• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.5
• /
• pp.59-64
• /
• 1998

In this study, a motor-integrated high-speed spindle system with $\psi$65mm $\times$ 25,000rpm is developed by introducing the oil-jet lubrication method, ceramic angular contact ball bearings, a built-in motor and so on. And oil-jet lubrication experiments fur evaluating the system performance are performed under various operation conditions. Especially, in order to establish the oillet lubrication conditions related to the development of a high-speed spindle system, the effects of oil supply rate and rotational spindle speed are investigated on the temperature rise, temperature distribution, motor current and so on.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2000.04a
• /
• pp.697-703
• /
• 2000

In design step of an active vibration control system, the stability analysis is required for obtaining a stable control region so that the system is protected from it violent natural vibration. This paper describes the procedure of stability simulation for the active magnetic bearing-main spindle of a machine tool. The characteristic equation of the overall system is derived by assembling the dynamic equation of a flexible shaft and the transfer functions of feedback components. And the stable region is obtained by calculating the eigenvalues of the characteristic equation. The simulated control stable region is good agreement by comparing the experiment. Therefore the stable control gain is selected in this paper.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.11a
• /
• pp.304-311
• /
• 2001

This research numerically analyzes the dynamic characteristics of a coupled journal and thrust hydrodynamic bearing due to its groove location which has the static load due to the weight of a rotor in the axial direction and the dynamic load due to its mass unbalance in the radial direction. The Reynolds equation is transformed to solve a plain member rotating type of journal bearing(PMRJ), a grooved member rotating type of journal bearing (GMRJ), a plain member rotating type of thrust bearing (PMRT) and a grooved member rotating type of thrust bearing (GMRT). FEM is used to solve the Reynolds equations in order to calculate the pressure distribution in a fluid film. Reaction forces and friction torque are obtained by integrating the pressure and shear stress along the fluid film, respectively. Dynamic behaviors, such as whirl radius or floating height of a rotor, are determined by solving its nonlinear equations of motion with the Runge-Kutta method. This research shows that the groove location affects the pressure distribution in the fluid film and consequently the dynamic performance of a HDD spindle system.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1996.03a
• /
• pp.47-51
• /
• 1996

Unsteady-state temperature distributions and thermal deformations of a spindle system are studied in this paper. Three dimensional model is built for analysis, and the amount of heat generation of bearing and the thermal characteristic values including heat transfer coefficient are estimated. Temperature distributions and thermal deformations of a model are analyzed using the finite element method and the termal boundary values. Numerical results are compared with the measured data. The results show that thermal deformations and temperature distributions of a high precision spindle system can be reasonably estimated using the three dimensional model and the finite element method.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.1
• /
• pp.238-244
• /
• 2017

A spindle with a built-in motor can be used to simplify the structure of a machine tool system, but the rotor inevitably has unbalanced mass. This paper presents an analysis of the dynamic behavior. The spindle was used in a CNC lathe and investigated using the finite element method and transfer matrices. The high-speed spindle can be very sensitive to the rotation of an unbalanced mass, which has a harmful effect on many machine tools. Thus, a balancing procedure was performed with a spindle-bearing system for the CNC lathe by numerical analysis. The balancing was performed through the influence coefficient method, and the whirl orbit radii before and after balancing were compared to evaluate the effects. The results show that the rotational speed of the spindle seriously affects the whirl responses of the spindle. The whirl responses were also affected by other factors, such as the unbalanced mass and bearing stiffness. The balancing of the assembled spindle model significantly reduced the whirl orbit magnitude.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.6 no.1
• /
• pp.43-49
• /
• 2007

Multi-function and miniaturization of the medical equipment and tele-communication systems need small and high precision machined parts. For the economic machining of the small size workpiece it should be machined by small and high precision machine tools with high speed machining. The belt type driving system in turning lathe has a limitation of spindle speeds because of the vibrations from driving mechanism, built-in type of driving mechanism is used to reduce the vibration. However, the main spindle of the built-in motor is connected directly to the motor, so the heat generation of the motor and bearing makes bad influence of the accuracy of machine tools. In this study, the analysis of heat generation from motor and bearings supporting main spindle and experiment were carried out. The results of theoretical simulation of temperature and deformation of the main spindle are good agreement with those of measured.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.05a
• /
• pp.748-752
• /
• 2004

Fluid dynamic bearings (FDBs) have been replacing ball bearings of the HDD spindle motor very rapidly. But there are several demerits of HDB, such as high friction torque, variable viscosity of the fluid lubricant depending on operating temperature, low stiffness, and etc. Eccentricity is one of the major parameters which affects the static and dynamic characteristics. As the static eccentricity is larger, the stiffness and the damping coefficients become bigger. But friction torque is relatively unaffected by the static eccentricity. This research proposes a new type of journal bearing with asymmetric journal grooves which results in better dynamic characteristics. The static and dynamic characteristics of the new journal bearing are investigated by solving the Reynolds' equation with FEM, and the transient analysis is performed to predict the dynamic behavior of rotor by solving the equations of motion of a HDD spindle system with Runge-Kutta method. The result shows that the proposed Journal bearings have much bigger stiffness and damping coefficients compared with the conventional symmetric ones. And consequently, it has smaller whirl radius and tilting angle.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2003.10a
• /
• pp.131-136
• /
• 2003

Five expensive sensors are necessary to control a magnetic bearing system. The sensor price rate of magnetic bearing system is high. So it is necessary that cheap and good sensor is developed. The optical fiber displacement sensor is adaptive to satisfy this condition. We can design magnetically suspended spindle based on static characteristic of optical fiber displacement sensor developed. The controller can be designed by decoupled feedback PD. Therefore, it is simpler than any other controller comparatively.

• Proceedings of the KIEE Conference
• /
• 2003.07b
• /
• pp.1039-1041
• /
• 2003

There are many advantages of the Magnetic Bearing system, compared with conventional contacting bearing systems. Since the spindle in the Magnetic Bearing system is levitated by electro-magnetic forces and rotates without mechanical friction, it can run without lubrication. So, it can run in the extreme circumstances, e.g. a vacuum condition in the space.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.05a
• /
• pp.530-532
• /
• 2002

This paper presents an optimum design of herringbone grooved journal bearing for spindle motor of hard disk drive (HDD) system. In addition to the conventional “rectangular” groove, various groove profiles are designed. The stiffness and damping coefficients of the oil film and frictional torque are calculated and compared for tile various groove profiles. The “circular”, “valley”, and “reversed saw tooth” grooves do not produce high direct stiffness, since they partly increase the groove depths in the direction of lubricant flow, causing to reduce the pumping action of the bearing. The maximum direct stiffness can be obtained by the “rectangular”, “saw tooth”, and “step” grooves. With the same cross sectional area of the grooves, these three grooves have the same maximum stiffness, damping coefficients, and frictional torque. Among these recommendable grooves, the saw tooth groove may keep its original profile for long, enduring metal-to-metal contact during startup and shutdown.