1,720,990 research outputs found
A Graph-based Software Tool for the CAD Modeling of Mechanical Assemblies
No full textThe challenge of reducing designing time for new mechanical assemblies, especially in the context of large companies, encourages the use of methods and tools aimed to support designing activities and to re-use the company know-how. Furthermore, the design choices must be rapidly check to avoid errors that could cause delay or expensive re-designing. In such a context, the graph theory and related algorithms could be used to define a transfer function, easily to implement, that governs a software tool able to support the designing activities. Therefore, the paper presents a designing approach, based on the graph theory, aimed to generate the geometric modeling of mechanical assemblies. The approach and the software tool are useful both for designer and companies that want to customize and improve such activities. Finally, the paper shows the case study related to the design of a transversal manual gearbox and the generation of a GUI, developed in MatLAB® environment, to validate the approach
A graph-based approach to CAD modeling: a digital pattern application to the sizing and modeling of manual transverse gearboxes
No full textPurpose - The paper proves that the representation of assembly/product dependencies based on graphs and represented through three levels of detail simplifies both the design of assembly/ product and the development of tools dedicated to the design activities.
Result - The comparison of directed-graphs (digraphs) related to two different manual gearboxes highlights the usefulness of a graph-based approach for CAD modeling and its use in the development of a related Graphical User Interfaces (GUI).
Discussion & Conclusion - One key issue for reduction the time to market of a mechanical product, of a software tool or any other product is the knowledge reuse. In such a context, a graph-based approach helps in those cases where a digital pattern setting is recommended. The approach and the software tool are useful both for designers and companies that want to customize and improve such reuse activity. Therefore, the paper presents the architecture of a three shafts gearbox and compare it with a classical architecture of a two shafts gearbox. The analysis of the differences existing between the two architectures are carried out by using a graph-based approach. Then, the comparison is used to set up a software tool useful for both gearbox architectures. Finally, the generation of a GUI, developed in MatLAB® environment, allows to easily generate the preliminary CAD models of different gearboxes, related to each architecture
Optimal dimensioning of the transmission shaft of a longitudinal gearbox
No full textPurpose - The purpose of the paper is to accomplish the analysis of a transmission shaft belonging to a longitudinal gearbox in order to reduce the axial clearances of the parts assembled on the shaft. The paper demonstrates also that the study of assembly conditions allows simplifying the analysis and the evaluation of different dimensioning schemes.
Method - A previous functional approach to optimal dimensioning is used but it is associated to the analysis of relationships between the parts assembled on the shaft, the corresponding functional surfaces and the related dimensioning schemes. Then, a statistical analysis of tolerance chain is accomplished by using different IT grades that characterize dimensional tolerances.
Result - The optimal functional dimensioning scheme of an automotive transmission shaft is accomplished. The scheme is able to guarantee the minimum axial clearances of parts assembled on the shaft.
Discussion & Conclusion - The paper deals with the application of a functional approach to the optimal dimensioning of an automotive transmission shaft. The automotive transmission set is characterized by different working conditions, geometrical constraints and design parameters. Therefore, a preliminary decomposition of the assembly in several subsystems or groups is necessary to clearly analyse the longitudinal gearbox. Then, the study of assembling conditions and related functional surfaces allow simplifying the evaluation of different dimensioning schemes. In fact, the functional approach, aimed to optimal dimensioning, uses a worst-case and statistical analyses to directly check the axial clearances of the wheels assembled on the shaft. Therefore, the effects of dimensioning are directly evaluated in terms of performances of the transmission. Therefore, the different dimensioning schemes are evaluated through the functional approach, as the optimal scheme is able to guarantee the whole set of functional requirements of the shaft
A sensor data fusion-based locating method for large-scale metrology
Full text linkThe measurement of geometric and dimensional variations in the context of large-sized products is a complex operation. One of the most efficient ways to identify deviations is by comparing the nominal object with a digitalisation of the real object through a reverse engineering process. The accurate digitalisation of large geometric models usually requires multiple acquisitions from different acquiring locations; the acquired point clouds must then be correctly aligned in the 3D digital environment. The identification of the exact scanning location is crucial to correctly realign point clouds and generate an accurate 3D CAD model.
