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Li X.,Chongqing Machine Tool Group Co. | Yang Y.,Chongqing Machine Tool Group Co.
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2017

In order to explore the hob cutting vibration characteristics of computer numerical control (CNC) gear hobbing machine, According to the machine tool structure, process parameters and Euler-Bernoulli beam vibration theory was established the hob spindle X direction of vibration response function model, the vibration test is carried out, the vibration frequency and X direction vibration acceleration and displacement curve of the hob spindle are obtained. Compared the theoretical results of calculation with the practical experimental values of the maximum amplitude of the vibration acceleration and displacement of the hob spindles, the relative error of the results are all lower than 5%. It shows that the theory and the experimental results are in good agreement, which proves the correctness of the theory model of the vibration response function model of the hob spindle of this type of gear hobbing machines. And From the test data analysis, it is known that this research has guiding significance to the spindle structure and processing parameter selection and the optimization, and the prediction of the machining error about gear hobbing machines, It can provide experience reference and reference value for the other series gear hobbing machines of the hob spindle of the vibration characteristic theory and experiment research, and also lay a theoretical and experimental foundation work for the further research on vibration characteristics of gear hobbling machine in future. © 2017 Journal of Mechanical Engineering.

Luo J.,Chongqing University of Posts and Telecommunications | Xiao H.,Chongqing University of Posts and Telecommunications | Li C.,Chongqing Technology and Business University | Yang Y.,Chongqing Machine Tool Group Co.
Proceedings of 2016 Prognostics and System Health Management Conference, PHM-Chengdu 2016 | Year: 2016

It is a pervasive problem to accurately estimate the frequency of sinusoids contaminated by random noise, which has existed in many signal processing areas, including the application in mechanical fault diagnosis and prognostics. The interpolation discrete Fourier transform (DFT) method, employed in frequency domain, is one of the most well studied frequency estimation methods. In this paper, a comparison has been made on the noise performance of various frequency estimators based on interpolation DFT algorithm with rectangular window or the Hanning window. The probability distribution of estimation errors returned by different frequency estimators as a function of frequency deviation, rather than the root mean square error of estimates which is usually adopted in the past references, is considered. The study presents a more thorough understanding of the advantages and deficiencies of the current interpolation DFT algorithms, which may provide a reference for researchers in selecting a proper algorithm so as to meet the specific requirements. © 2016 IEEE.

Chen Y.,Chongqing University | Cao H.,Chongqing University | Li X.,Chongqing Machine Tool Group Co. | Chen P.,Chongqing Machine Tool Group Co.
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2016

As the most widely used cylindrical gear machining approach, gear hobbing owns characteristics of high efficiency but complexity. On the basis of generating theory, a series of cutting edges which regularly distributed on the basic worm face of the hob is going to remove material from the gear blank successively and the involute tooth flank is shaped by enveloping. The study on its forming principle can provide effective guidance for performance improvement. In allusion to the characteristics of multi-edge cutting, the spatial forming model for cylindrical gear hobbing is established. The parametric equation of cutting edges sequence is established based on the theoretical constraint relationship of the geometrical and structural parameters of the hob. The kinematics relationship between the hob and gear blank is determined according to geometric parameters of hob and gear as well as machining parameters. The parametric model of the spatial forming surface generated by the cutting edge sequence is derived. Based on the model, the geometry and thickness of the chip corresponding to each cutting edge is obtained with numerical method by discretization. And the dynamic main cutting force in gear hobbing process is calculated according to the chip geometry. The established model can be utilized to support parameter optimization of gear hobbing process and the geometric design of hob. © 2016 Journal of Mechanical Engineering.

Li G.,Chongqing University | Li X.,Chongqing University | Li X.,Chongqing Machine Tool Group Co. | Liu F.,Chongqing University | Sun M.,Chongqing University
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2011

Since the contact lines between grinding wheel and gear are dynamically changing for form grinding with additional radial motion of topologically modified gear, the calculated wheel profile based on any cross-section of gear will cause a larger grinding error. For reducing grinding error, a method to optimize the profile of grinding wheel is proposed. Firstly, the mathematical models to solve the profile of grinding wheel with additional radial parabolic trajectory is established based on the space engagement theory. Secondly, multiple equidistant plane is used to intercept the gear and to obtain a number of cross-sections for solving the wheel profiles represented with points corresponding to the cross-sections of gear; then a cloud of points is formed by projecting the wheel profiles to a plane, the fitting points of each interval obtained by dividing the cloud into equal intervals is solved based on the least square method, and connecting all the fitting points to form an optimal wheel profile. Given a formula of deviation between actual tooth profile and ideal profile, a mathematical model of gear tooth profile is established based on the meshing condition between wheel and gear to verify the grinding effect of grinding wheel. As an example of axial modified gear, wheel profile both the un-optimized and optimized are calculated, and the results show that the method can be used in the profile calculation of form grinding wheel and effectively reduce the grinding errors of topologically modified gear. © 2011 Journal of Mechanical Engineering.

Cao H.-J.,Chongqing University | Li H.-C.,Chongqing University | Song S.-L.,Chongqing University | Du Y.-B.,Chongqing University | Chen P.,Chongqing Machine Tool Group Co.
Jisuanji Jicheng Zhizao Xitong/Computer Integrated Manufacturing Systems, CIMS | Year: 2011

According to the analysis of product structure and life cycle characteristics of machine tools, a method for assessing the carbon emissions of machine tools lifecycle was introduced based on the principles of Life Cycle Assessment (LCA). It was used to describe and calculate the carbon emissions of machine tools lifecycle in different stages quantitatively, and the influencing characteristics of life cycle stages was also analyzed. This method divided carbon emission of machine tools lifecycle into four stages, manufacturing, using, transporting and recycling. It also divided carbon emission characteristics into fixed emissions and varied emissions. The linear functions were established. Carbon emission efficiency was proposed to describe changing feature for carbon emission of machine tools. The validity of the method was demonstrated by the calculation and characteristic analysis of carbon emissions combined common numerical control gear hobbing machine tool with a high-speed dry cutting one.

