Adaptive direct slicing with non-uniform cusp heights for rapid prototyping

Adaptive slicing varies layer thickness by taking the geometry change of the CAD model in the build direction into account to improve surface finish. Direct slicing generates exact slice contours from the original CAD model and avoids an intermediate representation, known as an STL file. At present, most direct slicing approaches are restricted to some CSG solids or some CAD systems. In this paper, an approach toward adaptive direct slicing with non-uniform cusp heights independent of CAD systems for rapid prototyping is presented. First the geometry model is imported into the adaptive direct slicing system from CAD systems using the standard STEP format. Using OpenGL graphics libraries, the solid model is then displayed and the user is prompted to specify the allowable cusp height for each highlighted surface. Lastly, the CAD model is sliced adaptively with different cusp heights (tolerance requirements) for different surfaces. With non-uniform cusp heights, adaptive slicing has a higher efficiency. Implementation details and results are also presented.     

Adaptive slicing of functionally graded material objects for rapid prototyping

Slicing is a fundamental process planning task and an important procedure in rapid prototyping. However, most research currently focuses on the slicing of homogeneous objects and few approaches for slicing of heterogeneous objects have been reported in the literature. In this article, we present an approach for adaptive slicing of functionally graded material objects. Unlike homogeneous objects, functionally graded material objects contain both geometry and material information. The layer thickness is computed by considering not only geometry but also material variation along the build direction. The continuous material distribution in each layer is discretised into step-wise gradings by subdividing the slice into sub-regions, which can be regarded as homogeneous material regions. An algorithm that summarised the slicing procedure is described and an example is also presented.     

一种快速成形自适应分层层厚新算法

将现有的两种自适应层厚算法加以结合,阐述一种基于STL文件的快速成形自适应分层层厚的新算法。该算法弥补了上述两种算法原理上各自的不足,通过对该新算法的测试得到比较满意的结果。     

Improved intermediate point curve model for integrating reverse engineering and rapid prototyping

Direct integration of reverse engineering and rapid prototyping removes two intermediate steps of surface fitting from point cloud data and STL file generation from CAD models. Therefore errors introduced due to surface fitting and triangulations are eliminated and also the process of STL data validation and repair is avoided. Intermediate point based curve model (IPCM) method is one of the promising approaches for direct integration of reverse engineering and rapid prototyping however this approach has the limitation that it cannot handle objects, which result in multiple contoured slices. Moreover, IPCM based method is implemented with layers of constant thickness slices, and adaptive slicing with this method is not attempted. The present work is an attempt towards improving the capabilities of IPCM based method by overcoming the above-mentioned two limitations. The new system developed here has been tested on many parts, which demonstrates the capability of the proposed system. An erratum to this article can be found at     

AutoCAD环境下直接适应性切片方法及实现

数据分层处理是快速成型技术的核心.适应性分层可以有效解决快速成型中成形精度和速度之间的矛盾.利用AutoCAD二次开发技术,通过比较相邻层片截面的面积确定切片厚度,提出了一种基于CAD模型的直接适应性切片方法,并对该方法进行了实现,同时与定层厚切片方法进行了比较,最后给出了分层实例并对结果进行了分析.     

Direct integration of reverse engineering and rapid prototyping based on the properties of NURBS or B-spline

As product varieties increase and life cycles shorten, the need to reduce product development time becomes more critical to maintain competitiveness in the market. The reduction of the product development time, therefore, requires revolutionary improvements rather than gradual changes in technology. Based on a novel strategy the procedure for integration of reverse engineering and rapid prototyping was developed in this paper. Direct integration of reverse engineering and rapid prototyping is not a new issue and its importance has been demonstrated by many authors. However, all traditional algorithms for integration of RE and RP operate on scattered points directly such that some useful information for example curvature, normal and geometric shape, which are necessary for adaptive slicing in RP, cannot be obtained. To resolve the difficult dilemma a new algorithm is developed to build a bridge between scattered points and adaptive slicing.     

