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Additive Manufacturing (AM) is the fabrication of real three-dimensional objects from plastics and metals by adding material, layer by layer. One of the most common AM processes is the Material Extrusion (ME) based on different approaches: plunger, filament and screw. Material Extrusion technologies of metal-polymer composites is expanding and it mainly uses the filament or plunger-based approaches. The feedstock used is a mixture of metal powder (from 55 vol% to about 80 vol%) dispersed in a thermoplastic matrix, as the Metal Injection Molding (MIM) materials. The process consists of three steps: shaping, debinding and sintering. The first step provides the extrusion of filament to realize a primary piece called “green part”; subsequent steps, debinding and sintering, allow to obtain a full metal part by dissolving the polymeric binder. The latter can be carried out using solvents, heat and the combination of them. The interest toward this technology is driven by the possibility to replace other Metal AM technologies, such as Selective Laser Melting or Direct Energy Deposition, in sectors like rapid-tooling or mass production, with several benefits: simplicity, safety to use and saving material and energy. The aim of this keynote is to provide a general overview of the main metal ME technologies considering the more technical aspects such as process methodologies, 3D printing strategy, process parameters, materials and possible applications for the manufacturing of samples on a 3D consumer printer.

Purpose This paper aims to provide a comparison between the mechanical performance and microstructural aspects of stainless steel 17-4 PH processed using, respectively, two technologies: atomic diffusion additive manufacturing (ADAM) and metal fused filament fabrication (MFFF). Design/methodology/approach Different tensile specimens have been printed using an industrial system and a consumer three-dimensional (3D) printer, varying two main 3D printing parameters. Mechanical and microstructural tests are executed to make a comparison between these two technologies and two different feedstock material, to identify the main differences. Findings These 3D printing processes make parts with different surface quality, mechanical and microstructural properties. The parts, printed by the industrial system (ADAM), showed lower values of roughness, respect those produced using the 3D consumer printer (MFFF). The different sintering process parameters and the two debinding methods (catalytic or solvent based) affect the parts properties such as porosity, microstructure, grain size and amount of δ-ferrite. These proprieties are responsible for dissimilar tensile strength and hardness values. With the aim to compare the performances among traditional metal additive technology, MFFF and ADAM, a basic analysis of times and costs has been done. Originality/value The application of two metal extrusion techniques could be an alternative to other metal additive manufacturing technologies based on laser or electron beam. The low cost and printing simplicity are the main drivers of the replacements of these technologies in not extreme application fields.

The most relevant criticalities of parts produced by material extrusion additive manufacturing technologies are lower mechanical properties than standard material performances, the presence of pores caused by the manufacturing method, and issues related to the interface between layers and rods. In this context, heat treatments can be considered an effective solution for tailoring the material behavior to different application fields, especially when using precipitation hardening stainless steels. In this work, aging treatments were conducted on parts realized using three different extrusion-based processes: Atomic Diffusion Additive Manufacturing, bound metal deposition, and fused filament fabrication. Two conditions of direct aging (H900 and H1150) were considered with the aim of comparing the response of properties in the opposite conditions of peak-aged and overaged. The hardness tests revealed that H900 aging significantly influenced hardness (max increase of 52%), and porosity (− 34.3% with respect to the as-sintered condition). On the other hand, the H1150 aging decreased the hardness (− 18% max) and porosity (− 32.2% max). Substantial differences among the microstructures due to grain size and δ-ferrite were illustrated. A statistical test was included to better highlight the influence of the heat treatment on the investigated properties.

Fused filament fabrication (FFF) is one of the most extensively used 3D printing process for its several advantages and the possibility to obtain complex geometries. Different materials can be processed and polylactic acid (PLA), a thermoplastic biodegradable cost-effective material, is widely used for consumer FFF. Typically, PLA printed parts have high surface roughness, due to the staircase effect, the slice-to-slice construction texture and the filament deposition. In this work, authors propose a quantitative analysis of the effects of a chemical treatment based on ethyl acetate vapors, to improve the surface finish of PLA printed parts. The solvent was selected for its low toxicity, easy availability, and low cost. To validate the treatment, a 23 full factorial plan was designed and a roughness analysis before and after the chemical treatment was performed to highlight the influence of each parameter involved.

