Commercial CAD Systems Research Articles

Post-processing feature-mapping topology optimisation designs towards feature-based CAD processing

Feature-mapping (FM) optimisation frameworks have received much attention for structural topology optimisation with explicit geometric parameters. This paper presents a methodology for constructing parametric feature-based CAD models from designs generated using Moving Morphable Components (MMC). Emphasis is placed on constructing feature-based CAD models that conform to conventional modelling practices, where individual parameterised features are modelled using feature templates and united through Boolean union operations. This involves the use of algorithms to facilitate feature clean-up and identify connexions between features. The progression through several examples demonstrates how the developed algorithms can realise a feature-based CAD model from the results of an FM optimisation. Integration with a commercial CAD system provides a wide range of modelling capabilities to the designer for downstream design tasks.

Assessment of predictive probability models for effective mechanical design feature reuse

Abstract This research envisages an automated system to inform engineers when opportunities occur to use existing features or configurations during the development of new products. Such a system could be termed a "predictive CAD system" because it would be able to suggest feature choices that follow patterns established in existing products. The predictive CAD literature largely focuses on predicting components for assemblies using 3D solid models. In contrast, this research work focuses on feature-based predictive CAD system using B-rep models. This paper investigates the performance of predictive models that could enable the creation of such an intelligent CAD system by assessing three different methods to support inference: sequential, machine learning, or probabilistic methods using N-Grams, Neural Networks (NNs), and Bayesian Networks (BNs) as representative of these methods. After defining the functional properties that characterize a predictive design system, a generic development methodology is presented. The methodology is used to carry out a systematic assessment of the relative performance of three methods each used to predict the diameter value of the next hole and boss feature type being added during the design of a hydraulic valve body. Evaluating predictive performance providing five recommendations ( $k = 5$ ) for hole or boss features as a new design was developed, recall@k increased from around 30% to 50% and precision@k from around 50% to 70% as one to three features were added. The results indicate that the BN and NN models perform better than those using N-Grams. The practical impact of this contribution is assessed using a prototype (implemented as an extension to a commercial CAD system) by engineers whose comments defined an agenda for ongoing research in this area.

Using CAD – CAM Technology in The Design of Prosthetic Devices

During last years a lot of improvements have been put on in order to develop many products by the introduction of computer-aided tools, to reduce the cost and time of the Design and Manufacturing process, and to have a faster and cheaper evaluation for different variants of the same product. Also, a great interaction has been happened between the custom-fit of products character-rized with the human body or part of it. Innovative computer-aided tools could support to realize custom-fit products with a strict interaction with human body and definitely improve people’s life style, in particular of persons with disabilities. This research presented a specific-fit of the lower limb prosthesis, which can guide and support the user of prosthetic devices, it has been studied the history and improvement of prosthetics, the modular ones that mainly composed by commercial components, except for the socket that is highly customized and manufactured around the patient stump. All the product and process knowledge is strictly correlated to a specific set of parameters, which guides the whole prosthesis design process: the patient’s characteristics. In particular, these data are necessary to select the appropriate standard components, to model a functional socket according to the patient’s anatomy, and creates the 3D model of the socket. The proposed framework is centered on the digital model of the amputee and directly manages the experts’ knowledge in order to guarantee a product of high quality, commercial 3D CAD system has been adopted to create a library of 3D parametric models to represent standard components and for final prosthesis assembly.

Improving Virtual Reality Applications in CAD through Semantics

In this article we propose an architecture for the inclusion and exploitation of semantic aspects in a CAD environment. Our schema focuses on the enhancement and improvement of a commercial (general purpose) CAD system on its Virtual Reality (VR) capabilities. There is a need in combining CAD and semantics in the new generation of computer assisted engineering systems. Usually semantic aspects in traditional CAD applications relay on the user’s tacit knowledge, a fact that slows the learning curve while the user is getting trained with a new tool, no matter if he is an expert in others. Moreover, current CAD programs offer a myriad of options to the designer, but their limited integration of the non geometric information (e.g. PDM systems), and in general the semantics of the design process, can still be improved for the current needs of the industry. We argue that the use of semantics could improve the workflow and capabilities of the software and would benefit a new user (non experienced one) in order to produce better results in shorter times. In this paper our main focus is the enhancement of the visualization and VR capabilities in generic CAD applications. Our semantic CAD framework uses ontology modeling as well as engineering standards in order to conceptualize and exploit the information contained in a CAD model. To show some benefits of our proposed schema, we present two cases in different engineering domains (plant design and Steel detailing design), where the inclusion of semantics empowers a VR experience.

