Showing papers in "Computer-aided Design and Applications in 2018"

Reverse engineering modeling methods and tools: a survey

Abstract: Reverse Engineering (RE) is a long-term goal of engineering and computer science; it aims at the reconstruction of CAD models from measured data by means of 3D mathematical surfaces and geometrical features representing the geometry of a physical part. In the last two decades, reviews and surveys have occasionally covered this topic, but a systematic dissertation of modeling methods from a mechanical engineering point of view is still missing. The purpose of this paper is to fill this gap; starting from a general description of the overall RE framework (acquisition, segmentation, classification, fitting), both an up-to-date survey and a categorization of available modeling techniques and tools working on 3D data are provided. The main aspects of various strategies are discussed as well, in order to highlight strengths and weaknesses characterizing different approaches. Moreover, an overview of commercial software for RE is presented, considering both dedicated solutions and packages supplied as ad...

Manufacturability analysis for additive manufacturing using a novel feature recognition technique

Abstract: Additive Manufacturing (AM) increases much design freedom for designers to conceive complex parts. However, the increased complexity makes the manufacturability analysis difficult for the designed ...

Automated Fiber Placement Path Planning: A state-of-the-art review

Abstract: Design and manufacturing of composite structures are driving the next generation innovation cycles for the aerospace, automotive and energy markets. Automated fiber placement (AFP) is quickly becoming the preferred manufacturing method of those structures as it offers manufacturing automation, reduces production cycle times, and decreases human induced errors. One of the major steps towards manufacturing structures with AFP technology is the selection of the optimal layup strategy. This is limited by, not only geometrical and process parameters, but certification allowable and guidelines. This paper outlines a systematic review of the multiple layup strategies practices currently used and/or investigated for the AFP manufacturing process. The optimal layup strategy needs to be selected and verified to obtain laminates with little to no manufacturing defects. Through a methodical description, the different layup strategies found in the literature are described as well as their mathematical implementation. Following, a geometrical benchmark is presented so that new layup strategies can be compared to others based on the same reference. The article can be the foundation for any new layup strategy investigation.

Revisiting the design intent concept in the context of mechanical CAD education

Abstract: Design intent is generally understood simply as a CAD model’s anticipated behavior when altered. However, this representation provides a simplified view of the model’s construction and purpose, whi...

3D Facial Action Units and Expression Recognition using a Crisp Logic

Abstract: This work proposes a method for recognizing the main 13 Facial Action Units and the 6 basic emotions. The methodologies rely on Differential Geometry to extract relevant discriminant features from the query faces, and on some linear quantities used as measures: Euclidean, geodesic, and angles between 17 automatically extracted soft-tissue landmarks. A thresholding system which evaluates local properties of connected regions, selected through tailored geometrical descriptors, supports the identification of the AUs. Then, a technique based on crisp logic allows the identification of the global expression. The three-dimensional context has been preferred due to its invariance to different lightening/make-up/camouflage conditions.

Point cloud slicing for 3-D printing

Abstract: This paper revisits a more than half a century old problem: slice a free-form object into layers for manufacturing. A point based approach is taken that would have been prohibitive even a decade ag...

Reverse Engineering Techniques for Virtual Reconstruction of Defective Skulls: an Overview of Existing Approaches

Abstract: The surgical process adopted to repair cranial defects using an implant, typically called Cranioplasty, has seen an abrupt increase in recent years due to the introduction of Reverse Engineering (RE) and Additive Manufacturing (AM) techniques. By adopting these techniques, CT/MRI data can be used to reconstruct, in a pre-operative stage, the 3D anatomy of the defective skull in order to design a patient-specific digital model of the prosthesis. The sodesigned cranial plate can be then fabricated via AM, in a suitable metal alloy, and implanted. This allows for a perfect fit of the implant during the actual surgery, reducing the risks for the patient and increasing the efficacy of the treatment. This paper reviews existing approaches for the virtual reconstruction of defective skulls, and a basic classification, proposing four different classes of strategies (Mirroring, Surface Interpolation, Template-Based and Slice-based techniques) is provided. The findings of the study suggest that the reconstruction of skull defects is still an open problem, due to the complexities imposed by surface that needs to be retrieved (i.e. the human anatomy). All the presented approaches share weaknesses and limits, which are discussed in the article. Finally, possible directions to improve the existing techniques are briefly presented.