快速成型数据处理系统研究

简述目前国内快速成型数据处理方面的发展情况，及国外在此领域的发展方向。论述了当前快速成型数据处理技术需要进一步发展完善的现状，尤其在直接切片、边界补偿、分层方案优化方法等方向有待于进一步发展。     

快速成型技术中分层算法的研究与进展

根据对零件制造精度和效率的关注程度的不同,开发出了多种分层算法.在同等加工时间的情况下,根据加工精度的不同,将这些分层算法分为等层厚分层算法和适应性分层算法两类.通过对STL模型、原始CAD模型和点云数据的分析,讨论了两类分层算法的研究和发展,然后介绍了斜边分层算法和曲面分层算法等先进分层算法的原理和成果,最后讨论了快速成型分层算法的研究方向和趋势.     

快速成型数据处理系统研究

简述目前国内快速成型数据处理方面的发展情况，及国外在此领域的发展方向。论述了当前快速成型数据处理技术需要进一步发展完善的现状，尤其在直接切片、边界补偿、分层方案优化方法等方向有待于进一步发展。     

选区激光烧结(SLS)快速成型中CAD模型的工艺性研究

研究分析选区激光烧结 (SLS)快速成型中 ,不同尺寸和形状零件的CAD模型建立时的工艺性 ,根据实际经验得出了一些解决问题的方法     

快速成型技术中分层算法的研究综述

作为快速成型技术中必不可少的环节,根据对零件制造精度和装配要求及效率的侧重不同,多年来多种分层算法已被国内外学者开发出来。在同等加工条件下,根据加工精度要求和层厚变化的不同,将分层算法大致分为等层厚分层算法和适应性分层算法两类。从常用的立体光刻(STL)模型、原始计算机辅助设计(CAD)模型和点云数据3种数据模型入手,简述了两类分层算法的研究和发展;介绍了采用斜边的分层算法、基于区域划分的混合算法、曲面分层算法等先进分层算法;讨论了分层算法中待解决的问题:直接分层算法的文件格式标准和轮廓的精确拟合等问题。最后,总结得出了分层算法未来的研究方向和趋势。     

对CAD模型直接分层的方法研究

提出了直接对CAD实体模型进行分层处理以获取快速原型层片数据的方法,该方法无须进行从CAD到STL的数据转换,从而在根本上避免了由数据模型转换所引起的误差,且无需进行STL文件拓扑信息的提取及其错误的修复,极大地提高了快速原型的精度。     

面向快速成型制造的CAD平台内嵌式通用接口

面向快速成型设备的CAD平台中的内嵌式通用接口，可直接在CAD建模环境下零件模型实施自适应直接切片操作，同时生成以片层结构数据为单位的快速成型接口文件，该接口使用NURBS曲线对各截面的片层结构轮廓进行精确地解析重构；依据重构后的NURBS截面轮廓，自动填充功能可精确地生成快速成型设备的X，Y向栅线扫描路径。实验数据表明，与利用STL模型切片获得的得的多义线轮廓对比，经NURBS解析重构后的自适应直接切片轮廓与原始轮廓间的拟合误差降低98％以上，所需的NURBS线段数目减少77％以上。     

Determination of optimal build direction in rapid prototyping with variable slicing

Several important factors must be taken into consideration in order to maximize the efficiency of rapid prototyping (RP) processes. The ability to select the optimal orientation of the build direction is one of the most critical factors in using RP processes, since it affects part quality, build time, and part cost. This study aims to determine the optimal build-up direction when a part is built with the variable layer thickness for different RP systems. The average weighted surface roughness (AWSR) that is generated from the stair stepping effect, the build time, and the part cost using the variable layer thickness are all considered in the process. Using the multi-attribute decision-making method, the best orientation is determined among the orientation candidates chosen from the convex hull of a model. The validity of the algorithm is illustrated by an example. The algorithm can help RP users select the best build-up direction of the part and create an efficient process planning.     

