Commercial Computer-aided Design Systems Research Articles

Integrating Computer Vision and CAD for Precise Dimension Extraction and 3D Solid Model Regeneration for Enhanced Quality Assurance

This paper focuses on the development of an integrated system that can rapidly and accurately extract the geometrical dimensions of a physical object assisted by a robotic hand and generate a 3D model of an object in a popular commercial Computer-Aided Design (CAD) software using computer vision. Two sets of experiments were performed: one with a simple cubical object and the other with a more complex geometry that needed photogrammetry to redraw it in the CAD system. For the accurate positioning of the object, a robotic hand was used. An Internet of Things (IoT) based camera unit was used for capturing the image and wirelessly transmitting it over the network. Computer vision algorithms such as GrabCut, Canny edge detector, and morphological operations were used for extracting border points of the input. The coordinates of the vertices of the solids were then transferred to the Computer-Aided Design (CAD) software via a macro to clean and generate the border curve. Finally, a 3D solid model is generated by linear extrusion based on the curve generated in CATIA. The results showed excellent regeneration of an object. This research makes two significant contributions. Firstly, it introduces an integrated system designed to achieve precise dimension extraction from solid objects. Secondly, it presents a method for regenerating intricate 3D solids with consistent cross-sections. The proposed system holds promise for a wide range of applications, including automatic 3D object reconstruction and quality assurance of 3D-printed objects, addressing potential defects arising from factors such as shrinkage and calibration, all with minimal user intervention.

User Perspectives on Branching in Computer-Aided Design

Branching is a feature of distributed version control systems that facilitates the "divide and conquer" strategy present in complex and collaborative work domains. Branching has revolutionized modern software development and has the potential to similarly transform hardware product development via CAD (computer-aided design). Yet, contrasting with its status in software, branching as a feature of commercial CAD systems is in its infancy, and little research exists to investigate its use in the digital design and development of physical products. To address this knowledge gap, in this paper, we mine and analyze 719 user-generated posts from online CAD forums to qualitatively study designers' intentions for and preliminary use of branching in CAD. Our work contributes a taxonomy of CAD branching use cases, an identification of deficiencies of existing branching capabilities in CAD, and a discussion of the untapped potential of CAD branching to support a new paradigm of collaborative mechanical design. The insights gained from this study may help CAD tool developers address design shortcomings in CAD branching tools and assist CAD practitioners by raising their awareness of CAD branching to improve design efficiency and collaborative workflows in hardware development teams.

An automated topology optimization interpreter that generates space frames

This paper presents the methodology and theoretical foundation of topology optimization (TO) Results Spaceframe Interpreter, an automatic TO results interpreter that generates a closely associated space frame consisting of welded structural tubing or rectangular bars. TO is a computational technique that uses a finite element (FE) formulation to identify the most weight-efficient structure within a design domain. Density-based TO results in structures that take organic forms and is usually a tedious and cumbersome process to generate a computer-aided-design (CAD) model to manufacture through conventional techniques. The optimal topology frequently resembles a space frame, which is well-known as being a rigid, lightweight structure. The methodology of the TO results interpreter leverages several techniques from volumetric image processing and has four primary processes. First, the results are obtained from commercial FE/TO software and mapped into a cubic grid of voxels. Second, junction locations are extracted and member connectivity that represents a frame is identified. Third, a sizing optimization is incorporated to determine appropriate sectional dimensions of the circular or rectangular space frame members. Fourth, the optimized space frame geometry is imported into a CAD design tool to automatically create a design model. The logic and are implemented within the frame extraction processes. The automated TO interpreter is designed to interact with commercial FE analysis and CAD systems. The interpreter is demonstrated on various spatial examples including aerospace and automotive applications. In each case, the welded space frame closely resembles the TO result, with nearly equivalent stiffness and mass.

A decision-support method for multi-parameter editing of parametric CAD models

Parametric modeling is a computer-aided design (CAD) paradigm where a design can be created by defining geometric constraints with parameters. In design change as well as design optimization, the design is often edited by modifying the values of relevant parameters. Without guidance on allowable parameter ranges that can guarantee the intrinsic solvability of the geometric constraint system, the user could assign improper values to the model’s parameters, which would further lead to a failure in model updating. However, current commercial CAD systems provide little support on such guidance. Existing methods, though able to compute allowable ranges for individual parameters, face difficulties in handling multi-parameter situations. To solve this problem, a systematic method is proposed, supporting decision-making in multi-parameter model editing by computing allowable parameter ranges. In the method, a set of variable parameters from the geometric constraint system are first selected by the user; these variable parameters are to be sequentially edited within several editing operations. Before each editing operation, 1D allowable ranges of the variable parameters are computed. By editing parameter values within the provided ranges, the solvability of the geometric constraint system can be guaranteed. The effectiveness and efficiency of the proposed approach is verified by several experimental results.

