3D scanning

3D CAD techniques represent today a crucial tool in almost all the design fields. Nevertheless, due to a number of well known reasons, multi orthographic view drawings are still widely used; accordingly, the conversion of 2D drawings into 3D CAD models (known in the scientific literature as the "reconstruction problem") is still a key issue. During the last decades a number of works, dealing with the reconstruction problem, have been proposed. On the basis of these works, the authors have developed and implemented an automatic procedure that allows the reconstruction of 3D polyhedral models. The reconstruction procedure involves a number of software routines; by means of them, an initial 2D DXF file is processed and a set of 3D solutions, consistent with the initial drawing, is extracted. The obtained 3D models are subsequently output according to the most common 3D exchange formats (e.g. IGES, STEP, Parasolid, etc.). The proposed procedure and its implementation have been developed in order to achieve two main goals: to introduce researchers into the "reconstruction problem" and to create a common basis in order to methodologically compare different procedures dealing with the "reconstruction problem" itself.

Keywords: 3D reconstruction , CAD , Computational geometry , Engineering drawings , Orthographic projections , Pseudo-wireframe

Optical methods of contouring that utilise image recordings by cameras are based on a fundamental discipline, projective geometry. The 3-D world is projected in 2-D utilising a camera modelled in the technical literature by the pinhole camera. To get back 3-D information, the fundamental property measured is parallax. Parallax is a vector resulting from the difference of the projective coordinates of a point in space when projected onto a plane from two different points. The oldest method used for measuring parallax is photogrammetry. It is assumed to be the most precise technique, with the capability of obtaining 10 -5 of the largest dimension of the measured object. This study summarises the state-of-the-art methods based on projecting a spatial carrier. Starting with the concept of moiré as a form of photogrammetry, the different optical techniques for parallax determination are discussed. Although the moiré method has reached 1 μm accuracy in laboratory work, a question remains: can moiré become a standardised contouring technique yielding 10 -6 m accuracy? This study is devoted to the analysis of high accuracy contour measurements, through both theoretical derivations and experimental verifications. © 2010 Blackwell Publishing Ltd.

Keywords: contouring of surfaces , determination of parallax , geometrical primitives , merging of different views , optical measurement devices , projection moiré

Ballistic requirements in the design of military aerospace components are critical for the structural assessment. Although experimental tests remain fundamental, numerical analyses allow us to simulate such a very complex scenario. However, in order to improve the consistency of such simulations, several aspects have to be considered in detail. The material behavior is a key one: constitutive laws, able to describe the material behavior in terms of hardening, strain rate, damage criteria, temperature, etc⋯, is fundamental. Moreover a detailed validation of numerical results is needed. The analysis of ballistic data (such as the residual velocity and the direction of the bullet after the impact) is only one option, but reliable simulations of damage shape and size are the real target. Therefore the paper will focus on the comparison between the experimental damage and the simulated one using a 3D acquisition of the experimental impacted area. This approach allows us not only to evaluate the damage in the macroscale field but also in the near micro-scale: shape on the border of the damage. © 2011 Published by Elsevier Ltd.

Keywords: AL-6061-T6 shaft , Ballistic impact , NATO 7.62 mm , Numerical simulations , Reversal engineering

In this paper, the complete procedure to design and construct reusable moulds for implant-based ear prosthesis and manufacture substructures by means of a computer aided design-computer aided manufacturing (CAD-CAM) procedure and rapid prototyping (RP) technology is presented. The scan of the healthy ear, the virtual superimposition of its mirrored image on to the defective side, and the rapid manufacturing of the substructure and of the mould eliminate several steps of traditional procedures (wax, stone, try-in). Moreover, the precise design and customization of the substructure is presented, with the original and engineered shape for the retention of the silicone. The time and cost saving results of this protocol are presented together with a discussion of the main design features that make the prosthesis a stable and reproducible system to improve rehabilitation of patients with auricular defects or absence.

