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Total 39 records

    Numerical analysis of metal cutting with chamfered and blunt tools

    , Article Journal of Manufacturing Science and Engineering ; Volume 124, Issue 2 , 2002 , Pages 178-188 ; 10871357 (ISSN) Movahhedy, M. R ; Altintas, Y ; Gadala, M. S ; Sharif University of Technology
    American Society of Mechanical Engineers(ASME)  2002
    Abstract
    In high speed machining of hard materials, tools with chamfered edge and materials resistant to diffusion wear are commonly used. In this paper, the influence of cutting edge geometry on the chip removal process is studied through numerical simulation of cutting with sharp, chamfered or blunt edges and with carbide and CBN tools. The analysis is based on the use of ALE finite element method for continuous chip formation process. Simulations include cutting with tools of different chamfer angles and cutting speeds. The study shows that a region of trapped material zone is formed under the chamfer and acts as the effective cutting edge of the tool, in accordance with experimental observations.... 

    Configuration design in scalable reconfigurable manufacturing systems (RMS); a case of single-product flow line (SPFL)

    , Article International Journal of Production Research ; 2017 , Pages 1-23 ; 00207543 (ISSN) Moghaddam, S. K ; Houshmand, M ; Fatahi Valilai, O ; Sharif University of Technology
    Abstract
    The dynamic nature of today’s manufacturing industry, which is caused by the intense global competition and constant technological advancements, requires systems that are highly adaptive and responsive to demand fluctuations. Reconfigurable manufacturing systems (RMS) enable such responsiveness through their main characteristics. This paper addresses the problem of RMS configuration design, where the demand of a single product varies throughout its production life cycle, and the system configuration must change accordingly to satisfy the required demand with minimum cost. A two-phased method is developed to handle the primary system configuration design and the necessary system... 

    Using a combination of vibration absorber and a classical active controller to suppress the chatter vibration and increase the stability in turning process

    , Article 10th International Conference on Modern Circuits and Systems Technologies, MOCAST 2021, 5 July 2021 through 7 July 2021 ; 2021 ; 9781665418478 (ISBN) Ebadi, Y ; Moradi, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Abstract
    Free, forced, and self-excited vibrations are the three main types of machine tool vibrations. Self-excited vibration is the most important type of destructive vibration in machining. The most important factor in increasing the chipping rate, stability, and tool life is decreasing this type of destructive vibration. In this paper, we aim to introduce a method to control the self-excited vibrations by the means of the combining a vibration absorber as a passive controlling method and a classical active controller such as PID or compensator or the other classical methods. Utilizing the SIMULINK toolbox of MATLAB software, first, we designed and added the vibration absorber to the model... 

    Simulation of chatter vibrations in reaming

    , Article ASME International Mechanical Engineering Congress and Exposition, IMECE 2007, Seattle, WA, 11 November 2007 through 15 November 2007 ; Volume 3 , 2008 , Pages 441-447 ; 0791842975 (ISBN); 9780791842973 (ISBN) Sajjadi, M ; Movahhedy, M. R ; Sharif University of Technology
    2008
    Abstract
    A time domain approach is used to study the cutting conditions in reaming process that leads the system to regenerative chatter vibrations. The dynamic analysis of the system includes inertia of the tool, centripetal and Coriolis terms, damping and the first mode bending of reamer. A model of cutting forces proportional to chip cross sectional area and process damping proportional to cutting speed is considered. Numerical simulation based on the Euler integration scheme is carried out to obtain time domain solution of the equation. Despite linearization in force modelling, the model is nonlinear due to the change in the tool engagement area. Another nonlinearity included in the model jumping... 

    A speed-dependent variable preload system for high speed spindles

    , Article Precision Engineering ; Volume 40 , April , 2015 , Pages 182-188 ; 01416359 (ISSN) Razban, M ; Movahhedy, M. R ; Sharif University of Technology
    Elsevier Inc  2015
    Abstract
    High speed machine tools are required to operate in a wide range of spindle rotational speeds with high stiffness and high accuracy. The stiffness of the spindle is largely dependent on the axial preload of the angular contact bearings. A large preload is required at lower range of speeds to provide sufficient stiffness for vibration-free heavy cutting. However, at higher speeds, it results in rapid temperature rise and reduces the life of the bearing. For optimum performance, it is essential that the bearing preload is reduced as the rotational speed increases. In this paper, an automatic variable preload system is proposed that changes the preload on the bearings as a function of... 