On-machine verification is increasingly demanded in modern industry, due to the simultaneous necessity of high quality product and reduced time for production and verification. At the time being, contact probe systems are considered the most reliable ones, but they have many drawbacks, especially when they are used to measure free form surfaces in scanning mode. Optical techniques have the great advantage to acquire large amounts of points in very short time, and they can be used for several applications: from dimensional verification of manufactured products to the inspection of very expensive damaged parts for repairing processes in the aerospace industry. Although, they are affected by many kinds of error and they are very sensitive to the reflectivity or translucency of the sample. In this paper, a comparison between optical techniques potentially suitable to be implemented in on-machine dimensional verification is reported. The comparison involved two laser scanners, one structured light scanner and a photogrammetry-based scanner. The comparison was conducted through a free form reference object realized by the NPL Institute, with 150 × 150 × 40 mm3 of total volume.

The objective of the present work is to study materials properties and performance of the footwear thread to develop and implement an analytical-numerical model capable of simulating their performance. The numerical results simulation was carried out, analyzing the sliding mechanisms of shoe-floor and evaluating the contact pressure and vertical stress. An experimental procedure, supported by a numerical model, was implemented for computing the evolution of the tangential force over several load increments.

Micro-applications, especially in biomedical and optical sectors, require the fabrication of thin polymeric parts which can be commonly realized by micro-injection molding process. However, this process is characterized by a relevant constraint regarding the tooling. Indeed, the design and manufacturing of molds could be a very time-consuming step and so, a significant limitation for the rapid development of new products. Moreover, if the design displays challenging microfeatures, their realization could involve the use of more than one mold for the fabrication of a single thin part. Therefore, proper integration of different manufacturing microtechnologies may represent an advantageous method to realize such polymeric thin microfeatures. In this work, a micromanufacturing process chain including stereolithography, micromilling, and micro-injection molding is reported. The mold for the micro-injection molding process was fabricated by means of stereolithography and micromilling, which allowed us to produce low-cost reconfigurable modular mold, composed of insert support and a removable insert. The assessment of the proposed process chain was carried out by evaluating the dimensions and the surface finishing and texturing of the milled mold cavities and molded components. Finally, a brief economic analysis compares three process chains for fabricating the micromold showing that the proposed one reduces the manufacturing cost by almost 61% with the same production time.

The identification of bodies through the examination of skeletal remains holds a prominent place in the field of forensic investigations. Technological advancements in 3D facial acquisition techniques have led to the proposal of a new body identification technique that involves a combination of craniofacial superimposition and photogrammetry. The aim of this study was to test the method by superimposing various computerized 3D images of skulls onto various photographs of missing people taken while they were still alive in cases when there was a suspicion that the skulls in question belonged to them. The technique is divided into four phases: preparatory phase, 3d acquisition phase, superimposition phase, and metric image analysis 3d. The actual superimposition of the images was carried out in the fourth step. and was done so by comparing the skull images with the selected photos. Using a specific software, the two images (i.e. the 3D avatar and the photo of the missing person) were superimposed. Cross-comparisons of 5 skulls discovered in a mass grave, and of 2 skulls retrieved in the crawlspace of a house were performed. The morphologyc phase reveals a full overlap between skulls and photos of disappeared persons. Metric phase reveals that correlation coefficients of this values, higher than 0.998-0,997 allow to confirm identification hypothesis.