To achieve this, an acquisition method based on the use of a handling device is proposed that enhances reverse engineering scanning systems and is able to self-locate. The present paper tackles the device’s locating problem by using sensor data fusion based on a Kalman filter. The method was firstsimulated in a MatLAB environment; a prototype was then designed and developed using low-cost hardware. Tests on the sensor data fusion have shown a locating accuracy better than that of each individual sensor. Despite the low-cost hardware, the results are encouraging and open to future improvements
Automotive power window system design: Object-oriented modelling and design of experiments integration within a digital pattern approach
No full textThe paper tackles an integrated use of object-oriented modelling (OOM) and design of
experiments (DoE) to determine the performance of a double bowden power window system in
order to accomplish the expected system performances during the preliminary designing
phase and, therefore, by accelerating the product development process. A DoE has been
carried out by using the power window model, developed in Dymola environment. The response
surface method (RSM) and ANOVA analysis are used to identify the significant factors.
Then, an empirical equation is derived. It predicts the main system response i.e. the
stroke time, expressed as dependency related to the significant factors. Finally, the use
of the empirical relation inside a design flow of a power window, based on digital
patterns, is presented
Object-oriented model validation for single bowden power window system development
No full textThe paper deals with automotive power window systems and, in particular, tackles the problem of validating the object-oriented model of a single bowden system, to be used within a Model-Based System Engineering (MBSE) approach. Therefore, the paper tackles the problem of increasing accuracy of object-oriented models by defining model refinements i.e. by identifying objects whose modelling has to be improved. Firstly, the role of object-oriented modelling and the main characteristics of the power window system are summarized. Then, the object-oriented model of an automotive single bowden power window system is presented. Finally, the experimental phase, performed to characterize the behavior of the real system is summarised and the validation of simulation model, as well as the identification of model refinement, are accomplished
A Digital Pattern Approach to the Design of an Automotive Power Window by means of Object-Oriented Modelling
No full textThe paper deals with a digital pattern (DP) approach to the design of an automotive power window, using object-oriented modelling. Therefore, the paper faces the designing of a mechatronic system by using an integrated approach to product development. Then, Dymola/Modelica environment is used as a tool of a decision support system that makes possible the DP approach. The paper briefly sum up the results of simulations related to a power window system characterized by a double bowden sliding mechanism. Finally, the paper highlights the parameters that could be easily integrated in a graphical user interface, aimed to reduce both the development time of new power window system and to increase the accuracy of design activities
A graph-based method and a software tool for interactive tolerance specification
No full textThe paper deals with the problem of tolerance specification and, in particular, proposes a graph-based method and a preliminary software tool: (i) to accomplish the tolerance specification for a mechanical assembly; (ii) to verify the consistency of the specification and, (iii) to allow the tracing of relationships among parts and features of the assembly. The method adopts Minimum Reference Geometric Elements (MRGE), directed graphs (di-graphs) and a set of dedicated algorithms to tackle the problems of consistency that occur during an interactive tolerance specification activity. Finally, an application illustrates the proposed method and its actual implementation
Tolerance Prediction for Determinate Assembly Approach in Aeronautical Field
No full textThe optimization of the aeronautical assembly lines is one of the most challenging tasks in development of a new aircraft. To date the Aeronautical companies are founding project related to the optimization of the manufacturing processes, impacting on the reduction of the non-recurring costs. The work presented focuses on methods for the implementation of the determinate assembly approach in the case of manufacturing of aeronautical structures. The methods are based on the prediction of the coupling tolerances between airframe components in order to reduce the numbers of the features to be manufactured in assembly. All that to lead to a reduction of the non-recurring costs
A digital pattern approach to 3D CAD modelling of automotive car door assembly by using directed graphs
No full textThe present paper deals with methods for product development aimed to support designing activities and to re-use company know-how. The work is addressed to complex products i.e. products characterized by several components and dependencies among them. Then, the paper presents both the methodological approach and the application to the 3D CAD modelling of an automotive car door assembly. The work uses directed graphs and a series of algorithms to provide a Graphical User Interface (GUI) able to support a designer by reducing the development time of new car door assemblies and increasing the accuracy of the design activities. According to a digital pattern approach, the GUI is used to determine the set of changes to 3D CAD models that typically occur in the automotive field, during the development of new car door assemblies
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