Computer-aided Design Assembly Research Articles

Engineering Change Risk Assessment: Quantitative and qualitative change characterization

Currently, computer-aided design (CAD) systems are very important for the design of any engineering products. CAD systems have undergone enormous progress. They are becoming more and more intelligent and automated. However, those systems still need improvement and still have flaws that need to be corrected in order to improve and develop the productivity and efficiency of the design process. Mechanical products are often complex and composed of multiple components so, consequently, an Engineering Change (EC) that affects a module or a single component will certainly influence the rest of the assembly. This phenomenon is called Change Propagation (CP). Therefore, in order to propagate a change that affects an assembly component easily, it is important to predict the Change Propagation Path and the impact of this modification on the rest of the assembly components. Hence, CP becomes an easy task. This paper focuses on the risk assessment of an engineering change, in order to enhance the predictive capacity of engineering change management methods. In fact, a full analysis must be made to measure the real impact of such modifications as well as their feasibility. To this end, the authors proposed a matrix-based approach, which results in a Risk Matrix. This is the product of the Relationships Matrix and the Influences Matrix which are constructed based on the data extracted at an early stage. In fact, the CAD assembly model contains a lot of important information that is extracted using Application Programming Interface (API).

User-Driven Computer-Assisted Reverse Engineering of Editable CAD Assembly Models

Abstract This paper introduces a novel reverse engineering (RE) technique for the reconstruction of editable computer-aided design (CAD) models of mechanical parts’ assemblies. The input is a point cloud of a mechanical parts’ assembly that has been acquired as a whole, i.e., without disassembling it prior to its digitization. The proposed framework allows for the reconstruction of the parametric CAD assembly model through a multi-step reconstruction and fitting approach. It is modular and it supports various exploitation scenarios depending on the available data and starting point. It also handles incomplete datasets. The reconstruction process starts from roughly sketched and parameterized CAD geometries (i.e., 2D sketches, 3D parts, or assemblies) that are then used as input of a simulated annealing-based fitting algorithm, which minimizes the deviation between the point cloud and the adapted geometries. The coherence of the CAD models is maintained by a CAD modeler that performs the geometries’ updates while guaranteeing the possibly imposed constraints and model coherence. The optimization process leverages a two-level filtering technique able to capture and manage the boundaries of the geometries inside the overall point cloud in order to allow local fitting and interfaces detection. It is a user-driven approach where the user decides what are the most suitable steps and sequence to operate. It has been tested and validated on both real scanned point clouds and as-scanned virtually generated point clouds incorporating several artifacts that would appear with real acquisition devices.

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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.

Discovery of key function module in complex mechanical 3D CAD assembly model for design reuse

PurposeComplex mechanical 3D computer-aided design (CAD) model embodies rich implicit design knowledge. Through discovering the key function parts and key function module in 3D CAD assembly model in advance, it can promote the designers’ understanding and reuse efficiency of 3D assembly model in design reuse.Design/methodology/approachAn approach for discovering key function module in complex mechanical 3D CAD assembly model is proposed. First, assembly network for 3D CAD assembly model is constructed, where the topology structure characteristics of 3D assembly model are analyzed based on complex network centrality. The degree centrality, closeness centrality, betweenness centrality and mutual information of node are used to evaluate the importance of the parts in 3D assembly model. Then, a multi-attribute decision model for part-node importance is established, and the comprehensive evaluation for key function parts in 3D assembly model is accomplished by combining Analytic Hierarchy Process and Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS). Subsequently, a community discovery of function module in assembly model-based Clauset–Newman–Moore (CNM)-Centrality is given in details. Finally, 3D CAD assembly model of worm gear reducer is taken as an example to verify the effectiveness and feasibility of proposed method.FindingsThe key function part in CAD assembly model is evaluated comprehensively considering assembly topology more objectively. In addition, the key function module containing key function part is discovered from CAD assembly model by using CNM-Centrality-based community discovery.Practical implicationsThe approach can be used for discovering important design knowledge from complex CAD assembly model when reusing the assembly model. It can help designers capture and understand the design thinking and intent, improve the reuse efficiency and quality.Originality/valueThe paper first proposes an approach for discovering key function module in complex mechanical 3D CAD assembly model taking advantage of complex network theory, where the key function part is evaluated using node centrality and TOPSIS, and the key function module is identified based on community discovery.

