A new method for machining feature extracting of objects using 2D technical drawings

In this study, a new method called “3-Space” has been developed to obtain 3D models of prismatic machine parts using 2D technical drawings. This method uses 3 surfaces named Base, Top and Sweep Base for the determination of the objects. The edge colors have been given to the surfaces with meanings, and are used for the determination of the type and characteristics of the objects. 4 characteristics of the processing objects (namely external access direction, exit status, boundary geometry and the processing order of the features) have been determined. First, the object is considered a prismatic raw material, and the features to be processed on it are removed. Then the remaining object itself is created and thus a 3D view of the object is obtained.     

Identification of sections from engineering drawings based on evidence theory

View identification is the basic process for solid reconstruction from engineering drawings. A new method is presented to label various views from a section-involved drawing and identify geometric planes through the object at which the sections are to be located. In the approach, a graph representation is developed for describing multiple relationships among various views in the 2D drawing space, and a reasoning technique based on evidence theory is implemented to validate view relations that are used to fold views and sections in the 3D object space. This is the first automated approach which can handle multiple sections in diverse arrangements, especially accommodating the aligned section for the first time. Experimental results are given to show that the proposed solution makes a breakthrough in the field and builds a promising basis for further expansibility, although it is not a complete one.     

基于形体逼近的三维重建算法

该文提出一种新的由三视图重建三维实体的算法,能扩展自顶向下的三维重建算法的形体覆盖域,并在Auto-CAD平台上验证了算法的有效性。算法的主要步骤是首先用平扫-旋转-求交的实体运算法则构造出与所求实体形状相近的实体———第1参照体,再模拟人脑的识图过程:把第1参照体的三视图与初始三视图对比,根据两者之间的差别构造出差异体,再从第1参照体中逐一减去差异体,得到第2参照体、第3参照体......最后得到所求的实体。     

A generic approach to recognising isolated, nested and interacting features from 2D drawings

Many useful three-dimensional (3D)-feature recognition systems have been developed over the past few decades. However there is a shortage of feature recognition systems in the two-dimensional (2D) domain. This has an adverse effect on the realisation of CADCAM benefits in Small and Medium Enterprises. Here is an attempt to redress this deficit. This paper presents a hint-based feature recognition system which recognises machining features from 2D orthographic projections through a two-stage process of profile searching and feature completion. Three types of profiles: Type I, II or III are defined in this system. Together they are sufficient to describe most profiles, if not all, in any 2D drawing. Profile searching identifies these profiles while feature completion establishes the cavity emanating from these profiles using a multi-level top–down approach. This process enables the system to deal with the isolated, nested and interacting features using a common framework. The nested features are handled by applying the same reasoning used for isolated features recursively while interacting features are decomposed automatically by the process of profile searching into their constituent isolated features.     

Handling sectional views in volume-based approach to automatically construct 3D solid from 2D views

This paper presents an algorithm for solid model reconstruction from 2D sectional views based on volume-ba`sed approach. None of the existing work in automatic reconstruction from 2D orthographic views have addressed sectional views in detail. It is believed that the volume-based approach is better suited to handle different types of sectional views. The volume-based approach constructs the 3D solid by a boolean combination of elementary solids. The elementary solids are formed by sweep operation on loops identified in the input views. The only adjustment to be made for the presence of sectional views is in the identification of loops that would form the elemental solids. In the algorithm, the conventions of engineering drawing for sectional views, are used to identify the loops correctly. The algorithm is simple and intuitive in nature. Results have been obtained for full sections, offset sections and half sections. Future work will address other types of sectional views such as removed and revolved sections and broken-out sections.     

三维环境下的工程图自适应优化技术

工程图纸是企业生产的重要依据,对三维环境下的工程图纸进行优化以符 合企业的要求很有必要。论文利用模型与图纸的关联性,给出了以模型模板和工程图模板为 基础的自适应优化原理。提出了模板定制的原则,并给出了模板普通定制与特殊定制的方法, 为后续优化奠定基础。详细论述了实现自适应优化的几个关键技术,包括视图定位,比例匹 配,尺寸定位与明细栏优化,获得了大型复杂装配体工程图良好的优化效果。     

Skeleton-enhanced line drawings for 3D models

We present a novel line drawing approach for 3D models by introducing their skeleton information into the rendering process. Based on the silhouettes of the input 3D models, we first extract feature lines in geometric regions by utilizing their curvature, torsion and view-dependent information. Then, the skeletons of the models are extracted by our newly developed skeleton extraction algorithm. After that, we draw the skeleton-guided lines from non-geometric regions through the skeleton information. These lines are combined with the feature lines to render the final line drawing result using the line optimization. Experimental results show that our algorithm can render line drawings more effectively with enhanced skeletons. The resulting artistic effects can capture the local geometries as well as the global skeletons of the input 3D models.     