    Dynamic stability of a Hexaglide machine tool for milling processes

    , Article International Journal of Advanced Manufacturing Technology ; Volume 86, Issue 5-8 , 2016 , Pages 1753-1762 ; 02683768 (ISSN) Najafi, A ; Movahhedy, M. R ; Zohoor, H ; Alasty, A ; Sharif University of Technology
    Springer-Verlag London Ltd 
    Abstract
    One of the major issues related to parallel kinematic machine tools (PKMs) is their structural dependency on their configuration. In this paper, the machine configuration effect on its stability is investigated for the case of a Hexaglide machine tool. An FEM model of the Hexaglide machine tool is developed. The frequency response function (FRF) at the tool tip is obtained by a modal analysis. The numerical results are validated through comparison with those of an experimental modal test. The pose dependency of the PKM stability over its workspace is investigated. It is shown that the machine stability over the workspace is dependent on the spindle/tool/holder system characteristic. For... 

    Configuration design in scalable reconfigurable manufacturing systems (RMS); a case of single-product flow line (SPFL)

    , Article International Journal of Production Research ; Volume 56, Issue 11 , 2018 , Pages 3932-3954 ; 00207543 (ISSN) Moghaddam, S. K ; Houshmand, M ; Fatahi Valilai, O ; Sharif University of Technology
    Taylor and Francis Ltd  2018
    Abstract
    The dynamic nature of today’s manufacturing industry, which is caused by the intense global competition and constant technological advancements, requires systems that are highly adaptive and responsive to demand fluctuations. Reconfigurable manufacturing systems (RMS) enable such responsiveness through their main characteristics. This paper addresses the problem of RMS configuration design, where the demand of a single product varies throughout its production life cycle, and the system configuration must change accordingly to satisfy the required demand with minimum cost. A two-phased method is developed to handle the primary system configuration design and the necessary system... 

    Optimal design of the high-speed spindle bearings to minimize the non-repeatable runout

    , Article SAE World Congress Experience, WCX 2019, 9 April 2019 through 11 April 2019 ; Volume 2019-April, Issue April , 2019 ; 01487191 (ISSN) Khodaygan, S ; Farahani, M. R ; Sharif University of Technology
    SAE International  2019
    Abstract
    The production with high-quality at the lowest production time can be a key means to success in the competitive environment of the manufacturing companies. Therefore, in recent years, the need for the extra precise and high-speed machine tools has been impressively increased in the manufacturing applications. One of the main sources of errors in the motion of the high-speed spindles is the occurrence of non-repetitive runouts (NRRO) in the bearing. The NRRO can be caused by some factors such as the form of balls, the waveness of rings, the number of balls, and the permutation of one or two balls in the ball bearing. In this paper, a Taguchi-based approach is proposed for the optimal design... 

    Numerical simulation of interaction of mode-coupling and regenerative chatter in machining

    , Article Journal of Manufacturing Processes ; Volume 27 , 2017 , Pages 252-260 ; 15266125 (ISSN) Jafarzadeh, E ; Movahhedy, M. R ; Sharif University of Technology
    Elsevier Ltd  2017
    Abstract
    Chatter vibration is a major obstacle in achieving high performance machining. In order to present a realistic model of chatter vibration, in this research, a finite element simulation of orthogonal chip formation combined with a 2D model of machine tool dynamics is developed. The proposed approach has the ability to incorporate various, mostly nonlinear, phenomena affecting chatter occurrence. The dynamic allows the tool to vibrate as a result of chip load variation leading to chatter. The 2DOF model makes it possible to observe the occurrence of model coupling phenomenon, in addition to the regeneration of waviness mechanism. The investigation of mode-coupling and regeneration phenomena in... 

    Penetration-elimination method for five-axis CNC machining of sculptured surfaces

    , Article International Journal of Machine Tools and Manufacture ; Volume 47, Issue 10 , 2007 , Pages 1625-1635 ; 08906955 (ISSN) Hosseinkhani, Y ; Akbari, J ; Vafaeesefat, A ; Sharif University of Technology
    2007
    Abstract
    In this paper, a new tool positioning strategy for five-axis machining, called the penetration-elimination method (PEM), is introduced. The PEM gains from two innovative techniques that can considerably improve the computational efficiency during the calculation of the optimal tool orientations. The first technique includes developing a quantitative definition for the gouging concept and using this definition in conjunction with powerful numerical root-finder algorithms to determine the optimized tool orientations. The second technique dynamically detects the ineffective grid points and drops them from calculations and consequently takes a great role in reducing the computational burden. The... 

