3D scanning

In the context of styling products development, it is well known that sketches are the most immediate and used means for the 'external representation' of the industrial designers' intentions; the designer, however, also needs physical full-scale models, in order to evaluate the aesthetic solution. Reverse engineering techniques support the transformation of the physical mock-ups in digital ones, in order to perform the engineering developments. The observation of the design phases highlights the need to study new methodologies and computer-based tools, in order to simplify the reverse engineering process and to improve the quality of the final result. The conversion from real to virtual can be time consuming and strongly critical, in terms of product aesthetic and functional contents preservation. The process can be affected by several misunderstandings in the communication of the design values from the designer to the product engineers. In this paper, we propose a method for the formalization and recognition of the aesthetic properties within the different modes of design representation. The proposed method is based on the examination of the design principles used by the designer during the creative process (aesthetic intentions) and on techniques for the representation of creative ideas. In particular, we analyse the free-hand sketches and drawings to retrieve both the implicit (lines/curves) and explicit information (textual notes). Such information is used to develop a set of rules to support the identification of the styling lines on the points cloud data. The method has been experimented using a commercial computer-aided design system to manage the heterogeneous data (points cloud data, sketches and notes). The preliminary validation process shows good results in terms of time-saving. This is mainly due to two factors: the remarkable simplification of the surface reconstruction phase and the continuous monitoring of the aesthetic coherence.

Keywords: Character lines , Cognitive perspective , Design intent , Hand-made sketches , Reverse engineering

Identifying theories and methods to link geometrical tolerances specification and inspection processes is a widely spread research topic. The growing use of virtual product models which not only represent the geometry information, but also collect attributes, notes, parameters, rules and procedures, can facilitate the digital simulation of many real processes. In the present work we are interested in using such technologies for the purpose of simulating the inspection process of manufactured products. In particular, we propose an approach for virtual inspection of geometrical tolerances based on a feature-based 3D CAD model coupled with a 3D points cloud data model. The 3D CAD model stores the tolerances specifications defined by the designer as well as the specification of the inspection methods. The points cloud model is a complete representation of the manufactured product and it is defined by the digital acquisition of the real product. The acquisition phase is performed with non-contact techniques to ensure high performances in terms of speed. The information stored in the CAD model is used to select and drive the different inspection procedures to be performed on the acquired data. © 2007 Springer.

Keywords: Automated inspection , Feature-based model , Geometrical tolerances , Reverse engineering

Although the 3D shape recovery of a real object have been greatly improved in the last few years, modeling a complex virtual object by starting from the real prototype is still a very time-consuming activity. In this paper an originally conceived method and testing software to recover a CAD model from a real object is presented. The developed software tool joins a professional Computer-Aided Design (CAD) and a Mixed Reality (MR) tool in the same interface, enabling the operator to use standard CAD tools and features together with a camera, which provides external image streaming displayed in the workspace background. Moreover, a special programmed library performs a real-time calculation of camera position and other parameters with respect to standard markers in order to drive the CAD 3D virtual camera and align it to external world. In that way rendered virtual models may be superimposed to external images of reality grabbed by the video camera. Thus with MR-CAD tool the operator may easily recover a complex shape directly from the external views of a real object or may start the object re-design from the previous reconstructed geometry. Furthermore the interface is totally integrated in a CAD environment, both avoiding to work with unfamiliar new software and exploiting CAD geometry database and tools. Finally, MR-CAD can be considered a significant step ahead in the bi-directional interaction of virtual and real models, reducing also the gap between real prototypes and CAD data.

Keywords: Augmented reality , Mixed-reality , Reverse engineering , Virtual prototyping

Creation of a CAD model from a hard model is something necessary for design modification, part replication or rapid prototyping and surface inspection. This is reverse engineering. Scientific literature presents many different approaches, even if, actually all the systems, mechanical (contact devices) and optical (non contact devices), work with constant acquisition pitches. This became a great deal in relation to the different object morphology combinations that the same surface could show. Working in fact with a constant pitch on a free-form surface it is possible to struggle with an insufficient points cloud density, when the acquisition pitch would be a compromise between the complex and elementary features that describe the object to acquire, or with an excessive points cloud density, when the acquisition pitch represents the highest scanner resolution. Referring to this situation, this paper proposes, starting from a first raw acquisition, an automatic methodology, directly implemented on the acquisition device, for the selective individuation of surface zones which present sensible curvature. In this approach the curvature of the measured surfaces is analyzed by defining a threshold over which it is necessary to perform a deeper scansion of the surface. In the present paper a methodology for the definition of the threshold value based on the measurement system uncertainty is described. In the current description the method is applied to an algorithm for curvature analysis, but it could be extended to any other approaches. Furthermore, it will be demonstrated that this new methodology is simple to apply and can be easily automated directly in the control scanner software. In the end of the paper a practical example is described in order to give an experimental validation of the method. © Springer-Verlag London Limited 2007.

