• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 Handout for 2000 Inter. Machine Tool Technical Seminar
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• pp.109-115
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• 2000

The spindle unit is core parts in high precision machine tools. Diverse static, dynamic and thermal charateristics of spindle unit are needed for special purpose of machine tools. Compromise between those charateristics will be done in concept design phase. High static stiffness at spindle nose may be very important performance for heavy cutting work. High dynamic stiffness is also useful to high precision and high speed machine tools. Improvement of thermal charateristics in spindle lead to high reliability of positioning accuracy. For high speed spindle structure, the design parameter such as, bearing span, diameter, bearing type and arrangement, preload, cooling and lubrication method should be in harmony.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
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• pp.227-230
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• 1999

In this paper, the machining characteristics of high speed ball end milling affected by the rotational error of high speed spindle using air bearing are investigated. The error motions of a spindle have generally influenced on the surface roughness, the form accuracy, the tool life, etc. in end milling. Experiments are carried out over a wide range of rotational speeds(10,000-50,000rpm). The rotational errors of the spindle are measured by the gap sensor mounted on the spindle shaft at various cutting speeds. The relations between the surface roughness and the spindle error motion are presented. Results show that the rotational accuracy of the spindle directly affects the surface roughness of the machined surface.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.985-988
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• 2002

The Spindle-]fearing System is very important unit for geometrical accuracy in machine tools. To improve effectively the weak point of spindle system, it is necessary that the contribution ratio of spindle core parts to static and dynamic stiffness is clarified. In this paper, static contribution ratio of core parts is calculated by overlapping static deformation of basic spindle design with one flexible parts. The dynamic contribution ratio for natural frequency and dynamic deformation at spindle end is obtained by calculating correlation between original and basic spindle deformation, by curve fitting with regressive method. It is proved the validity of estimation result is correct.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.18-23
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• 2002

In this paper, The torque of CNC spindle motor during machining is estimated without speed measuring sensor. The CNC spindle system is divided into two parts, the induction spindle motor part and mechanical part. In mechanical part the variation of the frictional force due to the increment of the cutting torque and the effect of damping coefficient is investigated. Damping coefficient is found to be a function of spindle speed and not influenced by the weight of the load, while frictional force is a function of both the cutting torque and spindle speed. Experimental formulars are drawn for damping coefficient as a function of spindle speed and frictional force as a function of both cutting torque and spindle speed respectively, to estimate the cutting torque accurately. Graphical programming is used to implement the suggested algorithm, to monitor the torque of an induction motor in real time. Torque of the spindle induction motor is well monitored with 3% error range under various cutting conditions.

• 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.

• 한국소음진동공학회논문집
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• 제19권3호
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• pp.261-267
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• 2009

The spindle with a built-in motor can be used to simplify the structure of machine tool system, while the rotor has unbalance mass inevitably. Therefore, it is important to recognize the effect of unbalance mass. This paper presents analysis of dynamic behavior of a high speed spindle with a built-in motor. The spindle is supported by the angular contact ball bearings and the rotor is fixed at the middle of spindle. The spindle used in CNC automatic lathe has been investigated using combined methodologies of finite elements and transfer matrices. The Houbolt method is used for the integration of the system equations and the dynamic behavior of spindle is obtained considering unbalance mass of rotor. Results show that increasing rotational speed of spindle magnifies the whirl responses of spindle seriously. Also the whirl responses of spindle are affected by the other factors such as unbalance mass and bearing stiffness.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3156-3161
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• 2007

In the field of yarn dyeing, the most generally employed method is a type of package dyeing which uses a package of cheeses stacked on a spindle made of a perforated tube. In order to understand the process of level dyeing, it is essential to perform a study of the porous flow through the spindle for the cheese dyeing method. In this paper, the axisymmetric, incompressible, Navier-Stokes equations are solved for several spindle configurations using a fully implicit finite volume scheme. For investigating the flow patterns through the spindle, porous diameter and porosity is varied in the present study. The computational results show that the total pressure loss depends only on the velocity of inflow regardless of porous diameter and porosity and a large percentage of the mass flow rate through the spindle is discharged at the upside of the spindle. Therefore, it is required to design a new spindle to obtain the level dyeing.

• 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.

• International Journal of Precision Engineering and Manufacturing
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• 제4권5호
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• pp.15-21
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• 2003

In order to improve the quality of a spindle unit it is important to increase its rotational accuracy. The rotational accuracy of a spindle unit can be defined as the stability or immobility of its spindle axis while rotating. Spindle rotation in the rolling bearings causes the disturbing influence, which leads to the oscillation of a rotation axis. The purpose of this study is to investigate the oscillation sources and find a way to decrease the runout without additional expenses. The main source of oscillation is the interaction between rolling bodies and ring races. The first oscillation source was the out-of-shape imperfection of inner bearing ring. The mutual compensation of oscillation by proper rings orientation was proposed, which sometimes allow to decrease the radial runout of spindle rotation axis by approximate 40％ down. Also the outer ring harmonics were explored as the second oscillation source. The analysis shows the dependency between the number of rolling bodies and the outer ring race harmonics. The conclusion on the orientation of bearing cages and the bearing rings was made, which makes possible to obtain the optimal variant of their mounting in the spindle unit when the rotational accuracy of the spindle is maximal, and the spindle runout considerably less.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.995-999
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• 1995

In spindle-bearing system, the displacement characteristics of the bearing by the load applied on the spindle are affected greatly by the assembling tolerance between the spindle and housing assembled to support the bearing. Also in spindle system of rotational operation, the compliance characteristic of the bearing is expected to be varied frequently by the thermal deformation of the spindle and the housing. To predict the thermal deformation of the spindle including heat generation of the bearing, we need to examine the effect on the compliance of spindle-bearing system by the assembling tolerance. In this paper, we proposed the load-displacement relation expression considering the effect which the variation of contact pressure due to the radial directional assembling tolerance between the bearing and the housing influences on the axial and radial directional displacement characteristics of the bearing. Furthermore, for several assembling systems of bearings and housings having all different assembling tolerances, we proposed a method to predict exactly the variation of the bearing preload which is sensitive to the thermal deformation by showing the propriety with experimental results.