• 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.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.1045-1049
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• 1995

This paper proposes the state-space model of the thermal behavior of the spindle system to establish dynamic mathematical model of thermal characteristics in machine tool spindle system. the model is derived form physical law of heat transfer and thermoelasticity and represents the thermal behavior induced by uneven thermal expansions whitin a bearing. The model, which is sucessfully validated for two typical configurations of high speed spindle assembles, provides a tool for understanding the basis mechanics of induced thermal expansion as a function of initial preload, spindle speed and housing cooling conditions.

• 연구논문집
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• 통권27호
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• pp.127-139
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• 1997

투포원 연사기는 스핀들 1회전에 2회의 꼬임을 부가하여 실의 신축성과 인장강도 및 내마모성을 증가시키며, 특수한 목적의 의장사를 만드는 섬유기계이다. 스핀들 유니트는 고속 회전중에 안정화된 운동이 지속되도록 구조설계가 요구되는 핵심장치로서 스핀들 유니트의 동특성 해석은 고속 스핀들 유니트설계의 최적화를 도모할 수 있을 것이다. 스핀들 유니트는 블레이드와 로타리 디스크로 구성되어 있으며, 스핀들 축에 대하여 회전체 형상을 유지 하고 있다. 동특성 해석을 수행하기 위하여 전달 매트릭스 해석법을 정의하고 해석용 프로그램인 SPINDLE을 이용하여 비틀림과 굽힘 고유진동수를 해석하였으며, 운전회전수에서 변위모우드를 분석하였다.

• 한국산업융합학회 논문집
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• 제3권2호
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• pp.115-121
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• 2000

This paper presents reducing method of profile error on a mechanical tuning for multi-spindle control of NC machine tools. To reduce the profile error in the feed drive system, it is useful to adopt same transfer function of multi spindle machine tools. By selecting the correction vector of servo rigidity and natural vibration on JK map, multi spindle control can be tuned by mechanical parameters with small profile error.

• 한국정밀공학회지
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• 제15권12호
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• pp.188-193
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• 1998

This paper describes static and dynamic weak point analysis of spindle systems to eliminate high concentrated bending point on spindle and improve total stiffness of spindle systems. The weak point analysis is based on the evaluation of bending curves of spindles. For static weak point analysis the bending curve is derived from static deflection curve and for dynamic weak point analysis it is derived from the mode shape curves in consideration of the transfer function at exciting point. The validity of the weak point search methodology is verified by comparison of the static deflection, the natural frequency and the dynamic compliance between the original and the improved spindle.

• 한국정밀공학회지
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• 제13권10호
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• pp.139-145
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• 1996

The machining accuracy and performance is largely influenced by the static, dynamic and thermal characteristics of spindle systems in machine tools, because the spindle system is a intermedium for cutting force from tool and machine powef from motor. Large cutting force and power are transmitted by bearing with a point or line contact. So, the spindle system is the static and dynamic weakest point in machine structure. For improvement of static stiffness of spindle system can be changed design parameters, such as diameter of spindle, stiffness of bearing and bearing span. But for dynamic stiffness, the change of the design parameters are not useful. In this paper, the combined bearing arrangement is suggested for high damping spindle system. The combined bearing arrangement is composed of tandem double back to back arrangement type ball bearins and a high damping hydrostatic bearing. The variation of static deflection and amplitude in first natural frequency is evaluated with the location of hydrostatic bearing between front and rear ball bearing. The optimized location of hydrostatic bearing for high static and dynamic stiffness is determined rapidly and exactly using the mode shape and transfer function of spindle. The calculation of damping effect on vibration by unbalance of grinding wheel and pulley in optimized spindle system is carried out to verify the validity of the combined bearing arrangement. Finally, the simulation of grinding process show that the surface roughness of workpiece with high damping spindle system is 60% better than with ball bearing spindle system.

• 한국생산제조학회지
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• 제22권4호
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• pp.735-739
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• 2013

The error motion of a machine tool spindle directly affects the surface errors of machined parts. Spindle motion errors such as three translational motions and two rotational motions are undesirable. These are usually due to the imperfectness of bearings, stiffness of spindle, assembly errors, and external force or unbalance of rotors. The error motions of the spindle need to be reduced for achieving the desired performance. Therefore, the level of error motion needs to be estimated during the design and assembly process of the spindle. In this study, an estimation method for five degree-of-freedom (5 DOF) error motions for a spindle with an angular contact ball bearing is suggested. To estimate the error motions of the spindle, the waviness of the inner-race of bearings and an external force model were used as input data. The estimation model considers the geometric relationship and force equilibrium of the five DOFs. To calculate the error motions of the spindle, not only the imperfections of the shaft and bearings but also driving elements such as belt pulley and direct driving motor systems are considered.

• 한국정밀공학회지
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• 제32권2호
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• pp.127-133
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• 2015

The error motion of a machine tool spindle directly affects the surface errors of machined parts. Those are usually due to the imperfectness of bearings, stiffness of spindle, assembly errors, external force or unbalance of rotors. The error motions of the spindle have been needed to be decreased to desired goal of spindle's performance. The level of error motion is needed to be estimated during the design and assembly process of the spindle. In this paper, the estimation method for the five degree of freedom (5 D.O.F) error motions for rotary units such as a spindle and rotary table are suggested. To estimate the error motions of the rotary unit, waviness of bearings and external force model were used as input data. The estimation model considers geometric relationship and force equilibrium of the five degree of the freedom motions.

• 한국정밀공학회지
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• 제28권3호
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• pp.285-291
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• 2011

The error motion of a machine tool spindle directly affects the surface errors of machined parts. The error motions of the spindle are not desired errors in the three linear direction motions and two rotating motions. Those are usually due to the imperfect of bearings, stiffness of spindle, assembly errors, external force or unbalance of rotors. The error motions of the spindle have been needed to be decreased to desired goal of spindle's performance. The level of error motion is needed to be estimated during the design and assembly process of the spindle. In this paper, the estimation method for the five degree of freedom (5 D.O.F) error motions of the spindle is suggested. To estimate the error motions of the spindle, waviness of shaft and bearings, external force model was used as input data. And, the estimation models are considering geometric relationship and force equilibrium of the five degree of the freedom. To calculate error motions of the spindle, not only imperfection of the shaft, bearings, such as rolling element bearing, hydrostatic bearing, and aerostatic bearing, but also driving elements such as worm, pulley, and direct driving motor systems, were considered.

• 한국정밀공학회지
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• 제15권6호
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• pp.145-152
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• 1998

This paper presents an optimum design of a rotor-bearing spindle system for a ultra centrifuge (80,000 RPM) supported by ball bearings with nonlinear stiffness characteristics. To obtain the nonlinear bearing stiffnesses, a ball bearing is modeled in five degrees of freedom and is analyzed quasi-statically. The dynamic behaviors of the nonlinear rotor-bearing system are analyzed by using a transfer-matrix method iteratively. For optimization. we use the cost function that simultaneously minimizes the weight of a rotor and maximizes the separation margins to yield the critical speeds as far from the operating speed as possible. Augmented Lagrange Multiplier (ALM) method is employed for the nonlinear optimization problem. The result shows that the rotor-bearing spindle system is optimized to obtain 9.5％ weight reduction and 21％ separation margin.