• 한국생산제조학회지
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• 제13권2호
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• pp.39-44
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• 2004

• 전산구조공학
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• 제36권1호
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• pp.15-23
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• 2023

• 한국생산제조학회지
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• 제20권6호
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• pp.685-691
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• 2011

The Bearing preload units are used for stable rotational movements of high speed spindles. The feeding mechanism of the preload unit is important to prevent overheat of bearings and to keep constant bearing load under thermal deformation of spindle unit. In this study, ball slide guide and ball bush as feeding mechanism of preload unit are selected. The maximum static friction force, radial stiffness and damping ratio of ball slide guide with ball load, ball number and ball size are widely investigated. In conclusion, the surface of ball slide guide must be heat treated to reduce static friction force. The number and size of ball are increased to control sensitive bearing preload force.

• 한국유체기계학회 논문집
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• 제6권2호
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• pp.7-14
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• 2003

This paper describes reliability characteristics of an air foil journal bearing for high-speed turbomachinery at a room temperature. To verify the reliability of air foil journal bearing, lift-off characteristics, load carrying capacity, and 10,000 cycle start-stop test were performed with a motor-driven test rig. A lift-off test shows the relationship between the rotating speed of the shaft and the frictional torque with bearing surface. About a load-carrying capacity, the tested air foil journal bearing produced a load capacity of 500N at an operating speed of 15,000rpm, which is compared with results of numerical analysis and empirical coefficients. Finally, the trends in change of start torque, stop torque, and bearing temperature were shown during a 10,000-cycle start-stop test of an air foil journal bearing. We found that an air foil bearing performs well, as a supported bearing for the high-speed turbocompressor.

• 한국정밀공학회지
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• 제30권8호
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• pp.854-863
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• 2013

High-speed spindle systems typically employ angular contact ball bearings, which can resist both axial and radial loading, and exhibit high precision and durability. We investigated the effects of the arrangement of the angular contact ball bearings on the dynamics of high-speed spindle systems. The spindle dynamics were studied with a number of spindle-bearing models, and the location of the bearings was varied, along with the rotational speed and the preload. A finite element spindle model and a bearing model were used, and simulated data showed that the bearing arrangement significantly affected the spindle dynamics. Furthermore, the main effects were due to the cross coupling terms between the transverse and rotational motions of the ball bearings. The coupling stiffness terms were found to influence the spindle dynamics, depending on the mode shapes. An extensive discussion is provided on the effects of the bearing arrangement on the dynamics of the spindle.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.79-83
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• 2001

A cone-shaped active magnetic bearing spindle system for high speed internal grinding is designed and tested. The cone-shaped AMB system consists of only 4 couples of magnet, it can be smaller and lighter than conventional radial-axial-type AMB system. In this paper, the cone-shaped electromagnets are designed by magnetic circuit theory, and de-coupled direct feedback PID controller is applied to control the coupled magnetic bearings. The designed cone-shaped AMB spindle system is built and constructed with a digital control system, and tested its stbility and dynamic performances. As the results of the tests, this spindle runs up to 40,000 rpm with about 5 ${\mu}{\textrm}{m}$ of runout, and the AMB system provides high damping ratio eliminating overshoot and resonance speed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.24-28
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• 1996

Mirror-like polishing system of hemisphericall high-speed precision bearing for digital VTR drum was developed. Mechamism of the polishing process was analyzed in the view point of polishing contact range and contact length between the tool and the workpiece surface. It was suggested that the two stage polishing process adoptiong the diamond grinding wheel and polishing tool instead of multistage lapping processes, which enables the mass production of the bearing by reduction of polishing time.

• 한국생산제조학회지
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• 제19권6호
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• pp.717-723
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• 2010

Radial stiffness of angular contact ball bearings are decreased remarkably at high speed revolution, because the inner and outer ball contact angle with races arc changed under the ball centrifugal forces at high speed. In the past, the optimizations of spindle units were done under the assumption of unchanged bearing stiffness for the whole speed range. But the bearing stiffness is changed and the dimension of optimum spindle is also changed with speed. In the design phase, only one model of many optimum spindle models with speed should be selected. As optimization criterion, the area of transfer function at spindle nose is proposed to estimate simply and accurately improvement of dynamic characteristics in spindle units. Finally, according to many analyses of diverse spindle models with decreased bearing stiffness, the spindle with shorter bearing span is better than longer bearing span from the viewpoint of dynamic characteristics.

• 한국정밀공학회지
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• 제27권9호
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• pp.94-102
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• 2010

The spindle is the main component in machine tools. To develop high speed machine tools, a lot of studies have been carried out for high speed spindle. Bearing is very important part in spindle. The bearing clearance is influenced by shrink fit and thermal expansion during operation. The designer must take into account the reduction of shrink fits. The aims of this study are to grasp the shrink fits and behavior of a bearing which is a deeply connected with fatigue life of bearing and performance of spindle through FEM(Finite Element Method). This paper proposed optimum value of shrink fit considering deformation of spindle and stress of fitting area using design of experiments. Thus, the proposed formula can be used to obtain bearing internal clearance.

• 한국정밀공학회지
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• 제15권11호
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• pp.233-243
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• 1998

The demand of high speed machining is increasing due to the high speed cutting and grinding provides high efficiency of process, short process time, improved metal removal capacity and better surface finish. Active magnetic bearings allow much high surface speed than conventional ball bearings and therefore greatly suitable for high speed cutting or grinding. This paper describes a design process of an active magnetic bearing system for a high speed grinding spindle with power 5.5kW and maximum speed 60,000rpm. Magnetic actuators are designed by the magnetic circuit theory considering static load condition, and examined with FEM analysis. Dynamic characteristics are also considered, such as bandwidth, stiffness, natural frequency and static deflection. System characteristics are simulated with a rigid rotor model.