STL Model Research Articles

Digital (R)Evolution: Open-Source Softwares for Orthodontics

Among the innovations that have changed modern orthodontics, the introduction of new digital technologies in daily clinical practice has had a major impact, in particular the use of 3D models of dental arches. The possibility for direct 3D capture of arches using intraoral scanners has brought many clinicians closer to the digital world. The digital revolution of orthodontic practice requires both hardware components and dedicated software for the analysis of STL models and all other files generated by the digital workflow. However, there are some negative aspects, including the need for the clinician and technicians to learn how to use new software. In this context, we can distinguish two main software types: dedicated software (i.e., developed by orthodontic companies) and open-source software. Dedicated software tend to have a much more user-friendly interface, and be easier to use and more intuitive, due to being designed and developed for a non-expert user, but very high rental or purchase costs are an issue. Therefore, younger clinicians with more extensive digital skills have begun to look with increasing interest at open-source software. The aim of the present study was to present and discuss some of the best-known open-source software for analysis of 3D models and the creation of orthodontic devices: Blue Sky Plan, MeshMixer, ViewBox, and Blender.

Timing matters: crisis severity and occupancy rate forecasts in social unrest periods

Purpose The impact of demand fluctuation during crisis events is crucial to the dynamic pricing and revenue management tactics of the hospitality industry. The purpose of this paper is to improve the accuracy of hotel demand forecast during periods of crisis or volatility, taking the 2019 social unrest in Hong Kong as an example. Design/methodology/approach Crisis severity, approximated by social media data, is combined with traditional time-series models, including SARIMA, ETS and STL models. Models with and without the crisis severity intervention are evaluated to determine under which conditions a crisis severity measurement improves hotel demand forecasting accuracy. Findings Crisis severity is found to be an effective tool to improve the forecasting accuracy of hotel demand during crisis. When the market is volatile, the model with the severity measurement is more effective to reduce the forecasting error. When the time of the crisis lasts long enough for the time series model to capture the change, the performance of traditional time series model is much improved. The finding of this research is that the incorporating social media data does not universally improve the forecast accuracy. Hotels should select forecasting models accordingly during crises. Originality/value The originalities of the study are as follows. First, this is the first study to forecast hotel demand during a crisis which has valuable implications for the hospitality industry. Second, this is also the first attempt to introduce a crisis severity measurement, approximated by social media coverage, into the hotel demand forecasting practice thereby extending the application of big data in the hospitality literature.

Research on the slicing method with equal thickness and low redundancy based on STL files

ABSTRACT To preserve characteristics of triangles in random order, with high repetition between the adjacent layers in STL files, a uniform thickness algorithm is proposed to improve the slicing efficiency, which deletes the triangles below the slicing plane gradually to decrease the number of searches for intersecting triangles and establish the dynamic topology based on intersecting triangles to obtain orderly intersections and closed profiles. A slicing program is developed based on a VC++ platform and an OpenGL interface. This slicing program is validated by comparing the slicing efficiency of different slicing methods for three ASCII STL models. The results show that the slicing program developed in this work can significantly improve the slicing efficiency of STL models.

The Role of the Intramandibular Joint, Symphyseal Tissues, and Wrapping Muscles on Theropod Dinosaur Mandibular Function

