• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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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.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.536-542
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• 2002

There are two important variables in machining process control, which are feed and cutting speed. In this work, a two degree-of-freedom controller is designed and implemented to achieve on-line cutting force control and position control based on the modelling of cutting process dynamics which are established through step response test. Two schemes are proposed and implemented. The first is feed control under the constant spindle speed and spindle speed control under the constant feed speed. The second is a simultaneous control of feed and spindle speed. The last performs a position control under the constant cutting force. Those are confirmed to work properly. Especially the latter shows a faster response.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.219-224
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• 2002

There are two important variables in machining process control, which are feed and cutting speed. In this work, a two degree-of-freedom controller is designed and implemented to achieve on-line cutting force control based on the modelling of cutting process dynamics which are established through step response test. Two schemes are proposed and implemented. The first is feed control under the constant spindle speed and spindle speed control under the constant fled speed. The second is a simultaneous control of feed and spindle speed. Those are confirmed to work properly. Especially the latter shows a faster response and we'll be evaluated to pare away workpiece by simultaneous control of position and cutting farce sooner or later.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.4
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• pp.73-80
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• 1993

There and two important variables in machining process control, which are feed and cutting speed. It is possible to improve the machining accuracy and the productivity by maintaining the optimal feed and cutting speed. In this work, a controller is designed to achieve on-line cutting force control based on the modeling of cutting process dynamics established through step response test. Two schemes are proposed and implemented. The first is feed control under the constant spindle speed and the second is spindle speed control under the constant feed. Finally, both are proved to work properly through simulation and experimentation.

• 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.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.5
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• pp.13-19
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• 2011

In this paper, the active monitoring and control system is developed. This system can monitor the status of high the speed spindle in real time during its processing, and can analyze its influence of dimensional accuracy and processing if any, and can control the machining condition to realize the machining system equipped with active monitoring and self-diagnostic features. Machining experiment was performed on 3 materials Al, Brass and S45C in order to derive the relation between active monitoring and control algorithm by the machining load. In addition, we measured surface roughness of processing specimen along with the data change of spindle rotating speed and conveying speed according to variation of machining load. Based on these experiments, we derived relations for each material that can be applied to the control algorithm to allow self control of the rotating speed and conveying speed according to the machining load.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.51-55
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• 2003

In this paper, the authors propose a new high performance Built-in Type spindle motor drive using vector-controlled technique at 15,000 r/min. Control method is changed by variation of motor speed in a conventional Built-in type spindle drive. In the drive system to be presented, the conventional vector control is used in the low-speed range, and the vector control without encoder is used in the high-speed range. Furthermore, in order to drive the motor from 0 to 15,000 rpm smoothly, the vector control with encoder in the low-speed range (from 0 to 8,000 rpm) is utilized and the vector control without encoder in the high-speed range (from 8,000 to 15,000 rpm) is utilized. This paper describes problem of control method in conventional spindle drive and proposes control method as variation of motor speed

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.1
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• pp.28-34
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• 1999

According to the development of tool material and the improvement of machinability of cutting material like aluminium alloy, the higher spindle speed is needed. However, the higher speed causes the heat generation of bearings, the deformation of spindle unit parts, and the rotational accuracy of spindle to be worse. Therefore, it is essential to analyze and control the heat generation and the thermal behavior of spindle unit in order to have higher speed and better rotational accuracy. This paper shows the analogy between the analyzation of heat generation and thermal behavior of high speed spindle system by finite element method and the test results of actual temperature rise through running test, and shows the necessity of cooling the spindle and inner ring side of bearings for the thermal balance of high speed spindle system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.987-992
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• 2000

In a high speed spindle system, it is very important to monitor the operation of the spindle to prevent catastrophic damage to the system. Widely used sensors for monitoring are eddy-current and capacitive types. These sensors provide high accuracy of monitoring, but their steep prices lead to expensive high speed spindle systems. The main goal of our research is to develop technology for producing high speed spindle system utilizing magnetic bearings. As active magnetic bearings require position sensors for feedback control, a noncontact position sensor is being developed as a part of this main goal. Once developed, it will contribute to affordable high speed spindle system. This paper describes the selection process of the sensor types and the design of the driving circuit. We also report the experimental results that characterize the static and dynamic performances of the inductive sensor.

• 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.