Objective: The study has evaluated the accuracy (trueness and precision) of seven extraoral scan-ners when scanning two different types of jaws: simplified jaw with sharp edges and abutments and ...realistic jaw with natural teeth. The accuracies of extraoral scanners were compared, and their compliance with the required clinical accuracy levels was discussed.Material and methods: Ten scans were made with each scanner for both models. The comparison of the selected dental scanners relied on reference scans made for both models. Trueness, precision, and the distribution and value of laboratory scan points’ deviations were assessed for each scanner across the models. Results: The trueness for the model of the simplified jaw with abutments ranged from 16.15 to 49.78 μm. The measured precision values for the same model ranged from 4.33 to 29.49 μm. For the model of the realistic jaw with natural teeth, the trueness results ranged from 11.32 to 24.55 μm, while the obtained precision values were between 2.29 and 18.06 μm. Conclusion: The revealed dissimilarities in the accuracies of scanners and their ranking when scanning different models lead to the conclusion that model selection is critical for the research design. All the scanners met the clinical accuracy requirements and are suitable for use in laboratories for scanning jaws with abutments and jaws with natural teeth. However, the accuracy values reported by the manufacturers of scanners are better than those obtained in this study. Furthermore, the results suggested that blue light scanners outperform white light and laser scanners.
Floating covers used in waste water treatment plants are one of the many structures formed with membrane materials. These structures are usually large and can spread over an area measuring 470 m × ...170 m. The aim of this paper is to describe recent work to develop an innovative and effective approach for structural health monitoring (SHM) of such large membrane-like infrastructure. This paper will propose a potentially cost-effective non-contact approach for full-field strain and stress mapping using an unmanned aerial vehicle (UAV) mounted with a digital camera and a global positioning system (GPS) tracker. The aim is to use the images acquired by the UAV to define the geometry of the floating cover using photogrammetry. In this manner, any changes in the geometry of the floating cover due to forces acting beneath resulting from its deployment and usage can be determined. The time-scale for these changes is in terms of weeks and months. The change in the geometry can be implemented as input conditions to a finite element model (FEM) for stress prediction. This will facilitate the determination of the state of distress of the floating cover. This paper investigates the possibility of using data recorded from a UAV to predict the strain level and assess the health of such structures. An investigation was first conducted on a laboratory sized membrane structure instrumented with strain gauges for comparison against strains, which were computed from 3D scans of the membrane geometry. Upon validating the technique in the laboratory, it was applied to a more realistic scenario: an outdoor test membrane structure and capable UAV were constructed to see if the shape of the membrane could be computed. The membrane displacements were then used to calculate the membrane stress and strain, state demonstrating a new way to perform structural health monitoring on membrane structures.
Current 3D scanning and printing technologies offer not only state-of-the-art developments in the field of medical imaging and bio-engineering, but also cost and time effective solutions for surgical ...reconstruction procedures. Besides tissue engineering, where living cells are used, bio-compatible polymers or synthetic resin can be applied. The combination of 3D handheld scanning devices or volumetric imaging, (open-source) image processing packages, and 3D printers form a complete workflow chain that is capable of effective rapid prototyping of outer ear replicas. This paper reviews current possibilities and latest use cases for 3D-scanning, data processing and printing of outer ear replicas with a focus on low-cost solutions for rehabilitation engineering.
•A system that allows a user to generate a rigged 3D mesh from the raw-scanned 3D volume with simple annotations.•An algorithm to cut fused body parts using the skeleton information.•An algorithm to ...beautify the cut surface by mesh smoothing.
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RGB-D camera-based scanning has increased in popularity; however, raw-scanned three-dimensional (3D) models contain several issues, such as fused arms and legs, that hinder animation. Here, we describe a semiautomatic method that allows generation of a rigged 3D mesh from a raw-scanned 3D volume with simple annotations. The method allows a user to annotate a skeleton structure on registered photographs captured in the scanning step, followed by automatic cutting of fused body parts using the skeleton information to beautify the cut surface by applying mesh smoothing. The system then generates a skinned 3D mesh based on the user-specified 3D skeleton. We tested our method using several raw-scanned 3D plush toy models and successfully generated plausible animations.
This article proposes an indirect measurement method based on a dimensional and shape analysis of forgings for the evaluation of the manufacture and the proper operation of the key elements of the ...crank press, in which after modernization, a quick tool assembly based on SMED (Single Minute Exchange of Die) was implemented. As a result of the introduced changes aiming at improving the forging aggregate and increasing the production efficiency, errors were observed on the manufactured products-forgings in the form of twists and joggles. In order to solve the problem, a lot of advanced methods was used, including: dynamic system of deformation analysis, numerical modeling and as well as dimensional and shape analysis by 3d scanning. Despite the above, this approach (classic way) did not solve the problem. A proprietary method with the use of 3D reverse scanning was proposed, which allows to solve the problem of forgings errors. Based on the measurement results and analyses for a few variants of production cycles, the necessary changes were obtained, making it possible to minimize the errors and obtain proper products in respect of geometry and quality.
Purpose
This paper aims to analyse the effect of different polylactic acid (PLA) colours used on fused deposition modelling (FDM), considering the product finishing quality produced with the same ...process conditions.
