Extended 3D annotations as a new mechanism to explicitly communicate geometric design intent and increase CAD model reusability

A successful implementation of the Model-Based Enterprise concept (MBE) requires maximizing the potential benefits of annotated 3D models. The foundations of the MBE model are established by digital product definition data practices, which are currently regulated by standards such as ASME Y14.41-2003 and ISO 16792:2006. At the center of the MBE concept is the notion of CAD model reusability, which relies on the idea that 3D CAD models can be reused both throughout the entire product lifecycle and as a starting point for future development of new products. In this context, a critical aspect of CAD model reuse is the proper identification and understanding of the geometric design intent that is usually expressed implicitly within the CAD model.In this work, we present a method to communicate geometric design intent explicitly by overloading and extending the scope of the current annotation instruments available in the MBE approach. We propose a new broader type of model annotation that we call “extended annotation”, where design information is represented both internally within the 3D model and externally, on a separate repository. This structure naturally demands additional mechanisms to support the interaction of users with the information. In order to manage the information stored in these extended annotations effectively, we implemented an annotation manager that automatically synchronizes the dual representation of the annotations. To reduce the visual clutter in the 3D model, the software provides powerful filtering, editing, and visualization capabilities, giving users complete control of the information stored in the model. Finally, a study was conducted with 60 participants to evaluate the performance of the proposed model and the usability of the annotation manager. Results show a statistically significant benefit of using the extended annotation system, suggesting the use of this model as a valuable approach to improve design intent communication.     

Standardized data exchange of CAD models with design intent

Modern CAD systems generate feature-based product shape models with parameterization and constraints. Until recently, standards for CAD data exchange among different CAD systems were restricted to the exchange of pure shape information. These standards ignored the construction history, parameters, constraints, features and other elements of ‘design intent’ present in the model to be transferred. This paper suggests an implementational foundation for CAD data exchange with the preservation of design intent, based on the use of newly published parts of the International Standard ISO 10303 (STEP). Case studies are presented which employ a hypothetical STEP application protocol (AP) using Parts 55, 108 and 111 of ISO 10303. A prototype translator based on this AP has been implemented and tested. The paper reports on the experience gained in ‘intelligent’ data exchange.     

A quantitative analysis of parametric CAD model complexity and its relationship to perceived modeling complexity

Digital product data quality and reusability has been proven a critical aspect of the Model-Based Enterprise to enable the efficient design and redesign of products. The extent to which a history-based parametric CAD model can be edited or reused depends on the geometric complexity of the part and the procedure employed to build it. As a prerequisite for defining metrics that can quantify the quality of the modeling process, it is necessary to have CAD datasets that are sorted and ranked according to the complexity of the modeling process. In this paper, we examine the concept of perceived CAD modeling complexity, defined as the degree to which a parametric CAD model is perceived as difficult to create, use, and/or modify by expert CAD designers. We present a novel method to integrate pair-wise comparisons of CAD modeling complexity made by experts into a single metric that can be used as ground truth. Next, we discuss a comprehensive study of quantitative metrics which are derived primarily from the geometric characteristics of the models and the graph structure that represents the parent/child relationships between features. Our results show that the perceived CAD modeling complexity metric derived from experts’ assessment correlates particularly strongly with graph-based metrics. The Spearman coefficients for five of these metrics suggest that they can be effectively used to study the parameters that influence the reusability of models and as a basis to implement effective personalized learning strategies in online CAD training scenarios.     

Exemplar-based statistical model for semantic parametric design of human body

This paper presents an exemplar-based method to provide intuitive way for users to generate 3D human body shape from semantic parameters. In our approach, human models and their semantic parameters are correlated as a single linear system of equations. When users input a new set of semantic parameters, a new 3D human body will be synthesized from the exemplar human bodies in the database. This approach involves simpler computation compared to non-linear methods while maintaining quality outputs. A semantic parametric design in interactive speed can be implemented easily. Furthermore, a new method is developed to quickly predict whether the parameter values is reasonable or not, with the training models in the human body database. The reconstructed human bodies in this way will all have the same topology (i.e., mesh connectivity), which facilitates the freeform design automation of human-centric products.     

