3D scanning

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

Keywords: Cad , Cast modeling , Orthosis modelling , Personalized medicine , Reverse engineering

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

Keywords: Biomedical engineering , Cranioplasty , Reverse engineering , Skull reconstruction

This paper analyse and compare the methods to detect and represent the human symmetry line. In the last years, the development of 3D scanners has allowed to replace the traditional techniques (marking based methods) with modern methodologies that, starting from a 3D valid discrete geometric model of the back, perform the posture and vertebral column detection based on a complex processing of the acquired data. The purpose of the paper is a critical discussion of the state of the art in order to highlight real potentialities and limitations of the most important methodologies proposed for human symmetry line detection.

Keywords: Anatomical landmarks , Back shape analysis , Posture prediction , Rasterstereography , Symmetry line

Low-cost 3D sensors are nowadays widely diffused and many different solutions are available on the market. Some of these devices were developed for entertaining purposes, but are used also for acquisition and processing of different 3D data with the aim of documentation, research and study. Given the fact that these sensors were not developed for this purpose, it is necessary to evaluate their use in the capturing process. This paper shows a preliminary research comparing the Kinect 1 and 2 by Microsoft, the Structure Sensor by Occipital and the O&P Scan by Rodin4D in a medical scenario (i.e. human body scans). In particular, these sensors were compared to Minolta Vivid 9i, chosen as reference because of its higher accuracy. Different test objects were analysed: a calibrated flat plane, for the evaluation of the systematic distance error for each device, and three different parts of a mannequin, used as samples of human body parts. The results showed that the use of a certified flat plane is a good starting point in characterizing the sensors, but a complete analysis with objects similar to the ones of the real context of application is required. For example, the Kinect 2 presented the best results among the low-cost sensors on the flat plane, while the Structure Sensor was more reliable on the mannequin parts.

Keywords: 3D metrology , Biomedical applications , Low-cost 3D sensors , Resolution , Systematic error

In the world of powerboats competition, the high-performance sandwich-structured composites have completely replaced traditional materials. During the competition, the structure of this kind of ships is subjected to repeated impacts. It is then fundamental to understand the damage evolution in order to select the most appropriate materials and increase safety issues. The present study is aimed at analysing the behaviour of sandwich-structured composites undergoing repeated low-energy impacts. Three different materials have been analysed. Two are sandwich-structured composites used for the cockpit of offshore powerboats and differing only by the core cell thickness. The third material is composed only by the skin of the same sandwich structures, without the core. Impacts were made at three different energy levels: 15, 17.5 and 20 J. In addition to the parameters typically used for the assessment of the impact damage, a new damage assessment has been carried out by means of three-dimensional optical measurements of the imprinted volumes resulting from the impact events. This approach has allowed the definition of a correlation between the imprinted volumes and the number of impacts, until the complete perforation, for each single specimen. Finally, thanks to usual indexes and the imprinted volumes, some considerations are developed about the influence of the core cell thickness in powerboats design.

Keywords: damage accumulation , lightweight composites , offshore powerboats , optical measurements , Repeated impacts , safety design

The use of composite structures is increasing constantly in the last years, pushed by advantages of reduced weight and high strength. Moreover, the recent scenario points out a great attention on thermoplastic matrix composites due to their intrinsic recyclability as well for their possibility to re-use and re-manufacturing. However, the adoption of these materials can be further appreciated considering the secondary material workability as far as by demonstrating the possibility to re-manufacture the thermoplastic composite. The proposed work presents an experimental analysis carried out to investigate the downstream workability of a thermoplastic composite by one of the most versatile and flexible process. Glass fiber reinforced Polyamide 6 is the investigated material and the Single Point Incremental Forming is the implemented manufacturing approach. Since the composite matrix is characterized by a glass transition temperature higher than 50 °C, an external heating source has been necessary to perform the process in “hot” conditions. The process feasibility was fully demonstrated as well as the same was optimized in order to derive proper guidelines that can drive the process designer in the method star-up.