Keywords: CAD/CAM , facial rehabilitation , prosthetic rehabilitation , rapid prototyping , reverse engineering

Nowadays three-dimensional Computer Aided modeling is of out-standing importance in the mechanical design process since it impacts on several issues like visualization, simulation, machining, etc. Anyway, multi orthographic view engineering drawings have been widely used up to latest decade and still are, so they play an essential role in traditional engineering. The conversion from 2D drawings to 3D CAD models is still a key task in a wide range of applications. In order to cope with this issue a number of works have been proposed in the last decades, providing a series of methodologies for solving the reconstruction prob-lem. On the basis of such methodologies the main aim of the present paper is to suggest a comprehensive, orderly, unambiguous and automatic procedure meant to help researchers and practitioners who want to deal with the reconstruction problem. The procedure, by using an appropriate formal mathematic language, systematize and integrates some of the methods proposed so far. © 2011 Heldermann Verlag.

Keywords: 3D reconstruction , Computational geometry , Computer aided design , Engineering drawings , Or-thographic projections , Pseudo-wireframe

In the footwear industry there is growing methodological research linking advanced computer-based technologies to the traditional manufacturing process. This paper deals with the automation of shoe design phases and describes a computer aided design system that brings together theories and tools from geometric modeling, image processing, and reverse engineering. At first, the paper reviews the current technologies used for creating new shoe models. Then the paper presents an approach based on shoe 3D virtual modeling in order to overcome the traditional time-consuming manual operations. The approach is concretized into dedicated tools able to automatically perform design of the last shape model and flattening of the shoe styling curves represented in the virtual prototype. The modeling tool uses 3D geometric rules derived from the analysis of strategies adopted by skilled manual operators, while the styling curves recognition and flattening are based on specific image processing algorithms and geometrical deformation rules. Experimental results show a good compromise between quality results and modeling time. © 2011 Springer-Verlag.

Keywords: Design automation , Footwear industry , Reverse engineering , Time compression technologies

Spinal disease due to intervertebral disc degeneration represents a serious medical problem which affects many people worldwide. Disc arthroplasty may be considered the future "gold standard" of back pain treatment, even if problems related to available disc prostheses are considered. Hence, the aim of the present study was to improve the artificial disc technology by proposing the engineering of a pilot-scale device production process for a total multi-component intervertebral disc prosthesis. The device is made up of a poly(2-hydroxyethyl methacrylate)/poly(methyl methacrylate) (PHEMA/PMMA) (80/20 w/w) semi-interpenetrating polymer network (s-IPN) composite hydrogel reinforced with poly(ethylene terephthalate) (PET) fibers as annulus/nucleus substitute, and two hydroxyapatite-reinforced polyethylene composite (HAPEXTM) endplates in order to anchor the multi-component device to the vertebral bodies. Static and dynamic-mechanical characterization show appropriate mechanical behavior. An example of engineering of a suitable pilot-scale device production process is also proposed in order to manufacture custom made implants. © 2010 The Author(s).

Keywords: customized prosthesis , fiber-reinforced hydrogel , intervertebral disc , mechanical testing. , multi-component model , reverse engineering , technologies

In the field of 3D scanning, there is an increasing need for more accurate technologies to acquire 3D models of close range objects. Underwater exploration, for example, is very hard to perform due to the hostile conditions and the bad visibility of the environment. Some application fields, like underwater archaeology, require to recover tridimensional data of objects that cannot be moved from their site or touched in order to avoid possible damages. Photogrammetry is widely used for underwater 3D acquisition, because it requires just one or two digital still or video cameras to acquire a sequence of images taken from different viewpoints. Stereo systems composed by a pair of cameras are often employed on underwater robots (i.e. ROVs, Remotely Operated Vehicles) and used by scuba divers, in order to survey archaeological sites, reconstruct complex 3D structures in aquatic environment, estimate in situ the length of marine organisms, etc. The stereo 3D reconstruction is based on the triangulation of corresponding points on the two views. This requires to find in both images common points and to match them (correspondence problem), determining a plane that contains the 3D point on the object. Another 3D technique, frequently used in air acquisition, solves this point-matching problem by projecting structured lighting patterns to codify the acquired scene. The corresponding points are identified associating a binary code in both images. In this work we have tested and compared two whole-field 3D imaging techniques (active and passive) based on stereo vision, in underwater environment. A 3D system has been designed, composed by a digital projector and two still cameras mounted in waterproof housing, so that it can perform the various acquisitions without changing the configuration of optical devices. The tests were conducted in a water tank in different turbidity conditions, on objects with different surface properties. In order to simulate a typical seafloor, we used various concentrations of clay. The performances of the two techniques are described and discussed. In particular, the point clouds obtained are compared in terms of number of acquired 3D points and geometrical deviation.