    Prediction of spindle dynamics in milling by sub-structure coupling

    , Article International Journal of Machine Tools and Manufacture ; Volume 46, Issue 3-4 , 2006 , Pages 243-251 ; 08906955 (ISSN) Movahhedy, M. R ; Gerami, J. M ; Sharif University of Technology
    2006
    Abstract
    The Stability of machining process depends on the dynamics of the machine tool, among other things. However, the dynamics of the machine tool changes when the tool is changed. To avoid the need for repeating the measurements, sub-structuring analysis may be used to couple the tool and spindle frequency response functions. A major difficulty in this approach is the determination of joint stiffness and damping between the two sub-structures. In particular, the measurement of rotational responses (RDOFs) at joints is a difficult task. In this research, a simple joint model that accounts for RDOFs is proposed. It is shown that this model avoids RDOF measurement while taking into account the... 

    Prediction of chatter in high speed milling including gyroscopic effects

    , Article International Journal of Machine Tools and Manufacture ; Volume 46, Issue 9 , 2006 , Pages 996-1001 ; 08906955 (ISSN) Movahhedy, M. R ; Mosaddegh, P ; Sharif University of Technology
    2006
    Abstract
    Dynamic stability of machine tools during operations is dependent on many parameters including the spindle speed. In high and ultra high speed machining, the gyroscopic effect on the spindle dynamics becomes more pronounced and can affect the borders of stability of the rotating system. In this paper, a finite element based model of spindle, tool holder and cutting tool is presented which uses Timoshenko beam theory to obtain the frequency response of the system when gyroscopic terms are included. Using this response, the stability of a high speed spindle system in the presence of gyroscopic effect is investigated. It is shown that the gyroscopic effects lower the critical depth of cut in... 

    Configuration design of scalable reconfigurable manufacturing systems for part family

    , Article International Journal of Production Research ; 2019 ; 00207543 (ISSN) Moghaddam, S. K ; Houshmand, M ; Saitou, K ; Fatahi Valilai, O ; Sharif University of Technology
    Taylor and Francis Ltd  2019
    Abstract
    Intense global competition, dynamic product variations, and rapid technological developments force manufacturing systems to adapt and respond quickly to various changes in the market. Such responsiveness could be achieved through new paradigms such as Reconfigurable manufacturing systems (RMS). In this paper, the problem of configuration design for a scalable reconfigurable RMS that produces different products of a part family is addressed. In order to handle demand fluctuations of products throughout their lifecycles with minimum cost, RMS configurations must change as well. Two different approaches are developed for addressing the system configuration design in different periods. Both... 

    Configuration design of scalable reconfigurable manufacturing systems for part family

    , Article International Journal of Production Research ; 2019 ; 00207543 (ISSN) Moghaddam, S. K ; Houshmand, M ; Saitou, K ; Fatahi Valilai, O ; Sharif University of Technology
    Taylor and Francis Ltd  2019
    Abstract
    Intense global competition, dynamic product variations, and rapid technological developments force manufacturing systems to adapt and respond quickly to various changes in the market. Such responsiveness could be achieved through new paradigms such as Reconfigurable manufacturing systems (RMS). In this paper, the problem of configuration design for a scalable reconfigurable RMS that produces different products of a part family is addressed. In order to handle demand fluctuations of products throughout their lifecycles with minimum cost, RMS configurations must change as well. Two different approaches are developed for addressing the system configuration design in different periods. Both... 

    Configuration design of scalable reconfigurable manufacturing systems for part family

    , Article International Journal of Production Research ; Volume 58, Issue 10 , 2020 , Pages 2974-2996 Moghaddam, S. K ; Houshmand, M ; Saitou, K ; Fatahi Valilai, O ; Sharif University of Technology
    Taylor and Francis Ltd  2020
    Abstract
    Intense global competition, dynamic product variations, and rapid technological developments force manufacturing systems to adapt and respond quickly to various changes in the market. Such responsiveness could be achieved through new paradigms such as Reconfigurable manufacturing systems (RMS). In this paper, the problem of configuration design for a scalable reconfigurable RMS that produces different products of a part family is addressed. In order to handle demand fluctuations of products throughout their lifecycles with minimum cost, RMS configurations must change as well. Two different approaches are developed for addressing the system configuration design in different periods. Both... 

