专业英语作业2(答案)

1、中译英 1、 Current rapid prototyping software based on STL model has limitations in accuracy and flexibility that restricts its industrial application to some extent. A new software directly driven by the 3D CAD system GEMS 6.0 is developed with the abilities of adaptively slicing the object into layers,taking zigzag or spiral way of filling each layer, automatically generating auxiliary support structure and outputting CLI file. Some key algorithms and application examples are illustrated. 目前国内普遍使用的基于 STL 模型的快速成型软件在精确度和灵活性上都存在着很多缺陷， 在一定程度上影响了快速成型技术在生产中所起的作用.以三维儿何造型系统 EM56.0 为平 台，实现了一个基于 CAD 模型的直接快速成型软件，可进行分层、填充、构造支撑体以 及生成 CLI 文件等.针对其，1，的若干问题给出了相应的算法和应用实例. 2、 The tolerance and generation of the stair - error in RP were studied. By using the normal vector information of the tring on facets in ST L file ,a calaculating method of Stair - error was proposed and a slice adapt algorithm which will save the time of mold manufacturing was presented。 研究了快速成型过程中阶梯误差的产生与度量 ,并利用 ST L 文件中的三角形面片的 法矢量信息给出了阶梯误差的计算方法 ,提出了可变分层厚度的算法 ,采用自适应分层来减 少成型时间的方案. 3、 Th e method for obtaining geometrictopological informatin of CAD Models from STEP f i l e s i s d i s c u s s e d，a nd a STEP b a s e d direct slici n g metho d i s proposedTh e di r c c t s l i c i n g t e c h ni q u e b a s e d o n AutoCAD i s s t u di e d，a DXF ba s e d alone ope r a t e d s l i c i n g me t ho d f o r s u r f a c e f r a me CA D mo d e l s i s g i v e n，a n d a di r e c t s l i c i ng me t ho d op e r a t e d u nd e r AutoCAD f o r e nt i t y mo d e l s i s p r e s e nt e dTh e me t h o d s ha v e b e e n r e a l i z e d，and p r o v e d t o b e f e a s i b l e a n d e f f e c t i v e 探讨 了从 S T E P 中性物理文件 中获取 C A D 模 型几何拓扑信息的方法， 提 出了基 于 STEP 的直接分层 处理方法。研究 了基 于 Au t o CAD 的直接 分层处理技 术 ， 提 出了可独立运行的 基 于 DXF 文件的面框模型的直接分层处理方法以及 Au t o C A D 环境 下基 于 Au t o CA D 实体模型的直接分层处理方法并予以实现。 实践证明它是有 效可行的。 4、 Data error may be created from CAD model to STL model. It is hard that the operating time of uniform slicing coordinate with surface quality. In order to resolve these solutions, an adaptive direct slicing algorithm is proposed. The algorithm calls slicing function of commercial software to directly slice the model. The slicing thickness is variable. The algorithm firstly determines reference curves that can express vertical outline change of the model, and then select slicing thickness according to tangent of points in reference curves. This algorithm can avoid error that is created when triangle facets approximates CAD model. In addition, slicing thickness is decided by tangent of points in reference curves and neednt try to slice. This algorithm can insure precision of model surface and enhance modeling efficiency in the mean time 为了解决 CAD 模型转换成 STL 模型时出现误差、 均匀切片时加工时间和表面质量难 以协调的问题， 提出了自适应的直接切片算法。该算法调用商用软件中切片函数对模型直 接切片， 切片厚度选择采用自适应切片方法。首先求出能够表示模型垂直方向轮廓变化情 况的参考曲线， 然后在切片时根据参考曲线上各点处切线确定在该处的切片厚度。使用该 算法避免了用三角面片逼近 CAD 模型时的误差，而且根据参考曲线上点的切线决定切片 的厚度，不需要试切，在保证模型表面精度的同时提高了成型效率。 2、英译中 1、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。 :Since there were different concerns about precision and efficiency of partp s manufacturing , various slicingalgorithms were developed. According to the different machining precision in the same machining time of these slicing algorithms , they were divided into two kinds , namely uniform layer slicing and the adaptive layer slicing. The studies and development of the uniform layer slicing and the adaptive layer slicing were discussed by analysis of STL model , original Computer Aided Design (CAD) model and point cloud data. And then the principles and study re2 sult s of some advanced slicing algorithm including sloping slicing and curve surface slicing were int roduced. At last ,the research t rend in slicing method of rapid prototyping was discussed 2、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。 Most adaptive slicing approaches use a maximum allowable cusp height for the entire part . In practice ,however , some important faces of a part are required to be smooth while other unimportant faces can be rough.With non - uniform cusp height specifications , the high adaptive slicing efficiency can be gained. A STEP -based approach of adaptive slicing with non - uniform cusp height s for rapid prototyping is presented. Geometry model of a part is t ransferred f rom a CAD system to our slicing sof tware by the STEP standard format . Af ter the building direction of a part is selected , the user is prompted to specify different allowable cusp height s for different surfaces of the part . Then the CAD model is sliced adaptively and the sliced model is exported by SLC format . In the end , an instance is demonst rated and the result s are given. 3、逆向工程技术是随着计算机技术的发展和成熟以及数据测量技术的进步而迅速发展起来 的一门新兴学科与技术。它的出现，改变了原来 CAD 系统中从图纸到实物的设计模式， 为产品的迅速开发以及快速原型化设计提供了一条新的途径。曲线、曲面重建是逆向工程 中两个重要的问题，从已知的采样数据点出发，构造出物体的几何模型，它是对物体进行 分析、计算和绘制的根据，是研究曲面性质的重要工具。 Reverse engineering is a new subject and technology coming up with the development of computer science and data digitization. It s help to change the design mode from draft to models in conventional CAD systems. It s a new approach for rapid prototype manufacture. Curve and surface reconstruction are two basilica questions in reverse engineering. With the data acquired from one existent object, the geometrical models can be reconstructed which is a useful tools to study the existent object such as analysis, computing and rendering. 4、 本文针对散乱数据点曲线、曲面重建这一问题，提出了两种曲线重建算法曲线重 建的跟踪算法和基于场表示的曲线重建算法，以及基于切片表示的曲面重建方法。全文的 主要内容如下： 针对三维数据进行预处理的问题，提出了一种新的数据简化与表示方法。三维数据测量 是逆向工程的基础，所获得的数据点是进行曲面重建的根据。借助于医学图像中的切片技 术，提出了一种新的数据表示方法切片表示模型，将原始的无序数据点集转化为具有层 列结构的有序组织形式，不但确定了各点之间的相互关系，而且大量的减少了数据量。序 的概念的提出，为三维散乱数据点曲面重建做了重要的铺垫。 This thesis centers on the issue of curve and surface reconstruction from unorganized points. Two kind of curve reconstruction methodthe tracing algorithm and field