Sauropsids, unlike mammals, possess an intramandibular joint (IMJ) separating the dentary and postdentary bones, with different lineages either rigidifying (turtles & crocodilians) or maintaining compliance (lepidosaurs & birds) about the joint. IMJ construction and its role on mandibular performance is unclear, impeding our understanding of its function in extinct animals with extreme feeding behaviors like Tyrannosaurus rex. Sauropsids like T. rex pose a particular biomechanical paradox; feeding traces, coprolites, and their robust crania and teeth indicate that they regularly bit through and ingested bone, but their dorsoventrally-tall and mediolaterally-thin hemimandibles, IMJ, and patent mandibular symphyses suggest their mandibles were ill-suited for bone-crushing bites. Extant sauropsids also exhibit wrapping intramandibularis (mIRA) and pterygoideus ventralis (mPTv) muscles, whose effect on mandibular performance and interaction with the IMJ are unknown. Here we model the effect of the IMJ, symphyseal tissue properties, and wrapping muscle orientation on T. rex mandible biomechanical performance in order to give insight into the biomechanical constraints faced by sauropsids, and the link between their mandibular form and function. Joint tissue histology, gross dissection, and iodine contrast data of extant sauropsids were performed to inform model tissue properties, IMJ construction and muscle orientation. We imported a 3D STL model of the T. rex “STAN” and modeled the IMJ by differing material properties of modeled joint tissues to test the influence of linkage materials on mandibular performance. Muscles were mapped onto the model, and their corresponding muscle moments calculated from area centroids, muscle architecture, and volumes. Wrapping mIRA and mPTv muscles were simulated by directing their force vectors to appropriately positioned dummy points using extant sauropsids as a guide. The mandible was then constrained at the jaw joint and in a series of points along the tooth row from rostral to caudal, simulating both unilateral and bilateral bites. We find that while strains are quite high (>6000 µstrains) about the intramandibular joint, mediolateral bending stresses and strain are markedly reduced by the prearticular, which exhibits greater strain than the surrounding bone. Our results suggest the prearticular of T. rex acted as a strain sink to counteract bending about the IMJ and thereby rigidifying the mandible during feeding. We hypothesize that differences in IMJ articulation and prearticular construction may differentially facilitate or impede prearticular streptognathy, and thus intramandibular kinesis about the IMJ, in sauropsids. Forthcoming models will simulate other theropods within and without Tyrannosauridae to test this hypothesis.

Research on watermark printing technology of STL model based on Menger curvature

In order to solve the data protection problem of STL model, this paper proposes a 3D printing watermarking method based on Menger curvature and K-means clustering algorithm. By comparing the research contents of 3D mesh model watermarking algorithm and two 3D printing watermarking methods, the 3D printing watermarking method is applied based on Menger curvature and K-means clustering algorithm. The method flow, watermark embedding and watermark extraction are discussed. Finally, the experimental results show that this method can not only improve the invisibility of model watermark, but also be robust to geometric attacks such as rotation, scaling and translation.

Overall structure design of model management and data protection system based on STL

This paper realizes the development of STL model management and data protection system for 3D printing cloud platform. Firstly, the 3D printing cloud platform is briefly introduced, and the system requirements analysis, system technical architecture construction, system flow and system database design are completed. Then, based on ASP.NET, database and other technologies, combined with C# language, Web development is carried out. Finally, from the perspective of tourist users, registered users and background administrators, the functions of their respective modules are realized.

Design, Test and FEM Analysis of Customized Titanium Alloy Implant with Scaffold Based on Additive Manufacturing

In order to design the prosthesis which can mimic the surroundings for bone cell proliferation and cell attachment and avoid stress shielding effect by matching the Young’s modulus with different parts of human bone, we come up with the porous structure with scaffold design. This paper is presenting the scaffold of design, the mechanical property of the biomimetic scaffold and the relative error rate between the Finite element analysis (FEA) and compressive test. However, most of the models of the porous structure are designed in the STL format especially the high topological model which will make the FEM preprocessing procedure difficult. According to the reason above, we used the concept of the CT-based voxel mesh method for high complex STL model, which skips the time-consuming mesh and repairing reconstruction process. Lastly, we successfully designed the porous prosthesis according to the data from FEA and compressive test.