A CAD-based Procedure for Designing 3D Printable Arm-Wrist-Hand Cast

Abstract: Wrist injuries are one of the most common fractures, specifically around 25% of fractures among the pediatric population and up to 18% in the elderly age group are distal radius fractures. To date, the standard treatment entails the use of a tailor-made plaster of Paris cast. Although it is a simple and reliable treatment, it presents several disadvantages: its weight generally causes discomfort, it cannot be taken off without breaking it, it can cause skin rashes and prevents ventilation of the treated area. To overcome the limitations of the above mentioned treatment, 3D printed orthopaedic casts based on reverse engineering (RE) and additive manufacturing (AM) techniques have been proposed in literature. Despite these solutions prove to be a valid alternative to the standard treatment, the clinical use of AM-based devices is not trivial due to the need of expert CAD modelers to design the 3D model of the orthosis starting from the patient’s anatomy 3D acquisition. In this work, the authors identify a systematic procedure to create an orthosis model, compliant with medical guidelines, using common CAD tools. The systematic procedure, even still manually performed, envisages a set of tasks, grouped into five main blocks, that will be easy to be automatized in the future, thus eliminating the necessity of designing expertise to model the orthosis. The proposed procedure allows to design a device composed of two halves, to ease the application, locked through a zip tie-based mechanism. A preliminary ventilation pattern is proposed and tested with a FEM analysis to ensure structural resistance. The procedure has been tested on six case studies: all the orthoses models were correctly generated without major complications and positive user feedbacks were generally obtained throughout the tests.

An investigation and evaluation of computer-aided design model complexity metrics

Abstract: Computer-aided design (CAD) tools are vital to the modern product commercialization process. CAD models and modeling activities are evaluated for various industrial, educational, and research purpo...

A comparative analysis of computer-aided design team performance with collaboration software

Abstract: For the past several years, the BYU CAD Lab has been developing collaborative computer-aided design (CAD) software. As this software is being developed, industry seeks to better understand ...

Using 3D direct manipulation for real-time structural design exploration

Abstract: Before a new structure can be built, it must be designed. This design phase is a very important step in the building process. The total cost of the structure and its structural performance are largely dependent on the structural design process. The impact of decisions on the design process is initially high and declines as the design matures. However, few computational tools are available for the conceptual design phase; thus, an opportunity exists to create such tools. In the conventional workflow, the architect uses geometric modeling tools and the engineer uses structural analysis tools in sequential steps. Parametric modeling tools represent an improvement to this workflow, as structural analysis plug-ins are available. This allows the architect or engineer to receive structural feedback at an earlier stage, but still as a sequential step to the geometric modeling. The present work aims to improve this workflow by integrating structural feedback with geometric modeling.The user interfaces of conceptual design tools should be interactive and agile enough to follow the designer’s iterative workflow. Direct manipulation involves human-computer interaction, which enables an interactive user interface. In this user interface style, users can directly manipulate on-screen objects using real-world metaphors, which engages the users with their task and encourages further explorations. This is achieved by reducing the perceptual and cognitive resources required to understand and use the interface. New technologies have opened up the possibility of creating new design tools that make use of very direct manipulation. This possibility is further explored in this thesis through the development of two such applications. The first application makes use of multi-touch tablets. The multi-touch interface has literally closed the gap between humans and computers, enabling very direct manipulation interactions with two-dimensional user interfaces. The developed application is an interactive conceptual design tool with real-time structural feedback that allows the user to quickly input and modify structural models through the use of gestures. The second application extends these concepts and ideas into a three-dimensional user interface using an input device named the Leap Motion Controller.

5-Axis tool path planning based on highly parallel discrete volumetric geometry representation: Part I contact point generation

Abstract: While 5-axis CNC machines improve the manufacturing productivity, the tool-path programming demands human expertise and tremendous time investment to generate collision-free optimal tool trajectories. To address the challenge of multi-axis CNC programming, this work presents a new discrete volume based geometry representation that naturally enables highly parallel geometry processing. Then it formulates and discusses a methodology for tool path planning algorithms designed around the formulated geometric representation for 5-axis CNC milling machines and ball end tools. This paper is the first of two papers that deals with finding the XYZ locations of ball end mill centers that govern the tool trajectories. The experimental 5-axis machining using the resulting tool paths demonstrates that the designed algorithms are capable of producing collision- and gouge- free tool paths with a desired surface quality for a given target geometry by using the selected ball end tools.