A Design of New Product Database System for Supporting Step-Compliant Total Integration Applications

Computer technology has become a very important element in an advanced manufacturing system. The good and systematic data model for the exchange of manufacturing information between different stages of development of product life cycle is paramount to ensure the product is manufactured and delivered to the market successfully. As a result, ISO 10303, an international standard, or well known as Standard for Exchange of Product Model Data (STEP) is not just for providing a neutral data format within the heterogenous CAD systems, its functionality has extended to the whole life cycle of product. STEP Part 21 is the first implementation method from EXPRESS modelling language and implemented successfully as neutral product data to integrate heterogeneous CAD platform. However, this CAD STEP Part21 text file is hardly to be applied in manufacturing processes since it consists of purely geometrical and topological data. In this research, a nonprocedural approach is presented to translate the EXPRESS language model of STEP CAD data into a new product database system model. A new nonprocedural approach of data enrichment and automated machining feature recognition is proposed and implemented on this newly developed product database system and provide a solution for the interrelated tasks of automated machining feature recognition: (1) extraction of geometrical feature from STEP CAD model data of the part (2) formation of part representation suitable for form feature identification (3) matching of form features. This paper proves the validity of this newly developed product database system by translating STEP Part21 file from a commercial CAD system to database system format, data enrichment, performing automated machining feature recognition and lastly generating STEP standard data according to AP224 for supporting STEP based process planning and manufacturing applications.

Contribution of CAD to the Sensitivity for Detecting Lung Metastases on Thin-Section CT - A Prospective Study with Surgical and Histopathological Correlation.

To assess the sensitivity of radiologists and a CAD system for the detection of lung metastases on thin-section computed tomographic (CT) scans prior to pulmonary metastasectomy. All patients scheduled for resection of lung metastases were eligible for this prospective single-center trial. 95 patients with 115 surgical procedures (pulmonary metastasectomy using thoracotomy) were included. An experienced radiologist examined the CT scans for pulmonary metastases and documented his findings. A commercial CAD system was used as a second reader; additional CAD findings were recorded. A comparison of the sensitivity of the radiologist alone and with CAD was performed. Intraoperatively surgeons tried to identify the documented lesions and resected them as well as additionally palpable lesions. The standard of reference consisted of surgery and histopathology. Follow-up information for radiologically detected lesions missed during surgery was sought. 693 lesions (262 metastases) were detected radiologically or surgically, 646 of them were resected. The sensitivity of radiologists without CAD was 67.5 % for all lesions (87.4 % for metastases). CAD highly significantly (p < 0.001) increased the sensitivity to 77.9 % (92.7 %). During surgery, 143 additional lesions (19 metastases) were detected. 49radiologically detected lesions were not palpable during surgery: 4 metastases, 5 benign lesions, and 40 lesions of an unknown nature. CAD provides significant additional sensitivity for detecting lung metastases using MDCT compared to the performance of a radiologist alone. CT reveals a relevant number of non-palpable pulmonary lesions. · CAD significantly increased the sensitivity for the detection of lung metastases on CT.. · Surgical palpation of the lungs missed 8.5 % of all radiologically detected lesions.. · CT with CAD may increase the chance for complete metastasectomy.. · Meybaum C, Graff M, Fallenberg EM et al. Contribution of CAD to the Sensitivity for Detecting Lung Metastases on Thin-Section CT - A Prospective Study with Surgical and Histopathological Correlation. Fortschr Röntgenstr 2020; 192: 65 - 73.

Fabrication of 3D printed garments using flat patterns and motifs

PurposeThe purpose of this paper is to encourage the generation of 3D printed garments by developing a new software to open new potential of whole garment production in the fashion field.Design/methodology/approachThe authors developed a 3D printed garment design software using flat patterns and design motifs, to allow fast and easy generation of a 3D printed garment. Users can generate motif-based design easily using various user interfaces.FindingsA 3D printed garment could be printed not only by expensive SLS type printers but also by affordable FDM type printers with a simple assembly process using the software developed in this study.Originality/valueNewly developed 3D printed garment design software enables the users to generate 3D printed garments easily using flat patterns and design motifs, without having to go through a complex and arduous 3D modeling process using commercial CAD systems.

