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。     

Optimal part deposition orientation in FDM by using a multicriteria genetic algorithm

In rapid prototyping processes, the deposition orientation of the part is very important as it affects part surface quality, production time and the requirement for support structure and hence cost. Depositing the part with thinner slices results in a larger build time. At the same time, if a large slice thickness is chosen, the surface finish is very poor due to stair-stepping. These are two contradicting issues and are tackled by using adaptive slicing. In adaptive slicing, slice thickness is calculated based on local geometry of the computer-aided design model and rapid proto-typing machine specifications. Even though adaptive slicing controls part surface quality by compromising on build time for a deposition orientation, an optimum orientation can further reduce build time and enhance part surface quality. In the present work, an attempt has been made to determine the optimal part deposition orientations by considering two objective functions at a time, namely average part surface roughness (average part surface quality) and build time. The two objectives are minimized simultaneously using a multicriteria genetic algorithm.     

快速原型分层方案的优化及仿真研究

以表壳型芯的快速原型加工过程的仿真为例,在实际加工过程前,进行原型件CAD三维模型仿真,并对仿真结果进行综合的分析评价,进行分层方案的优化,实现了提高加工效率的目的。     

Application software system based on direct slicing for rapid prototyping

A direct-slicing approach might improve the accuracy and quality of small, complex parts produced with rapid prototyping technology. An application software based on direct slicing for rapid prototyping was used on the foundation of PowerSHAPE models. Lines, conic arcs and cubic bezier curves were adopted as the basic elements describing the direct-slicing contours. Moreover, a scheme to carry out subdivided software development was proposed. A picture (PIC) format file was selected as an interface for the slicing data, and a macro-AutoSection software, which collects the direct-slicing contour data of arbitrary complex computer-aided design models and provides power to produce the direct-slicing PIC files, was developed. On the above basis, an application software called PDSlice based on direct-slicing data processing was developed for the commercial selective laser sintering machine HRPS-III, which was made at the Huazhong University of Science and Technology (HUST), P. R. China. The major input and output interfaces as well as the PIC model reconstruction method of the PDSlice are described. Furthermore, a batch of direct-slicing polymer parts were successfully fabricated with the selective laser sintering machine. The application example shows that the accuracy and surface finish of three-dimensional complex curvature surface parts fabricated with the application software system based on a direct-slicing format were better than the application software system based on a stereolithography (STL) format.     

三维打印快速成型层面位图的生成算法

提出了新的基于轮廓边的快速求交算法,实现了快速成型系统中层面位图数据的生成.该算法不仅简单、效率高,而且可以处理求交过程中遇到的各种奇点问题,特别是用经典求交方法难以判断和处理的当扫描线通过带水平轮廓边的凸拐点和凹拐点带来的奇点问题.通过在自制的3DP快速成型样机上的试验运行,证明该算法有较好的鲁棒性.     

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。     

A generative process planning system for parts produced by rapid prototyping

This paper presents a generative process planning system for parts produced by the rapid prototyping process (i.e. fused deposition modelling–FDM). The proposed process planning involves optimal selection of orientating the model with a proper support structure and then provides an intelligent slicing methodology, such as direct or adaptive, to minimise the built up time, keeping the geometry and cusp height errors in control. Pre- and post-slicing processes have been used to minimise the sliced data error. The Computer Aided Process Planning (CAPP) model has been arranged into five modules: orientation, support structure generation, slicing, path planning and Numerical Control (NC) program generation, and model build up. The CAPP model has been implemented in C language having a unique methodology consisting of 42 simplified steps. The CAPP model has been tested for several examples and shows satisfactory results.     

