Current Computer-aided Design Systems Research Articles

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.

Intuitive approach for design of inner structure by mimicking magnetic effect

Abstract Three-dimensional (3D) printers enable the realization of parts with complex shapes, particularly parts with an internal structure as well as an external shape. They are beginning to be used in real production as well as for prototyping. Because 3D printers allow shapes for parts that could not be imagined when conventional machining processes were the only fabrication methods, designers need to design porous parts with minimum weights that can maintain the required load-bearing capability without concerns about the realization of those parts. However, designers cannot design the internal structure of the parts using the current computer-aided design systems as freely as they can design the external shape. Therefore, in this paper, an intuitive design tool is proposed for users to interactively design an internal structure inside given external shape. To create a porous structure inside given closed volume, we aimed to generate a honeycomb-like structure comprising cells whose size and crowdedness can be intuitively manipulated by a designer. Thus, fine cells exist in certain regions, while coarse cells exist in the remaining regions according to the design. To realize this aim, the phenomenon in which more iron particles are attracted near a magnet and fewer are attracted further away from the magnet is imitated. More and finer honeycomb-like cells are attracted near a magnet located on the external surface of the closed volume. The designer can add magnets and move them on the external surface until the desired internal honeycomb-like structure is obtained.

Shipbuilding 3D CAD Tools as an Integrated Solution from Concept to Product

In the naval design process, there is still no consensus on the use of 3D CAD (Computer Aided Design) systems in the early stages of design. However, the integration capability of different modules is currently making their incorporation in the initial stages more appealing. The objective of this paper is to study the early stages of design as part of the whole process and to demonstrate the convenience of using a single 3D tool during the whole project. Therefore, its impact on the whole design process will be analysed by considering the basic and early design capabilities of current CAD systems, reviewing how the main naval architecture and marine engineering demands match the features and what is the solution provided by the CAD for each case. The methodology presented offers advantages from a technical, economic and time point of view.

Constructing assembly design model capable of capturing and sharing semantic dynamic motion information in heterogeneous CAD systems

Over the last decades, collaborative assembly design has received much attention, which has provided fruitful results in terms of data models, knowledge-based, and top-down geometric modeling approaches, to name a few. Particularly, researchers have focused their efforts towards assembly relationships within product models, but have limited the scope to static assembly geometric description as currently stated in computer-aided design (CAD) systems. A disruptive vision is assumed in this research work, arguing that the assembly design itself presents a dynamic nature via, especially, dynamic motion. Such a paradigm shift requires an appropriate logical and semantic foundation to augment current CAD systems and data models’ capabilities with the capture of dynamic phenomena such as assembly motions and kinematic behaviors. Traditional CAD systems nowadays can handle the kinematics-related motion-related information; however, the interoperation of this motion-related information from one CAD system to the other is still a limitation of the interoperability standards. To tackle this research challenge, this paper aims at defining an original framework built upon a formal ontology to capture and share dynamic assembly motion among heterogeneous CAD systems. The formal ontology uses spatiotemporal mereotopology, which serves as a theoretical backbone to qualitatively describe the dynamic behavior of a product. This theory addresses the qualitative description of the temporal dimension over the spatial dimension of 3D objects. The proposed ontology is then enhanced to maintain semantic continuity of the spatial and temporal aspects embedded in assembly design ontology models. Built with a Web Ontology Language (OWL) data structure to interact with a CAD system and a motion visualization application, the ontology ensures the dynamic motion information capturing and sharing. SWRL (Semantic Web Rule Language) is utilized to show the semantic reasoning among the moving and non-moving parts of the product assembly. As a result, a semantic articulation ensuring flexibility and interoperability as a competitive industrial edge is demonstrated with proof of concept to be effective in a collaborative assembly design environment.

Problems of Creation and Usage of 3D Model of Structures and Theirs Possible Solution

This article describes problems that occur when creating three-dimensional (3D) building models. The first problem is geometric accuracy; the next is the quality of visualization of the resulting model. The main cause of this situation is that current Computer-Aided Design (CAD) software does not have sufficient means to precision mapping the measured data of a given object in field. Therefore the process of 3D model creation is mainly a relatively high proportion of manual work when connecting individual points, approximating curves and surfaces, or laying textures on surfaces. In some cases, it is necessary to generalize the model in the CAD system, which degrades the accuracy and quality of field data. The article analyzes these problems and then recommends several variants for their solution. There are described two basic methods: using topological codes in the list of coordinates points and creating new special CAD features while using Python scripts. These problems are demonstrated on examples of 3D models in practice. These are mainly historical buildings in different locations and different designs (brick or wooden structures). These are four sacral buildings in the Czech Republic (CR): the church of saints Johns of Brno-Bystrc, the Church of St. Paraskiva in Blansko, further the Strejc’s Church in Židlochovice, and Church of St. Peter in Alcantara in Karviná city. All of the buildings were geodetically surveyed by terrestrial method while using total station. The 3D model was created in both cases in the program AUTOCAD v. 18 and MicroStation.