Research and Development of Casting Process CAD System for Steel Casting based on OpenCASCADE and wxWidgets

With the development of computer technology, the casting process CAD system has become the main way of casting process design for process designers. Most of these systems are developed based on second development tools of commercial 3D CAD systems. Due to the version escalation of commercial 3D CAD systems and confidentiality and consistency of data in foundry enterprises, the application of casting process CAD systems are greatly limited. To handle these problems, this paper puts forward the casting process CAD system for steel casting based on OpenCASCADE and wxWidgets. The framework of casting CAD system is constructed by the 3D geometric modeling kernel (OpenCASCADE) and the interface design platform (wxWidgets). The system has the function of practical casting process design and modeling, including part information extraction, gating system, chill system and riser system and so forth. Finally, taking the articulation piece for example, the casting can be designed by the system. It shows that the system resolves the above difficulties and improves the speed of casting process design and the ability of casting information exchange.

CAD 모델의 특징형상기반 단순화를 지원하는 확장형 시스템 개발

Feature-based simplification among various CAD model simplification methods is known as a suitable method for various engineering activities such as engineering analysis, plant design, network-based distributed collaborative design, virtual prototyping, and digital manufacturing. Nevertheless, there is no commercial CAD system to support it. Therefore, it is still difficult to simplify CAD models designed by commercial CAD systems. In addition, since the simplification strategy depends on the purpose of simplification, there is a need for a way that the user can easily select or expand the strategy. To resolve this problem, we propose an extensible feature-based simplification system. The proposed system is designed to integrate with various commercial CAD systems and extend the simplification strategy. In this paper, the structure and interface method of the proposed system are described, and the implementation results are presented.

Decomposing complex thin-walled CAD models for hexahedral-dominant meshing

This paper describes an automatic method for identifying thin-sheet regions (regions with large lateral dimensions relative to the thickness) for complex thin-walled components, with a view to using this information to guide the hexahedral (hex) meshing process. This fully automated method has been implemented in a commercial CAD system (Siemens NX) and is based on the interrogation and manipulation of face pairs, which are sets of opposing faces bounding potential thin-sheet regions. Careful consideration is given to the mapping, merging and intersection of face pairs to generate topologies suitable for sweep meshing the thin-sheet regions, and for treating the junctions between adjacent thin-sheet regions. It is proposed that hex meshes be applied to thin-sheet regions by quad meshing one of the faces bounding the thin-sheet region and sweeping it through the thickness to create hex elements. Decisions on the generation and positioning of the cutting surfaces required to isolate thin-sheet regions are made by considering the likely impact on the quality of the resulting mesh. The method delivers a substantial step towards automatic hex meshing for complex thin-walled geometries. A significant reduction of the degrees of freedom (DOF) can be achieved by applying anisotropic hex elements to the identified thin-sheet regions.

Parametric design velocity computation for CAD-based design optimization using adjoint methods

This paper presents an efficient optimization process, where the parameters defining the features in a feature-based CAD model are used as design variables. The process exploits adjoint methods for the computation of gradients, and as such the computational cost is essentially independent of the number of design variables, making it ideal for optimization in large design spaces. The novelty of this paper lies in linking the adjoint surface sensitivity information with geometric sensitivity values, referred to as design velocities, computed for CAD models created in commercial CAD systems (e.g. CATIA V5 or Siemens NX). This process computes gradients based on the CAD feature parameters, which are used by the optimization algorithm, which in turn updates the values of the same parameters in the CAD model. In this paper, the design velocity and resulting gradient calculations are validated against analytical and finite-difference results. The proposed approach is demonstrated to be compatible with different commercial CAD packages and computational fluid dynamics solvers.

Formal ontology and CAD integration with macro parametric approach

ABSTRACTThis paper discusses an ontological integration framework in the context of mereotopological formal ontology and CAD systems. Based on a comprehensive literature review of current design knowledge management and formal ontology research works, the authors propose the integration framework that can incorporate design knowledge with CAD systems. The primary role of mereotopology in this research work is the formal representation of design knowledge for the 3D solid assembly models. Most of the existing research works about design ontology present an abstract form and often require significant additional efforts to be integrated into CAD systems. Thus, this work introduces a formal ontology for CAD (OCAD) and macro-parametric approach as a practical way to integrate design knowledge with CAD systems. For the implementation, Protege, SPARQL, and commercial CAD system are employed. We also propose the enhancement of the developed framework for the future use to aid dynamic modeling.

Integration of negative knowledge into MCAD education to support competency development for product design

ABSTRACTWith a steadily increasing use of CAD systems within digital prototypes in product design and development, the capacity to create viable geometric models that can be used in various computer-aided engineering processes is becoming an indispensable necessity. However, with the current trend of commercial CAD systems increasingly to promote hybrid geometric modeling environments, this requirement poses a new challenge for education, as it requires a teaching strategy that goes beyond the sum of subject learning in surface modeling and solid modeling. In this paper, a novel teaching approach is introduced, which integrates negative knowledge as one crucial element in combination with traditional teaching methods to support competency development that reaches beyond the acquisition of basic modeling skills and domain knowledge.

