1,721,022 research outputs found
Sviluppo di un Sistema di Prototipazione Virtuale per Protesi Odontoiatriche
No full textNella realizzazione di protesi totali removibili risulta assente una fase di progettazione che preveda la definizione di specifiche tecniche in grado di consentire la verifica funzionale sulla protesi realizzata. In questo articolo si presenta uno studio finalizzato allo sviluppo di un sistema di prototipazione virtuale di protesi dentarie totali removibili. Tale sistema costituisce il nucleo di un ambiente integrato per la progettazione e la simulazione funzionale dei singoli denti e della protesi con particolare riferimento alla loro configurazione cinematica e strutturale.
Il prototipo virtuale ottenuto può essere sottoposto ad indagine per la verifica della qualità funzionale dello schema di occlusione realizzato in termini di distribuzione dei contatti nella massima intercuspidazione e negli eventuali movimenti protrusivi e di lateralità, mediante algoritmi basati sull’analisi di interferenza.
Il sistema è stato validato mediante confronto tra protesi virtuale e protesi reale, sottoposta a scansione ottica. Tale confronto è basato sull’analisi delle posizioni e degli angoli di orientamento dei singoli denti e sull’identificazione dei punti di contatto, cardine della prestazione funzionale del dispositivo protesico
Functional geometric characterization of lifting airfoil: An ICP based metrological approach
Full text linkThis paper presents a novel metrological approach for the functional geometric characterization of lifting airfoils, utilizing an Iterative Closest Point (ICP) algorithm to assess deviations in camber, thickness, and form. Traditional geometric specification methods, such as line profile tolerances, often fail to capture the full impact of geometric deviations on airfoil performance. In response, the proposed methodology addresses this limitation by linking airfoil geometry more closely to functional requirements. The new methodology was validated using synthetic datasets and real-world data, demonstrating robustness in the absence of noise and highlighting areas for improvement in noise handling. The findings suggest that the ICP-based method is a valuable tool for airfoil manufacturing, enhancing conformity checks against design specifications. This study opens pathways for more accurate tolerance synthesis and enhanced quality control in the production of lifting airfoils
Outdoing best-fit approaches for the manufacturing accuracy evaluation of complete denture bases
Full text linkTo compare the reference geometry approach to the best-fit (or superimposition) approach in the estimation of geometric accuracy relevant to the digital and the analog workflow to fabricate a complete denture. Starting from a model of an edentulous maxilla, the two measuring methodologies were tested to estimate the geometric accuracy of the intaglio surface of the complete dentures fabricated by CNC milling and injection molding. Eight areas of interest were defined at the intaglio surface of the denture base; a sensitivity analysis determined the minimum number of measuring points to calculate a reliable Δ error value. A repeatability analysis was performed to assess the consistency of this experimental reference geometry approach with respect to the clinic acceptable requirements. For the analog workflow, the comparison of the reference geometry results to the best-fit results showed a − 76 (post-dam) ÷ 169 μm (right flange) range of the Δ mean value for the reference geometry approach, to be compared to − 15 (left crest) ÷ 146 μm (right tuberosity) range for the best-fit approach. For the digital workflow, the same comparison showed a − 21 (left crest) ÷ 51 μm (left flange) range for the reference geometry approach, compared to a − 20 (left crest) ÷ 23 μm (left flange) for the best-fit approach. The best-fit approach results in an underestimation of mean Δ error values and their distribution over the entire prosthesis. The reference geometry approach correctly estimates error values while focusing on the identification of sources of errors in the manufacturing process
Bridging the gap between design and manufacturing specifications for non-rigid parts using the influence coefficient method
Full text linkThe manufacturing process may lead non-rigid parts to endure large deformations which could be reduced during assembly. The manufacturing specifications of the single parts should refer to their free state or “as manufactured” state; the functional specifications should instead address the “as assembled” state. Therefore, a functional geometrical inspection requires dedicated fixtures to bring the parts in “as assembled” state. In this paper, through a linearized model that considers fixturing and elastic spring-back, we aim to correlate the functional specification to the manufacturing specifications. The model suggests a hybrid approach called “restricted skin model” that allows to reduce the degrees of freedom considering the form error when relevant. Firstly, the framework is verified in a mono-dimensional test case. Subsequently, it is verified including FEM simulation and actual measurement for two simple assemblies. The results show that the model can correctly interpret the theoretical assembly behaviour for actual applications. The use of the “restricted skin model” approach shows a negligible difference when compared to full FEM simulation with differences of 2.1 · 10e−7 mm for traslations and 6.0 · 10e−3 deg for rotations. The comparison with actual measurement values showed an error of ±0.2 mm at the assembly features. Furthermore, the linearized model allows a possible real-time application during production that enables to adjust manufacturing specification limits in case of process drifting