A Digital Twin-Oriented Lightweight Approach for 3D Assemblies

In the design and operation scenarios driven by Digital Twins, large computer-aided design (CAD) models of production line equipment can limit the real-time performance and fidelity of the interaction between digital and physical entities. Digital CAD models often consist of combined parts with characteristics of discrete folded corner planes. CAD models simplified to a lower resolution by current mainstream mesh simplification algorithms might suffer from significant feature loss and mesh breakage, and the interfaces between the different parts cannot be well identified and simplified. A lightweight approach for common CAD assembly models of Digital Twins is proposed. Based on quadric error metrics, constraints of discrete folded corner plane characteristics of Digital Twin CAD models are added. The triangular regularity in the neighborhood of the contraction target vertices is used as the penalty function, and edge contraction is performed based on the cost. Finally, a segmentation algorithm is employed to identify and remove the interfaces between the two CAD assembly models. The proposed approach is verified through common stereoscopic warehouse, robot base, and shelf models. In addition, a scenario of a smart phone production line is applied. The experimental results indicate that the geometric error of the simplified mesh is reduced, the frame rate is improved, and the integrity of the geometric features and triangular facets is effectively preserved.

A Novel Attribute-Based Encryption Approach with Integrity Verification for CAD Assembly Models

Cloud manufacturing is one of the three key technologies that enable intelligent manufacturing. This paper presents a novel attribute-based encryption (ABE) approach for computer-aided design (CAD) assembly models to effectively support hierarchical access control, integrity verification, and deformation protection for co-design scenarios in cloud manufacturing. An assembly hierarchy access tree (AHAT) is designed as the hierarchical access structure. Attribute-related ciphertext elements, which are contained in an assembly ciphertext (ACT) file, are adapted for content keys decryption instead of CAD component files. We modify the original Merkle tree (MT) and reconstruct an assembly MT. The proposed ABE framework has the ability to combine the deformation protection method with a content privacy of CAD models. The proposed encryption scheme is demonstrated to be secure under the standard assumption. Experimental simulation on typical CAD assembly models demonstrates that the proposed approach is feasible in applications.

Intelligent planning of product assembly sequences based on spatio-temporal semantic knowledge

PurposeThe implied assembly constraints of a computer-aided design (CAD) model (e.g. hierarchical constraints, geometric constraints and topological constraints) represent an important basis for product assembly sequence intelligent planning. Assembly prior knowledge contains factual assembly knowledge and experience assembly knowledge, which are important factors for assembly sequence intelligent planning. This paper aims to improve monotonous assembly sequence planning for a rigid product, intelligent planning of product assembly sequences based on spatio-temporal semantic knowledge is proposed.Design/methodology/approachA spatio-temporal semantic assembly information model is established. The internal data of the CAD model are accessed to extract spatio-temporal semantic assembly information. The knowledge system for assembly sequence intelligent planning is built using an ontology model. The assembly sequence for the sub-assembly and assembly is generated via attribute retrieval and rule reasoning of spatio-temporal semantic knowledge. The optimal assembly sequence is achieved via a fuzzy comprehensive evaluation.FindingsThe proposed spatio-temporal semantic information model and knowledge system can simultaneously express CAD model knowledge and prior knowledge for intelligent planning of product assembly sequences. Attribute retrieval and rule reasoning of spatio-temporal semantic knowledge can be used to generate product assembly sequences.Practical implicationsThe assembly sequence intelligent planning example of linear motor highlights the validity of intelligent planning of product assembly sequences based on spatio-temporal semantic knowledge.Originality/valueThe spatio-temporal semantic information model and knowledge system are built to simultaneously express CAD model knowledge and assembly prior knowledge. The generation algorithm via attribute retrieval and rule reasoning of spatio-temporal semantic knowledge is given for intelligent planning of product assembly sequences in this paper. The proposed method is efficient because of the small search space.

Structure-function correlations analysis and functional semantic annotation of mechanical CAD assembly model