    Study of Chatter Stability in Boring Using Operating Deflection Shape

    , M.Sc. Thesis Sharif University of Technology Mohammadi, Zohreh (Author) ; Movahhedy, Mohammad Reza (Supervisor)
    Abstract
    Chatter in machining systems is a limiting factor of workpiece surface, tool and machine life and material removal rate. Because of this, studying and modeling of vibrations is very important in the machining. This study is much importer in the boring operation because boring bar's length to diameter ratio is very high and so it is very sensitive to vibrations. As we know, vibration characteristics of a machine change between its operating condition and its resting mode. Because of this it's better to study machine's vibrations when it's working. This study requires some methods that can find operating parameters of machine. The aim of this work is to find these parameters. For finding these... 

    Extending the inverse receptance coupling method for prediction of tool-holder joint dynamics in milling

    , Article Journal of Manufacturing Processes ; Volume 14, Issue 3 , 2012 , Pages 199-207 ; 15266125 (ISSN) Rezaei, M. M ; Movahhedy, M. R ; Moradi, H ; Ahmadian, M. T ; Sharif University of Technology
    Elsevier  2012
    Abstract
    Recently, receptance coupling substructure analysis (RCSA) is used for stability prediction of machine tools through its dynamic response determination. A major challenge is the proper modelling of the substructures joints and determination of their parameters. In this paper, a new approach for predicting tool tip FRF is presented. First, inverse RCSA formulation is extended so that the holder FRFs can be identified directly through experimental modal tests. The great advantage of this formulation is its implementation in arbitrary point numbers along joint length. Therefore, in comparison with previous inverse RCSA approaches, a more realistic joint model can be considered. In addition, due... 

    Study of the effects of miniaturization on static and dynamic form errors in desktop milling machines

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings, 13 November 2009 through 19 November 2009 ; Volume 4 , 2010 , Pages 587-595 ; 9780791843772 (ISBN) Vazirian, M ; Movahhedy, M. R ; Akbari, J ; Sharif University of Technology
    Abstract
    Desktop and miniaturized machine tools are a new trend in small scale and customized manufacturing. The performance of these machines in terms of their energy consumption, machining fluid consumption and their precision have been investigated in the literature, but the effect of miniaturization on static deflection, stability against chatter and the resulting surface error has not been studied. In this paper, the performance of the desktop milling machine tool in terms of their static and dynamic form errors is studied. The performance of a miniature milling machine used for end milling of a typical workpiece is compared with a similar machine of conventional size through dimensional... 

    Multi-objective selection and structural optimization of the gantry in a gantry machine tool for improving static, dynamic, and weight and cost performance

    , Article Concurrent Engineering Research and Applications ; Volume 24, Issue 1 , 2016 , Pages 83-93 ; 1063293X (ISSN) Besharati, S. R ; Dabbagh, V ; Amini, H ; Sarhan, A. A. D ; Akbari, J ; Hamdi, M ; Ong, Z. C ; Sharif University of Technology
    SAGE Publications Ltd 
    Abstract
    In this investigation, the multi-objective selection and optimization of a gantry machine tool is achieved by analytic hierarchy process, multi-objective genetic algorithm, and Pareto-Edgeworth-Grierson-multi-criteria decision-making method. The objectives include maximum static deformation, the first four natural frequencies, mass, and fabrication cost of the gantry. Further structural optimization of the best configuration was accomplished using multi-objective genetic algorithm to improve all objectives except cost. The result of sensitivity analysis reveals the major contribution of columns of gantry with respect to the crossbeam's contribution. After determining the most effective... 

    Calibration of parallel kinematic machine tools using mobility constraint on the tool center point

    , Article International Journal of Advanced Manufacturing Technology ; Volume 45, Issue 5-6 , 2009 , Pages 531-539 ; 02683768 (ISSN) Abtahi, M ; Pendar, H ; Alasty, A ; Vossoughi, G. R ; Sharif University of Technology
    2009
    Abstract
    In the application of parallel kinematic machine tools (PKM), because of errors in the geometric parameters, it is necessary to calibrate the PKM to improve the positioning accuracy. In existing self-calibration methods, either some redundant sensors on passive joints or some mobility constraints on the kinematic chains are used. However, the mobility constraints imposed on kinematic chains might apply large forces during the test on legs and passive joints. Also, these kinds of calibrating are applicable only on PKMs in which their actuated joints can be used as passive joints. To overcome weaknesses of existing methods, a novel approach to calibration based on imposing position constraints...