焊接快速成形技术的发展现状

焊接快速成形技术是近几十年才发展起来的新型制造技术,具有高灵活性、低成本和高生产效率等优点,在军事、医疗、交通、教育等许多行业都得到了广泛应用。简单介绍了焊接快速成形技术的原理及特点,概述了以钨极氩弧焊、熔化极气体保护焊、等离子弧焊、激光焊、电子束焊为基础的焊接快速成形技术国内外的发展现状,指出了焊接快速成形技术在发展中存在的问题,并就关于成形精度、成形性能、成形材料的问题进行了分析。     

基于快速成型技术的陶瓷零件无模制造

概述了几种近几年发展起来的陶瓷零件快速成型技术,着重介绍了它们的原理及应用于陶瓷零件制造的研究现状,比较分析了各种快速成型技术的优缺点及在产业化应用中存在的问题,并对今后该技术的发展进行了展望.     

Rapid prototyping through scanned point data

Rapid prototyping (RP) is an emerging, non-traditional fabrication method and has been recognized as a valid tool to shorten the lead-time from design to manufacture effectively. Most of the current RP systems adopt the triangular meshes of stereolithoraphy (STL) as a standard format for data input. Thus, the construction of triangular meshes directly affects the quality of RP parts and their subsequent processes. Traditionally, STL data are output from 3D CAD models built using commercial 3D CAD/CAM software packages. This study, however, differs from the traditional way in that it generates the STL data directly from scanned 3D data points, thus preventing various problems associated with 3D CAD modelling from a large quantity of data points. Specific tasks involved in this study include: (1) development of the methodology to convert massive data points into numerous, connected triangular meshes, (2) determination of unit normal vector for each triangular mesh facet, (3) output of triangular meshes with normal vectors in STL format, and (4) slicing of triangular-mesh model into a series of 2D sections.     

Design of the FDM Scanning Mode Based on ANSYS

Fused deposition rapid prototyping is an important technology of rapid prototyping. In order to improve the processing technology,the process plan to change its scanning mode is put forward,through the finite element simulation. The verification in the accumulation of fewer layers change the long and short side scanning to improve the rationality of fused deposition rapid prototyping. Based on the ANSYS version of the classic Gauss heat source on the use of mobile technology,it is reasonable to describe the formation process of fused deposition rapid prototyping,and put forward the improvement scheme is put forward.     

Rapid hard tooling by plasma spraying for injection molding and sheet metal forming

Amidst the harsh competition over the development of new products around the world, rapid prototyping, especially rapid tooling methods have received widespread attention. Amongst the rapid hard tooling methods, thermal spraying can manufacture metal molds without limitation of pattern size. However, it has the disadvantage that only soft metals with low melting points such as zinc alloy can be sprayed to original mold, such as a rapid prototyping model or a natural material pattern, due to their lack of heat resistance and shrinkage of spray metals. So the wear resistance of spray tool is poor, it can be used only for trial or small-lot production. In this study, attempts were made to improve the heat resistance by using composite materials made of ceramic and metal powders as the sprayed original mold materials, and using stainless steel, tungsten carbide alloy, iron–nickel–chromium alloy with excellent wear resistance as spraying materials, respectively. The results show that injection molding spray mold and sheet metal forming spray die can be made by transferring from natural patterns and rapid prototyping models. As the durability and dimensional accuracy of the sprayed tools has sharply improved, the tools can be used for mass production.     

Decision support system for rapid prototyping process selection through integration of fuzzy synthetic evaluation and an expert system

A new method is proposed for selecting the most appropriate rapid prototyping process according to user's specific requirements by using the expert system and fuzzy synthetic evaluation. The selection process is divided into two stages. First, it is necessary to generate feasible alternatives, which are executed under the expert system environment. Second, given those feasible alternatives, the fuzzy synthetic evaluation approach is employed to produce a ranking order of the alternatives and to finalize the most suirapid prototyping system. One distinctive characteristic of this method is that quantitative as well as qualitative measures are employed, providing more accurate results. The decision system developed based on the proposed method is composed of four modules: a database to store the specifications of various rapid prototyping processes; a knowledge-based expert system for determining the feasible alternatives; a fuzzy synthetic evaluation model to select the most suitable rapid prototyping process; and a user interface and an expert interface to interact with the system. The fuzzy synthetic evaluation approach used in the system is illustrated in detail by a numerical example. Furthermore, a Java-enabled solution, together with web techniques, is employed for developing such a networked decision support system. Finally, two examples of rapid prototyping process selection are designed to demonstrate the application of the system. The system has been implemented and can run at a rapid prototyping and manufacturing networked service platform that the authors have developed.     

