• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.10 s.241
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• pp.1416-1429
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• 2005

In order to meet the increasing competitive pressures coupled with higher demands for component quality, whirling machines have been at the cutting edge of the automobile industry for more than 25 years. The hard whirling process can save on machining time and operation elimination. Hard whirling is done dry, without coolant. The chips carry away nearly all of the heat during cutting, leaving the workpiece cool and minimizing any thermal geometry variations. The surface finish and profile accuracy are close to grinding quality. Whirling machines usually consist of four major parts; 1) loading system that requires the necessary axial speeds, 2) head stock that needs high precision clamping and positioning system at the chuck and tailstock, 3) whirling unit that demands the high cutting speeds and cutting power fer cutting deep thread profiles and 4) unloading system that requires an easy workpiece unloading. Also, capabilities of the whirling machine can be improved by attaching a vision system to the machine. Most of whirling machines in Korean automobile industry are imported from the Leistritz company, Germany and the Hasegawa company, Japan. Tn this paper, a basic research will be performed to improve and enhance the existing whirling machines. Finally, a new Korean whirling machine will be proposed and developed.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.1
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• pp.8-14
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• 2013

This paper intends to provide the whirling characteristics of an asymmetric rotor-shaft system with a non-ideal DC motor. The equations of motion have been derived in terms of system parameters such as the internal/external damping, the asymmetry and the motor voltage. By imposing the conditions that the motor input power should be balanced by the dissipated power, steadystate whirling characteristics are obtained such as the whirling amplitude, the whirling frequency and the stability diagrams. Results show that the whirling stability is affected by the internal/external damping and the asymmetry as well as the motor voltage. Also, the whirling amplitude at the steadystate is increased and the motor speed is lowered as the internal damping becomes higher or the external damping is reduced. In addition, the asymmetry causes the variation of the whirling orbit, which becomes splitted into two distinct trajectories. Finally, non-ideal characteristics of the DC motor is found to reduce the whirling motion in case of steadystate whirling with high asymmetry and high internal damping.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.10
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• pp.44-51
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• 2020

We studied the heating characteristics of a whirling spindle. This spindle is an important component of a whirling machine for turning a ball screw shaft. In the manufacturing process for a conventional ball screw shaft, a single tool is used to form a spiral in a lathe machine tool. Thereafter, a high-frequency heat treatment process is performed. Recently, a whirling-type cutting method has emerged. This method can perform hard turning in the rotating direction of the spiral portion of the ball screw shaft by rotating and mounting multiple tools. The whirling method can be applied to the heat-treated material. In this study, an experimental apparatus was constructed to analyze the whirling spindle. The experiment proceeded in four steps. The rotating speed of the whirling spindle was set to ISO random and sequential rising conditions. Cooling and non-cooling modes in the cooling jacket were tested. As a result of the above experiment, the heating characteristics of the whirling spindle were derived.

• Journal of the Korean Society for Precision Engineering
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• v.34 no.3
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• pp.173-178
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• 2017

Recently, a high-precision ball screw is an essential part of high-speed machines. However, producing high-precision ball screws has been costly and time-consuming. Nowadays, a whirling machine is used to produce high-precision ball screws efficiently. Rotating multi-tips are used to turn the ball screw in the whirling machine. In this study, a structural analysis was performed by a finite-element method to develop a whirling machine. An improved model of the whirling machine was proposed by the analysis. In addition, a thermal analysis was performed to confirm the thermal stability. The results of the analysis can be applied in order to further develop the whirling machine.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.527-532
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• 2011

Whirling vibration in severe cases may result in shaft cracking and typically gap sensors are utilized to confirm its values under the outside underwater of ship. The bending stress value causing whirling vibration on the propulsion shafting system of a 40-ton small vessel was verified by theoretical analysis and its vibration measurement. However, because of underwater condition, the accuracy for this measurement method is presumed low. In this study, the strain gauge basic principle and the bending stress calculation method are considered. The relationships are then applied for obtaining the whirling vibration of the 40-ton small vessel. As a result, a new method in estimation of whirling vibration is reached and suggested.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.579-585
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• 2003

This paper investigates the whirling, tilting and flying motion of a HDD spindle system supported by FDB experimentally. Experimental setup is built to measure the flying, whirling and tilting motion of the HDD spindle system, and three capacitance probes fixed on the xyz-micrometers measure the displacement of a HDD spindle system in the xyz-directions. This research shows that the tilting and whirling motion is mostly dependent on the centrifugal force and the gyroscopic moment due to the unbalanced mass of a HDD spindle. It also shows that the rotating HDD spindle starts to float to the equilibrium position in the z-direction until the weight of the rotating spindle is equal to the supporting pressure generated in the upper and lower thrust bearing.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.271-272
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• 2007

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.143-148
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• 2001

Relatively high rotating speed propulsion shafting system of the large Ro-Ro Ferry has a greate risk of the resonance of the whirling vibration within the operating speed range. Therefore, it is necessary to control the whirling vibration characteristics of the shafting system in the initial design stage so as not to be resonant with the blade number order excitation in the normal operating speed range. The results of the whirling vibration analysis for l000P Ro-Ro Ferry with SHI's in-house program and the measured results during the sea trial are introduced. Additionally the outline of the program and the calculation method of the major properties are presented.

• International Journal of Fluid Machinery and Systems
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• v.4 no.2
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• pp.217-222
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• 2011

The rotordynamic fluid forces acting on a closed type impeller in whirling motion were measured and the influence of the clearance geometry on the stability of the impeller was examined. At small positive whirling speed, the rotordynamic forces acted as destabilizing forces for all casings. A small clearance between the shroud of the impeller and the casing caused large fluid force, but did not change the destabilizing region. Radial grooves in the clearance were effective for reducing the fluid forces and destabilizing region due to the reduction of the circumferential velocity without the deterioration of the pump performance. A rotating phenomenon like a rotating stall of the impeller occurred at low flow rate and the resonance between it and the whirling motion led to a sudden increase in force at the whirling speed ratio of 0.7.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1879-1882
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• 2005

Due to increase of demands on safety and convenience for automotive vehicle, the use of DC motor, such as power window, seat adjusting, pedal adjusting, sunroof, electric shift motor and so on, is increasing rapidly in the whole world. Worm gear is an important part to transmit torque to another gear in gear mechanism of automotive DC motor. But with current forming process, it has some problems in manufacturing and the quality. Also, the characteristics of automotive parts such as price and mass-production limit the quality improvement. Recently several methods are used in order to reduce a worm screw machining time and to maintain precision. In this paper, we introduce whirling tool machining and side milling cutter machining as effective manufacturing method of worm screw and study on the cutting force of side milling cutter and whirling tool in worm screw machining.