A single solution method for converting 2D assembly drawings to 3D part drawings

Although solid models play a central role in modern CAD systems, 2D CAD systems are still commonly used for designing products without complex curved faces. Therefore, an important task is to convert 2D drawings to solid models, and this is usually carried out manually even in present CAD systems. Many methods have been proposed to automatically convert orthographic part drawings of solid objects to solid models. Unfortunately, products are usually drawn as 2D assembly drawings, and therefore, these methods cannot be applied. A further problem is the difficult and time-consuming task of decomposing 2D assembly drawings into 2D part drawings. In previous work, the authors proposed a method to automatically decompose 2D assembly drawings into 3D part drawings, from which 2D part drawings can be easily generated. However, one problem with the proposed method was that the number of solutions could easily explode if the 2D assembly drawings became complex. Building on this work, here we describe a new method to automatically convert 2D assembly drawings to 3D part drawings, generating a unique solution for designers regardless of the complexity of the original 2D assembly drawings. The only requirement for the approach is that the assembly drawings consist of standard parts such as bars and plates. In 2D assembly drawings, the dimensions, part numbers and parts lists are usually drawn, and the proposed method utilizes these to obtain a unique solution.     

Reconstruction of 3D interacting solids of revolution from 2D orthographic views

3D CAD is replacing 2D CAD to improve efficiency of product design and manufacturing. Therefore, converting legacy 2D drawings into 3D solid models is required. CSG based approaches reconstruct solid models from orthographic views more efficiently than traditional B-rep based approaches. A major limitation of CSG based approaches has been the limited domain of objects that can be handled. This paper aims at extending the capabilities of CSG based approaches by proposing a hint-based recognition of interacting solids of revolution. This approach can handle interacting solids of revolution as well as isolated solids of revolution.     

Solid model reconstruction from engineering paper drawings using Genetic Algorithms

The wide applications of CAD/CAM technologies have promoted the development and application of many advanced technologies, such as digital manufacturing, rapid prototyping, enterprise resources planning, computer integrated manufacturing, concurrent engineering, virtual reality, and mass customization. These advanced technologies all need to be supported by three-dimensional (3D) solid models of products. Most enterprises, however, still organize their production using 2D paper drawings, which makes difficulties for the application of these advanced technologies. It is needed to convert engineering paper drawings into 3D solid models for applications. Based on holo-extraction of information from paper drawings, this paper develops a systematic 3D reconstruction method, which simulates an experienced human designer's thinking mode in transforming inaccurate outlines with inaccurate projection relationships in 2D drawings into 3D image, with the aid of Genetic Algorithms.     

基于哈希的二维工程 CAD 图纸检索技术

针对企业在设计创新过程中大量采用已有计算机辅助设计(CAD)图纸进行设计重 用的情况,提出了一种基于哈希的二维工程 CAD 图纸检索方法。首先基于环形分割算法提取 工程 CAD 图纸中每个组件对象几何特征;基于传统 LBP 算子提出了一种局部拓扑矢量量化模 式(T-LVQP),实现对各个组件拓扑特征的提取;然后基于协方差描述符融合几何特征和拓扑特 征,通过 LBG 算法将所有组件按照几何特征分组后得到工程 CAD 图纸的特征向量表达;最后 通过迭代量化哈希算法生成图纸的哈希序列。实验结果表明,该算法检索速度快、准确度高, 对于二维工程 CAD 图纸具有较好的检索效果。     

基于采矿CAD的硐室参数绘图系统设计及实现

CAD系统因其本身具有许多长处,得到了工程设计人员的广泛使用。但它只能处理图形的几何信息,真正具有工程实际意义的图形拓扑信息和参数约束信息均被抛弃了。为了保留更多的图形信息以及让工程设计人员更方便地进行硐室图形的绘制,文中根据采矿CAD图形的特点,把要绘制的硐室图形进行参数化分析,并通过编程调用采矿CAD的接口实现了硐室图形的自动绘制系统。此系统能根据用户输入的参数自动生成硐室的二维和三维图形,这大大减少了设计人员的工作量,提高了设计效率,也有利于计算机辅助设计的进一步发展。     

Reverse engineering applications for recovery of broken or worn parts and re-manufacturing: Three case studies

