• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.5
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• pp.1477-1485
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• 1996

Since the spindle bearing systme is the main source of the total cutting point compliance of machine tool structures, in this work, the static and dynamic characteristics of the spndle bearing systme driven by the gear located on the bearing span were investigated using analytical and finite elemtn methods to improve the performance of the spindle bearing system. Based on the theretical results, a specially designed prototype spindle bvearing systme was manufactured. Using the manufactured spindle bearing system, the static and dynamic characteristics were measured. From the comparison of the experimental results with the theoretical results, it was found that the finite elemetn method predicted well the static and dynamic characteristics of the spindle bearing system.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.2
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• pp.203-212
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• 2002

Active magnetic hearings allow much high surface speed than conventional ball bearings and therefore greatly suitable for high speed cutting. This paper describes a design and test of an active magnetic bearing system with 16-pole radial magnets. The spindle is originally designed for a CNC lathe and driven by outer motor with 5.5 kW power and maximum speed 10,000 rpm. Considering static load condition and geometric restrictions, radial magnet is designed 16-pole type for smaller outer diameter of the spindle system. Dynamic system characteristics such as natural frequency, critical speed, stiffness, damping and system stabilities are simulated with a rigid rotor model including direct feedback controller. The designed spindle system is realized with digital PIDD controller to compensate phase lag of PWM amplifier and magnet coils. With levitation and step response experiment the control system characteristics are tested, and the spindle is rotated up to 10,000 rpm stab1y.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.184-185
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• 2008

Modal analysis is an important and essential process in design of a high speed machining center. Generally, modal analysis of a built-in spindle system has not taken the work piece's shape and dimension into consideration. Since small and long work pieces influence greatly the natural frequency of the entire system, the high speed spindle system which continuously makes small machine parts by long work pieces for improvement of machining time has to consider the machining work pieces. Therefore frequency characteristics of the spindle system with long work pieces are studied in this paper.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.15-19
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• 2002

With the rapid development of industrial technologies, the demand for high precision products has been increasing drastically. For this reason, the need for developing of high performance machine tool, which can ensure high precision, is desired in the industrial fields. Technologies on the spindle system manufacture, guideway manufacture, error compensation, design of bed structure, protection against vibrations, and system integration are core technology for developing of high precision machine tools. Especially, among these, design of spindle system, which is leading precision and manufacturing technique. is one of the most important technologies. A high speed and high precision spindle system, which will be used for final machining of ferrule, is designed considering the effect caused by thermal, cutting torque, cutting farce, and work-piece materials. The detail process of analysis is presented.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1003-1007
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• 2003

In order to improve the international competitiveness of ferrule industry, the core technology of the second stage for ferrule grinding system is under developing. A high speed (10,000RPM) and high precision spindle system(Radial Runout 0.2 micrometer) bearing more cutting torque and force is designed considering the limitation of cost and size, the effect of heat, and various work-piece materials. A CAE software for machine elements and general machine system is used for preliminary evaluation and selection of design parameters. A dedicated program for the analysis of spindle system is used for final evaluation and selection of design parameter. The process how to evaluate and select using such tools are presented.

• Journal of Aerospace System Engineering
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• v.8 no.2
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• pp.33-39
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• 2014

Feathering spindle is one of the critical parts of the rotor system in the Smart Unmanned Aerial Vehicle(SUAV) that it was manufactured with special material, Maraging C300. During the initial ground and tie-down flight tests of the SUAV, surface of the feathering spindle contacting to the needle-roller bearings showed excessive wear and dent due to high vibrating loads transferred from the rotating blades. Gas nitriding process was applied to the bearing contact surface of the feathering spindle to increase surface hardness so as to improve the surface defects. This paper briefly presents the gas nitriding process adopted and the spindle quality improvements including wear and corrosion resistance.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.108-114
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• 2007

A new cutting force estimating approach and machining state monitoring examples are presented which uses a cylindrical displacement sensor built into the spindle. To identify the tool-spindle system dynamics with frequency up to 2 kHz, a home-built electro-magnetic exciter is used. The result is used to build an algorithm to extract the dynamic cutting force signal from the spindle error motion; because the built-in spindle sensor signal contains both spindle-tool dynamics and tool-workpiece interactions. This sensor is very sensitive and can measure broadband signal without affecting the system dynamics. The main characteristic is that it is designed so that the measurement is irrelevant to the geometric errors by covering the entire circumferential area between the target and sensor. It is also very simple to be installed. Usually the spindle front cover part is copied and replaced with a new one with this sensor added. It gives valuable information about the operating condition of the spindle at any time. It can be used to monitor cutting force and chatter vibration, to predict roughness and to compensate the form error by overriding spindle speed or feed rate. This approach is particularly useful in monitoring a high speed machining process.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.5
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• pp.1176-1181
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• 1995

Microdrilling is one of the most difficult operations because of the poor chip discharge and the weakness of tool. This study is concerned about the development of a microdrilling monitoring system that is useful for minimizing the tool breakage and enhancing the machinability in the air spindle based microdrilling. The system is composed of a drilling state detection unit and an adaptive step-feed control unit that controls the micro-stepping motor driven spindle axis. Drilling states such as overload, tood breakage are recognized by the change of the air spindle speed which is measured via the reflective photo sensor. Based on the monitoring results, the adaptive step-feed control algorithm adjusts the step increment to keep the decrease of spindle speed within a specified range. The results of evaluation tests have shown that the developed system is very effective to prevent the breakage of microdrill and improves the productivity in comparison with the conventional microdrilling.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.865-868
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• 2005

This paper presents analysis of dynamic characteristics of a high-speed milling spindle with a built-in motor. The spindle system with a built-in motor can be used to simplify the structure of machine tools. to improve tire machining flexibility of machine. tools, and to perform the high speed machining. In this system the shaft is usually assumed as a rigid rotor. In the spindle system design, it is very important to improve modal characteristics, and modal analysis is performed in the first place. Therefore in this paper, on the assumption that supporting bearings of spindle was selected most suitable condition, analyzed dynamic characteristics of a high-speed spindle according to its position. Optimal design was applicated to select most suitable position of bearings. Considered tile mass and stiffness effects of the built-in motor's rotor are analyzed by numerical method. The result shows the natural frequency of 1st bending mode of spindle.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.1
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• pp.119-119
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• 1998

The purpose of this study is to investigate the effects of operation factors of a typical main spindle system on the efficiency of machine tool. In this study. both static and dynamic analysis of typical main spindle system of the machine tool are performed using a finite element method. These finite element results are then used to predict the bearing stiffness. the amount of heat generation as well as the bearing life in the spindle system. Effects of material type of ball-bearing. bearing-lubricant type and main spindle bearing preload are examined.