Multi-agent collaborative 3D design with geometric model at different levels of detail

This paper presents a scheme for collaborative 3D design using product model at various levels of detail (LODs). Design features are selectively hidden at each level from certain participants, depending on their actual needs and individual accessibility in the collaboration. A tree data structure represents the feature hierarchy of CAD construction, the link between feature and LOD, and 2D mesh data for display control of each feature. An XML/XSLT-based approach is proposed to enable real-time visualization of different LOD models in distributed environment. A collaborative design system is implemented using multi-agent technologies, which focuses on function design of each agent, interactions among agents, the client–server structure, and generation of the LOD data using the XML/XSLT approach. A scenario of synchronous 3D mold assembly demonstrates that geometric categorization of product model provides an operational mechanism for assuring security of information sharing in engineering collaborations over the Internet. It also validates the effectiveness of the agent technologies for automating complex engineering activities.     

The design and realization of CoViD: a system for collaborative virtual 3D design

Many important decisions in the design process are made during fairly early on, after designers have presented initial concepts. In many domains, these concepts are already realized as 3D digital models. Then, in a meeting, the stakeholders for the project get together and evaluate these potential solutions. Frequently, the participants in this meeting want to interactively modify the proposed 3D designs to explore the design space better. Today’s systems and tools do not support this, as computer systems typically support only a single user and computer-aided design tools require significant training. This paper presents the design of a new system to facilitate a collaborative 3D design process. First, we discuss a set of guidelines which have been introduced by others and that are relevant to collaborative 3D design systems. Then, we introduce the new system, which consists of two main parts. The first part is an easy-to-use conceptual 3D design tool that can be used productively even by naive users. The tool provides novel interaction techniques that support important properties of conceptual design. The user interface is non-obtrusive, easy-to-learn, and supports rapid creation and modification of 3D models. The second part is a novel infrastructure for collaborative work, which offers an interactive table and several large interactive displays in a semi-immersive setup. It is designed to support multiple users working together. This infrastructure also includes novel pointing devices that work both as a stylus and a remote pointing device. The combination of the (modified) design tool with the collaborative infrastructure forms a new platform for collaborative virtual 3D design. Then, we present an evaluation of the system against the guidelines for collaborative 3D design. Finally, we present results of a preliminary user study, which asked naive users to collaborate in a 3D design task on the new system.     

Retrieving 3D CAD model by freehand sketches for design reuse

Reuse of existing designs can help companies save up a significant amount of time and money in large-scale product development. Searching out similar CAD models of products is a key to facilitating design reuse. This paper proposes a method for retrieving CAD models of mechanical parts by freehand sketches. Users can draw three2D outline sketches and a skeleton sketch to express their query intent. The 2D outline sketches describe the geometrical information of models and the skeleton sketch contains the topological information. A relevance feedback mechanism is introduced to combine the two similarity degrees measured by 2D outlines or skeleton into a unified one. Experiments are conducted to evaluate the performance of the proposed method.     

Exploring teachers' use of TPACK in design talk: The collaborative design of technology-rich early literacy activities

Research shows the benefits of collaborative design activity by teachers are that in their conversations (design talk) they develop technological pedagogical content knowledge (TPACK). While more and more teachers engage in collaborative design, little is known about how they use TPACK during design. The main question of this study was: “What is the nature of design talk of a group of teachers during the design of technology-rich early literacy activities?” Using a holistic case study on design talk, the analysis focused on the topics that were under discussion and how these topics were discussed. Three phases of coding were applied: (a) how design represents any of the seven domains of TPACK knowledge (Pedagogical, Content, Technological, Technological Pedagogical, Technological Content, Pedagogical Content or Technological Pedagogical Content Knowledge); (b), how design talk represented three aspects of reasoning (external priorities, practical concerns and existing orientations); and (c), and what levels of inquiry are reached (no-depth; sharing ideas; analyze; and plan). Findings indicate that design talk reflects moments in which teachers reach deeper levels of inquiry. Findings also indicate that TPACK was mostly linked to expressing practical concerns. However when engaging in deeper inquiry, teachers existing orientations featured more prominently in the conversations. External priorities hardly seemed to play any role in design talk. Also, when addressing TPACK or PCK, design talk mostly reflects practical concerns. Pedagogy was addressed not as a single knowledge domain, rather in conjunction with the other two domains. Practical implications are discussed regarding how to support teachers during collaborative design.     