Feature extraction for margin lines using region growing with a dynamic weight function in a one-point bidirectional path search

Abstract A margin line, defined as the boundary curve of the contact area between a prepared tooth and a dental restoration, considerably influences the end shape of the dental restoration design. Most studies that have extracted margin lines from mesh models representing prepared teeth have faced convergence problems in the path search and therefore pose the inconvenience of specifying multiple input points as intermediate goal points. To overcome these problems, in this study, we propose a bidirectional path-search algorithm using a single input point. First, the algorithm classifies all nodes in a mesh model into a margin or fuzzy region to increase search efficiency. Then, the search starts from one point and proceeds on two paths in opposite directions, using the current node of the opposite path as the temporary goal of the currently searched path. During the search, a dynamic evaluation function that varies weights according to the region type is employed to improve the path convergence. Finally, to increase the practicality of the algorithm, the jagged initial margin line is converted into a smooth spline curve using an energy-minimization function specialized for margin lines. To evaluate the proposed algorithm, margin lines extracted from various types of prepared teeth are demonstrated and compared with those created using some relevant previous works and a commercial dental computer-aided design (CAD) system. The comparison verified that accurate margin lines could be calculated with only one input point using the proposed algorithm. Moreover, the proposed algorithm showed better performance for crown and inlay/only experimental models compared with a commercial dental CAD system under the same conditions.

G-code generation in a NURBS workflow for precise additive manufacturing

Purpose Non-uniform rational B-splines (NURBSs) are the de facto standard for representing objects in computer-aided design (CAD). The purpose of this paper is to discuss how to stick to this standard in all phases of the additive manufacturing (AM) workflow, from the CAD object to the final G-code, bypassing unnecessary polygonal approximations. Design/methodology/approach The authors use a commercial CAD system (Rhino3D along with its programming environment Grasshopper) for direct slicing of the model, offset generation and trimming. Circular arcs are represented as quadratic NURBSs and free-form geometry as quadratic or cubic polynomial B-splines. Therefore, circular arcs are directly expressible as G2/G3 G-code commands, whereas free-form paths are rewritten as a succession of cubic Bézier curves, thereby admitting exact translation into G5 commands, available in firmware for AM controllers, such as Marlin. Findings Experimental results of this paper confirm a considerable improvement in quality over the standard AM workflow, consisting of an initial polygonization of the object (e.g. via standard tessellation language), slicing this polygonal approximation, offsetting the polygonal sections and, finally, generating G-code made up of polyline trajectories (G1 commands). Originality/value A streamlined AM workflow is obtained, with a seamless transfer from the initial CAD description to the final G-code. By adhering to the NURBS standard at all steps, the authors avoid multiple representations and associated errors resulting from approximations.

AutoMate

Assembly modeling is a core task of computer aided design (CAD), comprising around one third of the work in a CAD workflow. Optimizing this process therefore represents a huge opportunity in the design of a CAD system, but current research of assembly based modeling is not directly applicable to modern CAD systems because it eschews the dominant data structure of modern CAD: parametric boundary representations (BREPs). CAD assembly modeling defines assemblies as a system of pairwise constraints, called mates , between parts, which are defined relative to BREP topology rather than in world coordinates common to existing work. We propose SB-GCN, a representation learning scheme on BREPs that retains the topological structure of parts, and use these learned representations to predict CAD type mates. To train our system, we compiled the first large scale dataset of BREP CAD assemblies, which we are releasing along with benchmark mate prediction tasks. Finally, we demonstrate the compatibility of our model with an existing commercial CAD system by building a tool that assists users in mate creation by suggesting mate completions, with 72.2% accuracy.

Feature-based translation of CAD models with macro-parametric approach: issues of feature mapping, persistent naming, and constraint translation

Abstract Feature-based translation of computer-aided design (CAD) models allows designers to preserve the modeling history as a series of modeling operations. Modeling operations or features contain information that is required to modify CAD models to create different variants. Conventional formats, including the standard for the exchange of product model data or the initial graphics exchange specification, cannot preserve design intent and only geometric models can be exchanged. As a result, it is not possible to modify these models after their exchange. Macro-parametric approach (MPA) is a method for exchanging feature-based CAD models among heterogeneous CAD systems. TransCAD, a CAD system for inter-CAD translation, is based on this approach. Translators based on MPA were implemented and tested for exchange between two commercial CAD systems. The issues found during the test rallies are reported and analyzed in this work. MPA can be further extended to remaining features and constraints for exchange between commercial CAD systems.

