Models Of Mechanical Parts Research Articles

Interface-Based Search and Automatic Reassembly of CAD Models for Database Expansion and Model Reuse

This paper introduces a new framework for reassembling CAD models of mechanical parts. The generated CAD assemblies are well-constrained, with collision-free parts, and they are ready-to-use for downstream applications. First, input dead CAD models candidate for the reassembly are sorted following a part-by-part interface-based identification algorithm that is capable of characterizing each part according to the assembly slots and interfaces it offers. The slots are then hashed, and the resulting keys are used for fast search of parts in the database. Thus, the parts that can be assembled are quickly identified, and their assembly can be considered according to various scenarios. To support the reassembly steps and satisfy the constraints associated with the specified interfaces, a collision-free kinematic constraint solver is also proposed. During the reassembly steps, the geometry of the slots can also be automatically modified to adjust their dimensions, in order to ensure a perfect fit and to avoid interference at the level of the interfaces. The resulting database can also be further expanded while modifying the relative positions/orientations of the assembled parts. The approach is illustrated on several test cases covering different exploitation scenarios, ranging from simple model reuse to database expansion for machine learning-based applications. Such an automatic reassembly process is particularly innovative, and it clearly paves the way for smart assembly procedures.

Simplification of 3D CAD Model in Voxel Form for Mechanical Parts Using Generative Adversarial Networks

Most three-dimensional (3D) computer-aided design (CAD) models of mechanical parts, created during the design stage, have high shape complexity. The shape complexity required of CAD models reduces according to the field of application. Therefore, it is necessary to simplify the shapes of 3D CAD models, depending on their applications. Traditional simplification methods recognize simplification target shape based on a pre-defined algorithm. Such algorithm-based methods have difficulty processing unusual partial shapes not considered in the CAD model. This paper proposes a method that uses a network based on a generative adversarial network (GAN) to simplify the 3D CAD models of mechanical parts. The proposed network recognizes and removes simplification target shapes included in the 3D CAD models of mechanical parts. A 3D CAD model dataset was constructed to train the 3D CAD model simplification network. 3D CAD models are represented in voxel form in the dataset. Next, the constructed training dataset was used to train the proposed network. Finally, a 3D voxel simplification experiment was performed to evaluate the performance of the trained network. The experiment results showed that the network had an average error rate of 3.38% for the total area of the mechanical part and an average error rate of 14.61% for the simplification target area.

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.

Принципи 3d моделювання механічних деталей для застосування 3d принтера.

Розкрито принципи 3D моделювання механічних деталей для застосування 3D принтера. Визначено поняття «3D принтер», зазначено, що 3D принтер використовує метод пошарового створення фізичного об'єкта по цифровій 3D-моделі. Запропоновано опис тривимірного друку, такого як швидке прототипування, зазначається, що дана технологія має широкі перспективи розвитку та впровадження, тому що має ряд переваг, у порівнянні з традиційними методами створення різних деталей. Наведено класифікацію 3D принтерів за призначенням (орієнтація на споживача) та за технологією друку у вигляді таблиці. Охарактеризовано цифрові 3D технології і когнітивне програмування, які відкривають унікальні можливості відтворення найскладніших просторових форм, об'єктів та інженерних конструкцій, механізмів, та наголошується, що реалізація цих можливостей пов'язана з цифровою технологією управління матеріальними частками в об'ємному середовищі інструментів 3D технології. Визначено способи 3D-моделювання механічних деталей: 3D-моделювання у програмі КОМПАС-3D; 3D-сканування за допомогою 3D сканера. Окреслено можливості системи тривимірного моделювання, які забезпечують проектування машинобудівних виробів будь-якої складності і відповідно до самих передових методик проектування. У системі присутні інструменти для роботи за методом «зверху вниз», або методикою низхідного проектування, а також за методом «знизу вгору». Визначено принципи сканування деталі з чотирьох сторін на 3D-сканері Artec за допомогою поворотного столу, де точність сканування для даного 3D-сканера становить до 0,1% від розміру сканованого об'єкта. Наголошено, що сканування можна застосовувати для створення точних моделей складнопрофільних об'єктів, які в подальшому можуть бути використані для отримання прототипів виробу, побудови нових виробів на базі існуючих.

