• Title/Summary/Keyword: Hydrostatic journal bearing

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Performance Evaluation of Hydrostatic Bearing Guided Rotary Table for Large Volume Multi-tasking Vertical Lathe (대형 복합수직선반 가공기용 유정압베어링 회전테이블 성능 실험 및 분석)

  • Shim, Jongyoup;Oh, Jeong-Seok;Park, Chun-Hong;Shin, Heung-Chul;Park, Woo-Sang;Kim, Min-Jae;Kim, Min-Soo
    • Journal of the Korean Society for Precision Engineering
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    • v.31 no.7
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    • pp.635-642
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    • 2014
  • The large volume multi-tasking vertical lathe was developed for machining the bearing parts for a wind power generator. Although the machined part is large in size high precision tolerances are required recently. One of the most important components to achieve this mission is the rotating table which holds and supports the part to be machined. The oil hydrostatic bearing is adopted for the thrust bearing and the rolling bearing for the radial bearing. In this article experimental performance evaluation and its analysis results are presented. The rotational accuracy of the table is assessed and the frequency domain analysis for the structural loop is performed. And in order to evaluate the structural characteristic of table the moment load experiment is performed. The rotational error motion is measured as below 10 ${\mu}m$ for the radial and axial direction and 22,800 Nm/arcsec of moment stiffness is achieved for the rotary table.

A Study on the Determination of the Oil Gap in the Hydrostatic Spindle System for a Crank Shaft Grinding Machine (크랭크 샤프트 연삭기용 유정압 스핀들의 유막 간격 선정에 관한 연구)

  • Park, Dong-Keun;Choi, Chi-Hyuk;Lee, In-Jae;Lee, Choon-Man
    • Journal of the Korean Society for Precision Engineering
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    • v.28 no.4
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    • pp.410-415
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    • 2011
  • A cylindrical type of self-controlled restrictor is designed for hydrostatic bearing of crank shaft for a grinding wheel spindle. The effect of operation parameters, clearance between spindle and housing on bearing stiffness are analyzed to determine the optimum conditions of operation parameters. The lowest values of the supply pressure and the loads by the theoretical and experimental results assuming oil film thickness and shape of pocket are compared.

On Nanometer Positioning Control of Ultra-precision Hydrostatic Bearing Guided Feeding Table (초정밀 유정압 베어링 이송 테이블의 나노미터 위치결정 제어에 관한 연구)

  • Shim, Jongyoup;Park, Chun-Hong;Song, Chang-Kyu
    • Journal of the Korean Society for Precision Engineering
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    • v.30 no.12
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    • pp.1313-1320
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    • 2013
  • An ultraprecision multi-axis machine tool has been designed and developed in our laboratory. The machine tool has four moving axes which are composed of three linear axes and one rotational axis. It has a gantry type structure and the Z-axis is on the X-axis and the C-axis, on which a workpiece is located, is inside the Y-axis. This paper shows control performance improving method and procedure for the ultra-precision positioning control of a hydrostatic bearing guided linear axis. Through improvements of electrical and mechanical components for the control system such as control electronics and oil pumping systems, the control disturbing noise is decreased. Also by the frequency domain analysis of control system those problem-making system components are identified and modified with analytical methods. The controller is analyzed and designed from frequency domain data and system information. In the experimental control results the nanometer order control result is successfully presented.

Experimental Verification on the Corrective Machining Algorithm for Improving the Motion Accuracy of Hydrostatic Bearing Tables

  • Park, Chun-Hong;Lee, Chan-Hong;Lee, Husang
    • International Journal of Precision Engineering and Manufacturing
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    • v.5 no.3
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    • pp.62-68
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    • 2004
  • Effectiveness of a corrective machining algorithm, which can construct the proper machining information to improve motion errors utilizing measured motion errors, is verified experimentally in this paper, Corrective machining process is practically applied to single and double side hydrostatic bearing tables. Lapping process is applied as a machining method. The machining information is obtained from the measured motion errors by applying the algorithm, without any information on the rail profile. In the case of the single-side table, after 3 times of corrective remachining, linear and angular motion errors are improved up to 0.13 $\mu\textrm{m}$ and 1.40 arcsec from initial error of 1.04 $\mu\textrm{m}$ and 22.71 arcsec, respectively. In the case of the double-side table, linear and angular motion error are improved up to 0.07 /$\mu\textrm{m}$ and 1.42 arcsec from the initial error of 0.32 $\mu\textrm{m}$ and 4.14 arcsec. The practical machining process is performed by an unskilled person after he received a preliminary training in machining. Experimental results show that the corrective machining algorithm is very effective and easy to use to improve the accuracy of hydrostatic tables.