Developing a paving system for fabricating ultra-thin layers in ceramic laser rapid prototyping

“Step effect” is one of the major concerns for engineers because it affects the surface quality in layer manufacturing. Instead of constant thickness, adaptive slicing procedures use slices of variable thickness that are governed by the model geometry, manufacturing process, material, and rapid prototyping system. The RP system has the capability of fabricating the layer between a minimum and maximum thickness with certain intermediate thickness during the model making and is indispensable. Due to agglomeration of powder and upward deformation of the layer, the layer’s thickness in powder-based rapid prototyping processes is restricted. To improve surface quality, the current study constructs a paving system to minimize the layer thickness. Based on a wet process-ceramic laser rapid prototyping technique, a paving system, which can fabricate ultra-thin layers to a thickness of 20 μm and can achieve instant layer drying, was successfully constructed. A strategy of compensative layer was induced to improve accuracy of the Z-axis. Due to the ultra-thin layers, a plane surface finishing of R_z = 15∼24 μm was obtained.     

一种基于STEP的CAD模型直接分层方法

提出了一种基于产品模型数据交换标准的3维计算机辅助设计实体模型直接分层方法,零件的原始计算机辅助设计模型以产品模型数据交换标准中性文件的格式输入分层系统,系统提取其几何拓扑信息并重建计算机内部几何模型。用户选择零件的制作方向并指定分层厚度后,系统自动对计算机辅助设计模型进行直接分层,分层结果可直接送到各种快速成型系统加工。基于产品模型数据交换标准的计算机辅助设计模型直接分层不依赖任何特定的计算机辅助设计系统,通用性、灵活性好,而且产品模型数据交换标准文件的数据量大大小于STL文件,有利于网络化设计与制造环境下的数据传输与交换。     

基于STEP的非均匀自适应分层方法

现有的自适应分层方法,通常对整个零件采用同一个最大的尖顶高度要求,实际上,大多数零件由于表面的重要程度不同,而需要不同的尖顶高度要求。对零件的不同表面采用不同的尖顶高度要求,可以进一步提高自适应分层的效率。为此,提出了一种在CAD系统外直接对STEP标准CAD模型进行非均匀自适应分层的方法,CAD系统与分层系统之间的数据交换采用STEP中性文件的格式。选择好零件的制作方向后,用户可根据零件表面的重要程度指定不同的尖顶高度要求,然后系统自动对CAD模型进行自适应分层。最后给出了分层实例,并对结果进行分析。     

Development of a multi-optical source rapid prototyping system

Two sets of optical sources with different laser beam diameter are integrated into a rapid prototyping system for increased machining speed in this research. The smaller laser beam is used to scan the object contour to obtain an accurate machining surface and the larger laser beam is used to quickly scan the inner part of the contour without precision control limitation to save machining time. The fabrication parameters of this system are investigated based on product quality and accuracy of practical implementations. The path planning of the inner part and the outer contour are discussed. The user-friendly man-machine interface is developed using the Visual Basic program .     

The two-dimension hollowing algorithm for rapid prototyping technology

The hollowing process plays an important role in some rapid prototyping technologies such as stereo lithography apparatus (SLA), fused deposition modelling (FDM) and select laser sintering (SLS). This paper introduces an efficient two-dimensional hollowing algorithm. The principles of algorithm and implementation are presented. In addition, a detailed analysis is used to study the effect of the scanning path and online character in the actual fabricating process.     

Integrating rapid prototyping and tooling with vacuum casting for connectors

Connectors are developed to satisfy the needs of advanced technology in telecommunication switching systems and companies have several products designed to fulfil the needs of the many switching networks available. The Four-wall-header is one such product from one company. The traditional manufacturing line relies heavily on hard tooling which is both expensive and time-consuming. This paper presents an alternative method of integrating rapid prototyping technologies, in particular, stereolithography apparatus (SLA), with a vacuum casting system to produce a wide range of polyurethane parts. Altogether, three approaches are analysed and evaluated for making the moulds: rapid pattern, rapid tooling and a hybrid approach.