1,721,104 research outputs found
NURBS Surface Shaping in a Virtual Reality Environment
No full textThe use of 3D tracking systems in a Virtual Reality environment may definitely change CAD interfaces and free-form surface modelling. In this paper an original method for full 3D interactive surface shaping and modifying is described. VISM (Virtual Integrated Surface Modeller) has been developed with the leading idea that 3D tracking system can dramatically speed up modelling sessions. On the opposite of a W-I-M-P (Windows-Icons-Menu-Pointer), paradigm common to most current CAD systems, VISM demonstrates that Virtual Reality devices can manage all types of surface in a unique shape generative action. Unlike “Virtual Clay” based and “Metaball” modelling techniques, VISM both wants to give to engineers and designers a more intuitive and natural tool to get 3D shapes. Based on Polhemus Fastrak and stereoscopic vision, VISM doesn’t provide icons to the designer, leading to a “null icons” and “null menu” full 3D interface. The new interface is fully implemented on bi-manual input system on top of a Virtual Reality environment. The entity grabbing is also supported by pinch-enabled gloves. The designer exploits a NURBS curve tool to deform a NURBS surface and extracts drive curve direction from his right hand movement. The curve tool may be also real-time deformed with left hand through node-control point repositioning. Furthermore the modeller is fully implemented using NURBS curves and surfaces and a fast surface-over-curve positioning and deformation has been implemented, replacing both traditional snapping and picking activities
Controllable pitch propeller optimization through meta-heuristic algorithm
Full text linkThis paper describes a methodology to design and optimize a controllable pitch propeller suitable for small leisure ship boats. A proper range for design parameters has to be set by the user. An optimization based on the Particle Swarm Optimization algorithm is carried out to minimize a fitness function representing the engine’s fuel consumption. The OpenProp code has been integrated in the procedure to compute thrust and torque. Blade’s geometry and tables about pitch, thrust and consumption are the main output of the optimization process. A case study has been included to show how the procedure can be implemented in the design process. A case study shows that the procedure allows a designer to sketch a controllable pitch propeller with optimal efficiency; computational times are compatible with the design conceptual phase where several scenarios must be investigated to set the most suitable for the following detailed design. A drawback of this approach is given by the need for a quite skilled user in charge of defining the allowable ranges for design parameters, and the need for data about the engine and boat to be designed
Augmented vision and interactive monitoring in 3D printing process
No full textThis paper describes the beneficial impact of an augmented reality based technique on the 3D printing process monitoring within additive manufacturing machines. A marker is applied in a fixed point of the rapid prototyping machine, integral with the component being manufactured; as an alternative, a markerless approach can be followed too. A virtual model of the object to be printed is superimposed to the real one. In this way, the shape of the object in different printing stages can be viewed. An interactive comparison between real and virtual model can be carried out both in manual and automatic mode. If manufacturing errors are detected, the building process can be stopped. Augmented reality technique allows an intuitive shape check of a part being printed with rapid prototyping technologies. In case of complex objects it helps the operator in the detection of possible errors along the manufacturing process; stopping the machine as soon as an error appears avoids waste of machining time and material. The average precision of the augmented reality is useful to find significant geometrical errors; geometrical deviations less than 1 mm can hardly be assessed both in manual and in automatic mode, and further studies should be carried out to increase the technique precision and range of application. To the best of the authors’ knowledge it is the first time where experiments on the integration between augmented reality and rapid prototyping to interactively monitor 3D parts’ printing have been investigated and reported in literature
A Voxel-Based 2.5D Panel Method for Fluid-Dynamics Simulations