FeatureNet: Machining feature recognition based on 3D Convolution Neural Network

Automated machining feature recognition, a sub-discipline of solid modeling, has been an active research area for last three decades and is a critical component in digital manufacturing thread for detecting manufacturing information from computer aided design (CAD) models. In this paper, a novel framework using Deep 3D Convolutional Neural Networks (3D-CNNs) termed FeatureNet to learn machining features from CAD models of mechanical parts is presented. FeatureNet learns the distribution of complex manufacturing feature shapes across a large 3D model dataset and discovers distinguishing features that help in recognition process automatically. To train FeatureNet, a large-scale mechanical part datasets of 3D CAD models with labeled machining features is automatically constructed. The proposed framework can recognize manufacturing features from the low-level geometric data such as voxels with a very high accuracy. The developed framework can also recognize planar intersecting features in the 3D CAD models. Extensive numerical experiments show that FeatureNet enables significant improvements over the state-of-the-arts manufacturing feature detection techniques. The developed data-driven framework can easily be extended to identify a large variety of machining features leading to a sound foundation for real-time computer aided process planning (CAPP) systems.

Applying geometric constraints for perfecting CAD models in reverse engineering

An important area of reverse engineering is to produce digital models of mechanical parts from measured data points. In this process inaccuracies may occur due to noise and the numerical nature of the algorithms, such as, aligning point clouds, mesh processing, segmentation and surface fitting. As a consequence, faces will not be precisely parallel or orthogonal, smooth connections may be of poor quality, axes of concentric cylinders may be slightly tilted, and so on. In this paper we present algorithms to eliminate these inaccuracies and create “perfected” B-rep models suitable for downstream CAD/CAM applications.Using a segmented and classified set of smooth surface regions we enforce various constraints for automatically selected groups of surfaces. We extend a formerly published technology of Benkő et al. (2002). It is an essential element of our approach, however, that we do not know in advance the set of surfaces that will actually get involved in the final constrained fitting. We propose local methods to select and synchronize “likely” geometric constraints, detected between pairs of entities. We also propose global methods to determine constraints related to the whole object, although the best-fit coordinate systems, reference grids and symmetry planes will be determined only by surface entities qualified as relevant. Lots of examples illustrate how these constrained fitting algorithms improve the quality of reconstructed objects.

パラメータサーベイ解析のための機械部品四面体メッシュの寸法駆動変形

For realizing efficient CAE process, dimension-driven deformation of the FEM mesh models is required. In this paper, we propose a dimension-driven deformation of tetrahedral mesh models of mechanical parts. At first, in order to extract dimensions of the mesh models, a new surface segmentation method of tetrahedral mesh models is proposed. In our segmentation method, planar, cylindrical, conical, spherical, and torus surfaces are sequentially extracted by region-growing based on principal directions, normal vectors, and surface fittings. Secondly, a dimension-driven mesh deformation method in which vertices of the mesh models are moved using a space embedding method and the surface information obtained from the segmentation results is proposed. Our mesh deformation method can change parameters of form features of the mesh models such as radius of the fillet, angle of the chamfer, and so on. Finally, Phased Optimal Delaunay Triangulation (ODT) smoothing which improves element shape qualities from the boundary to the inside of the mesh model is extended. The extended Phased ODT smoothing can improve the surface mesh of the conical, spherical, and torus surface using local 2D parameter spaces.

Shape recognition of CAD models via iterative slippage analysis

A new slippage analysis method for recognizing basic primitive surfaces of CAD models is presented in this paper. Obtaining the exact normal and searching the appropriate local region of each point are found to be the key steps for determining the local slippage motion type. First, the tensor voting-based boundary point recognition method is integrated to preprocess the original points. Then, the local slippage analysis method is used to initialize the point type. Furthermore, the appropriate region of each point is acquired by the region growing method. Meanwhile, the middle level information (the basic primitive surface types and the representative parameters) is found, guiding the modification of the normal of each point and the iterative detection of the surface types. Finally, the middle level information-based smooth method is introduced to refine the boundary of each basic primitive surface. The empirical results show that the proposed algorithm is efficient and robust for recognizing primitive shapes from CAD models of mechanical parts.

Modeling and Identification of Nonlinear Cascade and Sandwich Systems with General Backlash

Abstract The paper deals with modeling and identification of nonlinear cascade and sandwich systems including general backlash, where instead of the straight lines determining the upward and downward parts of backlash characteristic, general curves are considered. This enables more precise modeling of mechanical parts and improves the performance of control systems. The analytical description of the general backlash leads to mathematical models of the cascade system with output general backlash and the sandwich system with internal general backlash, where all the model parameters are separated. Hence, the identification is solved as a quasi-linear problem. Iterative algorithms with internal variables estimation are proposed and illustrative examples are included.