In this work, the interaction between 3D optical scanners and objects realized with different materials and colours was investigated. The interaction is mainly related to the translucency of some materials, such as polymers, which is a category of materials in ever-increasing demand by industry. At the same time, the increase of the geometrical complexity of manufactured parts raises the need for the use of 3D optical scanners thanks to their rapidity and effectiveness. Translucency causes a subsurface scattering effect that has been modelled for certain cases and affects the dimensional accuracy of measurements, as well as the quality of reconstruction. Recently, an investigation considered its effect in dimensional verification using a structured light scanner with fringe projection. In this work, the investigation is extended to other 3D optical scanners exploiting different measuring principles: laser, structured light based on phase shifting and gray code, and photogrammetry. This was done in order to study how the subsurface scattering effect can vary with the materials, colours, and also the measuring principle used. To this end, five miniature step gauges made of different polymers and colours were used, and the effects due to their different optical properties investigated. The analysis focused on dimensional verification of bidirectional lengths, first calibrated with a traceable coordinate measuring machine. The quality of the reconstruction was also evaluated through the flatness values. According to the results obtained, translucency of materials has a dual and significant effect: a measurement bias and an increase of the uncertainty due to the different quality of reconstruction retrieved. Thus, it has to be considered properly for each case.

Performance verification of 3D optical based scanners is currently a topic of great discussion, since they are ever more used in the industrial manufacturing field for the dimensional verification of components. Among their advantages, there is the capability of acquire large amounts of points in a very short time, regardless the geometrical complexity of the object under measurement. Although, traceability is still critical and the uncertainty assessment conducted using artefacts calibrated through the more traceable Coordinate Measuring Machines (CMMs), is still the most implemented method. In this paper, some of the most interesting geometries used for the performance verification of optical based scanners have been reported, considering the most widespread measuring tasks which require the use of these instruments, both prismatic geometries and freeform shapes.

The aim of this paper is to develop a database to determine a new biomorphometric standard of attractiveness. Sampling was carried out using noninvasive three-dimensional relief methods to measure the soft tissues of the face. These anthropometric measurements were analyzed to verify the existence of any canons with respect to shape, size, and measurement proportions which proved to be significant with regard to the aesthetics of the face. Finally, the anthropometric parameters obtained were compared with findings described in the international literature. The study sample was made up competitors in the Miss Italy 2010 and 2009 beauty contest. The three-dimensional (3D) scanning of soft tissue surfaces allowed 3D digital models of the faces and the spatial 3D coordinates of 25 anthropometric landmarks to be obtained and used to calculate linear and angular measurements. A paired Student t test for the analysis of the means allowed 3 key questions in the study of biomorphometric parameters of the face to be addressed through comparison with the data available in the literature. The question of statistical evidence for the samples analyzed being members of the populations samples reported in literature was also addressed. The critical analysis of the data helped to identify the anthropometric measurements of the upper, middle, and lower thirds of the face, variations in which have a major influence on the attractiveness of the face. These changes involve facial width, height, and depth. Changes in measurements of length, angles, and proportions found in the sample considered were also analyzed.

Among the enabling technologies of the fourth industrial revolution, additive manufacturing (AM) is considered as a key factor for the success of the new production paradigm.

The use of additive manufacturing (AM) enables companies to directly produce complex end-use parts. Fused deposition modelling (FDM) is an AM technology based on an extrusion process of fabricating parts. This layer-by-layer method results in a poor surface finish, and as a result, manual finishing is often required, which consequentially reduces the definition of the geometrical features. This research proposes a novel way of achieving high surface finishing by using additive and finishing processes, followed by a physical vapor deposition (PVD) coating. Two test pieces were produced, the first one was subjected to computer numerical controlled (CNC) mechanical grinding with appropriate grades of grindstones; the second one was subjected to microsandblasting to remove excess material and the stair-stepping effect. Both test pieces were then subjected to a PVD coating process to provide a metal thin film. To benchmark the test pieces, the authors used a coordinate measure machine for dimensions and a roughness meter to verify the effectiveness of this postprocessing approach.

