Machine Tool Structure

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Bo Luo - One of the best experts on this subject based on the ideXlab platform.

  • A new approach based on modal mass distribution matrix to identify weak components of Machine Tool Structure
    The International Journal of Advanced Manufacturing Technology, 2015
    Co-Authors: Xinyong Mao, Liu Xiangqiu, Bo Luo, Fangyu Peng
    Abstract:

    The dynamics of the Machine Tool Structure are significant in high-precision machining and are meaningful to be evaluated. This paper proposes a new approach based on the modal mass distribution matrix to evaluate the dynamics and identify the weak components of Machine Tool Structure and then to investigate the various components’ effects on the machining process in different frequency bands. First, the approach is developed and verified by a designed mass-spring model whose weak components are known. Then, the proposed approach is used to identify the weak components of a Machine Tool Structure whose modal parameters are obtained by experimental modal analysis. The result shows that the same component presents different weakness levels at different modes and that the various components of the Structure present different weakness levels at the same mode. Finally, a cutting experiment is then conducted to verify the identification result. The result meets the former weak components’ identification result well.

  • Modal Testing for Heavy Machine Tool Using Active Excitation
    Applied Mechanics and Materials, 2014
    Co-Authors: Bo Luo, Xinyong Mao, Cai Hui
    Abstract:

    For application in large Machine Tools, the Machined part quality, accuracy as well as machining speed depende greatly on the dynamics of the Structure. In this paper, an active-excitation modal analysis (AEMA), using inertial force of the moving slider to excite the structural modes, is proposed. Modal parameters of the Machine Tool Structure estimated by AEMA are experimentally validated. Since the artificial excitation produced by elaborate excitation equipment is replaced by the inertial force of the slider, the proposed method is much more practical and economical than traditional methods.

  • An approach for measuring the FRF of Machine Tool Structure without knowing any input force
    International Journal of Machine Tools and Manufacture, 2014
    Co-Authors: Xinyong Mao, Bo Luo, Cai Hui, Hongqi Liu, Fangyu Pen
    Abstract:

    Abstract Measuring the dynamics of a Machine Tool is important for improving its processing or design. In general, the dynamics of the Machine Tool Structure is identified by the experimental modal analysis approaches that require the measurement of both the input loadings and the corresponding structural responses. However, the primary limitation for this method is that the input loadings are difficult or impossible to be measured when the Machine Tool is under operational conditions. In this paper, a method that is based on random decrement technology was used to identify the operational modal parameters of a Machine Tool without the knowledge of any of the inputs. To estimate the frequency response functions, FRFs, a structural change method was proposed. The approach is based on the sensitivity of the eigenproperties to structural modifications caused by the drive positions. The proposed method was verified experimentally by traditional hammer tests. Because no elaborate excitation equipment is used, the dynamics of the Machine Tool Structure with arbitrarily feed rate or working position can be easily identified using the proposed active excitation modal analysis method.

  • a new approach to identifying the dynamic behavior of cnc Machine Tools with respect to different worktable feed speeds
    International Journal of Machine Tools & Manufacture, 2013
    Co-Authors: Bo Luo, Xinyong Mao, Fangyu Peng, Hui Cai, Hongqi Liu
    Abstract:

    Abstract The dynamics of the Machine Tool Structure are important in high precision machining. Some researchers have studied that the dynamics are expected to change under different machining conditions. However, the dynamic behaviors of the Machine Tool at different worktable feed speeds are rarely studied. In this paper, an output-only modal identification available to predict the dynamics of the Machine Tool at different feed speeds is proposed. The excitation of this method uses the inertia force sequence caused by random idle running of the worktable. The first six modes of the entire Machine Tool Structure are estimated using the proposed method. The results indicate that the running state of the worktable can influence the modes in which the worktable vibrates. The estimated natural frequencies and damping ratios decrease obviously as the feed speed increases. Furthermore, because this method enable to determine modal parameters by measuring the response of Machine Tool Structure without using any artificial excitation, it can be used to predict the dynamic behaviors of the Machine Tool in entire working space effectively.

  • estimation of cnc Machine Tool dynamic parameters based on random cutting excitation through operational modal analysis
    International Journal of Machine Tools & Manufacture, 2013
    Co-Authors: Hui Cai, Xinyong Mao, Junbin Huang, Bo Luo
    Abstract:

