parts or tools. The process and key technologies are analysed in detail. The process has been used in the automotive, consumer products, casting, and toy industries. Applications show that the total costs for new products can be reduced by as much as 40–60%, and lead times can be reduced by 50–60%. The surface roughness is approximately Ra = 3.2, and it can be improved to better that Ra = 1.6 by polishing. The dimensional accuracy relative to size is about ±0.1 mm for dimensions less than 200 mm. ID="A1"Correspondance and offprint requests to: Mr Z. Shan, The Centre for Laser Rapid Forming, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, PR China. E-mail: shanzhongde@mails.tsinghua.edu.cn     

快速成形转向快速生产的主要障碍

快速成形制造 (RPM)技术是国外 80年代后期发展起来的一门新兴综合技术。它使直接从概念设计迅速转为产品设计的生产模式成为可能 ,工业界正在探索使用快速成形机器生产最终要制造的零件的问题。但是 ,它面临诸如材料性能、表面质量、零件的尺寸规格和成形速度等许多挑战。一旦克服了这些障碍 ,快速成形就将转向快速生产 ,并将促进大量定制生产模式的加快实现     

快速成形及其在快速制模中的应用

快速成形（ＲＰ＆Ｍ）作为一种新兴的先进制造技术,已成功地实现了快速原型制造,正向快速制模（ＲＴ）方向迅速发展。本文介绍了快速成形技术的现状及其在快速制模尤其是快速金属模具制造方面的应用,探讨了制约快速制模技术发展的关键问题和该技术的发展趋势。     

A New Slicing Procedure for Rapid Prototyping Systems

The current slicing rule of most rapid prototyping (RP) systems cannot ensure unilateral tolerances on the whole prototype and often results in problems of overcut and undercut on the same part. This drawback leads to unsatisfactory precision of the part in post processing. In order to reduce the above problems, a new slicing method is proposed in this paper. Based on the geometry information in a stereolithography (STL) file, an algorithm is developed. The appropriate slicing rule is selected according to the inner product of the normal vector and working direction of the part, together with the function of the part to be manufactured. The STL file is cut into 2D sections and an accurate contour is calculated. After the slicing computation, an appropriate working path is produced. The rules proposed in this paper have been verified. This work contributes to the improvement of slicing rules in existing RP systems, especially in systems using uniform thickness slicing. It also improves manufacturing efficiency and working tolerances.     

On-Line Layer Profile Dimensions Measurement of Model Maker Rapid Prototyping Using Vision Technology

The key principle of rapid prototyping (RP) is to fabricate a 3D object, layer by layer, which is a 2D fabrication process. Vision technology is being successfully applied in general industry to inspect object dimensions on-line, but most of the applications are limited to objects with 2D patterns. Hence, it should be possible to apply vision technology to inspect RP layer profile dimensions on-line. A CCD camera was employed to capture the layer profile image of the Model Maker (MM) RP system layer by layer. The captured image was processed to identify the RP profiles and further to calculate the real profile dimensions of the fabricated layer. The experimental results demonstrate that the dimensions of an RP part could be measured in situ, layer by layer, and could, potentially, be real-time monitored. This paper presents the vision calibration and the detailed image processing algorithms for the single layer profile identification and dimensions measurement. The results show that the measurement accuracy of the layer profile was about 98%.     

快速原型制造技术的集成应用方法

快速原型制造技术在企业新产品开发中具有重要的作用。在介绍几种典型快速原形系统工作原理和应用特点的基础上,指出快速原型、ＮＣ加工和机械手加工原型技术集成的必要性并提出建立集成快速原型制造的模型,最后讨论快速原型技术的应用现状和前景。     