Keywords: Design , Geometric morphology , Reverse engineering , Scanner 3D , Scanning strategy

In this paper, the feasibility of using optical methods to detect impact damage in thin laminates is investigated and discussed. Specimens impacted with different energy levels were analysed by a holographic procedure and by an electronic speckle pattern interferometry technique; the results obtained with the two techniques were compared with those acquired by a pulse-echo full-volume ultrasonic technique. The investigation showed that both optical methods were able to identify the presence of impact damage, with an efficiency dependent on the through-thickness location of the delaminations produced by impact. The adoptation of the ESPI technique allowed significant reductionn in inspectioon times, but quantitative estimates of impact damage were drastically impaired by the high level of speckle noise typical of the technique. © 2005 Elsevier Ltd. All rights reserved.

Keywords: B. Impact behaviour , C. Delamination , D. Ultrasonics , ESPI , Holography

Computing how a camera samples a scene is a common task in engineering and computer graphics. Though this concept is rather intuitive (sampling density is proportional to the number of pixels which sample a point in the scene), it is necessary to define it in a formal and rigorous way. This paper describes a method to evaluate the sampling density distribution of a camera. A definition of camera sampling density is given, and a simple computation method is presented. The proposed approach is based on the evaluation of the area reduction coefficient associated to the function which maps a generic point of the scene to a point in the image plane. The approach can be applied either to the ideal (pinhole) camera model or to real camera models with distortion. Experimental tests on a specimen are also presented and discussed.

Keywords: Camera sampling density , Image acquisition , Reverse engineering

The paper presents an innovative approach totally based on digital data to optimize lower limb socket prosthesis design. This approach is based on a stump's detailed geometric model and provides a substitute to plaster cast obtained through the traditional manual methodology with a physical model, realized with Rapid Prototyping technologies; this physical model will be used for the socket lamination. The paper discusses a methodology to reconstruct a 3D geometric model of the stump able to describe with high accuracy and detail the complete structure subdivided into bones, soft tissues, muscular masses and dermis. Some different technologies are used for stump acquisition: non contact laser technique for external geometry, CT and MRI imaging technologies for the internal structure, the first one dedicated to bones geometrical model, the last for soft tissues and muscles. We discuss problems related to 3D geometric reconstruction: the patient and stump positioning for the different acquisitions, markers' definition on the stump to identify landmarks, alignment's strategies for the different digital models, in order to define a protocol procedure with a requested accuracy for socket's realization. Some case-studies illustrate the methodology and the results obtained. © 2006 SPIE-IS&T.

Keywords: 3D geometrical model , Human body scanning , Lower limb prosthesis , Medical imaging , Rapid prototyping , Reverse engineering

The paradigm of Mass Customisation (MC) is today fundamental for the European fashion industry. Footwear industry is still labour intensive and companies need solution to reduce costs and remain competitive in the global market. In particular, specialized companies that produce customized medical shoes prescribed for people with feet malformations deal with small batches or unique pairs. This work presents some approaches and low-cost solutions related to foot measurement and CAD data elaboration for facilitating the diffusion of "made-to-measure" products. An integrated process made of hardware devices and customized software is explored and described aiming to increase production efficiency and reduce costs.

Keywords: 3D design tools , 3D foot measurement , Mass customization , Personalised shoes

Reverse engineering is a technique used during the project phase of a new product, which makes it possible to trace, in terms of mathematical expressions, the geometrical features of a given physical model. Scientific literature presents many different approaches to reverse engineering. Great part of those are based on the analysis of point clouds acquired through coordinate measuring devices, such as, for example, Coordinate Measuring Machines (CMMs), Optical Scanners or Interferometric Systems. Referring to this kind of approach, a common problem is to individuate the surface zones, which present sensible variations of curvature. Many algorithms, commonly implemented on commercial software through semi-automatic procedures, are already based on this method. In these cases the local curvature variation of the measured surfaces is analyzed by defining a threshold over which it is necessary to perform a deeper scansion of the surface zones. However, most of the problems are related to the definition of an appropriate value for the threshold level. In the present paper a methodology for the definition of the threshold value based on the measurement system uncertainty is described. In the current description the method is applied to an elementary algorithm for curvature definition, but it could be extended to any other kind of more complicated approach. Furthermore, it will be demonstrated that this new methodology is simple to apply and can be easily automated in commercial software for points selective sampling in industrial reverse engineering applications. In the end a practical example is described in order to give an experimental validation of the method. © 2005 Elsevier Ltd. All rights reserved.