The Current State of Model Based Definition

Abstract: A new methodology for communicating engineering information called Model Based De nition is gaining popularity. In this article a comparison will be made of the socalled traditional way that engineers communicate their ideas using engineering drawings, where the drawing is the authority, and this new Model Based De nition methodology, where the 3D model is the authority. The pros and cons of implementing Model Based De nition are critically analysed. The conclusions drawn from this analysis indicate where further development is needed if Model Based De nition is to become more widely accepted.

Integration of Virtual Reality in a Knowledge-based Engineering System for Preliminary Configuration and Quotation of Assembly Lines

Abstract: Realistic visualization of products is now a must-have for all companies facing worldwide and highly competitive market. Despite Virtual Reality technologies are appealing, its industrial use is still limited to conceptual design and prototyping activities. One of the reason is that generating Virtual Reality (VR) environment is a complex and time-consuming task, especially for complex products or systems. Many technical data are involved in their design and con guration. A meaningful example is the preliminary con guration of assembly lines devoted to deliver a quotation to the customer. To be competitive, the quotation should be completed in tight time and contain variants of the con gured system ranging di erent costs. Moreover, high-impact and successful quotation goes beyond the merely technical aspect. In this view, the automatic generation of a virtual reality environment can foster the adoption of this technology in industry, since its setup time is short and doesn't require any skills. In this paper, the integration of a VR module in product con guration and quotation process is proposed. The framework is a Knowledge-based Engineering (KBE) system that, taken the customer requirements as input is able to automatically generate a bunch of di erent solutions. Starting from technical data coming from a KBE system, a virtual environment is generated automatically tting the features of the con gured solution. Furthermore, the immersivity of the VR scene is enhanced by integrating the animation of the objects, like robots and pallets. After a brief description of the KBE system, the paper details the information is involved in, the implementation of the VR module and its integration within the KBE framework.

3D Mass Customization Toolkits Design, Part I: Survey and an Evaluation Model

Abstract: Mass customization (MC) allows consumers to design their own products or services through online MC toolkits. The application of geometric modeling through modern web-browsers allows for the presentation of a virtual 3D product, resulting in a number of commercial 3D MC sites. To gain a deeper understanding of the toolkits that drive these sites, this article provides a comprehensive investigation into web-based toolkit design. Based on this review, an evaluation model for 3D MC toolkits is proposed that considers four aspects: Individual Differences, Solution Space, Interaction Design and Enabling Technologies. This leads to a follow-up article that applies the 3D toolkit evaluation model to assess commercial 3D toolkits which are available on the current market.

Adaptive Tool Path Planning Strategy for Freeform Surface Machining using Point Cloud

Abstract: This paper reports the development of an efficient tool path planning strategy for machining of freeform surfaces directly from their representation in the form of point cloud without interim surface fitting. A grid based adaptive planar strategy has been designed and implemented for 3-axis CNC machining using ball end mill. Uniform CL grid points are initially computed by using tool inverse offset algorithm. Estimating the chordal and scallop errors likely to be produced, adaptive grid refinement is carried out iteratively till the errors converge below the prescribed tolerance limits. Adaptive grid (CL) points are subsequently processed to generate the final CNC part programs in the ISO format. The part programs were extensively tested for various case studies using the commercial CNC simulator as well on the actual CNC machine. Effects of variation of grid size and cloud point density were studied for grid optimality and their effect on the quality of CNC programs generated. The results were compared with those from the commercial software. Our system was found to generate more efficient tool paths in terms of enhanced productivity, part quality and reduced memory requirement.

Characteristics of 3D solid modeling software libraries for non-manifold modeling

Abstract: The aim of this paper is to provide a review of the characteristics of 3D solid modeling software libraries – otherwise known as ’geometric modeling kernels’ in non-manifold applications. ’Non-manifold’ is a geometric topology term that means ’to allow any combination of vertices, edges, surfaces and volumes to exist in a single logical body’. In computational architectural design, the use of non-manifold topology can enhance the representation of space as it provides topological clarity, allowing architects to better design, analyze and reason about buildings. The review is performed in two parts. The review is performed in two parts. The first part includes a comparison of the topological entities’ terminology and hierarchy as used within commercial applications, kernels, and within published academic research. The second part proposes an evaluation framework to explore the kernels’ support for non-manifold topology, including their capability to represent a non-manifold structure, and in performing non-regular Boolean operations, which are suitable for non-manifold modeling.