THE SLICING ALGORITHM FOR FAST PROTOTYPE PRODUCTION HAS BEEN IMPROVED AND OPTIMISED

An enhanced slicing algorithm is given as a solution to the problem of inefficiency that arises during the slicing phase of rapid prototyping that is based on STL models. The approach constructs the integral topology of STL models in advance by utilising a hash table. This makes it possible to acquire con- tours directly. The method then decreases the search range in slicing by building the slicing relation matrix, which may significantly reduce the time cost of slicing. The temporal complexity of the method has been shown to be roughly linear, according to the demonstrations. The approach has been shown to be effective and efficient via application examples, and the findings demonstrate that it performs better than other methods that are currently available, particularly when the STL model is either complicated or huge.

Effect of the Friction and Reduction Angle on the Accuracy of Cold Drawing Steel Tubes STL Model Based on FEM Analysis

Abstract The object of the study was to create a computer model that resembles the process of cold drawing seamless steel tubes, and evaluate the influence of selected process parameters on selected final dimensions and tolerances of STL models of the tubes obtained from DEFORM simulation software. The STL models of tubes generated from the simulations were evaluated, and the effects of the reduction angle and the friction coefficient on the inner/outer diameter, inner/outer roundness and concentricity were subsequently found. It was proven that the inner and outer diameters are not influenced by different values of the friction coefficient at the same reduction angle. On the other hand, increasing value of the reduction angle affects decrease of the outer and inner diamaters after drawing. Furthermore, this experimental investigation vindicates that friction coefficient and reduction angle have the minimal impact on the inner/outer roundness and outer concentricity.

DICOM segmentation and STL creation for 3D printing: a process and software package comparison for osseous anatomy

BackgroundExtracting and three-dimensional (3D) printing an organ in a region of interest in DICOM images typically calls for segmentation as a first step in support of 3D printing. The DICOM images are not exported to STL data immediately, but segmentation masks are exported to STL models. After primary and secondary processing, including noise removal and hole correction, the STL data can be 3D printed. The quality of the 3D model is directly related to the quality of the STL data. This study focuses and reports on the DICOM to STL segmentation performance for nine software packages.MethodsMultidetector row CT scanning was performed on a dry human mandible with two 10-mm-diameter bearing balls as a phantom. The DICOM image file was then segmented and exported to an STL file using nine different commercial/open-source software packages. Once the STL models were created, the data (file) properties and the size and volume of each file were measured, and differences across the software packages were noted. Additionally, to evaluate differences between the shapes of the STL models by software package, each pair of STL models was superimposed, with the observed differences between their shapes characterized as the shape error.Results: The data (file) size of the STL file and the number of triangles that constitute each STL model were different across all software packages, but no statistically significant differences were found across software packages. The created ball STL model expanded in the X-, Y-, and Z-axis directions, with the length in the Z-axis direction (body axis direction) being slightly longer than that in the other directions. The mean shape error between software packages of the mandibular STL model was 0.11 mm, but there was no statistically significant difference between them.ConclusionsOur results revealed that there are some differences between the software packages that perform the segmentation and STL creation of the DICOM image data. In particular, the features of each software package appeared in the fine and thin areas of the osseous structures. When using these software packages, it is necessary to understand the characteristics of each.

MODELING OF OPTIMAL ROUTES OF PASSENGER TRANSPORTATION OF THE TRANSPORT COMPANY

The purpose of the article is to build a model for optimizing passenger transport routes. The research used econometric methods to predict the demand for transportation and genetic algorithms for the formation of optimal routes of the transport company. The process of logistics optimization is very complex so an efficient NSGA-II algorithm is proposed to solve the problem. The algorithm for generating the initial set of routes is based on intuitive observation, maximizing the demand for travel, which is a key component when designing a logistics network. As a result of managing the efficiency of the system, we received a certain set of routes and balancing the costs of passengers and the carrier. It is concluded that route optimization allows companies to optimize business functions, to include parameters that they usually use to increase business efficiency as part of planning. The company's existing route selection system and traffic information are used in building the model. The study showed that various factors influenced the decisions of operators, including the characteristics of the trip, perception of the reliability of traffic reports. Another research found that providing high-quality information strongly influences the organization of the route planning process. Analysis of data on passenger demand for bus transportation shows that the data has a monthly seasonality. And the best models for forecasting passenger traffic are ARIMA, BATS and STL models. The characteristics of models (ME, RMSE, MAE, MPE, MAPE, MASE, ACF1) were determined to evaluate the best forecasting model. The lower these values, the better the model for predicting time series. Thus, it is recommended to use the ARIMA model to forecast the volume of passengers in the marketing department of the carrier. Due to the correct algorithm of construction and evaluation of route efficiency, the productivity of operators and drivers increases, as the constructed routes are optimized depending on the location of departure and destination points, vehicle and ancillary transportation services. A distinctive feature of the proposed model is to take into account the cost of passenger time and the productivity of the company's staff. The value of the proposed model for forecasting demand and optimizing passenger routes is that it allowed the company to reduce costs by 10.82%. Keywords: transport network, effective route, operating costs, genetic algorithm, ARIMA model.