Keywords: Downstream process , Short glass-fibers , SPIF , Thermoplastic composite

In the present work, sheet-forming processes, i.e. super plastic forming and single-point incremental forming, have been adopted for the manufacturing of custom prostheses, instead of subtractive and additive techniques that are time- and cost-consuming for a single-piece production. Regarding concerns of the material, three different titanium alloys were used: pure titanium and two grades of the alloy Ti-6Al-4V (the standard one and the extra low interstitial one). Since no standard protocol exists to assess the mechanical performance of cranial implants, an experimental procedure has been designed and used in this work for producing polymethylmethacrylate supports, on which the cranial prostheses were firmly connected and subjected to impact puncture tests (drop tests). An experimental campaign could thus be conducted to investigate the effect on the mechanical response of (a) the titanium alloy, (b) the initial blank thickness and (c) the manufacturing process. Drop tests, carried out according to the proposed procedure, have shown no failure of the prostheses, neither in the area of the impact nor in the anchoring region and have revealed that, irrespective of the adopted manufacturing process, which does not alter the material, the amount of energy absorbed by the implants is always larger than 70%.

Keywords: Drop test , Pure titanium , SPF , SPIF , Ti-6Al-4V , Ti-6Al-4V-ELI

The standard treatment for bones fractures entails the use of a tailor-made plaster cast which has several disadvantages: its weight generally causes discomfort, it cannot be taken off without breaking it, it can cause skin rashes and prevents ventilation of the treated area. Therefore, the application of traditional casts to orthopaedics patients does not represent, to date, the best option. To overcome the above-mentioned drawbacks, many strategies based on reverse engineering and additive manufacturing techniques have been proposed and proved to be a valid alternative for producing custom orthoses. Encouraged by the aforementioned results, the authors have developed a low-cost system (called Oplà), specifically dedicated to the hand-wrist-arm district of paediatric patients and capable of creating a 3D CAD model of the orthosis ready to be printed by using additive manufacturing techniques. Such a system comprises a 3D scanner, a control software and a semi-automatic CAD procedure to easily model the orthopaedic device on each patient, without the need of CAD modelling professionals. To evaluate if Oplà can be effectively used by the medical staff to design patient specific 3D printable orthoses in the clinical practice, a preliminary usability assessment has been performed. Five professional nurses from the Meyer Children's Hospital of Florence (Italy) have been selected and trained in the use of the system. Subsequently, each of them has been asked to perform the whole process for the same patient. Effectiveness, efficiency and satisfaction have been measured in accordance to ISO 9241-11. Results proved that the Oplà system is characterized by a good usability allowing the user to easily and intuitively perform all the tasks in a reasonable time.

Keywords: CAD , Cast modelling , Reverse engineering , Usability

The visualization and analysis of mosaics and pavements are often compromised by their large sizes, which do not enable the observer to perceive their whole arrangement or to focus on details placed in farthest areas from its boundaries. Moreover, the usual precarious state of conservation of these artefacts, often with damaged or missing areas, makes it difficult to perceive their original aesthetic value. To overcome these limitations, we propose an application of augmented reality able to support the observer in two ways: first, the application completes the missing surface of the mosaic or pavement by integrating the existent surface with a virtual reconstruction; second, it enables the analysis of the geometric pattern of the mosaic/pavement by overlaying virtual lines and geometric figures in order to explicit its geometric arrangements. The result is achieved via a custom Android application able to recognize and track the mosaic figure pattern and extra marker board, obtaining in that way a coordinate system used to render in real-time the reconstruction of the mosaic. Such rendering is overlaid to the video stream of the real scene. The application runs on a standard smartphone embedded in a Google Cardboard-compatible viewer and therefore is extremely affordable. As a case study, in order to reconstruct its aspects and to analyse its geometric pattern, we chose the roman mosaic re-found in Savignano sul Panaro (near Modena, Italy) in 2011, after 115 years from its first discovery, which is preserved less than half of its original 4.5 x 6.9 m surface.