Exchange of parametric assembly models based on neutral assembly constraints

It is difficult to exchange parametric assembly models using conventional neutral formats such as the standard for the exchange of product model data or the initial graphics exchange specification. These formats only support the boundary representation information that leads to the inability to perform parametric re-evaluation, once a model is exchanged. In order to exchange parametric information along with the design intent, a design history-based macro-parametric approach was proposed. Our method is macro-parametrics approach, however, supported only the exchange of individual part models. As most of the products are manufactured in assemblies, where several components are connected with multiple constraints, it is necessary to exchange the assembly model data. To overcome the issue of post-exchange editability, a collection of neutral assembly commands was introduced to extend the capabilities of the macro-parametric approach. A set of neutral assembly constraints was defined and a system for exchanging the parametric assembly models was implemented. An assembly model consisting of coaxial and incidence constraints was successfully exchanged between two commercial computer-aided design systems: CATIA and NX. It was possible to re-evaluate the assembly model parametrically after the exchange. The method can be further extended to exchange the remaining constraint types in different commercial computer-aided design systems.

ShapeGuide: Shape-Based 3D Interaction for Parameter Modification of Native CAD Data.

While Virtual Reality (VR) technologies are commonly used in industrial companies, loading and modifying CAD parts of commercial CAD systems in virtual environments are still challenging. A few VR applications for Computer Aided Design (CAD) enable users to modify native CAD data in an immersive environment. Even if such VR-CAD applications use 3D interaction space, interaction with parameter values of CAD parts could be enhanced. This paper presents ShapeGuide, a technique allowing users to modify native CAD parts using a shape-based 3D interaction technique. With ShapeGuide, users can achieve modification of parameter values by directly pushing or pulling the surface of a CAD object. In addition, force feedback can be integrated into the technique to enhance the precision of the users' hand motions in the 3D space. In a controlled experiment, we compared ShapeGuide to a standard one-dimensional scroll technique to measure its added value for parametric CAD data modification on a simple industrial product example with an adjusted modification capability. We also evaluated the effect of force feedback assistance on both techniques. Results of this experiment demonstrate that ShapeGuide is significantly faster and more efficient than the scroll technique. Furthermore, they show that the force feedback assistance enhances the precision of both techniques, especially of ShapeGuide.

Modeling and analysis for clearance machining process of end mills

Clearance of end mills has great impact on the performance of milling, and therefore a high demand for its machining theory and process is put forward. Based on the analysis of practical machining process, enveloping theory, principles of spatial geometry are introduced to establish the clearances processing model, as well as considering the geometries, orientations, and locations of wheels used to machine the clearances with convex, eccentric, or elliptic shapes. Accordingly, limitations of wheel geometry and location to machine a desired clearance are discussed. A commercial computer aided design system with API function programming is used to visualize the machining process. The solid model is finally obtained.

Model Consistency and Conflict Resolution With Data Preservation in Multi-User Computer Aided Design

Simultaneous multi-user computer aided design (CAD) allows multiple designers to contribute to the same model at the same time. The resulting parallel design workflow shortens product development cycles. In a replicated, simultaneous multi-user CAD system, modeling data must be kept consistent between clients. This paper presents a method that keeps independent copies of the models in sync between distributed CAD clients. This is accomplished by enforcing modeling operations to occur in the same order on all the clients. In case of conflict, a resolution method preserves conflicting operations locally for later reuse or resolution by the user. These methods are implemented in a commercial CAD system which has been enhanced to enable simultaneous multi-user. Validation tests are run to demonstrate that the methods implemented ensure model consistency and resolve conflicts while preserving conflicting operation data.

Approach to integrate product conceptual design information into a computer-aided design system

Commercial computer-aided design systems support the geometric definition of product, but they lack utilities to support initial design stages. Typical tasks such as customer need capture, functional requirement formalization, or design parameter definition are conducted in applications that, for instance, support “quality function deployment” and “failure modes and effects analysis” techniques. Such applications are noninteroperable with the computer-aided design systems, leading to discontinuous design information flows. This study addresses this issue and proposes a method to enhance the integration of design information generated in the early design stages into a commercial computer-aided design system. To demonstrate the feasibility of the approach adopted, a prototype application was developed and two case studies were executed.

