Search for: tolerance-allocation
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    Robust tolerance design of mechanical assemblies using a multi-objective optimization formulation

    , Article SAE Technical Papers ; Vol. 1 , 2014 Khodaygan, S ; Movahhedy, M. R ; Sharif University of Technology
    The design process always has some known or unknown uncertainties in the design variables and parameters. The aim of robust design is minimization of performance sensitivity to uncertainties. Tolerance allocation process can significantly affect quality and robustness of the product. In this paper, a methodology to minimize a product's sensitivity to uncertainties by allocating manufacturing tolerances is presented. The robust tolerance design problem is formulated as a multi-objective optimization based on the combined function-uncertainty-cost model. Genetic algorithm is utilized to solve the multi-objective optimization and a case study is presented to illustrate the methodology  

    Fuzzy-small degrees of freedom representation of linear and angular variations in mechanical assemblies for tolerance analysis and allocation

    , Article Mechanism and Machine Theory ; Volume 46, Issue 4 , April , 2011 , Pages 558-573 ; 0094114X (ISSN) Khodaygan, S ; Movahhedy, M. R ; Foumani, M. S ; Sharif University of Technology
    Tolerances naturally generate an uncertain environment for design and manufacturing. In this paper, a novel fuzzy based tolerance representation approach for modeling the variations of geometric features due to dimensional tolerances is presented. The two concepts of fuzzy theory and small degrees of freedom are combined to introduce the fuzzy-small degrees of freedom model (F-SDOF). This model is suitable for tolerance analysis of mechanical assemblies with linear and angular tolerances. Based on the fuzzy concept, a new index (called the assemblability index) is introduced which signifies the fitting quality of parts in the assembly. Graphical and numerical representations of tolerance... 

    Optimal Design of Tolerances in the Non-rigid Assemblies under the Thermal Impact

    , M.Sc. Thesis Sharif University of Technology Hemati Nik, Javad (Author) ; Khodaygan, Saeed (Supervisor)
    Tolerance allocation in the recent mechanical assembly is significant because it straightly affects product performance and cost. Loose tolerances may cause the quality defect while tight tolerances can increase the cost. Thermal effects and the temperature gradients are one of the factors that caused changes in the size and geometry of the components during the performance of mechanical assemblies. This thesis proposes a new approach for tolerance design considering the thermal effects, to achieve lower manufacturing cost and good product quality. Finite element analysis is used to determine the deformation of components in an assembly. The neural network is trained using experimental... 

    Tolerance Design of Mechanical Systems based on Reliability Modeling under Bayesian Inference

    , M.Sc. Thesis Sharif University of Technology Ghaderi, Aref (Author) ; Khodaygan, Saeed (Supervisor) ; Assempour, Ahmad (Supervisor)
    Mechanical production centers are seeking to produce the highest quality products at the lowest cost. Intrinsic processes of manufacturing are not precise processes, and factors such as tool wear, tool vibration and fixation, fixing defects, and other factors that occur during production, make the pieces deviate from the designer's desirable geometry. Usually, due to deviations of parts from their size, their dimensional and geometric characteristics change. Because the components are rarely just a part, often in the majority of parts of the assembly, the operation of the set may be impaired due to the accumulation of changes. Errors that are usually caused during component assembly due to... 

    Tolerance Design of Mechanical Parts Considering Degradation and Quality Loss in Manufacturing Process and Operating Conditions

    , M.Sc. Thesis Sharif University of Technology Dehghani Tafti, Mohammad Saleh (Author) ; Khodaygan, Saeed (Supervisor) ; Asempour, Ahmad (Supervisor)
    The tolerance stack-up in mechanical assemblies is closely related to the quality of finished products and to the costs of production. In practice, choosing a large tolerance range will result in performance reduction. On the other hand, with small tolerances considered, production costs will increase. Tolerance allocation is a useful tool to control the dimensional and geometric variables of the product, so design engineers can control the final product quality level, production cost, and other variables. The proposed method for tolerance design considers the effects of degradation and quality loss over time and allocates tolerances so that, the functional key characteristic satisfies, as... 

    A Bayesian-reliability based multi-objective optimization for tolerance design of mechanical assemblies

    , Article Reliability Engineering and System Safety ; Volume 213 , 2021 ; 09518320 (ISSN) Ghaderi, A ; Hassani, H ; Khodaygan, S ; Sharif University of Technology
    Elsevier Ltd  2021
    Tolerances significantly affect the assemblability of components, the product's performance, and manufacturing cost in mechanical assemblies. Despite the importance of product reliability assessment, the reliability-based tolerance design of mechanical assemblies has not been previously considered in the literature. In this paper, a novel method based on Bayesian modeling is proposed for the tolerance-reliability analysis and allocation of complex assemblies where the explicit assembly functions are difficult or impossible to extract. To reach this aim, a Bayesian model is developed for tolerance-reliability analysis. Then, a multi-objective optimization formulation is proposed for obtaining... 

    Intelligent tolerance allocation for a high duty brake

    , Article 2005 SAE World Congress, Detroit, MI, 11 April 2005 through 14 April 2005 ; 2005 ; 01487191 (ISSN) Movahhedy, M. R ; Atharifar, H ; Gholami, M ; Sharif University of Technology
    SAE International  2005
    In this paper, a tolerance allocation approach is proposed which attempts to select tolerances for individual dimensional variables of a product in a way that minimizes the cost while maintaining critical design requirements. The algorithm uses a reciprocal power cost-tolerance function which incorporates variable sensitivities computed in a DLM-based tolerance analysis technique. The process capabilities are applied as constraints and the genetic algorithm is used to find the optimum solution. The method is applied to a heavy duty brake problem and its results are presented. Copyright © 2005 SAE International