Keywords: Geometric morphology , Reverse engineering , Scanning strategy

Incremental forming applications are currently increasing in industry, especially for the production of small batches or single components. In fact, sufficient know-how is now available for the manufacture of simple products. However, further efforts are required to reduce the drawbacks of typical incremental forming processes, which compromise important advantages in terms of costs and flexibility. First of all the duration of the process, usually a few minutes, influences this kind of process, even if the operations are carried out on high-speed digitally controlled units. A tendency to produce inaccurate parts can reduce industrial interest with respect to incremental forming. Different approaches could be proposed to reduce this drawback, and a feasible and easily implemented strategy is the design of modified trajectories able to take into account both springback effects and stiffness reduction owing to specific clamping equipment. In this paper, such a strategy is pursued by integrating an on-line measuring system, composed of a digital inspector and a computer numerically controlled (CNC) open program. The geometry obtained is sampled in particular steps and an appropriate routine modifies the coordinates of the future punch path. This procedure of automatic control has been developed using an effective finite element (FE) code. An experimental design illustrates the potential use of the suggested methodology. © IMechE 2005.

Keywords: Incremental forming , Net shape , Sheet metal forming

Incremental Forming processes have been introduced in the recent past as an alternative to the money consuming stamping technology, when small batches have to be manufactured. Anyway, they introduce some advantages in terms of flexibility and material formability but, also, some problems such as the dimensional accuracy decreasing. In this paper, a particular application is carried out taking into account the development of an innovative technique to produce a customised ankle support. In this way Incremental Forming process has been selected for the sheet profiling, exalting the role that this technology may play when single complex product has to be manufactured. The producing procedure finishes with a measure of the dimensional accuracy that shown a good result for the desired application. © 2005 Elsevier B.V. All rights reserved.

Keywords: Ankle support , Incremental Forming , Reverse engineering

In this paper, the activity aimed at the contact less acquisition, the generation of polygonal descriptive models, the generation of NURBS-based models and the reproduction by means of rapid prototyping tools of pieces of interest in both the heritage and the automotive domains are presented. The work gives an insight of how three-dimensional range cameras and suitable data modeling can be helpful in the reverse engineering and in the virtual representation of complex shapes. In addition, the research represents a valuable example of Computer Support Collaboration Work (CSCW) for the restoration and the rapid prototyping of the objects. © 2005 Taylor & Francis Group.

Reverse Engineering is a rapidly evolving discipline. Nowadays shape acquisition systems have reached enough capabilities to reproduce complex free form objects. This paper presents a comparison between two different acquisition systems to evaluate their performances and their easy to use capabilities and to evaluate quality and accuracy of the 3D reconstructed models. To achieve this task, a complex free form object, a steam turbine blade, was acquired. After shape acquisition and data elaboration of this particular object an evaluation of the two systems characteristics and of the 3D CAD reconstructed models were done and results are illustrated here.

Keywords: Methods comparison , Reverse engineering , Turbine blade

Many applications in orthopaedic surgery require the creation of personalised design models that can serve as the basis for navigation in computer aided surgery systems or be used to create a personalised model to perform structural analysis during pre-operative planning or post-operative follow-up. The paper introduces a method for developing a three-dimensional (3D) patient-specific model of a femur bone from an antero-posterior radiograph. A generic femur was employed and was altered on the basis of bone boundaries visible on radiographs. Morphological errors were evaluated against 3D models obtained from computed tomography (CT) scans. When only the antero-posterior radiograph was used, the average radius estimation error was 4.8 mm, the average percentage area estimation error was 14%, and the average percentage estimation error for inertial moments was 15%. If both the medial-lateral and the anterior-posterior radiographs were used, these errors were 2.0 mm, 5% and 7%, respectively. The procedure described can be profitably employed whenever CT scans are not available, such as during a retrospective analysis, or when CT scans cannot be justified because of X-ray exposure and cost considerations. © IFMBE: 2005.

Keywords: 3D model , CT , Femur morphing , Radiographs

This article describes a procedure based on reverse engineering and CFD analysis to numerically evaluate the aerodynamic performances of physical components. The case study is represented by the investigation of the aerodynamic behaviour of a racing car air-box. An existing air-box has been digitised using a proprietary system which enables the acquisition of a point cloud of the surface of the object. A procedure has been developed to obtain a CAD model suitable for CFD analysis from the raw 3D data. A computational fluid-dynamics analysis has been performed using the digital model. The procedure described in this paper can be easily extended to the reconstruction and the analysis of similar classes of shapes such as wings and profiles.