Research on Design Strategies of Cognitive Training System Based on SCD Elderly Behavioral and Psychological Characteristics

Alzheimer’s disease (hereinafter referred to as AD) has become a major global health problem for the elderly. Combining with the current computer-aided design system design for prevention and training of Alzheimer’s disease is one of the important ways to solve this problem. This study aims at the early subjective cognitive decline of Alzheimer’s disease (hereinafter referred to as SCD) . Through investigation and research, the behavior and psychological characteristics of SCD elderly are sorted out, and the main functions of cognitive training system are located. The main functions, interactions, colors and layout of the current cognitive system are summarized by analyzing the existing cognitive training system, and compared with the research results, a more reasonable system function, interaction mode, interface color and layout are determined. Therefore, the cognitive training system design strategy based on the behavioral and psychological characteristics of SCD elderly is summarized.

Sustained Integration for Computer-Aided Manufacturing: Integrating With Successive Versions of Step or IGES Files

Computer-aided design (CAD)/computer-aided manufacturing (CAM)/computer-aided engineering (CAE) integration offers designers, analysts, and manufacturers the opportunity to share data efficiently throughout the product development process. CAM for NC programing and tool design integrated with solid model data from CAD systems represents a large portion of the CAD/CAM/CAE domain. Sustained integration whereby successive changes to a CAD model are reintegrated with downstream applications is considered the most advanced and useful integration. Sustained integration is typically maintained when working in a homogeneous CAD/CAM environment. However, when working with applications that do not share a common environment (i.e., heterogeneous integration), sustained integration fails, and this lack of sustained integration can result in a loss of detailed information as a design progresses through the engineering design process. In the current paper, the authors discuss and demonstrate a novel approach to achieve sustained integration when working in heterogeneous CAD/CAM environments. After providing basic background information to establish a context, then discussing state-of-the-art and emerging solutions, the paper discusses virtual persistent identifiers as described via design change vectors (VPI/DCV). A series of three case studies shows sustained integration based on neutral formats like STEP working as well as that observed in homogeneous environments. This novel approach demonstrates success as a generic solution using common export formats from the current CAD systems and avoids the need to establish any new standards to achieve sustained integration. The paper finishes with a summary of observations learned from these case studies along with possible future research topics.

A study of 4D printing and functionally graded additive manufacturing

PurposeThe purpose of this paper is to extend existing knowledge of 4D printing, in line with Khoo et al. (2015) who defined the production of 4D printing using a single material, and 4D printing of multiple materials. It is proposed that 4D printing can be achieved through the use of functionally graded materials (FGMs) that involve gradational mixing of materials and are produced using an additive manufacturing (AM) technique to achieve a single component.Design/methodology/approachThe latest state-of-the-art literature was extensively reviewed, covering aspects of materials, processes, computer-aided design (CAD), applications and made recommendations for future work.FindingsThis paper clarifies that functionally graded additive manufacturing (FGAM) is defined as a single AM process that includes the gradational mixing of materials to fabricate freeform geometries with variable properties within one component. The paper also covers aspects of materials, processes, CAD, applications and makes recommendations for future work.Research limitations/implicationsThis paper examines the relationship between FGAM and 4D printing and defines FGAM as a single AM process involving gradational mixing of materials to fabricate freeform geometries with variable properties within one component. FGAM requires better computational tools for modelling, simulation and fabrication because current CAD systems are incapable of supporting the FGAM workflow.Practical implicationsIt is also identified that other factors, such as strength, type of materials, etc., must be taken into account when selecting an appropriate process for FGAM. More research needs to be conducted on improving the performance of FGAM processes through extensive characterisation of FGMs to generate a comprehensive database and to develop a predictive model for proper process control. It is expected that future work will focus on both material characterisation as well as seamless FGAM control processes.Originality/valueThis paper examines the relationship between FGAM and 4D printing and defines FGAM as a single AM process that includes gradational mixing of materials to fabricate freeform geometries with variable properties within one component.