Generation of bi-monotone patches from quadrilateral mesh for reverse engineering

Thanks to recent improvements, computational methods can now be used to convert triangular meshes into quadrilateral meshes so that the quadrilateral elements capture well the principal curvature directional fields of surfaces and intrinsically have surface parametric values. In this study, a quadrilateral mesh generated using the mixed integer quadrangulation technique of Bommes et al. is used for input. We first segment a quadrilateral mesh into four-sided patches. The feature curves inside these patches are then detected and are constrained to act as the patch boundaries. Finally, the patch configuration is improved to generate large patches. The proposed method produces bi-monotone patches, which are appropriate for use in reverse engineering to capture the surface details of an object. A shape control parameter that can be adjusted by the user during the patch generation process is also provided to support the creation of patches with good bi-monotone shapes. This study mainly targets shape models of mechanical parts consisting of major smooth surfaces with feature curves between them.

Study on Sectional Curve Fitting in Reverse Modeling of Mechanical Parts

The flow of reverse modeling based on section feature is analyzed, and three algorithms of B-spline curve fitting are studied. Then by adopting the three methods, the sectional curve fitting of the point cloud data is achieved for the stator vane of hydraulic torque converter. Through comparing the errors and curvature of the fitting curves, the effect of curve fitting is analyzed and valuable conclusions are obtained.

Research on Reverse and Obverse Modeling for Mechanical Equipment Parts

The model reconstruction based on the reverse and obverse is a main method in reverse engineering applications at present. A new method is put forward for reverse modeling of mechanical parts, which is based on combining reverse software Geomagic Studio and Imageware with CAD system Pro/E. A detailed scheme is designed and it is put into practice by taking a mechanical part for example. The feasibility and practicability of the method is confirmed for model reconstruction of mechanical parts in reverse engineering.

Partial Matching Algorithm of 3D CAD Models Based on the Constraints of Transition Features

The CAD models of mechanical parts usually have many blends and chamfers, and the existence of these machining features can greatly change the geometric and topological patterns of the CAD models, but the existing partial matching algorithms cannot match the CAD models which contain machining features such as blends and chamfers. In this paper, a new approach to partial matching based on the constraints of transition features is proposed. Firstly, the transition features are identified by feature recognition, and then these machining features are removed to eliminate the impacts to the geometric and topological information of the CAD models, and the attribute adjacent graph is reconstructed, finally, the sub-graph isomorphism approach is used to achieve the partial matching. Experimental results show that this method can achieve partial matching of CAD models which contain machining features such as blends and chamfers, and the matching efficiency can satisfy the requirement of the engineering retrieval.

Segmentation of multi-material CT data of mechanical parts for extracting boundary surfaces

We introduce a method for segmentation of materials segmented in volumetric models of mechanical parts created by X-ray CT scanning for the purpose of generating their boundary surfaces. When the volumetric model is composed of two materials, one for the object and the other for the background (Air), these boundary surfaces can be extracted as isosurfaces using a surface contouring method. For a volumetric model composed of more than two materials, we need to classify the voxel types into segments by material and then use a surface contouring method that can deal with both CT values and material types. Here we propose a method for precisely classifying the volumetric model into its component materials using a modified and combined method of two well-known algorithms in image segmentation, region growing and Graph-cut. We then apply our non-manifold iso-contouring method to generate triangulated mesh surfaces. In addition, we demonstrate the effectiveness of our method by constructing high-quality triangular mesh models of the segmented parts.

Retrieving 3D CAD model by freehand sketches for design reuse

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

Radial Supershapes for Solid Modeling

In the previous work, an efficient method has been proposed to represent solid objects as multiple combinations of globally deformed supershapes. In this paper, this framework is applied with a new supershape implicit function that is based on the notion of radial distance and results are presented on realistic models composed of hundreds of hierarchically globally deformed supershapes. An implicit equation with guaranteed differential properties is obtained by simple combinations of the primitives’ implicit representations using R-function theory. The surface corresponding to the zero-set of the implicit equation is efficiently and directly polygonized using the primitives’ parametric forms. Moreover, hierarchical global deformations are considered to increase the range of shapes that can be modeled. The potential of the approach is illustrated by representing complex models composed of several hundreds of primitives inspired from CAD models of mechanical parts.