A hybrid solution to parallel calculation of augmented join trees of scalar fields in any dimension

Abstract: Scalar fields are used to describe a variety of data from photographs, to laser scans, to x-ray, CT or MRI scans of machine parts and are invaluable for a variety of tasks, such as fatigue detectio...

Fast generation of cartesian meshes from micro-computed tomography data

Abstract: Micro-finite element models (μFEMs) are one of the critical components of the microscale analyses that are typically performed on trabecular bone. These models are often derived from on micro computed tomography (μCT) data and tend to encompass an extremely large number of elements that in turn require significant processing time and power. To address the increased computational demands, the main goal of the current study was to devise an algorithm capable to manage the large μCT data in order to construct Cartesian μFEMs. For this purpose, the developed technique relies on the projection of μCT voxels to a structured grid and were designed to involve fast integer operations and hashing techniques for fast mesh constructions. The numerical tests performed on common computer hardware revealed that only 55.16 seconds are required to discretize more than 36.2M voxels. Furthermore, the linear time complexity of the developed algorithm ensures that its efficiency will be preserved even in case of larger datasets that tend to be prevalent in micro-structural biomechanical analysis.

On the Curvature Estimation for Noisy Point Cloud Data via Local Quadric Surface Fitting

Abstract: This paper presents an improved method of estimating surface curvatures at any point in a noisy point cloud data via local quadric surface fitting. Accurate estimation of curvatures is of particular importance in different applications of point cloud processing. One of the widely used methods for estimating curvatures is fitting a local quadric surface to the local neighborhood of the query point and using the fitted surface for curvature calculation. The performance of this technique however depends on the selected local neighborhood (i.e., neighboring points of the point of interest) for fitting. In particular, a scanned point cloud is noisy, and the distribution of points is non-uniform. Using the previously adopted neighborhood selection methods results in unbalanced local neighborhoods, therefore erroneous fitted surfaces and estimated curvatures. In this work, the utilization of Territory Claiming (TC) algorithm is proposed for selecting the neighboring points. Using TC, balanced local neighborhoods can be established, which contribute to more accurate estimation of surface curvatures. To evaluate the effectiveness of the proposed method, case studies have been performed on synthetic and scanned point cloud data. The principal curvatures estimated by the proposed method have been compared to the ones estimated from the quadric surface fitted over the other available neighborhoods, namely k-nearest neighbors (k-NN), mesh neighbors, and elliptic Gabriel graph (EGG) neighbors. The results demonstrate the superiority of the proposed method over other existing methods for noisy data and its robustness towards point density variation.

A dependencies satisfaction tool to support the cost oriented configuration of industrial products in the conceptual design stage

Abstract: Sustainability and cost optimization are actually the main drivers of product and system design in modern companies. However, cost assessments are usually carried out at the end of the design proce...

A novel hierarchical clustering algorithm for the analysis of 3D anthropometric data of the human head

Abstract: In recent years, the use of 3D anthropometry for product design has become more appealing because of advances in mesh parameterisation, multivariate analyses and clustering algorithms. The purpose of this study was to introduce a new method for the clustering of 3D head scans. A novel hierarchical algorithm was developed, in which a squared Euclidean metric was used to assess the head shape similarity of participants. A linkage criterion based on the centroid distance was implemented, while clusters were created one after another in an enhanced manner. As a result, 95.0% of the studied sample was classified inside one of the four computed clusters. Compared to conventional hierarchical techniques, our method could classify a higher ratio of individuals into a smaller number of clusters, while still satisfying the same variation requirements within each cluster. The proposed method can provide meaningful information about the head shape variation within a population, and should encourage ergonomists to use 3D anthropometric data during the design process of head and facial gear.