Design/methodology/approach
The methodology adopted was to design a virtual modelling object and three-dimensional (3D) print it with FDM with different PLA colours (natural, green and black), using the same parameters. 3D scanning and scanning electron microscopy was used to analyse the model finishing of each sample. Fourier-transform infrared spectroscopy analysis, thermogravimetric analysis and dynamic mechanical analysis were used to characterize the material and verify if the colour affected its thermal behaviour.
Findings
Findings showed that different PLA colours lead to distinct 3D printed finishings under the same process conditions. Thermal analysis showed a reason for the printing finishing difference. The degradation temperatures and the glass temperatures vary depending on the PLA colour. This affects the FDM working temperature.
Originality/value
This study will contribute to improving the finishing quality of 3D printed products by collaborating to the determination of its process conditions.
Severe hand injuries resulting from accidents can lead to the traumatic loss of an upper limb. The provision of an assistive device, such as an arm prosthesis, can help patients regain their courage ...and motivation to engage with the public. This project aimed to integrate 3D scanning and printing technology to develop a customized passive arm prosthesis for individuals who have experienced shoulder disarticulation due to a traumatic accident. The fabrication of the arm prosthesis was specifically designed and tailored to meet each patient’s unique needs and preferences. The prosthesis design was created based on 3D scan files obtained from the patients. Finite element analysis was employed to analyze the design and determine the optimal materials to use, as well as to optimize the overall design. The finalized model was then converted into STL file format and G-code for the 3D printing process. To ensure ease of use, the entire arm prosthesis and a harness system were assembled, and multiple tests and fittings were conducted on the patient. Several prototypes of the arm prosthesis were fabricated to achieve the best fit for each individual patient.
The publication covers the complex process of analyzing the accuracy of mapping models produced in AM (Additive Manufacturing) processes with a thermoplastic material – FFF (Fused Filament ...Fabrication) and polymerization of light-curing resin – PolyJet. The research was conducted with the use of an advanced optical measuring system – the GOM Atos 3D scanner. The part selected for the research in question was the water pump body as a representative example of an element with adequate dimensional and shape conditions (high degree of folding and geometric differentiation) allowing, based on the results of coordinate measurements determined in the research process, to define the potential area of application of AM models made of thermoplastic material and resin hardened with UV light. The performed tests showed the accuracy of individual AM methods at a level within the range declared by machine manufacturers. However, the PolyJet body is characterized by a much higher accuracy of the shape mapping compared to the FFF body. The dimensional accuracy is also higher for the resin model in relation to the thermoplastic model, which results primarily from the thickness of the elementary layer of the model material applied by the printing module defined for individual incremental processes – 16 μm for RGD 720 and 0.2 mm for ABS. Detailed elaboration and analysis of the research results are presented in this publication.
The purpose of the undertaken research work is to analyze the torsional strength of standard samples with a circular cross-section, produced additively using the SLS (Selective Laser Sintering) ...technique – sintering PA2200 polyamide powders. The studies conducted so far have not included a static torsion test, the results of which are crucial for parts such as machine shafts, hubs, couplings, etc. Hence the idea of conducting the research in question. The samples were made in different settings relative to the machine's working platform and subjected to post-processing in two variants – by water-soaking and furnace-heating – in order to determine the influence of the orientation of the model in the manufacturing process and the type of post-processing on torsional strength. The produced samples were additionally subjected to a preliminary dimensional and shape verification due to the significant impact of the accuracy of the models in the SLS process on the operation of the above-mentioned machine parts. Based on the analysis of the test results, it was found that the highest torsional strength was determined for the furnace-heated samples. In addition, the highest mapping accuracy was found for models positioned vertically in relation to the machine's working platform.
Spring-assisted cranioplasty (SAC) is a minimally invasive technique for treating sagittal synostosis in young infants. Yet, follow-up data on cranial growth in patients who have undergone SAC are ...lacking. This project aimed to understand how the cranial shape develops during the postoperative period, from spring insertion to removal. 3D head scans of 30 consecutive infants undergoing SAC for sagittal synostosis were acquired using a handheld scanner pre-operatively, immediately postoperatively, at follow-up and at spring removal; 3D scans of 41 age-matched control subjects were also acquired. Measurements of head length, width, height, circumference, and volume were taken for all subjects; cephalic index (CI) was calculated. Statistical shape modeling was used to compute 3D average head models of sagittal patients at the different time points. SAC was performed at a mean age of 5.2 months (range 3.3-8.0) and springs were removed 4.3 months later. CI increased significantly (P < 0.001) from pre-op (69.5% ± 2.8%) to spring removal (74.4% ± 3.9%), mainly due to the widening of head width, which became as wide as for age-matched controls; however, the CI of controls was not reached (82.3% ± 6.8%). The springs did not constrain volume changes and allowed for natural growth. Population mean shapes showed that the bony prominences seen at the sites of spring engagement settle over time, and that springs affect the overall 3D head shape of the skull. In conclusion, results reaffirmed the effectiveness of SAC as a treatment method for nonsyndromic single suture sagittal synostosis.
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