No full textThe Panel method is an approach for the estimation of the lift of 3D models which is faster than CFD. This can be useful especially in the conceptual design stage where several configurations should be evaluated in a reduced time with a limited computational cost. However, the meshing of the 3D body surface with rectangular panels can be a time-consuming activity because the designer should define from scratch a cloud of points that matches the external surfaces of the tested object to obtain consistent panelling. Therefore, a voxelization-based methodology has been developed to obtain the panels’ position, speeding up and automating the model preparation process. The obtained discretization has been integrated into a panel method available in the literature. Four case studies, of increasing complexity, have been analyzed to investigate the capability of the innovative voxel-based panel methodology. A parametric study has been carried out to study the effect of the voxel grid dimension on the accuracy of the results. Benchmarking values of lift coefficient obtained from literature or xFoil software have been used to evaluate the precision that can be achieved with this approach. The results show a good agreement between the voxel-based panel method and the literature when the overall pressure distributions and aerodynamic coefficient values are considered. Higher errors are noticed with drag
A 3D Voxel-based Approach for Fast Aerodynamic Analyses in Conceptual Design Phases
No full textThe panel method is a potential-flow numerical approach that shows valuable performances to solve aerodynamic problems in the preliminary design stages. It shows a lower computational effort compared with Computational Fluid Dynamics, wind tunnel tests or ‘on the field’ experiments. However, the 3D surface discretization in rectangular panels is tedious and must be often carried out
manually from scratch. Moreover, the panel method can’t be used to compute the overall drag force due to strong assumptions. To solve these two challenging aspects, the authors propose a voxel-based fluid dynamic approach integrating its programmed functions within a panel method. Voxelization is used to automatically distribute coherently the panels along the external surface of a 3D model in an
automated way. A parametric study is included to demonstrate how the voxel resolution affects the aerodynamic results and provide guidelines for future research. Overall drag is estimated using corrections for both the skin friction and the form drag sources. The Ahmed body case study is included and demonstrates a good agreement between the voxel-based fluid dynamics approach and the
literature benchmarking values, but with lower computational efforts. Further studies involving more complex shapes should be performed to better understand the performances and limitations of the approach
Towards Large Parts Manufacturing in Additive Technologies for Aerospace and Automotive applications
No full textWell-established advantages as design freedom, acceleration of design-to-manufacturing cycle, decreased internal logistics reflect on the wider application of Additive Manufacturing as the main manufacturing process. However, its application to large-scale components manufacturing is still an open challenge, because of the limited printing volume available in off-the-shelf machines, slow manufacturing process, and low production volume. After a review of the available contributions, this paper proposes a methodology to handle large-scale 3D models, to be applied before the slicing process. The methodology is based upon the large-scale component subdivision into subparts within CAD environments, using an innovative approach tailored to the problem, and exploits the multi-head capability of collaborative large-scale AM machines. A UAV fixed-wing shows the positive effects in terms of speeding up the manufacturing process. The approach can significantly reduce the printing time of large parts, but a new generation of Additive Manufacturing machines is required to exploit the methodology
Voxelization and one-dimensional lattice structures for industrial components using function representation
Full text linkThis paper presents a scalable, open-source method for designing strut-and-node lattice structures for industrial applications, including uniform and graded lattices. Traditional computer-aided design tools struggle with lattice structures with high complexity, prompting the need for alternative approaches. While function representation techniques are commonly applied to triply periodic minimal surface lattices, their use for strut-and-node lattices has been limited. The proposed method defines the unit cell geometry using function representation primitives to model cylindrical struts and spheres, followed by isosurface triangulation and spatial replication within a voxelized design space. To showcase its practical application, two case studies are presented in which industrial components are filled with uniform and graded lattice structures using the newly developed model. The paper includes a comprehensive analysis of the computational cost of the approach. Furthermore, the study evaluates the geometric accuracy and quality of the generated lattice, highlighting their suitability for lightweight design in additive manufacturing. This method eliminates the need for boundary representations of lattice structure models, leading to more efficient data handling. The results of this research have broad implications for developing 3D components optimised for additive manufacturing. The approach targets industrial use, enabling fast, efficient design of complex, lightweight geometries