Keywords: Dense reconstruction , Stereo vision , Structured-light , Underwater imaging

Accurately measuring an artefact of historical significance generally results in being able to extract information which is useful for evaluating what remains of the materials from a distant time. This allows scholars arrive at an exhaustive historical reading of the same artefact. Compared to the traditional measuring techniques, which can often be imprecise and complicated, 3D laser scanners measure the morphological characteristics of an artefact with extreme accuracy. Despite this, it is not always possible to choose the most appropriate sensors due to the geometric peculiarities, or indeed, the size of the object. The present work deals with two non-destructive analyses of an ancient stone sculpture, which for its morphology and size was scarcely compatible with the technical characteristics of either of the scanners used. Both scanners operate on the same technical principal, but are quite different from each other in terms of scale and precision. For these reasons, a complex 3D model (extremely appropriate given the original artefact) was draw out through a synergy of the two techniques. The virtual particularities of the model allowed it to be manipulated with the appropriate software. In fact, on the basis of qualitative parameters devised by researchers, it proved possible to reproduce the artefact's geometric form, both virtually and in the form of physical models, obtained through non-conventional restoration methods (R.P. techniques).It has also been possible to verify the state of degradation of the surface of the stone caused by the traditional methods of applying cataloguing or storage information to it.Finally, the results achieved provide opportunities for further research on certain geometrical characteristics of the stone which, as highlighted by the elaboration on the virtual model, seem to be traceable to non-manual, perhaps mechanical, processes. Therefore, the historical considerations which derive from this fact call certain scholars into play. © 2011 Elsevier Ltd.

Keywords: Arteafct , Rapid prototyping , Reconstructing , Scanner , Sculpture

When talking about reverse engineering, it is necessary to focus on the management of point clouds. Generally speaking, every 3D scanner device codifies simple and complex geometries providing different point cloud densities as an output. Point cloud density is usually more correlated with the technical specifications of the device employed rather than with the morphology of the object acquired. This situation is due to the frequent use of structured grids by a large quantity of devices. In order to solve this problem, we therefore need to integrate the classical structured grid acquisition with a smart selective one, which is able to identify different point cloud densities in accordance with the morphological complexity of the object regions acquired. Currently, we can reach the destination in many different ways. Each of them is able to provide different performances depending on the object morphology and the performances of 3D scanner devices. Unfortunately, there does not yet exist one universal approach able to be employed in all cases. For this reason, the present paper aims to propose a first analysis of the available methodologies and parameters, in order to provide final users with some guidelines for supporting their decisions according to the specific application they are facing. Moreover, the developed guidelines have been illustrated and validated by a series of case studies of the proposed method. © 2011 Elsevier Ltd. All rights reserved.

Keywords: 3D scanner , Morphological analysis , Point cloud management , Reverse engineering

The identification of C1 continuities is important in many applications involving point clouds or triangular meshes, such as surface segmentation, inspection and rendering. The methods in literature have some limitations which make them strongly dependent on some properties of the mesh (point typology, mesh resolution, uniformity of the shape of triangles and error in point location). Furthermore, some of them do not discriminate non-regular points from those that are inside a band around them. In this work, a new method for automatic detection of C1 continuities in triangular meshes is presented. The method introduces an original function, called sharpness indicator, which enables us to evaluate properties related to surface smoothness. The performance of the new method is compared with that of four methods presented in literature as regards the recognition of C1 continuities both in synthetic and real meshes. Results are analysed and critically discussed. © 2010 Elsevier Ltd. All rights reserved.

Keywords: C continuities detection 1 , Reverse engineering , Triangular meshes

This paper presents a new 3D design paradigmfor the development of specific custom-fit products, such as the soft socket of prostheses for lower limb amputees. It is centered on the digitalmodel of the human body and, contrarily to the traditional process almost manually based, it considers the integration of methods and tools coming from different research and application fields: Reverse Engineering, Medical Imaging, Virtual Prototyping, Physics-based Simulation, and Rapid Prototyping. The paper describes the techniques adopted to acquire and create the digital model of the residual limb, the procedure to generate the socket model, the strategy developed for the functional simulation of the socket-stump interaction and, finally, the realization of the physical prototype. Each design step is described with the related problems and the obtained results. Both trans-tibial and trans-femoral amputees have been considered; however, for now the complete process has been validated for trans-tibial prostheses. Major outcomes of the proposed approach stand in a better quality of the final product, in a shorter involvement of the amputee implying a lower psychological impact, in a limited use of physical prototypes, and in a shorter development time. Moreover, the resulting paradigm answers to the Collaborative Engineering guidelines by optimizing the interaction between different domains and enhancing their contributions in a homogeneous development framework. © 2010 Elsevier B.V. All rights reserved.

