CAD Objects Research Articles

Modelling of CAM systems to simulate of a milling machine work

Mechatronic is combination of three main disciplines: mechanics, electronics and theory of control. Part of them are CAD/CAM/CAE systems. This work presents the facilitating impact of CAD software on the design process. Basic modeling methods will be presented, including the creation of objects that are the composition of several smaller parts. There are many programs being CAD / CAM / CAE software, however, in order to achieve the assumed goals, Siemens software - NX will be used. It is used to create a simple CAD object and a more complex model that is a milling machine. The simple detail will be presented to describe the basic functions useful during modeling 3D objects, such as sketch-based generation and further modification of the created model. Describing the created milling machine is related with the presentation of the types of constraints. They were used and the way in which selected machine axes were generated, including kinematic and geometrical parameters.

Rounding, filleting and smoothing of implicit surfaces

© 2017 CAD Solutions, LLC We describe an approach for performing constant radius offsetting and the related operations of filleting, rounding and smoothing for implicit surfaces. The offsetting operation is used as the basic component for defining the remaining operations. These operations are important operations for any modelling system. While it is known how to perform these operations for parametric representation and polygon meshes, there is limited prior work for implicit surfaces and procedural volumetric objects. The proposed approach is based on repeatedly computing the distance to a given implicit surface and its offset surfaces. We illustrate the results obtained by this approach with several examples, including procedurally defined microstructures and CAD objects.

Effect of round curvature of anterior implant-supported zirconia frameworks: finite element analysis and in vitro study using digital image correlation

Two groups of 4-unit zirconia frameworks were produced by CAD/CAM to simulate the restoration of an anterior edentulous gap supported by 2 implant-abutment assemblies. Group 1 comprised straight configuration frameworks and group 2 consisted of arched frameworks. Specimens were made with the same connector cross-section area and were cemented and submitted to static loads. Displacements were captured with two high-speed photographic cameras and analysed with video correlation system. Frameworks and the implant-abutment assembly were scanned and converted to 3DCAD objects by reverse engineering process. A specimen of each group was veneered and the corresponding 3D geometry was similarly obtained after scanning. Numerical models were created from the CAD objects and the FE analysis was performed on the zirconia frameworks and on the FPDs bi-layered with porcelain (veneered frameworks). Displacements were higher for the curved frameworks group, under any load. The predicted displacements correlated well with the experimental values of the two framework groups, but on the straight framework the experimental vertical displacements were superior to those predicted by the FEA. The results showed that the round curvature of zirconia anterior implant-supported FPDs plays a significant role on the deformation/stress of FPDs that cannot be neglected neither in testing nor in simulation and should be considered in the clinical setting.

A method to improve the quality of 2.5 dimensional micro-and nano-structures produced by focused ion beam machining

The present work deals with a new technique to produce complex micro- and nano-scale patterns with high accuracy by FIB micro machining. The proposed method is related to the production of stream file, which is optimized through a software interface. A unique sampling approach is used to optimize the conversion from a 3D meshed CAD object to the focused ion beam (FIB) digital to analogue converter (DAC). The method uses a novel scan strategy, sensitive to the pattern local geometry and size, to define the optimal ion beam path, dwell time and the scanning pitch. This not only allows to minimize the redeposition but also to obtain accurate and scalable milling routines. In order to show the applicability of the method, a hemisphere and a pyramid shape are milled and compared to the shapes obtained using the conventional techniques. Results show that the method is very effective in producing complex shapes while overcoming the detrimental effect of conventional raster/serpentine FIB strategies, such as redeposition. Lastly, a fish-net structure with a pitch of ∼200nm as well as a series of truncated cones with sub-micrometrical details are realized to show the potential impact of this new method. Results show that a spatial resolution of less than 100nm is achievable with the help of this method.

Effective 3-D surface modeling for geographic information systems

Abstract. In this work, we propose a dynamic, flexible and interactive urban digital terrain platform with spatial data and query processing capabilities of geographic information systems, multimedia database functionality and graphical modeling infrastructure. A new data element, called Geo-Node, which stores image, spatial data and 3-D CAD objects is developed using an efficient data structure. The system effectively handles data transfer of Geo-Nodes between main memory and secondary storage with an optimized directional replacement policy (DRP) based buffer management scheme. Polyhedron structures are used in digital surface modeling and smoothing process is performed by interpolation. The experimental results show that our framework achieves high performance and works effectively with urban scenes independent from the amount of spatial data and image size. The proposed platform may contribute to the development of various applications such as Web GIS systems based on 3-D graphics standards (e.g., X3-D and VRML) and services which integrate multi-dimensional spatial information and satellite/aerial imagery.