Laser milling is a micro-machining process that uses a laser beam as a tool to remove material through the layer-by-layer ablation mechanism. Generally in laser ablation, the quality of parts is reduced by melt accretions and thermal damage, therefore, this problem is reduced with shorter pulse duration, although ablation efficiency decreases as well. Thus, laser ablation in the nanosecond range still offers a good compromise between process quality and efficiency. Therefore, laser milling with nanosecond laser ablation requires an accurate study to reduce geometric defects induced by the process. The aim of this paper was to study the shape geometry and roughness of Ti6Al4V parts fabricated by laser milling using a nanosecond Nd:YAG laser source. The impact of the laser processing parameters on machining outcomes was studied in order to determine the optimized processing conditions for reducing geometrical defects and improving surface quality. In particular, the influence of average laser power, frequency, and scanning speed was investigated. The geometry of micro-parts was revealed using a 3D digitizing system, the Optimet Mini Conoscan 4000, which combines a non-contact, single-point measuring sensor based on conoscopic holography technology. The use of this measurement technology yielded complete information of the shape geometry and dimensions of the built parts. In addition, the roughness of manufactured surfaces was assessed to complete the analysis.

A powerful and cost effective photogrammetric scanning methodology, suitable for reconstructing a full 3D digital model of parts with complex surfaces and sub millimeter-sized features, is described. The scanner employed for this purpose is composed of a computerized system that drives and control the movements of a rotary table, and a digital SLR camera for the images acquisition. The object is positioned on the rotary table that rotates at fixed angles, while the digital camera, mounted on the stator through a rigid frame, captures the images. The scanning process has been optimized with the aim to minimize the number of shots and thus, the time needed to obtain a complete 3D digital model, which is not dependent from the dimensions of the object. With the aim to demonstrate the effectiveness of the proposed scanning methodology, four benchmarks have been realized to provide complex examples. The 3D digital models were compared with those obtained with an Optimet™ Conoscan 4000 which uses a conoscopic holographic sensor.

Additive manufacturing techniques (AM) have enhanced product quality and exponentially increase their application both from the industrial point of view and from the consumer point of view. A decisive development in the “consumer” sector has been observed over the last 5 years thanks to open source projects (Fab@home, RepRap), which enabled the production of low cost machines with the use of cheap electronic and mechanical components and open source software. Among the possible future developments of low cost AM technologies, there is an improvement of finished product capabilities and appearance to obtain coloured components, made directly during printing phase. This paper tries to respond to this need by assessing the feasibility of realizing a low-cost AM system that integrates automatic colouring in a consumer 3D printer. The proposed system is a hybrid between a fused filament fabrication 3D printer, derived from an open-source project, and a 2D commercial inkjet printer; the two systems share the mechanics, but keep the movement control and the three-dimensional and two-dimensional printing process separate. The study continues with the theorization, modeling and creation of the interfaces required for conversion of control signals and a first experimentation of the same control. The two systems, using a different mechanics, use different motor control systems.

Digital close range photogrammetry as 3D optical measurement system has achieving a great success due to the several advantages which meet the ever more complex market requests for free-form components. The capability of the sensor to be moved automatically around the scene, varying the distance from the object and the magnification ratio in a single scanning session allows to reconstruct the 3D model of the sample even in presence of undercuts or complex geometries. The latter are typical of most industrial sectors, e.g. automotive and aerospace, biomedical sector, nature science, e.g. entomology, as well as cultural heritage and archeologic field. Photogrammetry based scanners can be designed in a simple, robust and very cheap way, obtaining results similar to more complex and expensive scanners based on other technologies. In the last years, several steps have been carried out to consolidate and metrologically characterize this methodology with the final aim of making it comparable with other ones already accepted. Although, there are some relevant questions which still represent criticalities for this technique.

Performance verification is a fundamental issue to assure the traceability of a measurement instrument. This issue is very important for non-contact 3D scanning systems, also for the limited number of existing standards. There are many factors affecting the process in a photogrammetric scanning system, and they have to be considered during a performance verification. In this context, it is crucial to completely define the camera model and its spatial locations and orientations during the scan, estimating the intrinsic and extrinsic parameters. There are two main proposals in this paper. Firstly, authors investigated on how the reliability of the adjustment procedure could be improved, adopting a more complex geometry of the reference object, using a three-dimensional one instead of a bi-dimensional pattern of targets. Secondly, an approach to a calibration procedure for photogrammetric scanning system has been drawn up and applied, using the same artifact used for the adjustment. The ISO 15530-3 2011 standard was adopted for the uncertainty assessment of the results.