Keywords: Aerodynamic analysis , Geometric modelling , Reverse engineering

This paper presents a 3D optical digitiser based on an active stereo vision aproach. The system is composed of a digital camera, a multimedia projector and software to control the hardware and process the images. The proposed solution integrates an active coded light method with a photogrammetric procedure in order to allow the acquisition of complex surfaces. In the work, experimental tests have been conducted with a nominal model and styling components of two-wheeler vehicles. The measurement process and the experimental results have been analysed to verify usability and accuracy of the methodology.

Keywords: Coded light , Photogrammetry , Reverse Engineering , Stereovision

As known, incremental forming is a flexible and innovative sheet metal forming process which allows complex shape shells forming without the need for any die. For these reasons, incremental forming is nowadays suggested for rapid prototyping and customised products. The present paper is focused on material formability in incremental forming and, in particular, on the evaluation and compensation of elastic springback. The latter significantly modifies the imposed shape. For this purpose, a deeper assessment of the process was developed following three different approaches. First of all, a wide experimental investigation on the influence of some relevant process parameters was developed. At the same time, an explicit FEM analysis of incremental forming process was carried out in order to verify its effectiveness and, as a consequence, its ability to be used as a design tool. Furthermore, the obtained parts were analysed by a reverse engineering technique and the measured geometry was numerically compared with the desired one, with the aim to quantify the geometrical discrepancies. In this way, an integrated numerical/experimental procedure is proposed in order to limit the shape defects between the obtained geometry and the desired one. © 2004 Elsevier B.V. All rights reserved.

Keywords: FEM , Geometrical accuracy , Incremental forming

Incremental forming is nowadays increasing its presence in industry as a new but interesting process, especially for production of small batches or unique components. Anyway, relevant efforts have to be spent in order to reduce the typical incremental forming processes drawbacks that risk to belittle the high advantages in terms of costs and simplicity. In fact, the process duration, usually equal to several minutes even if the operations are carried out on high speed numerical controlled units, and a certain tendency to produce no precise parts, can reduce industrial interest about incremental forming. A possible strategy to reduce the latter item is the design of modified trajectories able to take into account both the springback effects and the stiffness reduction due to the particular clamping equipment. In this paper the above introduced strategy is pursued integrating an on-line measuring system, based on a digital inspector, and a CNC open program. The actual geometry is acquired in some remarkable points and a compensation routine modifies the coordinates of the future punch path. The modification policy has been developed by using an effective FE code. An experimental verification shows the good potentiality of the suggested methodology.

Reverse engineering techniques are broadly used in the development process of products with meaningful aesthetic properties. Many stylists prefer to evaluate the product shape on the basis of a full-scale hand made physical mock-up. Such model has then to be converted into a 3D CAD model, to begin the product engineering and production processes. A critical aspect of the RE process is that the physical mock-up, made by the stylist, usually does not take into account the engineering production constraints. The surface reconstruction activity must then be followed by a modelling phase, where the engineering designer modifies the reconstructed model shape in order to make it suitable for production. At the end of this process, no matter how accurate and precise the surface reconstruction phase has been, the product model will be different from the original mock-up, and then it needs to be submitted to the stylist for the validation of its shape. For the stylist, getting used to working with physical models, the shape validation on a virtual model is not a trivial task. The objective of this research is to develop a software tool to support the identification of aesthetic and functional regions of the product model shape, that have been modified with respect to the original mock-up. The proposed approach is based on the decomposition of a 3D surface analysis problem into a simpler 2D curves analysis problem. This approach simulates the traditional method used by stylists to evaluate the quality of shapes. The implementation of the developed algorithms has been performed using a commercial software package (I-deas FreeForm by EDS/Unigraphics) and it has been successfully applied on real test cases. © 2003 Elsevier Ltd. All rights reserved.

Keywords: Physical mock-up , Product engineering , Style , Virtual mock-up

A Reverse Engineering- (RE) and Rapid Prototyping- (RP) based approach to (he development of a joystick handgrip with ergonomic features has been elaborated. The integration of Time Compression Techniques and Computer Aided Tools lead to a time-saving procedure for the design of a product whose ergonomic quality directly descends from users' sensations of comfort. The CAD model availability throughout the progressive steps of product development ensured all the potentialities of Concurrent Engineering, while Computer Aided Engineering (CAE) simulation on the definitive geometry allowed to close the Computer Integrated loop to the manufacturing process.

Keywords: Computer Aided Engineering , Design for Manufacturing , Ergonomics , Product Development , Reverse Engineering