Damaged or broken parts are generally too expensive to replace, or are no longer available. RE can be defined as: ‘Systematic evaluation of a product with the purpose of replication. This involves design of a new part, copy of an existing part, recovery of a damaged or broken part, improvement of model precision and inspection of a numerical model. Advantages of the technique include immediate feedback, data reduction, direct generation of geometry and higher precision of the final product. This paper shows some possibilities of use and benefit from utilising the RE-methodologies and techniques in production process, especially in the case when exists parts without 3D-CAD support.This paper, which defines obtaining CAD data step by step from damaged three different parts to reproduce or make a new design for some recoveries, has not get any technical drawings. When these parts had been recovered, some problems occurred. These problems have been solved by referring to some practical approaches. Establishing continuity across curve and surface patches is an important concept in the free form surface modeling. The CAD models were recovered and reconstructed to consider parametric and geometric continuity. The iso-phote method was used for surface continuity analysis. Hence, in this work, not only occurring problems but also solving methods were explained. Firstly, CAD models are created from damaged and broken parts by data digitization method by using CMM and the process was explored in detailed. Later, CAD models that had been obtained earlier are transferred into CAM module of the software and G codes are taken by the NC post-processor, and finally, the parts are manufactured by means of CNC milling machine. Additionally, this paper presents a review of the part digitization techniques available for reverse engineering.     

基于二维视图特征的三维重建

在分析现有ＣＡＤ二维参数化设计,三维参数化设计以及三维重建方法的基础上,基于工程图图形的整体宏观性,图形拓扑性及三维视图的投影规律,提出了二维视图特征的概念及一种新的工程图处理方法。     

Design reuse oriented partial retrieval of CAD models

As a huge number of 3D CAD models is generated each year, retrieval of 3D CAD models is becoming more and more important for achieving design reuse. However, the existing methods for partial retrieval of 3D CAD models are very few and far from the requirements of design reuse. In this paper, we present an approach to partial retrieval of 3D CAD models for design reuse. The criteria for determining whether a subpart of 3D CAD models is reusable for design is defined first. Based on the criteria defined, all the design reusable subparts involved in the 3D CAD models in the library are automatically extracted and stored in the library as reference models. Moreover, each design reusable subpart in the library is represented by all its local matching regions in a hierarchical way so as to support multi-mode partial retrieval. In our approach, three partial retrieval modes including normal retrieval, exact retrieval and relaxed retrieval are defined to meet various partial retrieval requirements of design reuse such as the incomplete and vague queries during the early design stage. And the multi-mode partial retrieval is achieved by performing multi-mode matching and similarity assessment between the query and the design reusable subparts in the library indexed by bitmap. Experimental results are presented to demonstrate the effectiveness of the approach.     

Computer-aided microfluidics (CAMF): from digital 3D-CAD models to physical structures within a day

In this paper, we introduce computer-aided microfluidics (CAMF), a process that allows the creation of complex microfluidic structures from their concept to the actual chip within a day. During design and testing of new microfluidic systems, rapid and frequent design modifications have to be carried out. For this purpose, a device using maskless projection lithography based on a digital mirror device (DMD) has been developed. Digital mask layouts may be created using any graphics program (Microsoft Paint, Adobe Photoshop) and can be used as such by the custom-written control software of the system. However, we suggest using another approach: direct importing of three-dimensional digital computer-aided design (CAD) models from which mask information can be directly parsed. This process is advantageous as commercial 3D-CAD systems allow the rapid generation of static or parameterized models which can be used for computerized analyses like, e.g., flow simulation. After model validation, the mask information is extracted from these models and directly used by the lithography device. A chip or replication master is then created by means of lithography using curable monomers or resists as, e.g., Accura 60 or SU-8. With CAMF, the whole process from digital 3D model creation to actually running the experiment can be done within a day.     

Mapping 2D midship drawings into a 3D ship hull model based on STEP AP218

Standard for the exchange of product model data (STEP) AP218 has a standard schema to represent the structural model of a midship section. While its schema facilitate the exchange of ship structural models among heterogeneous systems, most shipyards and classification societies exchange information using 2D paper drawings. We propose a feature parameter input method to generate a 3D STEP model of a ship structure from 2D drawings. We have analyzed the ship structure information contained in 2D drawings and have defined a data model to express the contents of the drawing. We also developed a GUI for the feature parameter input. To translate 2D information extracted from the drawing into a STEP AP218 model, we have developed a shape generation library and have generated the 3D ship model through this library. The generated 3D STEP model of a ship structure can be used to exchange information between design departments in a shipyard as well as between classification societies and shipyards.     