In medical field, a growing interest is now focused on non-invasive diagnostic 3D image-based methods. The aim of this work is to develop a powerful, easy and low cost scan-system, based on close-range photogrammetry, capable to perform a complete acquisition of a non-static subject over 360°. The proposed scanning system has some advantages compared to the scanning systems traditionally used in medical field for human application, it is a non-invasive systems alternative respect to laser and structured light scanners, and demonstrate to be accurate and reliable for medical diagnostic application on human body. Video abstract Download video (2MB) Help with mp4 files

Objectives The article describes a new methodology to scan and integrate facial soft tissue surface with dental hard tissue models in a three-dimensional (3D) virtual environment, for a novel diagnostic approach.The facial and the dental scans can be acquired using any optical scanning systems: the models are then aligned and integrated to obtain a full virtual navigable representation of the head of the patient. Methods In this article, we report in detail and further implemented a method for integrating 3D digital cast models into a 3D facial image, to visualize the anatomic position of the dentition. This system uses several 3D technologies to scan and digitize, integrating them with traditional dentistry records. The acquisitions were mainly performed using photogrammetric scanners, suitable for clinics or hospitals, able to obtain high mesh resolution and optimal surface texture for the photorealistic rendering of the face. To increase the quality and the resolution of the photogrammetric scanning of the dental elements, the authors propose a new technique to enhance the texture of the dental surface. Results Three examples of the application of the proposed procedure are reported in this article, using first laser scanning and photogrammetry and then only photogrammetry. Using cheek retractors, it is possible to scan directly a great number of dental elements. The final results are good navigable 3D models that integrate facial soft tissue and dental hard tissues. The method is characterized by the complete absence of ionizing radiation, portability and simplicity, fast acquisition, easy alignment of the 3D models, and wide angle of view of the scanner. Conclusions This method is completely noninvasive and can be repeated any time the physician needs new clinical records. The 3D virtual model is a precise representation both of the soft and the hard tissue scanned, and it is possible to make any dimensional measure directly in the virtual space, for a full integrated 3D anthropometry and cephalometry. Moreover, the authors propose a method completely based on close-range photogrammetric scanning, able to detect facial and dental surfaces, and reducing the time, the complexity, and the cost of the scanning operations and the numerical elaboration.

The present paper shows how a non-invasive and low-cost photogrammetric stereo device allows the assessment of morphometric variations of the nose following rhinoplasty. Six female patients, aged between 24 and 37 years, underwent 3D stereo-photogrammetric scanning. Three-dimensional computerised models were generated, extracting also information related to the coordinates of facial landmarks, distances between landmarks, angles, in pre- and postoperative situation. Two kinds of analysis were carried out: (i) statistical correlation between size variations and (ii) morphometric analysis, including General Procrustes Analysis (GPA), Principal Components Analysis (PCA) and Warping. The study shows the usefulness of the stereo-photogrammetric facial digitisation for morphometric analysis of the human face. Three-dimensional computerised models are also an important tool for the assessment of the surgeon's performance in the event of dispute between doctor and patient. Moreover, confirmation of the PCA as an analytical tool for the identification of components characterising the morphometric structure of the nose is highlighted.

In recent years, reverse engineering has achieved a relevant role in the cultural heritage field. The availability of 3D digital models of artefacts opens the door to a new era of cultural heritage: virtual museum creation, artefact cataloguing, conservation, planning and simulation of restoration, monitoring of artefacts subjected to environmental degradation, virtual reconstruction of damaged or missing parts, reproduction of replicas, etc. In this paper, two different non-contact reverse engineering scanning systems were utilized for 3D data acquisition of a cultural heritage artefact. The digital data acquisition and processing procedures of the scanned geometry have been illustrated and compared to evaluate the performance of both systems in terms of data acquisition time, processing time, reconstruction precision and final model quality. Finally, additive manufacturing technologies were applied to reconstruct a down scaled copy of the artefact.

