3D scanning

Recent innovations in laser scanner technology provide a potentially useful technique for accurate three-dimensional (3D) documentation of the face. Aim of this study was to evaluate and optimise facial surface acquisition parameters and measurements obtained by a Cyberware colour laser scanner and to compare those measures to the common anthropometric ones made by individual examiners. This preliminary study indicates that 3D scanning is a sufficiently precise and repeatable surface 3D acquisition method.

Keywords: Anthropometry , Laser scanning , Three-dimensional face

Styling design, as every creature of the modern world, is born from various and multiple parents: taste's, evolution, marketing requirements, technical design constraints, costs and qualitative standards of the project. Furthermore, the multiplying of material and technological resources, extends the creative potential of designers, yet requires the acquisition of new knowledge: this leads to the need, from the very preliminary stages, of concurrent engineering approaches to manage the product development process and the different product views depending on the specialists involved. Time Compression Techniques (Rapid Prototyping, Reverse Engineering, conceptual modelling, process simulation) are suitable tools in implementing Concurrent Engineering principles, especially if based on Internet applications. However, today, the research effort has to be oriented towards the definition of an effective and well-structured model of the design process to successfully integrate such technologies. In this context the goal of the present work is the study of a styling product development methodology to minimize the process iterations maintaining an aesthetically coherent product model representation. We focus on the product model definition (using functional-aesthetic features) and on the 3D digitizing phase, that is the most critical aspect for the shape preservation. A practical example, developed in the office furniture domain, is reported.

Focusing the attention on the first step of the reverse engineering cycle, the digitisation, it is possible to denote that the major part of the systems operate with punctual information measured with different technical approaches, light or laser beam or mechanical pointer. Anyway, even if the measuring technology employed could be different, these points, reached on a working plane, always come from a discretisation process. In fact working in a cartesian space and considering the orthogonal plane (XY) to the measuring direction (Z), the procedure divides the entire surface of the object in a grid deciding two step sizes and consequently the number of reachable points during the acquisition. So considering that the major part of the systems could employ one only step size value for the entire acquisition phase its choice became a big deal. From one side if the value is too small too many redundant information could occur, causing the unjustified growing up of the computational costs of the entire reverse engineering cycle. From the other side if the value is too large, there is the possibility to have few information about the real shape, causing in this way an inefficient reconstruction of the final mathematical model of the object. In order to solve this ambiguity the idea of the paper, working with a piezoelectric reverse engineering system, is to develop an operative methodology able to selectively subdivide the entire working plane in different zones in relation with the different step size that the specific object regions need. Working with an industrial application the procedure has been experimented in order to obtain an operative validation.

Keywords: Geometric morphology , Reverse engineering , Scanning strategy

Residual stresses exist in composite structures free from external forces or constrains and generally are very undesirable because can contribute to damage or failure. In this paper a moirè interferometric hole drilling procedure is applied for residual strain measurements in graphite/PEEK composite laminates. Experimental results obtained are reported and a numerical calibration procedure is proposed for residual stress evaluation from the experimental data.

Keywords: Composite Laminates , Hole Drilling , Moiré Interferometry , Residual Stress

The definition of a restoration project for a historical-artistic building is a high-skill operation. The preliminary survey and the following graphic representation of the artefacts, in particular, are two critical phases for good final results. The representation techniques called vectorial, including also the analytic photogrammetry, are nowadays surpassed by the wide introduction of digital techniques like the digital photogrammetry because of to excellent reproduction and low cost. Our paradigm for building restoration starts with a three-dimensional model of an edifice extracted from a set of 2-dimensional image using specific Image Assisted Modelling software. This digital model represents the artefacts both in its metric and morphologic complexity. Basically the result is a fully three-dimensional wireframe model with dimensional information while the appearance features are defined as a collection of bi-dimensional textures attached to the faces of the model. The most innovative aspect is the possibility to simulate the restoration process in two separate streams. On one side it is possible to adjust the original textures using common bi-dimensional digital painting software or specific tools that allow the user to interact with a three-dimensional image. On the other side, virtual environments permit to modify the model defining the dimension according to the desiderate restoration goal. We propose a new restoration project paradigm that integrates these innovative tools where artists and engineers work together and interactively. The restoration process is visualized in a specific immersive virtual environment developed by the authors in the VR3lab at Polytechnic of Bari-Italy. This is definitively an efficient way for designers, control agencies and building companies to immediately evaluate different solutions.