A Fragmentation Based Approach to the Free Form Surface Milling

In this paper, authors performs analysis of the free-form surface milling based on the fragmentation of the design elements which create active surfaces in tool making. Their analysis is based on fragmentation approach which makes the most of combining CAD, modelling and testing objects in tool making as well as selecting of the fragments with parts of free-form surfaces. Examples being introduced in this paper point out that it is volume based fragmentation of free form surfaces which allows to associate CAD design of tooling parts, their modelling and producing in chosen scale as well as testing different milling strategies. Results also showed that it is the Lining strategy of ball end milling which denotes desired compromise between machining time and surface quality when ball end milling fragments with different signed curvature radii.

Region segmentation for STL triangular mesh of CAD object

Region segmentation involves in breaking a polygonal mesh into 'meaningful' patches with characteristic geometrical property respectively. Considering the characteristics of nonuniformity, sparseness and known facet normal for STL model from CAD system, an efficient approach for region segmentation is put forward. The algorithm contains two steps: extracting region boundaries and segmenting regional meshes. Region boundaries are classified into sharp feature edge and non-sharp feature edge. The former is detected based on dihedral edge angle angle between facets, while the latter is identified by analysing intrinsic region properties of triangular facets distribution without curvature estimation. By means of unidirectional increment of feature edges, continuous region boundaries are generated. Finally, we withdraw meaningful patches from STL model based on advancing front algorithm depending on the boundaries. Examples are given to show the feature edges detection, boundaries generation and region segmentation based on the boundaries.

Enhancing Interoperability of Construction Data for Managing Integrated Active BIM Features

Recently, the visualization technique of numerical construction data has become essential in construction industry due to the extended application of BIM (Building Information Modeling) and various IT technologies. To build and apply a BIM tool, the interoperability between different modeling systems is being an important item. Specially, in the field of civil engineering project, the development of IFC (Industrial Foundation Class) code for 3D CAD object is under the conceptual phase. This study introduces cases of developing active BIM functions and IFC code that applicable to road project and proposes how to enhance data inter-operability to utilize the functions in an integrated manner.

Geometric graph comparison from an alignment viewpoint

In this paper we propose a new approach for the comparison and retrieval of geometric graphs formulated from an alignment perspective. The algorithm presented here is quite general in nature and applies to geometric graphs of any dimension. The method involves two major steps. Firstly graph alignment is effected making use of an optimisation approach whose target function arises from a diffusion process over the graphs under study. This provides, from the theoretical viewpoint, a link between stochastic processes on graphs and the heat kernel. The second step involves using a probabilistic approach to recover the transformation parameters that map the graph-vertices to one another so as to permit the computation of a similarity measure based on the goodness of fit between the two graphs under study. Here, we view the transformation parameters as random variables and aim at minimising the Kullback–Liebler divergence between the two graphical structures under study. We provide a sensitivity analysis on synthetic data and illustrate the utility of the method for purposes of comparison and retrieval of CAD objects and binary shape categorisation. We also compare our results to those yielded by alternatives elsewhere in the literature.

Optimal analysis-aware parameterization of computational domain in 3D isogeometric analysis

In the isogeometric analysis framework, a computational domain is exactly described using the same representation as the one employed in the CAD process. For a CAD object, various computational domains can be constructed with the same shape but with different parameterizations; however one basic requirement is that the resulting parameterization should have no self-intersections. Moreover we will show, with an example of a 3D thermal conduction problem, that different parameterizations of a computational domain have different impacts on the simulation results and efficiency in isogeometric analysis. In this paper, a linear and easy-to-check sufficient condition for the injectivity of a trivariate B-spline parameterization is proposed. For problems with exact solutions, we will describe a shape optimization method to obtain an optimal parameterization of a computational domain. The proposed injective condition is used to check the injectivity of the initial trivariate B-spline parameterization constructed by discrete Coons volume method, which is a generalization of the discrete Coons patch method. Several examples and comparisons are presented to show the effectiveness of the proposed method. During the refinement step, the optimal parameterization can achieve the same accuracy as the initial parameterization but with less degrees of freedom.