工业建筑预埋件三维快速装配设计方法

当前工业建筑结构预埋件设计主要采用二维CAD 软件,效率较低且容易 出错。为此提出基于广义参数化模板的三维预埋件快速装配设计方法。该方法建立包含三维 参数化形状结构、安装定位方式和二维投影简图等各种信息的预埋件广义参数化模板;通过 构建预埋件参数化模板库,采用基于历史的装配设计技术,实现预埋件的快速安装设计。该 文方法已经集成到商品化工业建筑结构三维CAD 软件InteRDS 中,并在实际工程设计中得 到应用。     

Algorithms for converting photographs of fossils to ink drawings

Both pen-and-ink drawings and dither algorithms process a continuous-tone picture and generate a two-level black-and-white picture, in which dot-density is used to represent different tones. However, dithered images look different from pen drawings, and are not suitable as substitutes for manually-executed drawings. This paper discusses algorithms specifically designed or modified to process photographs of palaeontological specimens into images so closely resembling a hand drawing that they can often be published with little or no manual editing.     

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.     

AutoCAD环境下基于三维模型的二维视图创建方法

对AutoCAD环境下根据三维模型创建二维平面视图,尤其是剖视图的方法进行了分析探讨。方法之一是将三维模型上平行于投影面的表面或表面的轮廓线经复制、编辑、补线等操作,即得到对应于该投影面的视图、剖视图。方法之二是利用截面命令（section）或截面平面命令（sectionplane）创建穿过三维模型的横截面,再经编辑、补线等操作,将该横截面创建成所需的剖视图。     

Scheduling a single vehicle in the just-in-time part supply for a mixed-model assembly line

This paper focuses on the scheduling of a single vehicle, which delivers parts from a storage centre to workstations in a mixed-model assembly line. In order to avoid part shortage and to cut down total inventory holding and travelling costs, the destination workstation, the part quantity and the departure time of each delivery have to be specified properly according to predetermined assembly sequences. In this paper, an optimisation model is established for the configuration that only one destination workstation is involved within each delivery. Four specific properties of the problem are deduced, then a backward-backtracking approach and a hybrid GASA (genetic algorithm and simulated annealing) approach are developed based on these properties. Both two approaches are applied to several groups of instances with real-world data, and results show that the GASA approach is efficient even in large instances. Furthermore, the existence of feasible solutions (EOFS) is analysed via instances with different problem settings, which are obtained by an orthodox experimental design (ODE). An analysis of variance (ANOVA) shows that the buffer capacity is the most significant factor influencing the EOFS. Besides this, both the assembly sequence length and distances to workstations also have noticeable impacts.     

Intelligent approaches for generating assembly drawings from 3-D computer models of mechanical products

In order to reduce the time of mechanical product design and ensure the high quality of their assembly drawings, this paper develops an intelligent approach for generating assembly drawings automatically from three-dimensional (3-D) computer assembly models of mechanical products by simulating the experienced human designer's thinking mode with the aid of computer graphics and knowledge-based expert system. The key issues include the strategies and methods for selecting the necessary views in an assembly drawing, determining necessary sectional views in each view, eliminating the unreasonable projective overlap of the components in each view, and minimizing the numbers of both the views in an assembly drawing and the sectional views in each view. Based on the approach, corresponding software prototype was developed. Finally, it is demonstrated, from an example of the fixture in a modularized drilling machine, that its assembly drawing was generated successfully using this intelligent software prototype.     

Assembly failures and action cost in relation to complexity level and assembly ergonomics in manual assembly (part 2)

Earlier studies have demonstrated strong relationships between manual assembly at high physical load levels and increased amounts of quality defects compared to assembly at low physical load levels. A recent Swedish interview study of engineers in design and manufacturing engineering indicated that assembly complexity factors are of additional importance for the assembly quality. The objective of this study was therefore to examine the significance of high and low complexity criteria and the relationships between assembly ergonomics and assembly complexity and quality failures by analyzing manual assembly tasks in car manufacturing. In total, 47 000 cars were analyzed and the results showed several significant correlations between assembly ergonomics and assembly complexity, assembly time, failures and action costs. The action costs for high complexity tasks were 22.4 times increased per task per car compared to low complexity tasks.     