    Abstract Dynamic properties of the whole Machine Tool Structure including Tool, spindle, and Machine Tool frame contribute greatly to the reliability of the Machine Tool in service and machining quality. However, they will change during operation compared with the results from static frequency response function measurements of classic experimental modal analysis. Therefore, an accurate estimation of the dynamic modal parameters of the whole Structure is of great value in real time monitoring, active maintenance, and precise prediction of a stability lobes diagram. Operational modal analysis (OMA) developed from civil engineering works quite efficiently in modal parameters estimation of Structure in operation under an intrinsic assumption of white noise excitation. This paper proposes a new methodology for applying this technique in the case of computer numerically controlled (CNC) Machine Tools during machining operations. A novel random excitation technique based on cutting is presented to meet the white noise excitation requirement. This technique is realized by interrupted cutting of a narrow workpiece step while spindle rotating randomly. The spindle rotation speed is automatically controlled by G-code part program, which contains a series of random speed values produced by MATLAB software following uniform distribution. The resulting cutting produces random pulses and excites the Structure in all three directions. The effect of cutting parameters on the excitation frequency and energy was analyzed and simulated. The proposed technique was experimentally validated with two different OMA methods: the Stochastic Subspace Identification (SSI) method and the poly-reference least square complex frequency domain (pLSCF or PolyMAX) method, both of which came up with similar results. It was shown that the proposed excitation technique combined successfully with OMA methods to extract dynamic modal parameters of the Machine Tool Structure.

Young Hun Jeong - One of the best experts on this subject based on the ideXlab platform.

  • thermal behavior of a Machine Tool equipped with linear motors
    International Journal of Machine Tools & Manufacture, 2004
    Co-Authors: Young Hun Jeong
    Abstract:

    Abstract Development of a feed drive system with high speed and accuracy has been a major issue in the Machine Tool industry. Linear motors can be used as efficient Tool to achieve the high speed and accuracy. However, a high speed feed drive system with linear motors, in turn, can generate heat problems. Also, frictional heat is produced at the ball or roller bearing of LM block when driven at high speed. It can affect the thermal deformation of the linear scale as well as that of the Machine Tool Structure. In this paper, important heat sources and resulting thermal errors in a Machine Tool equipped with linear motors were investigated when it was operated at high speed. The thermal deformation characteristics were identified through measuring the thermal error caused from thermal deformation of the linear scale and the Machine Tool Structure. The dominant thermal error components were identified from the thermal error analysis using finite element method. It was shown that the proposed analysis scheme is efficient in identifying the dominant thermal error components and its magnitudes such as the thermal expansion and movement of the linear scale, thermal deformation of the Machine Tool slide.

Jin Kyung Choi - One of the best experts on this subject based on the ideXlab platform.

  • thermal characteristics of the spindle bearing system with a gear located on the bearing span
    International Journal of Machine Tools & Manufacture, 1998
    Co-Authors: Jin Kyung Choi
    Abstract:

    High cutting speeds and feeds are essential requirements of a Machine Tool Structure to accomplish its basic function which is to produce a workpiece of the required geometric form with an acceptable surface finish at as high a rate of production as is economically possible. Since bearings in high speed spindle units are the main heat source of total cutting system, in this work, the thermal characteristics of the spindle bearing system with a tilting axis were investigated using finite element method to improve the performance of the spindle bearing system. Based on the numerical results, a specially designed prototype spindle bearing system was manufactured. Using the manufactured spindle bearing system, the thermal characteristics were measured and compared to the numerical results. From the comparison of the numerical results with the experimental results, it was found that the finite element method predicted well the thermal characteristics of the spindle bearing system.

Reza Kashani - One of the best experts on this subject based on the ideXlab platform.

  • improving surface roughness in turning using optimal control of Tool s radial position
    Journal of Materials Processing Technology, 2005
    Co-Authors: Ameen Elsinawi, Reza Kashani
    Abstract:

    Abstract Vibration suppression of the Tool results in improved surface texture, dimensional accuracy and enhanced productivity in machining operations. Vibrations of the Machine-Tool Structure, as well as the Tool-workpiece interaction are the main contributors to the Tool vibration. In light of this, abating the Tool vibration can be approached by isolating the Tool from the Machine Structure in the presence of a random process representing the Tool-workpiece interaction. An active Tool holder capable of isolating the cutting Tool from the vibration of the Machine-Tool Structure is constructed. Vibration isolation is accomplished by means of a Kalman estimator-based control strategy, a high bandwidth magnetostrictive actuator, and two accelerometers. The proposed control technique focuses on lowering the transmitted force to the Tool that is subject to the Machine Structure vibration (base excitation) in presence of cutting process disturbance. The important aspect of this control strategy is that, while it is designed based on a full order model of the plant, its implementation is reduced to the realization of a second order estimator irrespective of the order of the plant model. Machining experiments showed that an average of 25% improvement in surface roughness of the workpiece has been achieved using the proposed technique.

Xinyong Mao - One of the best experts on this subject based on the ideXlab platform.

  • A new approach based on modal mass distribution matrix to identify weak components of Machine Tool Structure
    The International Journal of Advanced Manufacturing Technology, 2015
    Co-Authors: Xinyong Mao, Liu Xiangqiu, Bo Luo, Fangyu Peng
    Abstract:

    The dynamics of the Machine Tool Structure are significant in high-precision machining and are meaningful to be evaluated. This paper proposes a new approach based on the modal mass distribution matrix to evaluate the dynamics and identify the weak components of Machine Tool Structure and then to investigate the various components’ effects on the machining process in different frequency bands. First, the approach is developed and verified by a designed mass-spring model whose weak components are known. Then, the proposed approach is used to identify the weak components of a Machine Tool Structure whose modal parameters are obtained by experimental modal analysis. The result shows that the same component presents different weakness levels at different modes and that the various components of the Structure present different weakness levels at the same mode. Finally, a cutting experiment is then conducted to verify the identification result. The result meets the former weak components’ identification result well.