Scanning trajectory optimisation using a quantitative Tuybased local quality estimation for robot-based X-ray computed tomography

ABSTRACT Robotic CT systems allow complex scanning trajectories. This work presents a workflow to automatically calculate optimised scanning trajectories for robotic CT systems. In particular, as a local quality estimation, this work introduces a quantitative measure to quantify local reconstruction quality based on the Tuy conditions. The proposed method is tested in two summation experiments using an STL model of a motorcycle. In both experiments, a trajectory is calculated using a quantitative Tuy-based local quality estimation and the reconstruction result is then compared to reconstructions using conventional scanning trajectories. The comparison results indicate that the proposed approach automatically finds trajectories that enable 3D reconstructions with high image quality using much less projection data, which allows a significant reduction of scanning time.

Evaluation of the accuracy of the optical scanners used in the modern dental practice

The aim of this study is to evaluate the accuracy of the laboratory optical scanning method used in modern dental practice in a CAD/CAM workflow. The assessment was made using the most common case in practice – tooth prepared for a metal-ceramic crown. An acrylic resin tooth was prepared for the metal-ceramic crown according to standard guidelines. The master matrix was scanned by an extraoral Ceramill Map 400 digital scanner. The scanned data of the prepared tooth was processed to an STL model and a digital copy was created. The same sample was measured by a high-precision contact coordinate measuring machine (CMM) and a second digital model was created. The two scans were aligned in one coordinate system and compared. Comparative analysis was used to evaluate the accuracy of the optical scanning method and the advantages and disadvantages of such equipment were highlighted. The conclusion was drawn that the comparative analysis with the results of contact CMM scanning is a very appropriate approach to validating the accuracy of the digital extraoral scanners, whose significance in the modern dental medical practice is expected to grow rapidly.

Assessment of the morphology and dimensional accuracy of 3D printed PLA and PLA/HAp scaffolds

IntroductionIn complex clinical conditions when physiological bone regeneration is insufficient, there is a need to develop synthetic material-based scaffolds. The morphologic properties of porous scaffolds are of crucial importance. The dimensional accuracy of 3D printed scaffolds can be affected by a variety of factors. Materials and methodsThree groups of 3D printed scaffolds were investigated: PLA1 (pure polylactic acid) printed with an FDM Ultimaker Original printer, PLA2 and composite PLA/hydroxyapatite (PLA/HAp) scaffolds printed with a Pharaoh XD 20. PLA/HAp filament was created with hot-melt extrusion (HME) equipment. The morphology of the prepared scaffolds was investigated with SEM, micro-CT and superimposition techniques, gravimetric and liquid displacement methods. ResultsLayer heights of PLA1 scaffolds varied the most. PLA1 scaffold volume statistically significantly differed from PLA2 (p < 0.001) and PLA/HAp (p < 0.01) groups. Filament composition had no effect on the volumes of the scaffolds printed with the Pharaoh XD 20 printer (p > 0.05). The total porosity of printed PLA/HAp scaffolds deviated the least from the original STL model. ConclusionsThis study showed that PLA/10% HAp filament fabricated with HME and printed with FFF 3D printer produced equal or even better accuracy of printed scaffolds than scaffolds printed with pure PLA filament. Further research is needed to analyze the effect of HAp on 3D scaffold morphology, accuracy, mechanical and biologic properties.