Finite Element Analysis on the Motion Accuracy of Hydrostatic Table ($2^{nd}$. Analysis and Experimental Verification on Double Sides Table) (FEM을 이용한 유정압테이블의 운동정밀도 해석 (2. 양면지지형 테이블의 해석 및 실험적 검증))

  • Park, Chun-Hong;Lee, Hu-Sang;Kim, Tae-Hyoung;Kim, Min-Gi
    • Journal of the Korean Society for Precision Engineering
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    • v.19 no.1
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    • pp.65-70
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    • 2002
  • An analysis method for calculating motion accuarcy of double sides hydrostatic table is proposed in this paper. In this method, profiles of each rails are assumed as periodic function, therefore it is represented as the sum of spacial frequencies. Bearing clearance at any position rail is depended on the variation of linear, angular motion error of table and the form errors of both sides of a rail. Finite element method is applied to calculate pressure distributions in bearing clearance. In order to simplify the analyzing process, double sides table model is converted into equivalent single side table model. Results calculated by the proposed modeling method agree well with the results directly caculated by double sides modeling method, and also agree well with experimental results. From the theoretical and experimental analysis, it is verified that the proposed analysis method is very effective to analyze the motion accuracy of double sides hydrostatic table.

Analysis of Cylindrical Hydrostatic Bearing (진원형 정수압 베어링의 해석)

  • 문호지;한동철
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1989.11a
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    • pp.94-99
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    • 1989
  • This paper analyzes file stiffness, damping coefficient, friction force and flow coefficient of externally pressurized oil journal beating, including the effect of journal rotation according to the Sommerfeld number. This paper assumed that the oil in the whole pocket has constant pressure, and that the oil in the whole bearing region has constant viscosity, temperature and density. Reynolds equation is derived from Nuvier - Stokes equation and continuity equation. And solved bearing pressure by ADI method for whole bearing region and fitted with out flow rate of pocket region. The model for numerical simulation is hydro - static oil journal bearing for high-speed, high-accuracy lathe spindle.

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Experimental Verification on a Motion Error Analysis Method of Hydrostatic Bearing Tables Using a Transfer Function

  • Park, Chun-Hong;Oh, Yoon-Jin;Lee, Chan-Hong;Joon hee Hong
    • International Journal of Precision Engineering and Manufacturing
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    • v.4 no.2
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    • pp.57-63
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    • 2003
  • A new method using a transfer function was proposed in the previous paper for analyzing motion errors of hydrostatic tables. The calculated motion errors by the new method, named as the transfer (unction method (TFM), were compared with the results by the conventional multi pad method, and the validity of the proposed method was theoretically verified. In this paper, the relationship between rail form error and motion errors of a hydrostatic table is examined theoretically in order to comprehand so-called 'the averaging effect of an oil film', and the characteristics of the motion errors in a hydrostatic table is tested. The tested hydrostatic table has three single-side pads in the vertical direction and three pairs of double-sides pads in the horizontal direction. The motion errors are tested for three rails which have different form errors. The experimental results are compared with the theoretical results calculated by the TFM, and both results show good agreement. From the results, it is shown that the TFM is very effective to analyze the motion errors of hydrostatic tables.

Development of a Multi-Tasking Machine Tool for Machining Large Scale Marine Engine Crankshafts and Its Design Technologies (대형 선박엔진 크랭크샤프트 가공용 복합가공기 기술 개발)

  • An, Ho-Sang;Cho, Yong-Joo;Choi, Young-Hyu;Lee, Deug-Woo
    • Journal of the Korean Society for Precision Engineering
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    • v.29 no.2
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    • pp.139-146
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    • 2012
  • A multi-tasking machine tool for large scale marine engine crankshafts has been developed together with design technologies for its special devices. Since work pieces, that is, crankshafts to be machined are big and heavy; weight of over 100 tons, length of 10 m long, and diameter of over 3.5 m, several special purpose core devices are necessarily developed such as PTD (Pin Turning Device) for machining eccentric pin parts, face place and steady rest for chucking and resting heavy work pieces. PTD is a unique special purpose device of open-and-close ring typed structure equipped with revolving ring spindle for machining eccentric pins apart from journal. In order to achieve high rigidity of the machine tool, structural design optimization using TMSA (Taguch Method based Sequential Algorithm) has been completed with FEM structural analysis, and a hydrostatic bearing system for the PTD has been developed with theoretical hydrostatic analysis.

Structural Characteristic Analysis on the Hydrostatic Guide Way and Feeding System of a High-Precision Centerless Grinder for Machining Ferrules (페룰 가공용 초정밀 무심 연삭기의 유정압 안내면 및 이송계에 대한 구조 특성 해석)

  • Kim, Seok-Il;Park, Chun-Hong;Cho, Soon-Joo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.7
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    • pp.896-903
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    • 2004
  • This paper proposes the structural characteristic analysis and evaluation on the hydrostatic guide way and feeding system of a high-precision centerless grinder for machining ferrules. In order to realize the required accuracy of ferrules with sub-micron order, the axial stiffness and motion accuracy of feeding system have to become higher level than those of existing centerless grinders. Under these points of view, the physical prototype of feeding system composed of steel bed, hydrostatic guide way and ballscrew feeding mechanism is designed and manufactured for trial. Experimental results show that the axial and vertical stiffnesses of the physical prototype are very low as compared with those design values. In this paper, to reveal the cause of these stiffness difference, the structural deformations on the virtual prototype of feeding system are analyzed based on the finite element method under experimental conditions. The simulated results illustrate that the deformation of front ballscrew support-bearing bracket is the main cause of reduction in the axial stiffness of feeding system, and the deflection of bed structure and the bending deformation of hydrostatic guide rails are the main causes of reduction in the vertical stiffness of feeding system.