Sketch-based shape exploration using multiscale free-form surface editing

AbstractThe hierarchical construction of solid models with current computer-aided design systems provide little support in creating and editing free-form surfaces commonly encountered in industrial design. In this work, we propose a new design exploration method that enables sketch-based editing of free-form surface geometries where specific modifications can be applied at different levels of detail. This multilevel detail approach allows the designer to work from existing models and make alterations at coarse and fine representations of the geometry, thereby providing increased conceptual flexibility during modeling. At the heart of our approach lies a multiscale representation of the geometry obtained through a spectral analysis on the discrete free-form surface. This representation is accompanied by a sketch-based surface editing algorithm that enables edits to be made at different levels. The seamless transfer of modifications across different levels of detail facilitates a fluid exploration of the geometry by eliminating the need for a manual specification of the shape hierarchy. We demonstrate our method with several design examples.

Formula omitted] quintic polynomial approximation for Generalised Cornu Spiral segments

Within Computer Aided Design (CAD) there is a need to construct fair curves. The Generalised Cornu Spirals (GCSs) are a set of curves with a monotonic curvature profile and are hence considered fair but implementation in current CAD systems is not straightforward, partly due to not being in the usual polynomial form.A method to approximate a GCS using a quintic polynomial curve is presented. The method seeks to interpolate the GCS to satisfy the G3 constraints at the end points with a quintic Bézier, leaving two degrees of freedom.An initial approximation is shown to be effective for the majority of GCS curves. Moreover, it is possible to determine when an initial approximation is likely to be poor. If this approximation does not meet the tolerance required, a search involving two parameters is performed. Characteristics of the search domain are used to establish a suitable starting value.

Automated design knowledge capture and representation in single-user CAD environments

Current computer-aided design systems excel at recording the final design solution for an engineering problem; however, they are not as adept at capturing the individual designer's rationale, knowledge or the process used during the design session. Being able to access this information will give insight into the reasons why key design decisions were made which, in turn, will support engineers who have to make revisions to the product in the future. Therefore, it would be beneficial if CAD systems were able to record design knowledge automatically. The research in this paper attempts to address this issue with a system that unobtrusively captures design processes and design knowledge by logging individual designer behaviour and system interactions while a CAD system is being used; user trials generated around 700 log files that were then analysed to extract these. In addition, various CAD system-independent representations were output to give a visual and formal representation of the processes that occurred. Overall, although carried out within a constrained design environment, this early knowledge capture work demonstrates the potential for automated knowledge capture and subsequent representations within CAD environments as well as the feasibility of design information push.

Problems in current CAD systems

In this paper, problems of current computer aided design (CAD) systems are discussed. One problem is the existence of tolerance. Because of tolerance, geometric operations become unstable and CAD data-exchange becomes a troublesome task. The second problem is CAD data durability. There is almost no compatibility between CAD data of different versions of the same system. Thus, users of CAD systems are confronted with great difficulties when they try to keep CAD data for a long time. As a solution to these problems, a CAD kernel based on history-based parametrics is proposed.

A Focus On Use

This article analyses the need and benefit of the working of industrial designers and product engineers together. According to engineers and others at the forefront of product development, to do the job right requires a collaboration involving design engineers, industrial designers, manufacturing engineers, and several other players, like marketing people, all of whom have important knowledge that needs to influence a design. Companies such as Trek Bicycle Corp. and Empire Level Manufacturing Corp. have developed practices that foster innovative, human-centered product development. Experts agree that computer-aided design (CAD) and rapid prototyping applications are the two most helpful systems, even though the two types of designers may use the tools in somewhat several ways. According to Rainer Gawlick, vice president of marketing at SolidWorks in Concord, Massachusetts, current CAD systems can help bridge the design-to-engineering-to-manufacturing gap.

Virtual customisation of product physical properties: a case of real time product stiffness customisation

In the early design stage, frequent design changes are often made. In order to assist the designer to make sensible changes easily and quickly, a computer system should provide functions that model not only product geometry, but also some aspects of product properties such as stiffness in real time. Current Computer-Aided Design (CAD) systems mainly support product geometric properties and visualisation. Physical properties such as stiffness are difficult or even impossible to be perceived in existing CAD systems. In this paper, a haptic system is developed to evaluate the product physical properties such as product surface textures and stiffness that are directly related to customer comfort. A toothbrush design and evaluation case study is implemented to showcase how effectively the haptic system could help a designer in the early design stage. Since these physical properties of a product, traditionally evaluated based on physical prototypes, can now be perceived and customised in a virtual environment in real time, the product development cycle can be shortened and the cost in making prototypes can be reduced.