Towards the standardized exchange of parameterized feature-based CAD models

The paper describes the status of work aimed at extending the international standard ISO 10303 (STEP) to permit the exchange of parameterized feature-based models between different CAD systems, in terms of the constructional history of the models concerned. Such procedural models have the advantage of being easy to edit following an exchange, by contrast with the models that can be exchanged using current STEP methodology, which prove to be difficult or impossible to edit in the receiving system. The use of the approach described has already been demonstrated in the exchange of realistic procedural shape models of mechanical parts, and the paper includes a brief account of some of the tests performed and the projected benefits of the use of this extension of STEP technology.

4025 液晶パネル製造装置開発への有限要素法解析の適用(G10-5 柔軟系のダイナミクス,G10 機械力学・計測制御)

In this paper we describe how to use the finite element method (FEM) in development of flat panel display (FPD) product equipment. Nowadays the size of mother-glass used in production of FPD is growing rapidly. So FPD product equipments are being required not only the rising of basic performance but also the enlargement of equipment and reduction of the process time. To satisfy these requirements, we used the FEM to develop the resist coater, which is one of key FPD product equipment. At first we tried to construct the models of mechanical parts like ball-screw and non-linear vibration region. In these processes, we used spring-damper elements. And we could confirm that these models are effective. And then we constructed the full size model of resist coater with mechanical parts models consist of spring-damper elements and other models confirmed by modal analysis. With that model, we could predict, improve and produce the high performance next-generation resist coater.

B-Rep model simplification by automatic fillet/round suppressing for efficient automatic feature recognition

The CAD models of real-world mechanical parts usually have many fillets and rounds that are essentially important to ensure the manufacturability and assembability. In feature-based modeling, fillets and rounds are often referred as secondary features that are used to modify the local details of the primary features such as holes, slots and pockets. Although the major shape of the primary features may not be affected, fillets and rounds can greatly change the geometric and topological patterns of the primary features. The geometric and topological variations can result in inefficient feature semantics classification in feature recognition. When feature interactions occur, it may become even worse to identify the regular patterns of the primary features. In addition, the fillets and rounds consist of no-linear surfaces such as cylindrical surfaces, spherical surfaces and toroidal surfaces, which bring the difficulties in volumetric feature extraction by half-space partition. In order to facilitate volumetric feature extraction and feature semantics classification, we pre-process the input B-Rep models by suppressing fillets and rounds before the feature recognition. Thus the input B-Rep models can be simplified without altering the major shapes of primary features, the targets of the feature recognition. The B-Rep simplification can be viewed as the reverse process of the edge blending in feature-based design. In this paper, several issues on fillet/round suppressing are discussed and a relatively general and robust approach is proposed to suppress blendings in B-Rep models of mechanical parts before the surface feature recognition and volumetric feature extraction.

Virtual Technology Based Associative Integration of Modeling of Mechanical Parts

Advanced application of powerful computer tools at engineering design of advanced products related activities means creating integrated product models in advanced computer systems. Leading application oriented master model concepts and standards as STEP serve this purpose. Engineers are working simultaneously on product design. Results of engineering decisions are analyzed for loads, aesthetics and manufacturability. Product design, results of analyses, processes of manufacturing of parts and much more are described in integrated product model. This model is accessed by several engineers simultaneously and is communicated with other engineering design environments. Because most of prototype development activities are being moved into computer systems, advanced modeling is often cited as virtual pro-, totyping. This paper summarizes and relates some advanced modeling approaches and methods to emphasize main trends in fulfilling demands for modeling tools in the early 21th century. As one of the key issues a manufacturing process model associative with form feature based part model is introduced. This model was proposed by the authors. The motivation is that low level integration of design and manufacturing of mechanical parts is still a main drawback of efficient application of expensive modeling systems. The proposed method ’allows for creating part models simultaneously with their analysis of machineability. In this paper chapter 2 outlines the scene of modeling based decision making of engineers as well as levels of product model creation. Chapter 3 explains the prevailing modeling principles, while chapter 4 emphasizes structure descriptions. In chapter 5 the proposed associative, Petri net model representation based manufacturing process modeling and its potential applications are explained are detailed. Two additional key subject areas are discussed in chapter 6 and chapter 7, namely effects of globalization on modeling and product data management. The main aspect of discussion is model and communication based group work of engineers.