A semi-automated tool for digital and mechanical articulators comparative analysis of condylar path elements
Full text link: Digital workflows have revolutionized dentistry, especially when it comes to fabrication of complete dentures through Computer-Aided Design and Computer-Aided Manufacturing (CAD-CAM) procedures. Digital articulators manage to simulate mandibular movements and are emerging as alternatives to mechanical articulators like the Gerber semi-adjustable model. Despite being a promising tool, digital articulators require refinement in order to grant consistent functionality and effective occlusal balance. The aim of this research is to present a semi-automated MATLAB tool designed to compare trajectories from different articulator types-digital versus analog-used in dental practice. Validation of the MATLAB tool compared to existing data demonstrates its reliability and effectiveness. Sensitivity analyses assess the tool's robustness under various settings. Results suggest optimal input parameters and settings ensuring precision. Future developments may include integrating anatomically-based reference systems and advanced metrics for rotational analysis of condylar path elements (CPEs), thereby enhancing digital dentistry potentialities. Ultimately, the semi-automated MATLAB tool represents a significant step towards improving dental occlusal analysis, bridging the gap between analog and digital methodologies and enabling comparison among these tools
Surface Texture Characterization by means of db4 wavelets
No full textThe objective of the paper is to show that wavelets may be used to analyse surfaces for determining the contributions of (1) roughness, (2) waviness and (3) form to the surface texture. The ability to separate the different contributions could be useful, for instance, when geometrical characteristics of waviness are to be analysed for evaluat-ing manufacturing performances. In those cases, roughness contribution to surface texture is a sort of noise.
Matlab has been chosen as a suitable framework for developing this work, because (1) it has a specific toolbox for studies requiring use of wavelets, (2) a programming language is available for developing specific applications, and (3) it has facilities for developing user-tailored outputs.
11 components have been analysed, with materials ranging from Aluminium alloys to Fe 360, to PVC, brass, grey iron and high-alloyed steel. The relevant manufacturing processes are (i) sand casting, (ii) die casting, (iii) wire edm, (iv) forging, (v) milling, (vi) turning, and (vii) injection moulding
A modified volumetric energy density–based approach for porosity assessment in additive manufacturing process design
Full text linkSoundness of additively manufactured parts depends on a lot of process and geometrical parameters. A wrong process design leads to defects such as lack of fusion or keyhole porosity that have a detrimental effect on the mechanical properties of the printed parts. Process parameter optimization is thus a formidable challenge that requires in general a huge amount of experimental data. Among the others, heat source power and scan speed are the most defects-affecting parameters to be optimized. The energy density is used in literature to quantify their combination. Unfortunately, in different works it was demonstrated that it fails if used as design parameter mainly because it does not take into account the material properties and the interaction between heat source and the powder bed. In this contribution, a modified volumetric energy density equation that takes into account the powder-heat source interaction to optimize the combination of power-scan speed values for porosity assessment in powder bed fusion process design is proposed and verified on both AlSi10Mg alloy and Maraging steel 300
Process optimization in glass polishing based on a material removal model
No full textIn the industrial world there are different production processes for the manufacturing of spectacle lens. Nowadays casting is the most common lens manufacturing method. Here, the mould production is based on three stages: grinding, polishing and hardening, where, in the second step, different sets of process parameters play a key role in quality, time and cost. To optimize the polishing process of moulds a model for the correlation between the material removal and the process parameters is proposed. The model is developed for CNC ball polishing of free-form surfaces, where the pad, made of a polyurethane layer superimposed to a rubber bulk, moves along a scanning path, in a suspension of cerium oxide. The material removal can be derived through pressure and sliding velocity between polishing pad and workpiece and consequently can be related to the CAD-CAM- CNC parameters e.g., tool and workpiece shape, dimension and modulus of elasticity, feed rate, feed step, tool rotational speed and radial tool deformation. The model has been validated on ground glass flat samples polished varying the process parameters and it shows a satisfactory estimation of material removal as a function of the process parameters. © 2013 American Scientific Publishers.All rights reserved
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