In the 3D reconstruction field, photogrammetry is a powerful and robust measurement technology for lots of dimensional ranges, from macro and aerial photogrammetry to close-range and micro-photogrammetry, emerging recently with good results also in the survey of small object with sub-millimeter features. A fundamental issue is still the calibration, for the estimation of both internal and external parameters, mostly in the case of very small dimensional ranges. In previous works, some aspects of the photogrammetric process have been taken into account and analyzed by 3D comparisons with a reference model, while the present work is firstly focused on the outputs of the camera’s alignment phase, in which the computation of internal and external parameters is carried out. By repetition of the process in the same conditions, it has been noticed that alignment results, in terms of camera coordinates and internal calibration parameters, are affected by a sort of variability. Thus, the aim of this work is to estimate the uncertainty component over the 3D reconstruction accuracy attributable to the repeatability of the photogrammetric software. For this purpose, several factors, linked to the shooting geometry and to the alignment process, have been considered.

A precise 3D body scanning system, designed for applications in the medical and biomedical field, is described. The system consists of 12 digital cameras, mounted on a rigid frame which maintains the B/H ratio constant. An LED lighting system, integrated with the rigid frame, ensures a homogenous illumination of the subject. A modified firmware installed on each device enables the synchronised remote release driven by remote control. Data transmission to the computer is carried out wirelessly. A process for the estimation of the extrinsic camera parameters has been implemented with the aim of obtaining a 3D model in 1:1 scale. Analyses have been performed in order to state the repeatability of the process used to estimate the external camera calibration parameters as well as the precision of the 3D digital models of a body obtained for a mannequin and for a live human subject.

This paper presents a scanning methodology based on close-range stereo photogrammetry, suitable for precise and accurate 3D digitization of objects of few millimeters in length and features in sub-millimeter scale. The authors propose an efficient alternative to other scanning methodologies currently used for such applications, as the conoscopic holography, with the aim to reduce the scanning time and obtain a result which also contains information related to the real texture of the object. An experimental plan has been designed and implemented in order to investigate the accuracy and precision of the 3D scans.

This paper is focused on the development, implementation and testing of a semi-automated low cost motorized active 3D slit laser scanning system. The scanner is based on the software platform of the DAVID LaserScanner Vision Systems GmbH's. The authors implemented motorized movements on a CNC milling machine, controlling the systems by the Mach3 CNC software. The authors have combined and personalized different software, mainly low cost or open-source: a specific program was written and compiled for processing; establishing communication between the scanning software (David-Laserscan) and control software/hardware of the milling machine (Mach3) throw two double virtual communication ports. Video abstract Download : Download video (2MB)

In the last years close-range photogrammetric scanning systems, are acquiring a larger market share. This is due to low-cost hardware, components and to new user-friendly software. The ultimate, photogrammetric 3D scanning systems are very accurate and precise because, of the high-resolution cameras (over 10 Mpixels) they are equipped of and, the more precise algorithms of their software. The calibration phase is the primary step for the development of a, precise photogrammetric scanner. Through a good calibration it is indeed, possible to eliminate optical aberration issues and to obtain precise and, accurate three-dimensional measurements. In this study a powerful, calibration method, named full-field calibration, was implemented to, obtain high-precision values, using an original three-dimensional, calibrator, developed so as to increase the performance of this type of, calibration. Prior to using any measurement or 3D scanning system, precision and, accuracy have to be assessed. In this study a robust validation method, for photogrammetric scanning systems has been proposed. The validation, procedure consisted in: (1) operator error analysis, (2) reproducibility, error-analysis, (3) control-system error analysis, (4) scanning system, error analysis., The measurements taken using the “control system” (certified equipment in, terms of precision and accuracy) were considered as “gold standard”. The, photogrammetric measurements, subsequently obtained by the scanning, system, were aligned to the “gold standard” using Procrustes, registration. The system error was expressed as the displacement between, these two sets of measurements.