Parameterization of computational domain in isogeometric analysis: Methods and comparison

Parameterization of computational domain plays an important role in isogeometric analysis as mesh generation in finite element analysis. In this paper, we investigate this problem in the 2D case, i.e., how to parametrize the computational domains by planar B-spline surface from the given CAD objects (four boundary planar B-spline curves). Firstly, two kinds of sufficient conditions for injective B-spline parameterization are derived with respect to the control points. Then we show how to find good parameterization of computational domain by solving a constraint optimization problem, in which the constraint condition is the injectivity sufficient conditions of planar B-spline parameterization, and the optimization term is the minimization of quadratic energy functions related to the first and second derivatives of planar B-spline parameterization. By using this method, the resulted parameterization has no self-intersections, and the isoparametric net has good uniformity and orthogonality. After introducing a posteriori error estimation for isogeometric analysis, we propose r-refinement method to optimize the parameterization by repositioning the inner control points such that the estimated error is minimized. Several examples are tested on isogeometric heat conduction problem to show the effectiveness of the proposed methods and the impact of the parameterization on the quality of the approximation solution. Comparison examples with known exact solutions are also presented.

A METHOD FOR THE REGISTRATION OF A KNOWN CAD MODEL INTO THE WORKSPACE FRAME OF A ROBOT

In many robotic applications it is required to manipulate a specific rigid object whose CAD model is known a priori, but its position and orientation in space are unknown. This category of tasks includes piercing, painting or iron welding on some specific points of the rigid object's surface. For this kind of tasks to become feasible the CAD data of the rigid object should be registered into the robot's workspace frame, so that the robot arm becomes aware of the position and orientation of the rigid body with reference to its own flange or base coordinate frame. In order to achieve this goal several techniques from the fields of image processing, 3D modeling and robot kinematics should be combined. This paper provides a convenient combination of such methods that can be used for the successful on-line registration of a rigid object's CAD data to the robot's workspace frame.

A Novel Boundary Extraction Algorithm on Triangular Meshes of STL Model

The generation of boundaries from the triangular meshes of CAD object is very important for successful surface segmentation and subdivision. Considering the characteristics of non-uniformity, sparseness and known facet normal for STL model, which is generated by a CAD system, a new and efficient approach for extracting boundaries on STL model is presented in this paper. Boundaries are classified into sharp feature edge and non-sharp feature edge embedded in the filleting and transitive region. The former is detected based on dihedral edge angle (angle between facets), while the latter is identified by analyzing intrinsic region properties of triangular facets distribution without curvature estimation. By means of unidirectional increment of feature edges, continuous region boundaries are generated. Successful examples are presented to illustrate the feasibility of the proposed algorithm.

Shape-based clustering for 3D CAD objects: A comparative study of effectiveness

3D shape retrieval and clustering is of current interest in several different fields, including mechanical engineering. Several new shape representations for 3D objects are continuing to emerge. Most shape representations are embedded in a variety of feature spaces. However, some of the recently reported shape representations are embedded in arbitrary metric spaces, i.e. distance spaces, rather than in multi-dimensional feature space. For such representations, the only operations available on the data objects are distance calculations between the objects. In addition, some of the view-based representations are embedded in non-metric spaces where the representations and the corresponding distances do not follow the triangle inequality. For shape clustering applications, most existing algorithms assume the shape representations either to be embedded in a multi-dimensional feature space or a metric distance space, making it difficult to evaluate several shape representations that do not conform to these assumptions. Therefore, two different approaches were evaluated for using the distance features of a shape to obtain clustering results. In the first method, the original distances are transformed into feature space using a multi-dimensional scaling approach for use with K -means clustering. The second approach directly uses the original distances with a distance-based clustering algorithm. We compared the clustering effectiveness of these two approaches using a classified benchmark database of 3D models. The effect of using different shape descriptors and number of clusters was studied using four measures of clustering effectiveness. Several statistical methods, including the Rand Index and Mutual Information Index, were used to objectively evaluate the clustering efficacy.