当前快速成型技术研究和应用的热点问题

ＲＰ技术是近年来发展相当迅速的一项综合应用技术。就ＲＰ制造工艺、ＲＰ材料、ＲＰ系统软件、ＲＰ集成技术以及ＲＰ技术的应用等一些热点问题进行了综述。     

Rapid Prototyping Applications in Medicine. Part 1: NURBS-Based Volume Modelling

Rapid prototyping (RP) technology has extended traditional manufacturing applications in areas other than product engineering. Using RP to fabricate custom implants and prostheses for surgical planning and education is now an important area of research. Although, in theory, RP is capable of producing objects of any complexity, designing freeform shapes is difficult using current CAD systems. These CAD systems are geared toward the design of parts manufactured by traditional methods; they do not help designers exploit the extended opportunities offered by RP technology. Medical data cannot be input into these CAD systems directly for further modification and manipulation. The purpose of this project is to explore a new approach for modelling and prototyping biomedical objects. The work extends from volume modelling to RP and medicine. In this paper, Part 1 of two papers, a new approach to modelling complex objects, NURBS-based volume modelling, is proposed. A NURBS representation of volumes is developed to represent not only the surface boundary but also the interior of a 3D object. NURBS-based volume modelling inherits advantages from both NURBS modelling and voxel-based modelling. The key idea of the NURBS-based volume modelling is to exploit the flexibility of NURBS modelling and use the voxelised NURBS volumes as components for constructing complex objects. Part 2 deals mainly with issues of interfacing volume models to RP systems. A new approach to generate STL files through volume modelling and iso-surface extraction is proposed. This approach guarantees the validity of the final STL file inherently. Software development and case studies are also given.     

CAD系统的实体输出——快速成型

简要介绍了快速成型方法的基本原理，并对当今所用的六种快速成型方法作了具体说明，阐述了不同方法的特点。     

Multiresolution Hybrid Mesh for Rapid Prototyping

Stereolithography (STL) is the prevailing technology in rapid prototyping (RP) applications. The STL process involves mesh triangulation of a sculptured object from a CAD model and then the extraction of cross-sections from the mesh model. In most current systems, the resulting model suffers from topological problems, such as degenerate facets, undesired holes, or flipped normals, which lead to invalid cross-sections that cannot be manufactured as layers. This paper proposes a hybrid system that takes advantage of structured and unstructured mesh geometry in order to optimise the RP process and make it more robust and accurate. The system has been developed as part of a joint project between the 3S Laboratory at Grenoble University, France and the Laboratory for Computer Graphics and CAD at the Technion, Israel. Within the system, a constrained mesh simplification model (3S Lab) is integrated with a multilevel model (CAD Lab).     

Direct Slicing from PowerSHAPE Models for Rapid Prototyping

Rapid prototyping processes produce parts layer by layer directly from CAD models. An efficient method is required to slice the geometric model of a part into layers. Several slicing methods are introduced in this paper: slicing from STL files; tolerate-errors slicing; adaptive slicing; direct slicing; adaptive and direct slicing. PowerSHAPE is a powerful package for building models, and it provided macro language and picture files for its secondary development work. To meet rapid proto-typing slicing demands, the author proposes a direct slicing approach based on PowerSHAPE models. In this method, lines, arcs and Bezier curves are used to describe the section contours. This approach can be used in stereolithography, selective laser sintering, fused deposition modelling, and other rapid prototyping processes, e.g. laminated object manufacturing. It may be the future solution to existing slicing problems.     

逆向工程与快速成型技术的应用

介绍了逆向工程技术和快速成型技术的定义和逆向工程与快速成型的一般流程。并通过一个简单球面的反求工艺实例,阐述了逆向工程中数据采集、产品建模以及产品快速成型的一般过程。从而证明了逆向工程技术是一个多领域、多学科的系统工程,是基于新的设计思想和方法,在计算机技术、数控测量技术和CAD/CAM技术发展基础上产生的一项新技术,能广泛运用于模具行业,并有一定的影响力。本文证实了逆向工程技术和快速成型技术的前沿性和可靠性,并展望了逆向工程技术与快速成型应用的前景。     

On Line Model Accuracy Inspection of Model Maker Rapid Prototyping Using Vision Technology

The principle of rapid prototyping (RP, or layer manufacturing) is to fabricate a 3D object layer by layer. Vision technology has been employed and has demonstrated its ability to measure the single-layer profile dimensions of the Model Maker (MM) RP system model. The on-line profile dimensional inspection and accuracy analysis of multiple layers is presented in this paper. The image-processing algorithms, developed to measure the layer profile dimensions, were adapted to process the captured profiled image of multiple layers, layer by layer. Hence, the layer profile dimensions of multiple layers were inspected on-line and layer by layer. The problems of vision inspection associated with colour mixing of multiple layers are addressed. A colour CCD camera was employed to resolve the colour mixture problem, but it is too expensive and too much memory is required. A new image difference algorithm was proposed to solve the problem of colour reflected from adjacent layers. The results demonstrate the promise of on-line profile dimensions inspection and accuracy analysis using vision technology.     