Background The objective of this study is to define an acquisition protocol that is clear, precise, repeatable, simple, fast and that is useful for analysis of the anthropometric characteristics of the soft tissue of the face. Methods The analysis was carried out according to a new clinical-instrumental protocol that comprises four distinct phases: (1) setup of portable equipment in the space in which field analysis will be performed, (2) preparation of the subject and spatial positioning, (3) scanning of the subject with different facial expressions, and (4) treatment and processing of data. The protocol was tested on a sample comprising 66 female subjects (64 Caucasian, 1 Ethiopian, and 1 Brazilian) who were the finalists of an Italian national beauty contest in 2010. To illustrate the potential of the method, we report here the measurements and full analysis that were carried out on the facial model of one of the subjects who was scanned. Results This new protocol for the acquisition of faces is shown to be fast (phase 1, about 1 h; phase 2, about 1.5 min; phase 3, about 1.5 min; phase 4, about 15 min), simple (phases 1 to 3 requiring a short operator training period; only phase 4 requires expert operators), repeatable (with direct palpation of anatomical landmarks and marking of their positions on the face, the problem of identification of these same landmarks on the digital model is solved), reliable and precise (average precision of measurements, 0.5 to 0.6 mm over the entire surface of the face). Conclusions This standardization allows the mapping of the subjects to be carried out following the same conditions in a reliable and fast process for all of the subjects scanned.

In the literature, several papers report studies on mathematical models used to describe facial features and to predict female facial beauty based on 3D human face data. Many authors have proposed the principal component analysis (PCA) method that permits modeling of the entire human face using a limited number of parameters. In some cases, these models have been correlated with beauty classifications, obtaining good attractiveness predictability using wrapped 2D or 3D models. To verify these results, in this paper, the authors conducted a three-dimensional digitization study of 66 very attractive female subjects using a computerized noninvasive tool known as 3D digital photogrammetry. The sample consisted of the 64 contestants of the final phase of the Miss Italy 2010 beauty contest, plus the two highest ranked contestants in the 2009 competition. PCA was conducted on this real faces sample to verify if there is a correlation between ranking and the principal components of the face models. There was no correlation and therefore, this hypothesis is not confirmed for our sample. Considering that the results of the contest are not only solely a function of facial attractiveness, but undoubtedly are significantly impacted by it, the authors based on their experience and real faces conclude that PCA analysis is not a valid prediction tool for attractiveness. The database of the features belonging to the sample analyzed are downloadable online and further contributions are welcome.

The diffusion of Digital Additive Manufacturing technologies is leading to new needs by industrial research and development sectors. For instance mating additive manufactured parts is not a simple task, due to low accuracy typical of several additive technologies, such as Fused Deposition Modeling. Several papers report studies on how Fused Deposition Modeling accuracy is affected by process parameters. One of the most important aspects is the role of shrinkage during the transition from a semi-liquid state to solid and cooling at solid state. To avoid this drawback a Shrinkage Compensation Factor (SCF), an operator-controlled variable that affects the overall accuracy of the product, is embedded in the control software of FDM machines. In this paper the authors report a study on the influence of working parameters on FDM dimensional accuracy, focusing their attention on the validity of the Shrinkage Compensation Factor, especially when applied to cave parts and proposing a method to improve the accuracy of parts.

The surface finish of Fused Deposition Modeled (FDM) parts can be improved by performing chemical dipping based on immersion in a dimethylketone–water solution. The authors aim to gain a more in-depth knowledge of this process, by analyzing and comparing the mechanical properties and the surface quality of treated and untreated FDM parts. Tensile and bending mechanical properties have been investigated by designing and performing four Central Composite Designs (CCDs) of experiments, totalizing about two-hundred tests. The results have been verified by testing an FDM marine turbine blade employed to generate energy.