CAD based shape optimization for gas turbine component design

In order to improve product characteristics, engineering design makes increasing use of Robust Design and Multidisciplinary Design Optimisation. Common to both methodologies is the need to vary the object’s shape and to assess the resulting change in performance, both executed within an automatic loop. This shape change can be realised by modifying the parameter values of a suitably parameterised Computer Aided Design (CAD) model. This paper presents the adopted methodology and the achieved results when performing optimisation of a gas turbine disk. Our approach to hierarchical modelling employing design tables is presented, with methods to ensure satisfactory geometry variation by commercial CAD systems. The conducted studies included stochastic and probabilistic design optimisation. To solve the multi-objective optimisation problem, a Pareto optimum criterion was used. The results demonstrate that CAD centric approach enables significant progress towards automating the entire process while achieving a higher quality product with the reduced susceptibility to manufacturing imperfections.

Integrated Framework for Vehicle Interior Design Using Digital Human Model

Evaluating the human friendliness of vehicles is essential for designing new vehicles since large numbers of human-machine interactions occur frequently inside vehicles. In this research, we develop an integrated framework for vehicle interior design using a digital human model (DHM). In this framework, the knowledge-based parametric modelling function of vehicles is implemented using a commercial computer-aided design (CAD) system. The combination of the DHM and the CAD system enables designers into carry out ergonomic evaluations of various human-vehicle interactions and understand the effects of modifications of vehicle design parameters on occupants during designing. Further, the information on human-vehicle interaction obtained using this system can be transmitted to dedicated biomechanical analysis software. By analysing human motions inside vehicles using such software, we can obtain optimized interior design parameters.

Synthesis of the web-based CAD viewer for interference verification of injection moulds

This paper describes the development of a web-based interference examination system in mould design processes. Although several commercial computer-aided design (CAD) systems offer interference inspection functions, those systems are very expensive and inadequate to perform collaborative works over the Internet. In this paper an efficient and precise hybrid interference examination algorithm applicable to multilevel assemblies is studied for injection mould design processes. In order to design a collaborative system over the distributed environment, lightweight CAD files produced from the optimally transformed CAD data through ACIS kernel and InterOp are applied to develop a web-based interference verification system. Collaborators related to the development of a new product can verify the interference over the Internet without commercial CAD systems. The system reduces production cost, errors and lead-time to the market. The validity of the developed system is confirmed through case studies.

A Methodology for Building Up an Infrastructure of Haptically Enhanced Computer-Aided Design Systems

This paper presents an infrastructure that integrates a haptic interface into a mainstream computer-aided design (CAD) system. A haptic interface, by providing force feedback in human-computer interaction, can improve the working efficiency of CAD/computer-aided manufacturing (CAM) systems in a unique way. The full potential of the haptic technology is best realized when it is integrated effectively into the product development environment and process. For large manufacturing companies this means integration into a commercial CAD system (Stewart, et al., 1997, “Direct Integration of Haptic User Interface in CAD Systems,” ASME Dyn. Syst. Control Div., 61, pp. 93–99). Mainstream CAD systems typically use constructive solid geometry (CSG) and boundary representation (B-Rep) format as their native format, while internally they automatically maintain triangulated meshes for graphics display and for numerical evaluation tasks such as surface-surface intersection. In this paper, we propose to render a point-based haptic force feedback by leveraging built-in functions of the CAD systems. The burden of collision detection and haptic rendering computation is alleviated by using bounding spheres and an OpenGL feedback buffer. The major contribution of this paper is that we developed a sound structure and methodology for haptic interaction with native CAD models inside mainstream CAD systems. We did so by analyzing CAD application models and by examining haptic rendering algorithms. The technique enables the user to directly touch and manipulate native 3D CAD models in mainstream CAD systems with force/touch feedback. It lays the foundation for future tasks such as direct CAD model modification, dynamic simulation, and virtual assembly with the aid of a haptic interface. Hence, by integrating a haptic interface directly with mainstream CAD systems, the powerful built-in functions of CAD systems can be leveraged and enhanced to realize more agile 3D CAD design and evaluation.