建筑安装工程施工图设计与管理系统的实现

对安装工程施工图综合设计与管理系统的背景、总体设计作简要的介绍,由传统的二维图生成三维建筑构造图,建筑师可直接在三维空间设计水、风、电等安装子系统,进行碰撞检查和工程量统计,并对由三维模型图自动生成二维施工图的实现技术作较为详尽的叙述。     

基于Visual C++环境下的叶轮CAD系统设计

本文在 Visual C 环境下开发了一个渣浆泵叶轮设计的可视化 CAD系统。该系统按照软件工程的设计方法进行了程序系统的设计 ;系统采用可视化编程语言—Visual C 6.0编写 ;建立了便于维护与更新的叶轮设计数据库 ;该系统能根据设计结果自动生成工程图纸。该软件界面友好 ,易于使用 ,具有较强的实用性。     

工程设计中多图联动建模技术的研究与应用

工程设计中多图联动建模技术提供用户友好的工程设计空间,建立了工程原理图和多个工程布置图之间的信息关联。采用3D数据存储——2D图形可视转换技术,得到图形变换矩阵。把设备的各个视图的图块预存入图形库中,绘图时,设置相应的绘图图层,只要在布置图的一个视图中插入设备图,系统会在其他视图中自动插入相应的投影图形,并且当修改或者删除一个视图中的图形时,其他视图对应的图形也会自动完成相应的操作,实现了多个工程视图的联动。     

Automatic analysis and integration of architectural drawings

Recognition and integration of 2D architectural drawings provide a sound basis for automatically evaluating building designs, simulating safety, estimating construction cost or planning construction sequences. To accomplish these targets, difficulties come from (1) an architectural project is usually composed of a series of related drawings, (2) 3D information of structural objects may be expressed in 2D drawings, annotations, tables, or the composites of above expressions, and (3) a large number of disturbing graphical primitives in architectural drawings complicate the recognition processes. In this paper, we propose new methods to recognize typical structural objects and architectural symbols. Then the recognized results on the same floor and drawings of different floors will be integrated automatically for accurate 3D reconstruction.     

Topology based 2D engineering drawing and 3D model matching for process plant

Process plant models mainly include 3D models and 2D engineering drawings. Matching calculation between these CAD models has wide applicability in model consistency check and retrieval. In process plant, engineering design standards make 2D engineering drawing and 3D model differ in geometry, proportion and structure, leading to the inapplicability of current shape-feature based matching approaches. Since connection relationships between components are the core of a process plant, a topology based algorithm is proposed. Firstly, by exploiting components as vertices and relationships as edges, both 2D engineering drawing and 3D model are preprocessed into graph structures. Then each model’s relationship types are extracted from the graph. Finally, regarding the extracted relationship types as primary feature, feature similarity is calculated to measure the matching degree between their corresponding models. The proposed algorithm is geometric deformation invariant. Experiments with industrial applications are presented, which demonstrates the effectiveness and feasibility of the proposed algorithm.     

3D CAD技术的课程设计教改探讨

作为工程设计和产品开发工具的3D CAD技术必将普及。3DCAD技术的发展对高校教学也提出了严峻的挑战,3DCAD技术的课程设计教学是一个重要环节,应充分结合传统工程制图与二维CAD、三维CAD的教学,开展3D CAD技术的课程设计教学以提高运用计算机技术建立三维产品模型的能力。     

Identifying and constructing elemental parts of shafts based on conditional random fields model

Semantic information is very important for understanding 2D engineering drawings. However, this kind of information is implicit so that it is hard to be extracted and understood by computers. In this paper, we aim to identify the semantic information of shafts from their 2D drawings, and then reconstruct the 3D models. The 2D representations of shafts are diverse. By analyzing the characteristics of 2D drawings of shafts, we find that there is always a view which represents the projected outline of the shaft, and each loop in this view corresponds to an elemental part. The conditional random fields (CRFs) model is a classification technique which can automatically integrate various features, rather than manually organizing of heuristic rules. We first use a CRFs model to identify elemental parts with semantic information. The 3D elemental parts are then constructed by a parameters template method. Compared with the existing 3D reconstruction methods, our approach can obtain both geometrical information and semantic information of each part of shafts from 2D drawings. Several examples are provided to demonstrate that our algorithm can accurately handle diverse 2D drawings of shafts.     

超二维环境下尺寸驱动和参数设计的研究

超二维环境的最大特点在于使用了二维数据表示三维模型，实现了不建立三维模型直接对三维模型的各向投影进行参数设计，直接修改复杂工程图，由于相对三维工程实体，纯二维数据信息量不足，而按以往方法用多视图来弥补，又因视图间缺乏必要联系，无法建立和描述三维信息，因而，超二维模型引入视图投影信息，使之具有一定的三维信息。通过结合当前尺寸驱动和参数设计的现状，在超二维环境下，引和高等画法几何学多视图间的投影原理，