Repairing CAD model errors based on the design history

For users of CAD data, few things are as frustrating as receiving unusable, poor quality data. Users often waste time fixing or rebuilding such data from scratch on the basis of paper drawings. While previous studies use the boundary representation (B-Rep) of CAD models, we propose an approach to repairing CAD model errors that is based on the design history. CAD model errors can be corrected by an interdependency analysis of the feature commands or of the parametric data of each feature command, as well as by a reconstruction of the feature commands through rule-based reasoning of an expert system. Unlike other correction methods based on B-Rep models, our method repairs parametric feature models without translating them to a B-Rep shape, and it also preserves parametric information.     

Distributed design review using tangible augmented technical drawings

In this work we integrate augmented reality technology in a product development process using real technical drawings as a tangible interface for design review. We present an original collaborative framework for Augmented Design Review Over Network (ADRON). It provides the following features: augmented technical drawings, interactive FEM simulation, multimodal annotation and chat tools, web content integration and collaborative client/server architecture. Our framework is intended to use common hardware instead of expensive and complex virtual or augmented facilities. We designed the interface specifically for users with little or no augmented reality expertise proposing tangible interfaces for data review and visual editing for all the functions and configurations. Two case studies are presented and discussed: a real-time “touch and see” stress/strain simulation and a collaborative distributed design review session of an industrial component.     

A model for capturing and representing the engineering design process

This paper presents a Collaborative Model for capturing and representing the engineering Design process (CoMoDe). CoMoDe is a deductive object-oriented model that, in relation to an engineering design process, is able to capture the different elements that participate in a design process in an integrated fashion. In particular, it is able to represent (i) the activities, operations, and actors that have generated each design product, (ii) the imposed requirements, and (iii) the rationale behind each decision. Furthermore, it also offers an explicit mechanism to represent and trace the different model versions that have participated in the design process. On such a basis, this proposal introduces specific procedures to handle various situations appearing in cooperative environments. They are: (i) different design teams perform independent concurrent activities on “a priori” independent parts of the artefact being designed and afterwards their results need to be made consistent; (ii) distinct teams concurrently work on slightly coupled parts of the artefact being designed and conflict handling must be addressed along their “parallel” course of actions.     

An educational exercise examining the role of model attributes on the creation and alteration of CAD models

Computer-aided design (CAD) is a ubiquitous tool that today’s students will be expected to use proficiently for numerous engineering purposes. Taking full advantage of the features available in modern CAD programs requires that models are created in a manner that allows others to easily understand how they are organized and alter them in an efficient and robust manner. The results of a class-based exercise are presented to examine the role of model attributes on model creation, alteration, and student perception. Two popular CAD programs are used for the exercise: SolidWorks and Pro|Engineer. General results from both programs are reported. Fewer more complex features are found to be correlated with reduced modeling time. Simple features are shown to be positively correlated with the number of features retained without change. More complex features are found to be negatively correlated with the number of new features. Student perceptions of model quality and intuitiveness are positively correlated with the amount of feature reuse. Student survey data shows a preference for simpler features, the naming of features, and the use of reference geometry. The results do not allow for a generic approach regarding feature complexity to be prescribed. Overall, properly conveying design intent is shown to be positively correlated with design retention and negatively correlated with alteration time.     

