• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.398-403
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• 2004

The demand of high speed machining is increasing because the high speed cutting providers high efficiency of process, short process time, improved metal removal capacity and better surface finish. Active magnetic bearings allow much high surface speed than conventional ball bearings and therefore greatly suitable for high speed cutting. The automatic control concept of magnetic bearing system provides ability of intelligent control of spindle system to increase accuracy and flexibility by means of adaptive vibration control. This paper describes a design and development of a milling spindle system which includes built-in motor with power 5.5㎾ and maximum speed 70,000rpm, HSK-32C tool holer and active magnetic bearing system. Magnetic actuators are designed for satisfying static load condition. The Performances of manufactured spindle system was examined for its static and dynamic stiffness, load capacity, and rotational accuracy. This spindle was run up to 70,000 rpm stably, which is 3.5 million DmN.

• 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 2000년도 춘계학술대회 논문집
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• pp.922-925
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• 2000

Generally, the machining accuracy in ball end milling directly depends on the rotational accuracy affected by the spindle speeds. The effects of spindle speeds for rotational accuracy in the high speed regions are more dominant than those in the low speed regions. This paper will investigate effects that the Increased speed affects on the rotational error according to the increase of a rotational speed and machining characteristics of the high speed ball-end milling in various rotational speeds and on various materials by using the high speed air-bearing spindle.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 Handout for 2000 Inter. Machine Tool Technical Seminar
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• pp.51-60
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• 2000

High-speed milling machine is being sold mainly in the market of die and mold industries, because it reduces machining time greatly as proportion to the spindle speed of machine tool. From the experimental milling tests, it has been cleared that the ball end mill is quite suitable for high speed milling and also tool wear reduces in higher speed milling condition. And a new milling concept with ultra high speed over 100, 000 rpm is proposed for solving the various problems such as NC cutter path generation and NC feed conformity etc.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1640-1643
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• 2005

This paper presents analysis of dynamic characteristics of a high-speed milling spindle with a drawbar and a built-in motor. The spindle system with a built-in motor can be used to simplify the structure of machine tools, to improve the 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 this paper, the modal characteristics of drawbar in high-speed milling spindle system due to supporting stiffness between drawbar and shaft and considering the mass and stiffness effects of the built-in motor's rotor are analyzed by numerical method. The result shows enough stiff supports must be provided between shaft and drawbar to prevent occurring drawbar vibration lower than the natural frequency of 1st bending mode of spindle. And considering the mass and stiffness of built-in motor's rotor is important thing to derive more accurate results.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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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.

• 한국정밀공학회지
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• 제16권9호
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• pp.62-67
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• 1999

In milling, cutting tool ins directly attached to spindle and this tells that spindle can provide very useful information on the cutting tool condition such as wear or breakage. Since spindle is rotating at a high speed, measuring spindle velocity using a noncontacting measurement system gives the best information which can be obtained. Due to the force applied to spindle through cutting tool, velocity of spindle changes. And any change in cutting tool condition affects cutting force and consequently spindle vibration. With the intent of continuously monitoring cutting tool condition in intermittent machining operations in a benign manner, a noncontacting velocity measurement system using a laser Doppler velocimeter was assembled to measure spindle torsional vibration. Spindle vibration was measured and analysis of it in the frequency domain yielded a measure which corresponded to amount of cutting tool wear in milling.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.484-487
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• 2003

In designing AMBs (active magnetic bearings) for high-speed spindle system, the shaft is usually assumed as a rigid rotor. For automatic tool change process, there should be a tool clamping system with drawbar using spring or hydraulic force, and the drawbar in the spindle can be in various condition of support during design and manufacturing error. In this paper, the modal characteristics of drawbar in high-speed milling spindle system due to supporting stiffness between drawbar and shaft are analyzed by numerical method. The result shows enough stiff supports must be provided between shaft and drawbar to prevent occurring drawbar vibration lower than the natural frequency of 1$\^$st/ bending mode of spindle.

• 대한기계학회논문집A
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• 제24권7호
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• pp.1681-1688
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• 2000

A dynamic model for the prediction of surface topography in high speed end milling process is developed. In this model the effect of tool runout, tool deflection and spindle vibration were taken in to account. An equivalent diameter of end mill is obtained by finite element method and tool deflection experiment. A modal parameter of machine tool is extracted by using frequency response function. The tool deflection, spindle vibration chip thickness and cutting force were calculated in dynamic cutting condition. The tooth pass is calculated at the current angular position for each point of contact between the tool and the workpiece. The new dynamic model for surface predition are compared with several investigated model. It is shown that new dynamic model is more effective to predict surface topography than other suggested models. In high speed end milling, the tool vibration has more effect on surface topography than the tool deflection.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.321-325
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• 2000

To obtain precise surface and high productivity, high speed end milling has been studied recently. Though high speed end milling is explicitly effective for precision surface generation geometrically, tool deflection, chatter vibration and frequency characteristics of end milling system deteriorate the theoretical surface. In this study, simulation algorithm and programming method are suggested to simulate machined surface using acceleration signal in high speed end milling. This simulation is conducted by considering vibrational effect of spindle system which was not considered by other researchers. Between simulated results and experiment results, good agreements were obtained.