Keywords: Augmented Reality , Cultural heritage , Geometric pattern , Photogrammetry , Real-time visualization , Roman mosaic

This paper proposes the integration of photogrammetric reconstruction, 3D modelling and augmented reality application in order to achieve the complete visualization of a stone sculpture even if highly damaged or fragmentary. The first part of the research aims to the reconstruction of the original aspect of an incomplete sculpture, by using photogrammetry techniques based on standard resolution photos and free software in order to obtain a first model; then, we integrate this model with other 3D digital data (from other sculptures of the same period) or with 3D modelling based on historical sources and views from historians, aiming to achieve the original aspect of the sculpture. The second part of the research consists of the embedding of the obtained model in a custom application able to render in real-time the 3D reconstruction of the lion. Then, the rendering is overlaid to the video stream of the real scene and, as a result, a complete 3D digital model of the sculpture is achieved and could be visualized through a VR viewer. As a case study, we focus on a Roman stone sculpture of a male lion conserved in the Museo Estense of Modena (Italy), which lacks of its head and its four legs. The original aspect of the lion may be achieved by integrating the damaged sculpture with other photogrammetric reconstructions of lions sculptures of the same period and with 3D model based on historical sources. Finally, the lion is visualized through an augmented reality application which digitally overlays the reconstructed models on the original one.

Keywords: Augmented Reality , Cultural heritage , Photogrammetry , Real-time visualization , Virtual modeling

Meniscectomy significantly change the kinematics of the knee joint by reducing the contact area between femoral condyles and the tibial plateau, but the shift in the contact area has been poorly described. The aim of our investigation was to measure the shift of the tibiofemoral contact area occurring after meniscectomy. We used laser scans combined to surface texturing for measuring the 3D position and area of the femoral and tibial surfaces involved in the joint. In particular, natural condyles (porcine model) were analysed and the reverse engineering approach was used for the interpretation of the results from compression tests and local force measurements in conjunction with staining techniques. The results suggested that laser scans combined to surface texturing may be considered as a powerful tool to investigate the stained contours of the contact area. Beside the largely documented reduction of contact area and local pressure increase, a shift of the centroid of the contact area toward the intercondylar notch was measured after meniscectomy. As a consequence of the contact area shift and pressure increase, cartilage degeneration close to the intercondylar notch may occur.

Keywords: Biomechanics , Centroid , Image analysis , Laser scanning , Surface texturing , Tibiofemoral contact area

3D recording, digital surveying and mapping are efficient and manageable tools for reconnaissance, documentation and monitoring in underwater archaeology. Lab4Dive project, co-funded by the European Union's EMFF Programme, through the EASME and DG MARE call on 'Blue Labs', aims to design, develop and validate an innovative, marketable and competitive technology, which will assist underwater archaeologists in the field and will contribute significantly to the successful outcome of the survey process, documentation and preservation of submerged archaeological sites. In this article, the Lab4Dive system and its preliminary testing results, will be presented. The system is based on an underwater tablet coupled with an intelligent underwater case embedded with environmental sensors, a high-resolution camera and compatible with different commercial acoustic positioning systems, which will be integrated with a cloud data gathering system. During the dive, the tablet provides the diver with an augmented navigation interface, which guides him towards the selected targets. The cloud data gathering system allows the archaeologists to produce a 3D reconstruction of the site, which encompasses all the acquired information, enabling them to further study and analyze the data before the next mission.

Keywords: 3D documentation , 3D Reconstruction , IoT , Marine Robotics , Underwater Archaeology

Images obtained in an underwater environment are often affected by colour casting and suffer from poor visibility and lack of contrast. In the literature, there are many enhancement algorithms that improve different aspects of the underwater imagery. Each paper, when presenting a new algorithm or method, usually compares the proposed technique with some alternatives present in the current state of the art. There are no studies on the reliability of benchmarking methods, as the comparisons are based on various subjective and objective metrics. This paper would pave the way towards the definition of an effective methodology for the performance evaluation of the underwater image enhancement techniques. Moreover, this work could orientate the underwater community towards choosing which method can lead to the best results for a given task in different underwater conditions. In particular, we selected five well-known methods from the state of the art and used them to enhance a dataset of images produced in various underwater sites with different conditions of depth, turbidity, and lighting. These enhanced images were evaluated by means of three different approaches: objective metrics often adopted in the related literature, a panel of experts in the underwater field, and an evaluation based on the results of 3D reconstructions.