Reverse engineering of aesthetic products: use of hand-made sketches for the design intent formalization

In the context of styling products development, it is well known that sketches are the most immediate and used means for the ‘external representation’ of the industrial designers' intentions; the designer, however, also needs physical full-scale models, in order to evaluate the aesthetic solution. Reverse engineering techniques support the transformation of the physical mock-ups in digital ones, in order to perform the engineering developments. The observation of the design phases highlights the need to study new methodologies and computer-based tools, in order to simplify the reverse engineering process and to improve the quality of the final result. The conversion from real to virtual can be time consuming and strongly critical, in terms of product aesthetic and functional contents preservation. The process can be affected by several misunderstandings in the communication of the design values from the designer to the product engineers. In this paper, we propose a method for the formalization and recognition of the aesthetic properties within the different modes of design representation. The proposed method is based on the examination of the design principles used by the designer during the creative process (aesthetic intentions) and on techniques for the representation of creative ideas. In particular, we analyse the free-hand sketches and drawings to retrieve both the implicit (lines/curves) and explicit information (textual notes). Such information is used to develop a set of rules to support the identification of the styling lines on the points cloud data. The method has been experimented using a commercial computer-aided design system to manage the heterogeneous data (points cloud data, sketches and notes). The preliminary validation process shows good results in terms of time-saving. This is mainly due to two factors: the remarkable simplification of the surface reconstruction phase and the continuous monitoring of the aesthetic coherence.

Volume Parameterization for Design Automation of Customized Free-Form Products

This paper addresses the problem of volume parameterization that serves as the geometric kernel for design automation of customized free-form products. The purpose of volume parameterization is to establish a mapping between the spaces that are near to two reference free-form models, so that the shape of a product presented in free-form surfaces can be transferred from the space around one reference model to another reference model. The mapping is expected to keep the spatial relationship between the product model and reference models as much as possible. We separate the mapping into rigid body transformation and elastic warping. The rigid body transformation is determined by anchor points defined on the reference models using a least-squares fitting approach. The elastic warping function is more difficult to obtain, especially when the meshes of the reference objects are inconsistent. A three-stage approach is conducted. First, a coarse-level warping function is computed based on the anchor points. In the second phase, the topology consistency is maintained through a surface fitting process. Finally, the mapping of volume parameterization is established on the surface fitting result. Compared to previous methods, the approach presented here is more efficient. Also, benefitting from the separation of rigid body transformation and elastic warping, the transient shape of a transferred product does not give unexpected distortion. At the end of this paper, various industry applications of our approach in design automation are demonstrated. Note to Practitioners-The motivation of this research is to develop a geometric solution for the design automation of customized free-form objects, which can greatly improve the efficiency of design processes in various industries involving customized products (e.g., garment design, toy design, jewel design, shoe design, and glasses design, etc.). The products in the above industries are usually composed of a very complex geometry shape (represented by free-form surfaces), and is not driven by a parameter table but a reference object with free-form shapes (e.g., mannequin, toy, wrist, foot, and head models). After carefully designing a product around one particular reference model, it is desirable to have an automated tool for "grading" this product to other shape-changed reference objects while retaining the original spatial relationship between the product and reference models. This is called the design automation of a customized free-form object. Current commercial 3-D/2-D computer-aided design (CAD) systems, developed for the design automation of models with regular shape, cannot support the design automation in this manner. The approach in this paper develops efficient techniques for constraining and reconstructing a product represented by free-form surfaces around reference objects with different shapes, so that this design automation problem can be fundamentally solved. Although the approach has not been integrated into commercial CAD systems, the results based on our preliminary implementation are encouraging-the spatial relationship between reference models and the customized products is well preserved

Real-Time Collaborative Design With Heterogeneous CAD Systems Based on Neutral Modeling Commands

This paper presents an integration-based solution for developing a real-time collaborative design (co-design) platform on heterogeneous computer-aided design (CAD) systems. Different from the visualization-based approaches, the product models are allowed to be constructed and modified from various sites together in the proposed collaborative design platform. Our approach is based on a mechanism for the translation between system modeling operations (SMOs) and neutral modeling commands (NMCs). Every operation given by a user on one site is translated into a NMC and transmitted to all the other sites through the network, and then the received NMC is converted into corresponding SMOs on every other site, instantaneously. Since only the commands but not the product data are transferred, the data size under transmission is greatly reduced, so that a real-time synchronization can be achieved with a standard network bandwidth. In addition, by developing system-dependent SMO↔NMC translators on different client CAD systems, users on different sites could join the collaboration by using their familiar CAD systems; this is the benefit that cannot be offered by the homogeneous co-design systems. The prototype implementation proves that our approach works well for integrating various current popular commercial CAD systems into a real-time collaborative design platform.