陶瓷零件快速成型机铺料机构控制系统的研究

  加快陶瓷零件快速成型设备的研究对于缩短陶瓷制件的制造周期以及提高企业的生产效率具有重要的意义.简述了目前陶瓷零件快速成型设备的发展状况,着重介绍了基于陶瓷零件层合速凝技术所设计的一种陶瓷零件快速成型设备铺料机构的基本结构、工艺流程和工作原理,设计了该设备铺料机构PLC控制系统.该系统运行良好,满足了产品自动化生产的要求,提高了工作效率.     

摩擦电沉积快速成形新技术

针对电沉积工艺中沉积层表面和边缘容易产生积瘤、毛刺等缺陷,在电沉积过程中加入了摩擦辅助装置,并与快速成形技术相结合,提出了一种基于离散/堆积原理的摩擦电沉积快速成形技术,用于简单、快捷、低成本地直接成形金属零件。通过快速成形金属铜制件试验表明:紧贴阴极表面的实时动态的撞击和摩擦,能有效地去除沉积层表面的吸附气泡和积瘤,获得表面平整光亮的电铸层;摩擦电沉积快速成形技术能够综合快速成形和电铸技术的优点,有效降低设备复杂度和零件成本,直接快速制造出形状复杂、结构致密、组织均匀的精密金属零件。     

快速成型技术中分段算法的研究综述

在快速成型技术中,模型分段处理是分层处理的前一步骤,对分段算法进行研究十分有必要。为此,对快速成型技术中的分段算法进行总结,主要从人机交互分段和自动分段两方面展开。对于人机交互分段算法,主要从根据不同成型要求进行分段方面展开叙述;对于自动分段算法,主要介绍了体素化分段算法、特征识别式分段算法、多目标优化分段算法和聚类式分段算法。分析结果表明,现有分段算法仍存在适用范围受限、应用快速成型工艺单一、未考虑后续拼接环节以及测试模型多为非工程用零件等问题。因此,开展关于分段算法效果评价准则的建立、结合多种快速成型工艺的应用以及考虑模型拼接后的性能分析等方面的相关研究,可有效提高分段算法的实用价值,为后续分层处理奠定基础。     

Hybrid approach in prototyping functional medical safety devices: A case study

Utilisation of functional prototypes during the upstream design stage is able to shorten the product development cycle of a medical device and quicken the transfer process to mass manufacturing. Innovative synergy of conventional manufacturing techniques and rapid prototyping techniques is thus needed to fabricate functional prototypes successfully. This case study reports on the development of an automatically activated safety needle using different prototyping approaches for the fabrication of functional prototypes. The approaches include rapid prototyping, computer numerical control (CNC) machining and vacuum casting. The challenges of each technique are discussed and solutions are presented. A hybrid technique involving CNC machining and vacuum casting is adopted to fabricate the prototypes. This hybrid prototyping approach was able to expand the choices for materials to fabricate the prototypes and thus enabling the validation of the design mechanism in a shorter time.     

Hybrid approach in prototyping functional medical safety devices: A case study

Utilisation of functional prototypes during the upstream design stage is able to shorten the product development cycle of a medical device and quicken the transfer process to mass manufacturing. Innovative synergy of conventional manufacturing techniques and rapid prototyping techniques is thus needed to fabricate functional prototypes successfully. This case study reports on the development of an automatically activated safety needle using different prototyping approaches for the fabrication of functional prototypes. The approaches include rapid prototyping, computer numerical control (CNC) machining and vacuum casting. The challenges of each technique are discussed and solutions are presented. A hybrid technique involving CNC machining and vacuum casting is adopted to fabricate the prototypes. This hybrid prototyping approach was able to expand the choices for materials to fabricate the prototypes and thus enabling the validation of the design mechanism in a shorter time.