  • Modal Testing for Heavy Machine Tool Using Active Excitation
    Applied Mechanics and Materials, 2014
    Co-Authors: Bo Luo, Xinyong Mao, Cai Hui
    Abstract:

    For application in large Machine Tools, the Machined part quality, accuracy as well as machining speed depende greatly on the dynamics of the Structure. In this paper, an active-excitation modal analysis (AEMA), using inertial force of the moving slider to excite the structural modes, is proposed. Modal parameters of the Machine Tool Structure estimated by AEMA are experimentally validated. Since the artificial excitation produced by elaborate excitation equipment is replaced by the inertial force of the slider, the proposed method is much more practical and economical than traditional methods.

  • An approach for measuring the FRF of Machine Tool Structure without knowing any input force
    International Journal of Machine Tools and Manufacture, 2014
    Co-Authors: Xinyong Mao, Bo Luo, Cai Hui, Hongqi Liu, Fangyu Pen
    Abstract:

    Abstract Measuring the dynamics of a Machine Tool is important for improving its processing or design. In general, the dynamics of the Machine Tool Structure is identified by the experimental modal analysis approaches that require the measurement of both the input loadings and the corresponding structural responses. However, the primary limitation for this method is that the input loadings are difficult or impossible to be measured when the Machine Tool is under operational conditions. In this paper, a method that is based on random decrement technology was used to identify the operational modal parameters of a Machine Tool without the knowledge of any of the inputs. To estimate the frequency response functions, FRFs, a structural change method was proposed. The approach is based on the sensitivity of the eigenproperties to structural modifications caused by the drive positions. The proposed method was verified experimentally by traditional hammer tests. Because no elaborate excitation equipment is used, the dynamics of the Machine Tool Structure with arbitrarily feed rate or working position can be easily identified using the proposed active excitation modal analysis method.

  • a new approach to identifying the dynamic behavior of cnc Machine Tools with respect to different worktable feed speeds
    International Journal of Machine Tools & Manufacture, 2013
    Co-Authors: Bo Luo, Xinyong Mao, Fangyu Peng, Hui Cai, Hongqi Liu
    Abstract:

    Abstract The dynamics of the Machine Tool Structure are important in high precision machining. Some researchers have studied that the dynamics are expected to change under different machining conditions. However, the dynamic behaviors of the Machine Tool at different worktable feed speeds are rarely studied. In this paper, an output-only modal identification available to predict the dynamics of the Machine Tool at different feed speeds is proposed. The excitation of this method uses the inertia force sequence caused by random idle running of the worktable. The first six modes of the entire Machine Tool Structure are estimated using the proposed method. The results indicate that the running state of the worktable can influence the modes in which the worktable vibrates. The estimated natural frequencies and damping ratios decrease obviously as the feed speed increases. Furthermore, because this method enable to determine modal parameters by measuring the response of Machine Tool Structure without using any artificial excitation, it can be used to predict the dynamic behaviors of the Machine Tool in entire working space effectively.

  • estimation of cnc Machine Tool dynamic parameters based on random cutting excitation through operational modal analysis
    International Journal of Machine Tools & Manufacture, 2013
    Co-Authors: Hui Cai, Xinyong Mao, Junbin Huang, Bo Luo
    Abstract:

    Abstract Dynamic properties of the whole Machine Tool Structure including Tool, spindle, and Machine Tool frame contribute greatly to the reliability of the Machine Tool in service and machining quality. However, they will change during operation compared with the results from static frequency response function measurements of classic experimental modal analysis. Therefore, an accurate estimation of the dynamic modal parameters of the whole Structure is of great value in real time monitoring, active maintenance, and precise prediction of a stability lobes diagram. Operational modal analysis (OMA) developed from civil engineering works quite efficiently in modal parameters estimation of Structure in operation under an intrinsic assumption of white noise excitation. This paper proposes a new methodology for applying this technique in the case of computer numerically controlled (CNC) Machine Tools during machining operations. A novel random excitation technique based on cutting is presented to meet the white noise excitation requirement. This technique is realized by interrupted cutting of a narrow workpiece step while spindle rotating randomly. The spindle rotation speed is automatically controlled by G-code part program, which contains a series of random speed values produced by MATLAB software following uniform distribution. The resulting cutting produces random pulses and excites the Structure in all three directions. The effect of cutting parameters on the excitation frequency and energy was analyzed and simulated. The proposed technique was experimentally validated with two different OMA methods: the Stochastic Subspace Identification (SSI) method and the poly-reference least square complex frequency domain (pLSCF or PolyMAX) method, both of which came up with similar results. It was shown that the proposed excitation technique combined successfully with OMA methods to extract dynamic modal parameters of the Machine Tool Structure.