Visualization Research of STL Model Based on OpenGL Technology

With the OpenGL visualization as the background, some important attributes in the OpenGL application data table are processed by using the STL model visualization method. According to the advantages and disadvantages of OpenGL technology, it is rationally optimized. According to the computer display mode, the scale of visual graphics is designed. The OpenGL visualization data and the OpenGL STL model visualization method are reasonably combined, and the corresponding human-computer interaction technology is applied, which allows the user to customize the data according to the task goals.

МОДЕЛЬ АНАЛИЗА РЕЗУЛЬТАТОВ СКАНИРОВАНИЯ ГЕОМЕТРИИ СОПЛОВЫХ АППАРАТОВ ТУРБИН

Traditionally, the blades of gas turbine engines are assembled manually using special techniques (sorting by mass or by several geometric parameters). The use of manual assembly leads to the need to perform reassembly of units and is characterized by non-optimal operating parameters achieved. The data obtained from the scanners when monitor-ing the geometry of the blades can be used to improve the quality of the assembly processes of compressors and engine turbines. In particular, parts can be picked based on key parameters. The results of the work will automate the receipt of such parameters. The paper presents a mathematical model for performing a computer calculation of the flow area of turbine nozzles. The model is used to work with objects of *.stl format when processing data after scanning. With the use of the developed model, the calculations will not depend on the qualifications of the controller, and the proposed approach will not require a unique adjustment and expensive repair and storage of standards for all standard sizes of nozzles. The calculation was carried out in three sections, which increases the accuracy of the calculations while reducing the complexity and cost of measurement. An increase in the number of sections practically does not increase the complexity of calculations, so there are no significant restrictions on the performance of virtual measurements in four or more sections. The model is implemented in the mathematical package MATLAB. The model was tested by the example of processing the STL model of the sector of the turbine nozzle blades.

Distortion Prediction and NURBS Based Geometry Compensation for Reducing Part Errors in Additive Manufacturing

Additive Manufacturing (AM) is a process in which a part is typically fabricated by depositing materials layer by layer. Powder Bed Fusion Additive Manufacturing Process (PBFAM) is one type of AM process which utilizes a high energy laser source to heat and fuse metal powders into a solid part. The constant cycle of heating and cooling in each layer causes thermal deformation associated with residual stresses that reduce the geometric accuracy of the build. To remedy this problem, a compensation algorithm is presented in this paper which modifies the native NURBS CAD geometry of the part to counteract the thermal distortion. An inherent strain-based fast distortion prediction model is used to predict the thermal distortion of the part. The resulting distorted FEA nodes are used to construct a NURBS based compensated geometry using nonlinear least square fitting approach using the original NURBS parameters. Compensating the native NURBS geometry of the model provides more accuracy for the part build rather than compensating STL models. Validation of the algorithm is performed using two case studies by comparing the thermal deformation of pre and post compensated NURBS geometries. The accuracy and robustness of the algorithm for achieving geometric tolerances are further assessed by comparing the flatness and cylindricity tolerances values of the part feature from the two case studies.

An extensible software platform for interdisciplinary cardiovascular imaging research