This experimental research work was aimed to develop a 3D photographic method to be used in orthodontics diagnoses, having particular characteristics: precision of measurement, robustness of the method, speed of relief, ease of scanning, portability and low weight of the final system, low cost, non-invasive equipment. Various solutions of the experimental set-up have been implemented for the non-contact detection and measurement of the face soft tissues. This paper highlights the advantages and disadvantages of different set-up designed during the trials, comparing them to identify the best solution that meets the characteristics listed above. Mainly two different types of photogrammetric approach were designed: the first one uses three cameras and projected grids in a dark environment; it is based on point triangulation. The second one uses 4 or 5 cameras and operates with applied on the background and on the face in ambient light; it is based also on the DSM methodology, and obtains more dense point clouds. The systems were tested scanning the head of a mannequin and real human faces. Within each type, several variants were tested to evaluate the differences, changing the conditions of projection, lighting, shooting. Moreover, the results for each approach were compared with those obtained by laser scanning (both on real face and on a mannequin), for which are already known the performances. The system that best meets the requirements for diagnostic use in orthodontics proved to be the second one, in which coded targets applied directly on the face were used, shooting in ambient light, adopting digital photo sensors having 10 megapixels, and using 4-5 shots synchronized. The commercial software PhotoModeler was used for the CAD reconstruction of the face, and Geomagic for measures and comparisons.

Most rapid prototyping (RP) additive techniques are expensive and suffer from a lack of efficiency when massive products are to be manufactured. The authors propose to reduce the density of rapid prototyped parts, finding alternative building styles. Topologically optimized parts have been created with internal geometry, using a narrow-waisted structure that avoids the need for building supports. In order to characterise and study the behaviour of the obtained low density parts, an experimental plan has been designed and executed. The approach has been tested using a fused deposition modelling (FDM) machine, but it is of a general nature and can be applied to other layered manufacturing (LM) technologies that use supports, dealing with slow building of massive parts.

Photogrammetry is a passive 3D digitization technique, mainly oriented to large sized objects, since its origins are in architectural and civil engineering. With the continuos development of digital imaging hardware and software, photogrammetric applications are involving smaller and smaller fields of view, with some critical aspects such as the depth of field getting narrower. In this conditions the lack of focus becomes important and affects heavily the possibility of accurately calibrate cameras. Bi-dimensional calibration patterns are affected by this problem when the camera principal axis has an angle with the pattern plane higher than a critical value. Moreover, the accuracy of the pattern, in terms of both shape and 3D positions of the targets, becomes critical decreasing the size of the pattern. In this paper the authors address these problems through a comparison of several calibration patterns included into the open source computer vision software library called OpenCV. 3D digitization of a small object is presented to test the best resulting calibration, using a consumer reflex camera equipped with macro lens and extension tube.

The authors developed a method and a specific photogrammetric 3D scanning equipment for acquiring, analyze and measure the characteristics of the facial soft tissues. The system can be used in anthropometry and for the diagnosis and monitoring of therapy for maxillofacial surgery and for orthodontics. The experiments were conducted on a sample composed of 66 female subjects (64 Caucasian, 1 Ethiopian, 1 Brazilian) finalists at an Italian national Beauty competition done in the year 2010. The subjects were submitted on the same day to the acquisition of faces, according to a new clinical protocol. Morphometric characteristics of the faces were investigated extracting linear measurements, angles, distances and relationships between angles, calculated thanks to the measurement of facial soft tissue landmarks, through which it is possible to reconstruct simplified volumetric models of faces for each candidate. These data were compared with the historical ones available in literature. Performing a statistical analysis on the average values of the samples it was possible to obtain a very interesting indication of which facial parameters are related to facial attractiveness that diversify more different samples of attractive girls. An objective was to identify the aesthetic canons in the form and dimensions of the face of the 66 subjects. The protocol standardization has made it possible to carry out the relief of the sample recreating for all subjects scanned the same conditions in a reliable and fast way. The developed scanner confirmed to be precise for measurements, robust, fast in the relief, easy in the scanning operations, and furthermore it is portable, it has a low weight, low cost, being also completely non-invasive.

In this paper an analytical dimensional performance evaluation and comparison is illustrated, done on benchmarks manufactured using two different 3D FDM printers: an industrial system, and an open-source one (a modified Fab@Home Model 1 printer). Using a factorial analysis design of experiment (DOE), optimum process parameters were found to improve dimensional accuracy on rectangular test specimens, minimizing changes in length, width and height. Fab@Home printer demonstrated to be a good platform, simple, flexible and inexpensive. Video abstract To view the video inline, enable JavaScript on your browser. However, you can download and view the video by clicking on the icon below Help with MP4 files Options Download video (2234 K)