Collaborative design in the era of cloud computing

The paper describes the application of the latest Information Technologies in business processes such as design and manufacturing. More specifically it examines the use of cloud computing in the mechanical drawing and design process of an enterprise. It proposes a specific architecture with different servers, for the implementation of a collaborative cloud based Design system. Finally as an application example, it compares the operating cost of an industry’s design department before and after the use of the proposed system. This example uses a private cloud deployment model so that the comparison of the operating cost would be feasible. While public cloud may offer more functionality and economy, private cloud is best suitable to make conclusions and comparison between on-premise and cloud operation, because all of the cost is handled by the organization that uses it.     

三维设计方法在地下矿山开拓设计中的应用

针对采用二维设计方法难以快速有效地获得最佳开采方案的问题,系统地介绍了三维设计方法的应用基础、"工作面+切片"功能、三维井巷工程模型创建和设计指标统计功能等。采用三维设计方法设计了云南某铁矿开拓系统方案,并对各方案进行了比较分析,最终确定了合理的开拓方案。     

Automation in the design of EDM electrodes

Plastic parts, especially those designed for consumer electronics products, are becoming more compact and freeform in shape. This requires the construction of compact and delicate geometric features in the injection moulds that produce these parts. It is now common practice to employ electric discharge machining (EDM) whenever the conventional machining process fails to machine such delicate features. Although CAD/CAM systems are widely used in mould design and manufacturing, and specific commercial CAD/CAM systems that are customized for injection mould applications are also available, there are still no intelligent CAD tools that address the specific requirements of EDM electrode design. The aim of this research is to develop an intelligent CAD tool that supports EDM electrode design. This CAD tool uses a new technique that recursively splits the EDM region into sub-regions until machinable electrodes can be constructed. The CAD tool has been implemented and integrated into a commercial CAD/CAM system, and 40 different real designs has been used to test its capability in handling a wide variety of geometric shapes. Performance data show that the efficiency of the design process can be improved by at least 50%, with a potential to achieve 85% through improved implementation and further research.     

基于几何特征的三维模型变形与编辑*

在三维计算的基础上针对三维颅面模型,提出了一种基于几何特征的三维模型变形与编辑算法。该算法采用迭代过程,即每进行一次变形便可以重新计算调整后的颅面几何特征值,如果满足需要则退出编辑并保存模型;否则继续变形,直到得到满意的三维模型为止。在局部变形中,为了弥补自由变形技术在变形控制和用户交互方面的不足,对点约束局部变形算法进行了改进。实验证明,该算法实现简单,且具有良好的交互性,变形效果良好。     

Common design structures and substitutable feature discovery in CAD databases

It has been widely reported that the reuse of previously created components, or features, in new engineering designs will improve the efficiency of a company’s product development process. Although the reuse of engineering components has established metrics and methodologies, the reuse of specific design features (e.g. stiffening ribs, hole patterns or lubrication grooves, etc.) has received less attention in the literature. Typically, researchers have reported approaches to partial design reuse that identify patterns predominately in terms of geometrically similar shapes (i.e. a set of features) whose elements are adjacent, cohesive, and decoupled from the overall form of a component.In contrast, this paper defines a common design structure (CDS) as collections of frequently occurring features (e.g. holes) with common parametric values (e.g. diameters) in a CAD database (irrespective of their locations or spatial connectivity between other features on a component). By exploiting the established data-mining technology of association rules and item-sets the authors show how CDSs can be efficiently computed for hundreds of 3D CAD models. A case study, with hole data extracted from a publicly available dataset of hydraulic valves, is presented to illustrate how item-sets associated with CDS can be computed and used to support predictive design by identifying potentially ‘substitutable features’ during an interactive design process. This is done using a combination of association rules and geometric compatibility checks to ensure the system’s suggestion are implementable. The use of the Kullback–Leibler divergence to assess the degree of similarity between components is identified as a crucial step in the process of identifying the “best” suggestions. The results illustrate how the prototype implementation successfully mines the CDSs and identifies substitutable hole features in a dataset of industrial valve designs.