Background and objectiveCardiovascular imaging is an exponentially growing field with aspects ranging from image acquisition and analysis to disease characterization, and evaluation of therapy approaches.The transfer of innovative new technological and algorithmic solutions into clinical practice is still slow. In addition to the verification of solutions, their integration in the clinical processing workflow must be enabled for the assessment of clinical impact and risks. The goal of our software platform for cardiac image processing – CAIPI – is to support researchers from different specialties such as imaging physics, computer science, and medicine by a common extensible platform to address typical challenges and hurdles in interdisciplinary cardiovascular imaging research. It provides an integrated solution for method comparison, integrated analysis, and validation in the clinical context. The interface concept enables a combination with existing frameworks that address specific aspects of the pipeline, such as modeling (e.g., OpenCMISS, CARP) or image reconstruction (Gadgetron). MethodsIn our platform, we developed a concept for import, integration, and management of cardiac image data. The integration approach considers the spatiotemporal properties of the beating heart through a specific data model. The solution is based on MeVisLab and provides functionalities for data retrieval and storage. Two types of plugins can be added. While ToolPlugins usually provide processing algorithms such as image correction and segmentation, AnalysisPlugins enable interactive data exploration and reporting. GUI integration concepts are presented for both plugin types. We developed domain-specific reporting and visualization tools (e.g., AHA segment model) to enable validation studies by clinical experts. The platform offers plugins for calculating and reporting quantitative parameters such as cardiac function, which can be used to, e.g., evaluate the effect of processing algorithms on clinical parameters. Export functionalities include quantitative measurements to Excel, image data to PACS, and STL models to modeling and simulation tools. ResultsTo demonstrate the applicability of this concept both for method development and clinical application, we present use cases representing different problems along the innovation chain in cardiac MR imaging.Validation of an image reconstruction method (MRI T1 mapping)Validation of an image correction method for real-time 2D-PC MRIComparison of quantification methods for blood flow analysisTraining and integration of machine learning solutions with expert annotationsClinical studies with new imaging techniques (flow measurements in the carotid arteries and peripheral veins as well as cerebral spinal fluid). ConclusionThe presented platform can be used in interdisciplinary teams, in which engineers or data scientists perform the method validation, followed by clinical research studies in patient collectives. The demonstrated use cases show how it enables the transfer of innovations through validation in the cardiovascular application context.

Preparation of “Ready-Made STL (RMS)” for build assurance in additive metal manufacturing (AMM): A review

In this paper “Ready-Made STL (RMS)” is defined as an STL model sophisticatedly planned and managed in advance in order to provide with all information needed for the build using an additive manufacturing process. Generating “RMS” from a raw STL model for build preparation typically undergoes three main processes for full optimization; diagnosis & repair of model geometry for geometric integrity and validity, modification of designed features for design compatibility, and specification of process parameters tight enough for process feasibility. In addition, as a subsidiary process for aid quality verification before the build, visualization of part build geometry simulated with surface roughness or build layers can also help full assurance of the build. This paper provides an executive review of previous approaches preparing “RMS” models and briefly addresses crucial issues resolved by corresponding approaches for build assurance in additive metal manufacturing as quick, efficient, and zero-fault printing process.

An approach to automated measuring morphological parameters of proximal femora on three-dimensional models.

Analyses of the morphology of proximal femora are essential for preoperative planning and designing customized femoral stems in total hip arthroplasty as well as intramedullary nailing fixation. Various studies reported measurements and analyses on the general geometry of proximal femora three-dimensionally. However, the modeling and measurements are time-consuming and unfriendly to surgeons. Thus, automated measurement and modeling of the femoral medullary canal are critical to promote the clinical application. An approach to automated measuring morphological parameters of proximal femur was proposed, and a software allowing importing femur models and manually locating the related anatomic landmarks was developed in the current study. 3D modeling of the femoral medullary canal was created by the semispherical iterative searching algorithm, and 16 key anatomic parameters of the proximal femur were automatically calculated by the least-squares fitting algorithm. By experimenting on 196 femur STL models, the average execution time of single measurement was 0.88 (SD = 0.13)s, and the intra-class correlation coefficient of 10 anatomic parameters was between 0.880 and 0.996, showing high intra-rater and inter-rater reliability. The parameters of proximal femur can be easily measured, and the 3D modeling of the femoral medullary canal can be rapidly achieved. The approach will be easily applicable to clinical practice and has the potential to be applied in the design of customized femoral stems.