Keywords: Custom-fit products , Human-centric soft product design , Physics-based modeling for soft products , Prosthesis development process

In the last few years, many methodologies of reverse engineering have been proposed for 3D shape measurement using optical systems. All the proposed 3D scanning solutions require user interactions concerning the alignment process of partial measures to reconstruct the complete shape of a target object. This paper presents an innovative solution based on the integration of a robotic arm and an optical stereo system, which minimizes user intervention both in the acquisition and in the reconstruction phases. The procedure is divided into two steps: 1) complete and accurate identification of the integrated system, using optical measurements of a reference surface (calibration process); 2) planning of scanning strategies in order to automatically obtain a complete 3D CAD representation. Results of experimental tests conducted on nominal samples and on industrial contexts are presented and discussed. © 2010 Taylor & Francis Group.

Complex periodontal surgeries can be performed using preoperative planning based on CT or MRI data that permit a 3D reconstruction of the patient bone anatomy. This allows a more accurate assessment of the surgical difficulties by the surgeon. The precise placement of dental implants is a crucial step to optimize both prosthetic considerations and functional aspects and the use of physical guiding systems has been recognized as a fundamental tool to control their positions and angulations. The weak point of the procedure relies on the accuracy of transferring CT planning information to the surgical field by means of custom-made stereolithographic guides. This paper concerns the study of an innovative methodology for the monitoring of the loss in the clinical accuracy through the various steps concurring in this transfer. The procedure is based on the integration of an optical scanner, with a structured coded light approach, within the CT scan based preoperative planning process. The higher resolution and accuracy, compared to CT scanning systems, has allowed for the use of the optical scanner as a standard to evaluate the precision of CT data and fabrication processes of the guiding templates. A clinical case if finally presented and discussed. © 2010 Taylor & Francis Group.

Free electrons in the surface of metals can produce surface plasmons if they are excited by evanescent waves. The surface plasmons are electromagnetic waves that by decaying can generate photons. These photons produce propagating waves that feed energy to an oscillating cavity. From this effect a Fabry-Perot like interferometer is generated. In view of this basic knowledge a truly novel application on how these plasmons can be used experimentally is introduced in this article. Essentially, by using the transformation of evanescent waves into propagating waves via the plasmon generation it is possible to perform high accuracy contouring of any metal surface as well as the determination of its contact stresses. A laser beam illuminates a glass-air-metal interface and through a proper optical setup it will produce double evanescent illumination. This illumination generates interference fringes that contain surface depth information as well as in-plane strain information. In order to show the robustness of the proposed technique, three different applications are presented in the paper. First, the surface roughness mapping of a copper plate is determined and the obtained values are in statistical agreement with the data measured by a mechanical profilometer. Second, the surface profiles of nickel alloy surfaces used as calibrated standards for the determination of R a values are obtained. The measured Ra values statistically agree with the values of the different standards. Finally, the contact strains of a copper cylinder on glass are also measured. The contact strains follow the trend predicted by the K.L. Johnson's model of contact. Local regions (asperities) experiment large plastic deformations. © 2010 Blackwell Publishing Ltd.

Keywords: contact between asperities , contact mechanics , contact strains at the micron range , plasmons , surface contouring at the micron range

In this paper the set up and the carrying out of experimental ballistic tests on a tail rotor transmission shafts for helicopter, which are impacted by a 7.62 NATO projectile, are presented. After the tests, a 3D acquisition of the impacted area on each shaft has been performed in order to acquire exactly the shape of the damage. The acquisition has been carried out with a 3D range camera. The experimental activities have been compared with the results of a numerical simulation of the impact, which has been computed with an explicit finite element code. The direct comparison has been done by superimposing the two meshes (from FE analysis and from 3D acquisition). This method has proved to be effective for identifying analogies and differences and for giving the possibility to promote a "quantitative" discussion with the aim of improving the accuracy of the numerical models and simulation conditions. The adoption of the Reverse Engineering practice has proved to be a powerful method for integrating and comparing the simulation data with real data, and give suggestions to further analysis. Copyright © 2010 by ASME.