Using virtual topology operations to generate analysis topology

Virtual topology operations have been utilized to generate an analysis topology definition suitable for downstream mesh generation. Detailed descriptions are provided for virtual topology merge and split operations for all topological entities. Current virtual topology technology is extended to allow the virtual partitioning of volume cells and the topological queries required to carry out each operation are provided. Virtual representations are robustly linked to the underlying geometric definition through an analysis topology. The analysis topology and all associated virtual and topological dependencies are automatically updated after each virtual operation, providing the link to the underlying CAD geometry. Therefore, a valid description of the analysis topology, including relative orientations, is maintained. This enables downstream operations, such as the merging or partitioning of virtual entities, and interrogations, such as determining if a specific meshing strategy can be applied to the virtual volume cells, to be performed on the analysis topology description. As the virtual representation is a non-manifold description of the sub-divided domain the interfaces between cells are recorded automatically. This enables the advantages of non-manifold modelling to be exploited within the manifold modelling environment of a major commercial CAD system, without any adaptation of the underlying CAD model. A hierarchical virtual structure is maintained where virtual entities are merged or partitioned. This has a major benefit over existing solutions as the virtual dependencies are stored in an open and accessible manner, providing the analyst with the freedom to create, modify and edit the analysis topology in any preferred sequence, whilst the original CAD geometry is not disturbed. Robust definitions of the topological and virtual dependencies enable the same virtual topology definitions to be accessed, interrogated and manipulated within multiple different CAD packages and linked to the underlying geometry.

Design guidelines for remote laser welding in automotive assembly lines

Remote laser welding which has benefits for both productivity and energy saving is receiving increased attention for automotive assembly lines. Introducing this innovative equipment requires a redesign process for assembly elements, for example to substitute resist spot welding with remote laser welding. The mating surfaces related to the welding need to be updated as well, but this is complicated when the shape design includes manufacturing and assembly elements based on current practice which hide the design intent. The challenge is to establish guidelines with the design parameters of automotive door frames and the process parameters of the joining process in order to maintain the design intent. In order to maintain the original design intent of the process planner, the author proposes a propagation model for the production stage which is defined as the interplay between parameters and quantitative comparison. The process parameters of remote laser welding are applied to the flange of the door frame. Also, the shape of each flange is synchronised with the changes according to the result of a quantitative comparison of the productivity and eco-efficiency. A design guideline tool to redesign the flanges was developed inside a commercial CAD system to show the proposed concept. Five flanges of a car door were subjected to redesign for introducing 4-kw remote laser welding with considerations of eco-efficiency, process time and weight change. The tools are shown to illustrate how to maintain design intent in the redesign process, and the concept was realised in a commercial CAD system.

A method for posture prediction of the upper trunk of video terminal operators

ABSTRACTThis paper presents a method for posture prediction of the upper trunk of video terminal (VDT) operators, which is then verified by means of some test cases. The prediction of the upper trunk posture is, in fact, a very difficult task to carry out due mainly to the complexity of the anatomy of the spine and the surrounding muscles. The method being proposed in this paper is based on the integration of the knowledge which is obtained experimentally through the posture analysis of real cases into a configured human multi-body kinematic model which has been implemented in a commercial CAD system. A trained artificial neural network retains the knowledge concerning the VDT operator’s postures detected in different working positions. The posture simulations obtained with the proposed method are subsequently compared with the real ones determined by a 3D scanner. The results obtained confirm the effectiveness of such a method, which is deemed promising to implement other anthropometric data and further ...

Automatic Decomposition of Complex thin Walled CAD Models for Hexahedral Dominant Meshing

This paper describes an automatic method for identifying thin-sheet regions (regions with large lateral dimensions relative to the thickness) for complex thin walled components, with a view to using this information to guide the hex meshing process. This fully automated method has been implemented in a commercial CAD system (Siemens NX) and is based on the interrogation and manipulation of face pairs, which are sets of opposing faces bounding thin-sheet regions. Careful consideration is given to the mapping, merging and intersection of face pairs to generate topologies suitable for sweep meshing thin-sheet regions, and for treating the junctions between adjacent thin-sheet regions. The quality of the resulting hexahedral mesh is considered when making decisions on the generation and positioning of the cutting surfaces required to isolate thin-sheet regions. The resulting decomposition delivers a substantial step towards automatic hexahedral meshing for complex thin-walled geometries. It is proposed that hexahedral meshes be applied to the identified thin-sheet regions by quad meshing one of the faces bounding the thin-sheet region and sweeping it through the thickness to create hexahedral elements.