The definition of a restoration project for a historical-artistic building is a highskill operation. The preliminary survey and the following graphic representation of the artefacts, in particular, are two critical phases for good final results. The representation techniques called vectorial, including also the analytic photogrammetry, are nowadays surpassed by the wide introduction of digital techniques like the digital photogrammetry because of to exceIIent reproduction and low cost. Our paradigm for building restoration starts with a threedimensional model of an edifice extracted from a set of 2-dimensional image using specific Image Assisted Modelling software. This digital model represents the artefacts both in its metric and morphologic complexity. Basically the result is a fully 'three-dimensional wirefiame model with dimensional information while the appearance features are defined as a collection of bi-dimensional textures attached to the faces of the model. The most innovative aspect is the possibility to simulate the restoration process in two separate streams. On one side it is possible to adjust the original textures using common bi-dimensional digital painting software or specific tools that allow the user to interact with a three-dimensional image. On the other side, virtztal environments permit to modify the model defining the dimension according to the desiderate restoration goal. We propose a new restoration project paradigm that integrates these innovative tools where artists and engineers work together and interactively. The restoration process is visualized in a specific immersive virtual environment developed by the authors in the VR3lab at Polytechnic of Bari-Italy. This is definitively an efficient way for designers, control agencies and building companies to immediately evaluate different solutions.

A method for a conservative reconstruction of damaged or incomplete geometrical models into flawless and consistent Brep based solid models are introduced. Practical experiments employing the approach of space point tolerance driven face sewing within a prototype testbed implemented showed already promising results for a limited range of investigated models containing structural errors and data exchange inflicted errors.

Over the last decade the use of composite materials in automotive industries has increased considerably. Relatively low cost, good stiffness and strength-to-weight ratio, corrosion resistance and design flexibility are properties that make them attractive. Although steel is still widely used in automobile body panels, many companies are developing the technology needed to expand the use of these materials. Polyester sheet moulding compound is the material preferred. FIAT-IVECO is one company that some years ago decided to expand the use of SMC to its full line of trucks. The object of this paper is the static analysis of a SMC truck bumper manufactured by FIAT-IVECO. To analyse the structural behaviour two different experimental techniques were used: holographic interferometry and centesimal comparators. The experimental results were then compared with numerical data obtained from a finite element model of the bumper.

We present a highly efficient, automatic method for the generation of hierarchical surface triangulations. Given a set of scattered points in three-dimensional space, without known connectivity information, our method reconstructs a valid triangulated surface model in a two-step procedure. First, we apply clustering to the set of given points and identify point subsets in locally nearly planar regions. Second, we construct a surface triangulation from the output of the clustering step. The output of the clustering step is a set of 2-manifold tiles, which locally approximate the underlying, unknown surface. We construct the triangulation of the entire surface by triangulating the individual tiles and triangulating the gaps between the tiles. Since we apply point clustering in a hierarchical fashion we can generate model hierarchies by triangulating various levels resulting from the hierarchical clustering step.

Keywords: Data Reduction , Hierarchical Clustering , Multiresolution Representation , Reverse Engineering , Surface Reconstruction , Triangulation

The realization of sculptured shapes using CAD systems is still today a very complex and time consuming operation. For these reasons, design by physical modeling is still in use and remains in force in many industries (automotive, ski boots, sport articles). For the manufacturing of complex free-form surfaces, in situations in which it is more desirable to proceed from a physical model to a numerical definition rather than use mathematics to derive the physical part, copy milling techniques are widely used. This paper gives a brief overview about copy milling techniques for 3 axis copy milling machines, and proposes a feature based method to support an automatic tool path generation for the super-finishing phase. The proposed method is divided in two parts: super-finishing features recognition and tool path generation. Using copy milling techniques, the model of the object to be milled is obtained by digitizing. Therefore a global mathematical surface description of the model does not exist. In such a situation a model interpretation phase is required to recognize the super-finishing features and thus proceed to the tool path generation. A two step algorithm for super-finishing feature recognition on a digitized model is proposed: features are recognized on the basis of the digitized point density and the normal vectors of the triangles generated by the surface reconstruction (based on Delaunay triangulation method). The tool path is then generated using a method based on the calculation of the Voronoi diagram on the area identified as super-finishing feature. The super-finishing feature recognition and tool path generation modules have been integrated as part of a more general CAM system for copy milling called HICAM. The architecture of such a system will be presented together with examples of solutions obtained by means of the use of the implemented prototype modules.