Keywords: 3D reconstruction , Automatic colour equalization , Benchmark , CLAHE , Colour correction , Dehazing , Lab , Non-local dehazing , Screened poisson equation , Underwater image enhancement

The Underwater Cultural Heritage represents a key aspect of our historical memory still little known due to a number of limitations imposed by the underwater environment. The aim of this paper is to explore the use of digital three-dimensional reconstructions to support the research about this immeasurable archaeological and historical resource. The whole virtual reconstruction process is described step by step, focusing on the iterative feedback allowing for reaching the best virtual reconstruction solutions, helping the archaeologists to better focus their reasoning through a detailed visual representation, and the technical experts to avoid misleading details in the final virtual reconstruction.

The use of polymer composites has been increasing over the years and nowadays the requirements for designing high performance and lightweight fabrics and laminates for sail manufacturing have become more stringent than ever. The present paper offers an effective methodology that enhances the understanding of the influence of fibres orientation and arrangement of panels on sail performance. Constitutive characteristics of the ten commonly used sail cloths are experimentally measured and their influence on sail dynamic performance is compared using an aerodynamic approach. As expected also in industry 4.0 the method allows to control the production process and final product optimization.

Keywords: Aerodynamic coefficient , Apparent wind angle (AWA) , Apparent Wind Speed (AWS) , CFD analysis , Digital photogrammetry , RE , Turbulence model

Sail manufacture has undergone significant development due to sailing races like the America's Cup and the Volvo around the World Race. These competitions require advanced technologies to help increase sail performance. Hull design is fundamentally important but the sails (the only propulsion instrument) play a key role in dynamic of sailboats. Under aerodynamic loads, sail cloth deforms, the aerodynamic interaction is modified and the pressure on the sails is variously distributed resulting in performance inconsistencies. The interaction between fluid and structure necessitates a solution which combines aerodynamic and structural numerical simulations. Furthermore, in numerical simulations the aeroelastic sail characteristics must be known accurately. In this paper, the dynamic performance of a Spinnaker was studied. Digital photogrammetry was used to acquire the images, make the 3D reconstruction of the sail and validate the models in Computational Fluid Dynamics (CFD) analysis. Orthotropic constitutive characteristics of ten different sail cloths were measured by experimental test. The methodology allowed to compare dynamic performance in terms of forces, pressure and vibration for the different sail cloths and different fiber orientations.

Keywords: CFD analysis , Detached eddy simulations , Pressure distributions , Sail aerodynamics , Turbulence models

Additive manufacturing is a rapidly expanding technology. It allows the creation of very complex 3D objects by adding layers of material, in spite of the traditional production systems based on the removal of material. The development of additive technology has produced initially a generation of additive manufacturing techniques restricted to industrial applications, but their extraordinary degree of innovation has allowed the spreading of household systems. Nowadays, the most common domestic systems produce 3D parts through a fused deposition modeling process. Such systems have low productivity and make, usually, objects with no high accuracy and with unreliable mechanical properties. These side effects can depend on the process parameters. Aim of this work is to study the influence of some typical parameters of the additive manufacturing process on the prototypes characteristics. In particular, it has been studied the influence of the layer thickness on the shape and dimensional accuracy. Cylindrical specimens have been created with a 3D printer, the Da Vinci 1.0A by XYZprinting, using ABS filaments. Dimensional and shape inspection of the printed components has been performed following a typical reverse engineering approach. In particular, the point clouds of the surfaces of the different specimens have been acquired through a 3D laser scanner. After, the acquired point clouds have been post-processed, converted into 3D models and analysed to detect any shape or dimensional difference from the initial CAD models. The obtained results may constitute a useful guideline to choose the best set of the process parameters to obtain printed components of good quality in a reasonable time and minimizing the waste of material.