Holo-extraction of information from paper drawings for 3D reconstruction

The research on the conversion from 2D paper drawings to 3D computer feature models has been stuck in low-level coding. One of the reasons for it is that the three phases of understanding process has been isolated and people have been doing their research on only one of the phases since the whole conversion is very complicated and more difficult. For instance, the vectorization methods for the first phase were developed only for getting straight lines, arcs, circles, etc. so that much information contained in the drawing has been lost after the vectorization. This paper develops a holo-extraction method of information from paper drawings, the networks of single closed regions (SCRs), which can not only provide a unified base for recognizing both the annotations and the outlines of projections of parts, but also build the holo-relationships among SCRs so that it is convenient to extract lexical, syntactic and semantic information in the subsequent phases for 3D reconstruction.     

ArchiDNA: An interactive system for creating 2D and 3D conceptual drawings in architectural design

We present an interactive system called ArchiDNA for creating 2D and 3D conceptual drawings in architectural design. We developed a novel principle of shape generation called match-and-attach by analyzing drawing styles of a contemporary architect, Peter Eisenman. The process consists of user interaction techniques and a set of rules that decide how one or more shapes attach to another shape. One key ingredient of our process is a unique concept for the interactive semi-automatic shape generation that uses the combination of algorithmic rules of a computer and designers’ manual inputs. These techniques enable designers to use CAD software in the early stages of architectural designs to explore conceptual building forms. ArchiDNA dynamically responds to drawing inputs, configures 2D shapes, and converts them to 3D shapes in a similar style. We intend to complement existing CAD software and computational drawing pipelines for intuitive 2D and 3D conceptual drawing creation.     

A new recognition model for electronic architectural drawings

Current methods for recognition and interpretation of architectural drawings are limited to either low-level analysis of paper drawings or interpretation of electronic drawings that depicts only high-level design entities. In this paper, we propose a Self-Incremental Axis-Net-based Hierarchical Recognition (SINEHIR) model for automatic recognition and interpretation of real-life complex electronic construction structural drawings. We design and implement a series of integrated algorithms for recognizing dimensions, coordinate systems and structural components. We tested our approach on more than 200 real-life drawings. The results show that the average recognition rate of structural components is about 90%, and the computation time is significantly shorter than manual estimation time.     

制图标准中剖切面后结构画法的探讨

针对机械制图标准中有关旋转剖视图画法的规定,围绕剖视图中剖切面后 结构的画法,提出了“剖切面后的其他结构”和“剖切结构及其有关部分”的具体界限,当一些 结构没有直接被剖切到时,若它所在的形体的轴线为两剖切面的交线,应按剖切面后的其他 结构,按原来的位置投射;否则应按照“剖切结构及其有关部分”,随其所在结构旋转到新的 位置,使画法进一步明确。针对有些学者建议,删去制图标准中“剖切面后面的其他结构, 应按原位置投射”的规定,认为不能删去,并证明了自己的观点。     

A model for calculation of the costs of poor assembly ergonomics (part 1)

In product development there are many design requirements to meet and often tough project budgets to keep. Requirements that are considered not profitable will often be neglected, which affects assembly ergonomics. The objective of this study was to develop a calculation model for application in practice that enables calculation of costs of poor assembly quality related to assembly ergonomic conditions. The model is meant to be used by engineers and stakeholders in the design or redesign of manual assembly solutions. For that purpose, manual assembly tasks of 47061 cars at high, moderate and low physical load levels were analyzed with respect to assembly-related quality errors and corresponding action costs during production and on the market. The results showed that ergonomics high risk issues had 5–8 times as many quality errors as low risk issues and the earlier these were found the less were the action costs. The action costs for errors that were discovered late in assembly were 9.2 times more costly compared to early repair of errors in the factory. The action costs for quality errors that were found and corrected on the market were further 12.2 times more expensive to correct compared to actions taken in the factory. Examples are shown of how to apply the calculation model that was developed based on the obtained quality data.     

A gap-based approach to capture fitting conditions for mechanical assembly

An approach, called the GapSpace model, is proposed to find the sufficient and necessary conditions—we call these the ‘fitting conditions’ (FC)—for non-interfering mechanical assemblies. When different parts are assembled, some features will be in contact while other features may not be able to touch one another or they may interfere. We refer to the ‘gap size’ relating two features as zero, positive or negative. In the GapSpace approach, the linear sum of some gaps forms the FCs that are determined by the dimensions and tolerances. After all FCs are identified, tolerance analyses can be easily performed. The model can be integrated with commercial CAD products (such as Pro/E) for tolerance analysis.