Enhancing visualization of 4D CAD model compared to conventional methods

PurposeThe 4D CAD model has been accepted for better conceptualizing and comprehending the sequences and spatial constraints in a construction schedule. The purpose of this paper is to identify the deficiencies of the visualization of the 4D CAD model and to propose improvements.Design/methodology/approachThe presentation abilities of the existing 4D CAD model are analyzed and compared with the other conventional methods, namely Gantt chart, network diagram, and the calendar. Four aspects of the visualization are addressed, namely the overview of a schedule, the duration of an activity, the relationship of an activity, and the project progress tracking. The proposed improvements employed different visual properties of 3D CAD objects such as color, line weight, and line type to represent the different activities' performing statuses. A prototype of the 4D CAD model with enhanced visualization was developed on a construction project case.FindingsThe model evaluation showed that this development could enhance the visualization of the 4D CAD model and provide a more informative construction schedule.Original/valueIt is anticipated that the 4D CAD model with these enhancements can substitute for conventional presentation methods of construction schedules.

3D CAD Models and its Feature Similarity

Knowing the geometrical object pose of products in manufacturing line before robot manipulation is required and less time consuming for overall shape measurement. In order to perform it, the information of shape representation and matching of objects is become required. Objects are compared with its descriptor that conceptually subtracted from each other to form scalar metric. When the metric value is smaller, the object is considered closed to each other. Rotating the object from static pose in some direction introduce the change of value in scalar metric value of boundary information after feature extraction of related object. In this paper, a proposal method for indexing technique for retrieval of 3D geometrical models based on similarity between boundaries shapes in order to measure 3D CAD object pose using object shape feature matching for Computer Aided Testing (CAT) system in production line is proposed. In experimental results shows the effectiveness of proposed method. Keywords—CAD, rendering, feature extraction,feature classification.

Fusion of multiple image types for the creation of radiometrically-accurate synthetic scenes

The Digital Imaging and Remote Sensing Image Generation (DIRSIG) model is an established, first-principles based scene simulation tool that produces synthetic multi-spectral and hyperspectral images from the visible to long wave infrared (0.4 to 20 microns). Over the last few years, significant enhancements such as spectral polarimetric and active Light Detection and Ranging (lidar) models have also been incorporated into the software, providing an extremely powerful tool for algorithm testing and sensor evaluation. However, the extensive time required to create large-scale scenes has limited DIRSIG's ability to generate scenes "on demand." To date, scene generation has been a laborious, time-intensive process, as the terrain model, CAD objects and background maps have to be created and attributed manually. To shorten the time required for this process, we have developed a comprehensive workflow aimed at reducing the man-in-the-loop requirements for many aspects of synthetic hyperspectral scene construction. Through a fusion of 3D lidar data with passive imagery, we have been able to partially-automate many of the required tasks in the creation of high-resolution urban DIRSIG scenes. This paper presents a description of these techniques.

Algorithm to Offset and Smooth Tessellated Surfaces

AbstractThe paper describes a new geometric algorithm to offset CAD objects, described as surfaces tessellated with triangular facets, transforming the original geometry in a new smoothed offset model. Different approaches to cope with convex and concave geometries and to prevent overlapping cases are suggested and investigated. Furthermore, an STL-file preprocess algorithm is proposed in order to obtain an errors-free final surface modifying starting tessellated model. The developed algorithm has been named Offset Weighted by Angle (OWA). Different test cases are reported and commented.

Applying multi-user technology for modeling Complex Cad Objects

Complex CAD modelling occurring in engineering design and construction processes relies upon the effective management of teamwork where a variety of specialists work together on the development of one compound object that leads to the following issues which have to be dealt with in order to make this process time- and cost-effective: i) difficulties in exchanging technical information (including drawings) due to modifications in the CAD model; ii) difficulties in tracking modifications performed by other project participants; iii) difficulties in working with elements connected to another element already used by other participants; iv) assessment of various object versions. To facilitate these processes and manage the flow of technical information between project partners, multi-user technology is considered. It operates with a complex CAD object in the same way as an electronic archive system in engineering document management systems and offers a level of control over the information flow within the construction process.

Transformation from IFC data model to GML data model: Methodology and tool development

To facilitate the incorporation of 3D CAD objects into the 3D‐GIS environment, this paper proposes a feasible approach to transform the 3D geometric information of CAD objects expressed by the IFC model into geometric objects for the GML model. The discussions include not only the proposed model transformation methodology but also the development of a software tool that implements the proposed methodology. In addition, a simple model transformation example is provided to demonstrate the feasibility of the proposed methodology and the functionalities of the developed tool.