Efficient part orientation algorithm for additive manufacturing in industrial applications
Full text linkOver the past few decades, the scientific community’s and industry’s interest in additive manufacturing technologies has surged. This technology is distinguished by the layer-by-layer deposition of the raw materials and the piece’s growth in a
predetermined build orientation. This factor impacts the process’ overall cost, surface quality, and other crucial parameters. Numerous methods to solve competing aspects have been proposed in the literature, with the more promising that iteratively uses ray-tracing techniques. Existing algorithms iterate for each discrete element of the model’s bounding box projection onto the building platform. However, when optimisation algorithms are used on real-life industrial parts, computational time problems arise due to the high number of faces in the models. A new computational technique to determine the appropriate part orientation to reduce the support volume is proposed to address the problem. The method reduces the computational time, cycling the ray-tracing only on the triangles where the model surface is discretised. This approach has been integrated into an enhanced particle swarm optimisation algorithm to prove its efficiency. The approach is intended for industrial applications where it is necessary to handle complicated geometries quickly and efficiently to find the best orientation. Based on the computer’s resources and the complexity of the faceted model, a set of case studies with an industrial engineering
significance is used to demonstrate the approach’s effectiveness
Thermal simulation for enhanced control in innovative ironing processes on 3D-printed components
Full text linkThis study investigates an innovative surface finishing process for 3D-printed components using Material
Extrusion (MEX). By applying controlled heating to the outer layer with a heated, semi-spherical tip, surface
quality can be enhanced without adding material, effectively reducing imperfections caused by nozzle deposi
tion. Using a prototype tool with distinct thermal properties, simulations were conducted to assess the optimal
process parameters, including tool temperature, movement speed, and depth of influence within the material.
Thermal simulations of the tool were performed to analyse temperature distribution and efficiency, identifying
potential heat losses. Additionally, interactions between the tool tip and the material were simulated, high
lighting temperature distribution at various depths. The simulations reliably model the tool’s performance,
providing a solid foundation for precise process parameter calibration while minimising reliance on experimental
testing. Analyses conducted on PLA, PETG, ABS, PEEK, and PEKK demonstrated a clear correlation between
speed and temperature in achieving optimal results. For materials with a high glass transition temperature, either
a lower speed or a higher tool temperature is required, depending on the material’s thermal properties
Static analysis of laminated composite curved shells and panels of revolution with a posteriori shear and normal stress recovery using Generalized Differential Quadrature method
No full textThe Generalized Differential Quadrature (GDQ) Method is applied to study laminated composite shells and panels of revolution. The mechanical model is based on the so called First-order Shear Deformation Theory (FSDT) deduced from the three-dimensional theory, in order to analyze the above moderately thick structural elements. In order to include the effect of the initial curvature from the beginning of the theory formulation a generalization of the kinematical model is adopted for the Reissner–Mindlin theory. The solution is given in terms of generalized displacement components of points lying on the middle surface of the shell. The results are obtained taking the two co-ordinates into account, without using the Fourier expansion methodology, as done in semi-analytical methods. After the solution of the fundamental system of equations in terms of displacements and rotations, the generalized strains and stress resultants can be evaluated by applying the Differential Quadrature rule to the generalized displacements themselves. The transverse shear and normal stress profiles through the laminate thickness are reconstructed a posteriori by simply using local three-dimensional equilibrium equations. No preliminary recovery or regularization procedure on the extensional and flexural strain fields is needed when the Differential Quadrature technique is used. By using GDQ procedure through the thickness, the reconstruction procedure needs only to be corrected to properly account for the boundary equilibrium conditions. In order to verify the accuracy of the present method, GDQ results are compared with the ones obtained with 3D finite element methods. Stresses of several composite shell panels are evaluated. Very good agreement is observed without using mixed formulations and higher order kinematical models. Various examples of stress profiles for different shell elements are presented to illustrate the validity and the accuracy of GDQ method
- …