Rapid Prototyping and Tooling of Custom-Made Tracheobronchial Stents

Rapid prototyping (RP) and rapid tooling (RT) techniques can be applied to the field of medicine primarily because of their ability to produce customised profiles and geometries in relatively short lead times. In this paper, the process by which these techniques can be applied for the production of customised tracheobronchial stents for the purpose of maintaining patency in an occluded respiratory tract is described. A comparison of RP systems was carried out to establish the preferred RP method to produce the master model. The vacuum casting RT process was then used to produce the stent.     

基于叠层实体制造技术的热敏打印机快速设计与制作

介绍叠层实体制造技术快速成型方法的基本原理和主要应用领域,并以上盖零件为例叙述热敏打印机原型的制作工艺过程,指出叠层实体制造技术在从结构设计评估、零部件间的装配检验到产品定型及样品生产的快速设计与制造模式中的作用。     

基于快速成型的快速模具制造工艺分析

介绍了基于快速成型的快速模具制造技术的工艺原理、分类、成型方法、技术特点以及与传统成型方式的区别。从模具的寿命,模具的制作成本,模具的生产周期等方面对几种典型快速模具制造技术系统进行了比较和归纳。分析了快速模具制造技术面临的关键问题,展望了基于快速成型原理的快速模具制造的应用前景。     

Study of Trapped Material in Rapid Prototyping Parts

Since the launch of the first commercial system in 1988, rapid prototyping (RP) technology is fast being accepted in the fields of product design and development, in the tool and die making industry and recently, for biomedical applications. Although, in theory, RP is able to produce an object of any complexity, problems such as having material trapped inside parts with hollow features still frequently occur during normal operation. This research project seeks to achieve a better understanding of the formation of trapped material inside RP parts, with the eventual aim of developing an algorithm to avoid this problem. In this paper, the causes and effects of trapped material will be discussed for stereolithography apparatus (SLA), solid ground curing (SGC), selective laser sintering (SLS), and laminated object manufacturing (LOM). Finally, current remedies will be presented.     

快速原型制造技术及研究

简要介绍了快速原型制造技术的概念、基本原理和特点,对目前的主要成型方法及其研究方向作了初步介绍和探讨。     

聚氨酯耳廓软骨支架的快速成形工艺

在体外构建外形逼真、机械强度可调节的个性化耳廓软骨支架,是组织工程方法修复外耳耳廓缺损的重要方向之一。针对这一研究目的,采用基于快速成形原理的熔融挤出成形方法,使用颗粒状聚氨酯生物材料,通过搭建试验平台,设计一系列工艺因素对成形过程及支架力学性能的影响试验,研究制造耳廓软骨支架的最优工艺参数范围。试验发现:喷头温度影响材料挤出稳定性和弹性;成形室温度影响结构整齐度和层间结合度;送料速度和扫描速度,与挤出速度的匹配关系,影响出丝的均匀度和成形过程的稳定性;不同扫描速度的喷头所形成的温度场分布,影响已成形结构的弹性;成形过程存在最小局部反复造型面积;温度以及CLI数字模型离散处理参数,影响支架力学性能。结果表明,熔融挤出成形方法制备的聚氨酯材料耳廓软骨支架,不仅可以实现逼真的耳廓外形,还可通过控制各种工艺参数,得到接近天然耳廓的力学强度,以满足临床中不同病患的个性化需求。     

生物假体模型的快速成型制作技术

介绍了几种用于赝复体制作的快速成型方法,提出采用选区激光烧结成型快速制造医学假体,在人造五官医学假体特别是整容术赝复体的设计及制造方面,具有良好的应用前景,并采用选区激光烧结蜡粉得到赝复体原型蜡模,用于赝复体的快速制作。