Keywords: 3D printing , Additive manufacturing , Process parameters , Reverse engineering

Aim of this work is to investigate the behaviour of a new reverse shoulder prosthesis, characterized by a humeral metaphysis with a variable offset, designed to increase the range of movements and to reduce the impingement. In particular, by means of virtual prototypes of the prosthesis, different offset values of the humeral metaphysis have been analysed in order to find the best positioning able to maximize the range of movements of the shoulder joint. The abduction force of the deltoid, at different offset values, has been also estimated. The study has been organized as follows. In the first step, the point clouds of the surfaces of the different components of the prosthesis have been acquired by a 3D scanner. This kind of scanner allows to convert camera images into three-dimensional models by analysing the moiré fringes. In the second step, the acquired point clouds have been post-processed and converted into CAD models. In the third step, all the 3D reconstructed models have been imported and assembled through a CAD system. After, a collision analysis has been performed to detect the maximum angular positions of the arm at different metaphysis offset values. In the last step, FEM models of shoulder joint with the new prosthesis have been created. Different analyses have been performed to estimate how the deltoid abduction force varies depending on the offset of the humeral tray. The study allowed to understand how the offset of the metaphysis affects the performances of the shoulder. The obtained results can be effectively used to give surgeons useful guidelines for the installation of these kinds of implants.

Keywords: CAD , Range of movements , Reverse engineering , Reverse shoulder prosthesis

In this work, a multidisciplinary experience, aimed to study the permanent deformations of the hull of a regatta sailing yacht is described. In particular, a procedure to compare two different surfaces of the hull of a small sailing yacht, designed and manufactured at the University of Palermo, has been developed. The first one represents the original CAD model while the second one has been obtained by means of a reverse engineering approach. The reverse engineering process was performed through an automatic close-range photogrammetry survey, that has allowed to obtain very accurate measures of the hull, and a 3D modelling step by the well-known 3D computer graphics software Rhinoceros. The reverse engineering model was checked through two different procedures implemented by the graphical algorithm editor Grasshopper. The first procedure has allowed to compare the photogrammetric measurements with the rebuilt surface, in order to verify if the reverse engineering process has led to reliable results. The second has been implement to measure the deviations between the original CAD model and the rebuilt surface of the hull. This procedure has given the possibility to highlight any permanent deformation of the hull due to errors during the production phase or to excessive loads during its use. The obtained results have demonstrated that the developed procedure is very efficient and able to give detailed information on the deviation values of the two compared surfaces.

Keywords: CAE tools , Close range photogrammetry , Generative algorithms , Reverse engineering , Sailing yacht

Different sensor technologies are available for dimensional metrology and reverse engineering processes. Tactile systems, optical sensors, and computed tomography (CT) are being used to an increasing extent in various industrial contexts. However, each technique has its own peculiarities, which may limit its usability in demanding applications. The measurement of complex shapes, such as those including hidden and twisted geometries, could be better afforded by multisensor systems combining the advantages of two or more data acquisition technologies. In this paper, a fully automatic multisensor methodology has been developed with the aim at performing accurate and reliable measurements of both external and internal geometries of industrial components. The methodology is based on tracking a customized hand-held tactile probe by a passive stereo vision system. The imaging system automatically tracks the probe by means of photogrammetric measurements of markers distributed over a plate rigidly assembled to the tactile frame. Moreover, the passive stereo system is activated with a structured light projector in order to provide full-field scanning data, which integrate the point-by-point measurements. The use of the same stereo vision system for both tactile probe tracking and structured light scanning allows the two different sensors to express measurement data in the same reference system, thus preventing inaccuracies due to misalignment errors occurring in the registration phase. The tactile methodology has been validated by measuring primitive shapes. Moreover, the effectiveness of the integration between tactile probing and optical scanning has been experienced by reconstructing twisted and internal shapes of industrial impellers.

Keywords: industrial impeller , multisensor system , structured light scanning , tactile-optical measuring system