PurposeThree-dimensional computer-aided design (CAD) assembly model has become important resource for design reuse in enterprises, which implicates plenty of design intent, assembly intent, design experience knowledge and functional structures. To acquire quickly CAD assembly models associated with specific functions by using product function requirement information in the product conceptual design phase for model reuse, this paper aims to find an approach for structure-function correlations analysis and functional semantic annotation of mechanical CAD assembly model before functional semantic-based assembly retrieval.Design/methodology/approachAn approach for structure-function correlations analysis and functional semantic annotation of CAD assembly model is proposed. First, the product knowledge model is constructed based on ontology including design knowledge and function knowledge. Then, CAD assembly model is represented by part attributed adjacency graph and partitioned into multiple functional regions. Assembly region and flow-activity region are defined for structure-function correlations analysis of CAD assembly model. Meanwhile, the extraction process of assembly region and flow-activity region is given in detail. Furthermore, structure-function correlations analysis and functional semantic annotation are achieved by considering comprehensively assembly structure and assembled part shape structure in CAD assembly model. After that, a structure-function relation model is established based on polychromatic sets for expressing explicitly and formally relationships between functional structures, assembled parts and functional semantics.FindingsThe correlation between structure and function is analyzed effectively, and functional semantics corresponding to structures in CAD assembly model are labeled. Additionally, the relationships between functional structures, assembled parts and functional semantics can be described explicitly and formally.Practical implicationsThe approach can be used to help designers accomplish functional semantic annotation of CAD assembly models in model repository, which provides support for functional semantic-based CAD assembly retrieval in the product conceptual design phase. These assembly models can be reused for product structure design and assembly process design.Originality/valueThe paper proposes a novel approach for structure-function correlations analysis and functional semantic annotation of mechanical CAD assembly model. Functional structures in assembly model are extracted and analyzed from the point of view of assembly structure and function part structure. Furthermore, the correlation relation between structures, assembled parts and functional semantics is expressed explicitly and formally based on polychromatic sets.

Classification, representation and automatic extraction of adhesively bonded assembly features

PurposeThis paper aims to present the classification, representation and extraction of adhesively bonded assembly features (ABAFs) from the computer-aided design (CAD) model.Design/methodology/approachThe ABAFs are represented as a set of faces with a characteristic arrangement among the faces among parts in proximity suitable for adhesive bonding. The characteristics combination of the faying surfaces and their topological relationships help in classification of ABAFs. The ABAFs are classified into elementary and compound types based on the number of assembly features exist at the joint location.FindingsA set of algorithms is developed to extract and identify the ABAFs from CAD model. Typical automotive and aerospace CAD assembly models have been used to illustrate and validate the proposed approach.Originality/valueNew classification and extraction methods for ABAFs are proposed, which are useful for variant design.

Associations management and change propagation in the CAD assembly

Engineering changes (ECs) are a kind of changes and/or modifications in forms, fits, functions, materials or dimensions of products and its constituent components. ECs usually stimulate a series of downstream changes. Therefore multiple disciplines and responsibilities are involved in managing those changes. The management of ECs affects the agility of the product development process of the enterprise. But Computer Aided Design (CAD) systems are limited in supporting the multi disciplinary teamwork in engineering change management (especially when they are distributed in terms of location and time). So, in this context of engineering change management we establish our work concerning engineering change propagation from Part to Assembly. This research paper explain the CAD Management Model, which enable us to better manage the Digital Mockup (DMU) and propagate changes to the hole assembly after a modification that affects one of its component, that has been sent to a partner modified an then reinserted. The aim of this model is to easily and automatically propagate this change by creating certain necessary correspondences which aim to precise the targeted entities (that will be affected by the change propagation).

An interoperability process between CAD system and CAE applications based on CAD data

Over the last years, computer-aided design (CAD) has developed rapidly thanks to integrated applications. These applications, namely CAD-integrated applications, have the ability to resolve many industrial challenges related to the design process such as assembly/disassembly sequence planning or computer-aided process planning. The implementation of these applications depends essentially on data extracted from the CAD model. However, the accessibility to these data remains a complex task for CAD-integrated application developers. The aim of this work is modelling and implementing a CAD-integrated system named CADLAB $$^{\copyright }$$ which automatically identifies and generates a diversity of data from a CAD assembly model under exploitable forms. The modelling of this system is performed using MBSE tool which is systems modelling language. The computer implementation of CADLAB is carried out with several software packages such as Solidworks $$^{\copyright }$$ , Excel $$^{\copyright }$$ and MATLAB $$^{\copyright }$$ . With CADLAB system, the identifiable CAD data are the assembly components and constraints’ data. Whereas, the generated CAD data represent the assembly interference matrices as well as several assembly related matrices. The developed system was tested on several CAD examples and the obtained results were verified. The correctness of these results proves the efficiency of CADLAB to carry out CAD data extraction and then enhance the interoperability process between CAD system and CAE applications. The proposed method can help designers find the CAD assembly data in complex mechanical assembly model, facilitate the structuring of the useful designing data, and thereby improve the efficiency of product knowledge reuse.