Study regarding the virtual prototyping of garments for paraplegics

The sitting position is very common in everyday life and therefore any garment should be comfortable in that positon. It is especially important for those who are disabled and are confined to a sitting position throughout life. These include paraplegics whose restricted movements are due to paralysis of the lower limbs and restrict them to a wheelchair. Garments for a sitting position should meet certain particular needs like the body dimensions and postures of each individual. Design considerations should provide ergonomic comfort in a sitting position and include functional requirements due to limitations of strength and mobility in such a way that they do not cause additional health problems to paraplegics, e.g. skin irritations, pressure sores, obstruction of the blood flow etc., but rather to improve the quality of life for paraplegics. Today, the development of garments is practically impossible to imagine without the assistance of 3D CAD systems for the virtual prototyping of garments, which usually provide only the 3D body models in a standing position. The aim of this study was to explore the possibilities for the virtual prototyping of garments in regard to the sitting position, using the OptiTex 3D commercial CAD system. For this purpose 3D scans of subjects in sitting position were performed using a general-purpose ATOS II 3D optical scanning system. In addition, processing techniques of the human body mesh modeling and surface reconstruction techniques were involved to obtain a sitting 3D body model. The garments’ basic pattern designs for a standing position were constructed according to the rules of the M. Muller&Sohn construction system. Their reconstruction into garments’ basic pattern designs for a sitting position were performed by using the virtual measured dimensions of the scanned 3D body model in a sitting position, and virtual prototyping of the garments. Comparisons between the dimensions of the real and the 3D body models were carried out, as well as a comparison between the real sewn and virtually developed garments. The research showed that a reliable sitting 3D body model was achieved by used scanning technology, modeling and reconstruction techniques, as well as the usefulness and effectiveness of the virtual prototyping of the garments for a sitting position. In this study fully mobile individuals were involved to avoid unnecessary burdening of paraplegics in this stage of the research. The experiences gained from this study will enable us to include paraplegics within the study during the scanning and anthropometric survey with the aim of designing a general parametric 3D body model. Its body dimensions and postures would be possible for adapting from able-bodied persons with the purpose of developing individual garments for paraplegics.

Multibody system dynamics simulator for process simulation of ships and offshore plants in shipyards

Since various existing simulation tools based on multibody system dynamics focus on conventional mechanical systems, such as machinery, cars, and spacecraft, there are some problems with the application of such simulation tools to shipbuilding domains due to the absence of specific items in the field of naval architecture and ocean engineering, such as hydrostatics, hydrodynamics, and mooring forces. Thus, in this study, we developed a multibody system dynamics simulator for the process simulation of ships and offshore structures. We based the simulator on six kernels: the multibody system dynamics kernel, the force calculation kernel, the numerical analysis kernel, the hybrid simulation kernel, the scenario management kernel, and the collision detection kernel. Based on these kernels, we implemented a simulator that had the following Graphic User Interfaces (GUIs): the modeling, visualization, and report GUIs. In addition, the geometric properties of blocks and facilities in shipyards are needed to configure the simulation for the production of ships and offshore plants, so these are managed in a database and connected to a specific commercial CAD system in shipyards. We used the simulator we developed in various cases of the process simulation of ships and offshore plants. The results show that the simulator is useful for various simulations of operations in shipyards and offshore industries.

Generating Analysis Topology using Virtual Topology Operators

Virtual topology operations have been utilized to generate an analysis topology definition suitable for downstream mesh generation. Detailed descriptions are provided for virtual topology merge and split operations for all topological entities, where virtual decompositions are robustly linked to the underlying geometry. Current virtual topology technology is extended to allow the virtual partitioning of volume cells. A valid description of the topology, including relative orientations, is maintained which enables downstream interrogations to be performed on the analysis topology description, such as determining if a specific meshing strategy can be applied to the virtual volume cells. As the virtual representation is a true non-manifold description of the sub-divided domain the interfaces between cells are recorded automatically. Therefore, the advantages of non-manifold modelling are exploited within the manifold modelling environment of a major commercial CAD system without any adaptation of the underlying CAD model. A hierarchical virtual structure is maintained where virtual entities are merged or partitioned. This has a major benefit over existing solutions as the virtual dependencies here are stored in an open and accessible manner, providing the analyst with the freedom to create, modify and edit the analysis topology in any preferred sequence.