The paper presents a haptic device that allows a user to explore a virtual object along a continuous line. In particular the device is developed with the aim of supporting designers during the evaluation of the aesthetic quality of a virtual product. This is generally done by means of the global and local analysis of the shape in terms of curvature characteristics, presence of inflections points and discontinuities. In order to evaluate such features, designers are used to work on physical prototypes, relying on their skilled sense of touch. It is known that physical prototypes are expensive in terms of cost and time for their re-alization, and a modification on a physical prototype implies a reverse engineering process for appling such modifications on the virtual model. A linear haptic interface, that adapts its shape reproducing a generic curve on a surface, has been developed to replicate the behavior of a physical strip. This is the way to replace real prototypes with virtual ones without changing the evaluation paradigms that designers are used to. The physical limitations encountered in representing discontinuities in po.sition, tangency and curvature, not renderable by bending and de-forming a physical strip, have been overcome thanks to the application of some principles of the theory of haptic illusions by means of sonification of some curve characteristics, The paper describes the linear haptic interface developed and the solution based on haptic illusion that has been implemented to overcome the strip limitations. Copyright © 2009 by ASME.

This paper describes the development of an innovative harware and software tool useful to sketch planar shapes in Computer-aided Industrial Design and Computer Aided Design systems. The whole system is composed by a portable hand-held small touch-screen, a large fixed main screen and an optical tracking equipment. The touch-screen is added by a simple camera for Mixed Reality optional functionality and its 6 degrees of freedom movements are tracked through four groups of Light Emitting Diodes located on back of the monitor. A Nintendo® WiiMote with infrared camera is used to acquire Light Emitting Diodes relative positions for real-time tracking. A 6 degrees of freedom Inertial Measurement Unit has been added to improve the stability of the pose estimation: an Extended Kalman Filter provides the data fusion. Furthermore, a custom software has been implemented for optimal exploitation of a such configured hardware and facilitate input and 3D sketching. The physical tablet can be used in three different ways: as a 3D mouse which sets the point of view of the main screen according to its attitude, to set a plane in the main screen so that a 2D sketch can be referenced in the 3D space and as a support device to improve the manual draw of an object by overwriting the image contour. The results obtained confirms the usefulness of the virtual tablet in design, modelling, and reverse engineering of industrial products. © Organizing Committee of TMCE 2010 Symposium.

Keywords: Computer aided sketching , Pose estimation , Reverse engineering , Sensor fusion , Virtual tablet

A new protocol for making an immediate provisional eyeglasses-supported nasal prosthesis is presented that uses laser scanning, computer-aided design/computer-aided manufacturing procedures, and rapid prototyping techniques, reducing time and costs while increasing the quality of the final product. With this protocol, the eyeglasses were digitized, and the relative position of the nasal prosthesis was planned and evaluated in a virtual environment without any try-in appointment. This innovative method saves time, reduces costs, and restores the patient's aesthetic appearance after a disfiguration caused by ablation of the nasal pyramid better than conventional restoration methods. Moreover, the digital model of the designed nasal epithesis can be used to develop a definitive prosthesis anchored to osseointegrated craniofacial implants.

Keywords: CAD/CAM , Computer-aided design , Facial disfigurement , Facial rehabilitation , Immediate temporary prosthesis , Maxillofacial rehabilitation , Nasal prosthesis rapid prototyping , Reverse engineering , Silicone prosthesis , Virtual molding

Ear defects in patients affected by Treacher Collins syndrome necessitate the replacement of the existing anatomic residuals of the ears with custom-made prostheses. This paper describes a multidisciplinary protocol involving both medicine and computer-aided design/computer-aided manufacturing for manufacturing ear prostheses. Using innovative prototyping technologies together with conventional silicone processing procedures, a step-by-step procedure is presented. The complete workflow includes laser scanning of the defective regions of a patient's face, the use of 3D anatomic models from an ear digital library and rapid prototyping of both substructures for bar anchoring and moulds for silicone processing. © 2010 Taylor & Francis.

Keywords: Computer-aided design , Ear prostheses , Maxillofacial rehabilitation , Rapid prototyping , Reverse engineering , Treacher Collins syndrome