Wang S.,Chongqing University | Yang Y.,Chongqing University | Yang Y.,Chongqing Machine Tool Group Co. | Li X.,Chongqing Machine Tool Group Co. | And 2 more authors.
Journal of Mechanical Science and Technology | Year: 2013

Research on thermal deformation of large-scale computer numerical control (CNC) hobbing machines is on the purpose of obtaining the law of thermal deformation of gear hobbing machines to improve machining precision. According to the structure characteristics of hobbing machines, this paper presents a novel computing model of thermal deformation based on the theory of the thermal expansion deformation of metallic materials, the extensional beam theory, non-uniform temperature distribution of the Euler-Bernoulli beam and Kirchhoff theory of plane-section assumption. Then, the coupling theory of axial and bending deformation of hobbing machines based on the deformation element and equilibrium element method is proposed. The experimental measurement system and platform for thermal deformation of gear hobbing machines is established. The temperature and displacement data of thermal deformation of a certain type gear hobbing machine is analyzed, which has demonstrated the law of thermal deformation of hobbing machines. The locus curves for overall displacement error of cutting points and teeth trace error are obtained. Comparing deformation theory and experimental data, the relative error is lower than 5%, which verifies the computing model proposed by this paper, and shows the research method has great significance for structural optimization, local temperature control, and prediction and compensation for thermal deformation error of gear hobbing machines. © 2013 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

Li C.,Chongqing University | Li L.,Chongqing University | Cao H.,Chongqing University | Wang Q.,Chongqing Machine Tool Group Co.
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2013

In view of the uncertainties inherent in remanufacturing process, a fuzzy petri net based remanufacturing process model is proposed to explicitly represent the variations in remanufacturing process routings and process time with respect to product conditions. A fuzzy learning system with an adaptive learning mechanism is designed to estimate the remanufacturing process time of used component under specific conditions, and to dynamically reshape the distributions of actual process time to improve future predictions. The proposed method is illustrated through the remanufacturing of a batch of used lathe spindles with a Matlab-based simulation system. ©2013 Journal of Mechanical Engineering.

Li X.-G.,Chongqing University | Li X.-G.,Chongqing Machine Tool Group Co. | Li C.-B.,Chongqing University | Liu F.,Chongqing University | Li L.-L.,Chongqing University
Jisuanji Jicheng Zhizao Xitong/Computer Integrated Manufacturing Systems, CIMS | Year: 2012

As the big typical consumer of energy resources, the machine tool manufacturing industry's carbon emission had significance on realization of our country's energy-conservation and emission-reduction. The boundary of carbon emission in machine tool manufacturing process was defined, and the characteristics of carbon emission were also analyzed. A carbon emission model for machine tool manufacturing process was constructed based on Petri net, and the dynamic quantification methods for carbon emission in the manufacturing process were proposed. The proposed methods were applied in a machine tool manufacturing factory, and its carbon emission condition was obtained. Thus the suggestions for energy-conservation and emission-reduction were given.

Li X.,Chongqing Machine Tool Group Co. | Yang Y.,Chongqing Machine Tool Group Co.
Zhongguo Jixie Gongcheng/China Mechanical Engineering | Year: 2016

In order to master the abrasion properties of composite sliding guideways of gear hobbing machines, based on the principle of crawl of vibration theory, Reynolds theory, and the working condition parameter of composite sliding guideway, a model of the stable attrition phase was established to calculate the attrition depth of changing with time, the experimental project for test the attrition depth of composite sliding guideway of the gear hobbing machine was proposed, and the corresponding experimental apparatus were developed successfully. The attrition depth were tested with the sample parts of composite sliding guideway of gear hobbing machine, the theoretical calculations were compared with the experimental values.It is shown that the relative error of the results is lower than 5%. The above analyses indicate the effectiveness and validity of the proposed method, which has beneficial reference value and instructive significance for optimum oil groove structure, geometry parameter, and oil film load-bearing capacity design, and type selection of composite sliding guideways on gear hobbing machines. © 2016, China Mechanical Engineering Magazine Office. All right reserved.

He K.,Chongqing University | Li G.,Chongqing University | Li X.,Chongqing University | Li X.,Chongqing Machine Tool Group Co.
International Journal of Advanced Manufacturing Technology | Year: 2016

A conventional worm wheel profile is obtained by establishing the meshing equation of the wheel and gear and determining the contact trace, which is difficult to use in calculating the non-standard profile gear. The second envelope method of point-vector (PV) is then proposed, which is actually a digital calculation method. The grinding wheel profile is formed by generating motion of the gear surface. The generating motion is divided into the first and second envelope motion. Using a PV approximation method, a gear profile is dispersed into a series of PVs to establish the PV envelope principle and the envelope approximation algorithm, determine the envelope point with the minimal orientation-distance to the wheel in the PV group, and obtain the wheel profile by fitting all the envelope points. In this paper, a detailed description of the wheel profile forward and gear profile backward calculation processes is provided using the second envelope method of PV. Experimental verification of the calculation results demonstrates that this method can be employed to calculate and machine any gear profile and achieve high accuracy. © 2016 Springer-Verlag London

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