Subassembly generation algorithm from a CAD model

Assembly or disassembly sequence planning is a very hard combinatory problem while the assembly parts numbers become important. To reduce this difficulty, especially for the case of complex products, the subassembly identification concept can constitute an original way. It aims to decompose the complex assembly product into some subassembly entities containing a small number of parts. Consequently, the generation of assembly or disassembly sequence planning of parts becomes between the subassemblies and, in that case, can be determined relatively easily. Despite the prettiness of the subassembly method, the identification of subassembly from a computer-aided design (CAD) model remains a relevant research subject to be improved. In this paper, a subassembly identification approach is presented. The proposed approach begins with the exploration of the CAD assembly data to carry out an adjacency matrix. Then, to identify the subassemblies, the extracted matrix is transformed through three steps. The first step consists of idealizing this matrix by removing all connection parts identified by the Feature-Manager, which permits reducing its size. Afterward, based on the reduced matrix, an all-direction matrix is constructed to identify the base part of a subassembly. The third step consists of enriching the all-direction matrix by mounting conditions to construct the set of subassemblies. An example of a CAD assembly mechanism is presented in all sections of this paper in order to explain and discuss the steps of the proposed approach.

Generating complete disassembly sequences by utilising two-dimensional views

This research work proposes a novel method to generate the complete disassembly sequences for mechanical products by utilising the part interference matrix which contains the removal directions of the parts and the part connection graph which indicates the contact among the parts in the assembly. Contrary to the earlier methods, the proposed method considers the two-dimensional views generated from the computer-aided design assembly model for automatically identifying the part removal directions and for generating the part connection graph. Rules are formulated in the proposed method to identify the part removal directions effectively and also to reduce the size of part connection graph, since the method of identifying the part removal directions and the size of the formulated graph plays a vital role in the generation of disassembly sequence. Finally, a heuristic method is developed to generate the best feasible disassembly sequences. The effectiveness of the approach is illustrated with three examples.

Relationship matrix based automatic assembly sequence generation from a CAD model

Currently in industry, design and communication of a product assembly is through the use of computer-aided design (CAD) systems. However, there are no commercial systems that can automatically generate feasible assembly sequence plans. There is past and current academic research in methods to provide automatic assembly sequence planning. Assembly sequence planning using a commercial system often relies on an expert assembly sequence planner, and it is predominantly done manually. This requires a great amount of time and expert knowledge; assembly sequence plans generated may not even be the most efficient. The ability to automatically generate assembly sequence plans will lead to the reduction of planning time, less reliance on the amount of knowledge required, and better plans at earlier stages of the design process. CAD models are based on feature constraints to create and define an assembly. The challenges to automatically generate assembly sequences using CAD models lie in intelligent reasoning and analysis of the modelled assembly data. Based on past research findings, there is a reason to believe that assembly constraints used in CAD assembly models can provide essential information related to the assembly process. This paper presents a system that can analyse and utilize assembly data available from a CAD model to generate assembly sequences. The system also considers a user input as a type of assembly constraint. The system is capable of producing a set of ranked feasible assembly sequence plans for an operator to evaluate. A matrix approach has been adopted to process the information retained from a CAD model. Interference and stability studies are carried out during the creation of assembly sequence plans. The outputs are ranked based on the ease of assembly and the stability of the generated assembly sequence plans. Case studies are used to evaluate the system and the feasibility of the output. A case study using a two stroke engine is presented, which demonstrates how the system generates assembly sequence plans.

Representation and Propagation of Engineering Change Information in Collaborative Product Development using a Neutral Reference Model

As modular production becomes increasingly widespread in globalized manufacturing industries, many components constituting a final product are being developed and produced by collaborating part suppliers who have the ability to design their own parts by themselves without aid from the original equipment manufacturer (OEM). In this collaborative product development, the important aspect to expedite engineering changes is that engineering change information should be represented precisely in a designer-friendly form and shared among participating companies in an effective manner. However, all part suppliers and an OEM typically do not use the same computer-aided design (CAD) system and they are reluctant to share their CAD data with other cooperating companies owing to the policy of protecting corporate intellectual property. These circumstances make it difficult for collaborating companies to conduct engineering changes, since a part supplier who is responsible for one part of a product needs other CAD part model data designed by other companies for the engineering changes in the typical CAD assembly modeling of a product. In this article, a neutral reference model that consists of a neutral skeleton model and an external reference model is proposed as a new medium for the sharing and propagation of engineering change information among collaborating companies.