An Exploratory Study on the Application of Reverse Engineering in the Field of Small Archaeological Artefacts

Abstract: In Italy’s artistic heritage, there are numerous small artefacts that are rich in details usually invisible to the naked eye. In the last decade, the need to document and create digital archives of cultural heritage has triggered research on the application of well-known reverse engineering techniques. Despite the applications in the field of virtual heritage, the 3D digitalization and reconstruction of small archaeological artefacts remains an open issue due to their small dimensions and handling constraints. In this context, this paper presents a methodology to compare the performance of two different techniques for 3D digitalization, one using a triangulation laser scanner and one using Structure from Motion (SfM) photogrammetry. The methodology is based on a QFD approach to identify and quantitatively evaluate the differences between the achieved 3D models. It has been applied to the famous limestone sculpture called “Venus of Frasassi”. The main advantages and limits of both techniques are discussed with a focus on their ability to allow the identification of hidden shape features.

Persistent Naming Based on Graph Transformation Rules to Reevaluate Parametric Specification

Abstract: The ability of 3D modeling tools to generate automatically various versions of a similar model is an increasing need in several and diferent domains such as Archaeology, Architecture or Geology. To address this issue, we propose to use both the Jerboa library designed to assist the development of application-specific modelers and the reevaluation methods used for parametric systems in the CAD domain. Unlike most approaches, Jerboa is independent from any application domain and allows rapid development of new operations using graph transformation rules to automatically check the consistency of different objects properties. But it do es not support any reevaluation mechanism and especially not a persistent naming system , that is used to identify entities of the initial model and match them with entities of the reevaluated model. Using the capacity of graph transformation rules, we address naming problems through a very precise characterization of the basic elements forming the model.

Artificial intelligence aided CFD analysis regime validation and selection in feature-based cyclic CAD/CFD interaction process

Abstract: Multiple-view feature modeling is supposed to keep the information consistency during product development. However, for products involving fluid flow, the information consistency is difficult to ke...

STEP-Compliant CAD/CNC Systems for Feature-Oriented Machining

Abstract: STEP-NC is proposed for the next generation of data exchange between CAD/CAM and CNC systems. However, the STEP-compliant CAD/CAM systems and STEPcompliant CNC systems are researched individually in the last decade, which hinders the practical applications of STEP-NC. In the paper, STEP-compliant CAD/CNC system is proposed that consists of STEP-CAD and STEP-CNC, and feature-oriented machining is introduced for 2.5D feature and freeform surface machining, wherein T-spline is introduced for the representation and data exchange of freeform surface. A practical machine tool is constructed under the proposed STEP-compliant CAD/CNC system. Some workpieces are tested to verify the feasibility of the proposed STEP-compliant CAD/CNC system for the featureoriented machining.

Surface Model Deficiency Identification to Support Learning Outcomes Assessment in CAD Education

Abstract: Recent efforts to reform CAD education are aimed, among other things, at increasing the development of strategic knowledge and modeling skills within CAD competency. This requires better structured and more frequent assessment and feedback than can be achieved with current, mostly summative-based, techniques. Here, formative assessment and formative feedback appear to offer a viable solution. Unfortunately, within CAD education, dedicated techniques and tools are not yet available to support the implementation of formative assessment, and, in particular, to assist learning goal and outcome oriented assessment of CAD models produced by students. Moreover, those frameworks and tools for CAD model analysis and evaluation that are available and deployed within commercial and industrial settings cannot be directly used in educational settings, due to differences in assessment criteria and evaluation goal settings. The aim of the current paper is, firstly, to present a novel approach for surface model assessment in the educational context, which is based on deficiency analysis in relation to learning outcomes, and, secondly, to report on the implementation and application of a newly developed software tool to enable and put into practice this novel surface model assessment approach.

Multilevel topology optimization

Abstract: The paper proposes an extension of the Function-Behaviour-Structure (FBS) framework to multi-levelc design representation. The ontology based on function, behaviour and structure has been enriched with a new design entity, the topology, with the aim of connecting more levels of representation. According to this new paradigm, design activity is not focused exclusively on working principle, shape and material at macro level, but goes beyond, to greater levels of detail, designing for example how to dispose material in the inner structure of the product parts at microscopic level. Structural optimizers are excellent tools to design the topology of a structure according to its function and behaviour, but they have been conceived for working only at mono-level. This paper proposes a multi-step optimization process for improving the versatility of structural optimization tools allowing them working also in both macro and microscopic dimensional scales.