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.

Haptic rendering: An approach to tactile property perception in early product design

In today's competitive market place, product designers need to elaborate their design with respect to not only the form and function but also the tactile properties, which make the product safe and comfortable to use. Several examples of these tactile properties are stiffness, surface finish, and trigger actuation force. Because of the expensive redesign processes, requirements on these tactile properties should be considered as constraints and should be brought into the product development cycle as early as possible. However, current visual feedback-based computer-aided design (CAD) systems focus mainly on product geometrical properties, such as dimension and appearance. Tactile properties are difficult or even impossible to be perceived in current CAD systems. In this paper, haptic rendering techniques are introduced as an approach to the perception of tactile properties and hand tool design case studies are demonstrated. With the aid of a force feedback device, Phantom(R), designers can perceive the surface roughness of a handle, the stiffness of a toothbrush, and examine the actuation force of a switch button. With these tools, designers can not only design the form of a product but also evaluate some physical properties of a product design in real time before the product is made, thus shortening the product development cycle.

Document-Driven Design for Distributed CAD Services in Service-Oriented Architecture

Current computer-aided design (CAD) systems only support interactive geometry generation, which is not ideal for distributed engineering services in enterprise-to-enterprise collaboration with a generic thin-client service-oriented architecture. This paper proposes a new feature-based modeling mechanism—document-driven design—to enable batch mode geometry construction for distributed CAD systems. A semantic feature model is developed to represent informative and communicative design intent. Feature semantics is explicitly captured as a trinary relation, which provides good extensibility and prevents semantics loss. Data interoperability between domains is enhanced by schema mapping and multiresolution semantics. This mechanism aims to enable asynchronous communication in distributed CAD environments with ease of design alternative evaluation and reuse, reduced human errors, and improved system throughput and utilization.

Development of an automatic design and optimization system for industrial silencers

Current computer-aided design (CAD) software tools focus on rapid production of computer models, which usually takes place after the product design is completed. The product design process, which has more significant influence on product life-cycle costs, is not fully supported. This work documents the development of an automatic design and optimization system for industrial silencers. The developed system greatly reduces the silencer design time from one day to a few minutes. Moreover, the system proves the feasibility of developing an open-architecture CAD system supported by design of experiment (DOE) based optimization methods to integrate product life-cycle considerations into the design. It is expected that the developed system can help the development of similar systems for other products. Through the development of this system, some further research issues are identified.

A dual-stage functional modelling framework with multi-level design knowledge for conceptual mechanical design

Supporting the conceptual stage of mechanical product design has been recognized as a challenging research work. This is an area that is not addressed by current computer-aided design systems. In this paper, we present our work on the identification of functional design knowledge and the strategies for its organization. The functional design knowledge is aimed at assisting the conceptual stage of mechanical product design using a dual-stage functional modelling framework proposed by us. Several aspects of functional design knowledge are identified and represented, including function decomposition and functional mapping knowledge, physical structure and physical phenomena knowledge, as well as schematic geometry knowledge. These different aspects of knowledge are organized into three levels: meta level, physical level, and geometric level. A number of libraries are used to implement the design knowledge and its organization. The strength of the approach is that it encompasses very comprehensive aspects of functional design knowledge, and it provides a useful means for compiling past design experience in a formalized and structured form. To demonstrate how the approach can be applied, an example of automatic assembly system design is also studied.

Developments in the trans-tibial prosthetic socket fitting process: a review of past and present research.

A revolution in trans-tibial prosthetic design began at the end of World War II with the development of new materials and a dramatic improvement in the understanding of biomechanics. Early research was based mainly on the improvement of existing prosthetic design practice. Today, research has been focused on providing a better understanding of stump/socket interface biomechanics and improving socket fit by attempting to quantify the normal/direct stresses at the interface. The purpose of this review paper is to question whether research and prosthetic education/training to date has significantly improved our understanding of what makes a good socket. Although there is no doubt that advances in socket fitting techniques have been made what is not clear is the actual extent to which these advances have improved the quality of sockets fitted. It is suggested that a new approach is needed which can overcome some of the inherent problems of designing and manufacturing a comfortable high quality socket. It is also suggested that current research and education/training in the fields of pressure/interfacial interaction measurement and Finite Element Analysis techniques have limited potential to address many of these problems. There is also little evidence that current computer aided design systems offer any significant advantages over more conventional techniques.