• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.4
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• pp.38-43
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• 2010

By generating 2-directional vibration in a xy plane of workpiece table, a newly developed micro drilling using 2-directional vibration was carried out. The vibration was produced by applying sinusoidal voltages to the orthogonally arranged piezoelectric materials built in the workpiece excitation table. Through the micro-drilling experiments using poly-carbonate and brass material, it was found that micro drilling using 2-directional vibration in a workpiece table could be an efficient method to enhance the form accuracy of machined workpiece by suppressing burr formation at both entry and exit region. A higher form accuracy could be obtained by increasing stiffness of feeding mechanism, decrease of geometric tolerance of combining jig, and development of high performance excitation table which generates amplified vibration at higher frequency.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.9
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• pp.95-103
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• 1995

Recently the trends toward reduction in size of industrial products have increased the application of micro drilling. But micro drilling has still much difficulty so that the needs for active control which give adaptation to controller are expanding. In this paper initial cutting condition was determined for some sorkpieces by experiment and GA-based Fuzzy controller was devised by genetic algorithms and fuzzy inference. The fuzzy inference has been applied to the various prob- lems. However the determination of the membership function is one of the difficult problem. So we introduce a genetic algorithms and propose a self-tuning method of fuzzy membership function. Based on this intelligent control, automation of micro drilling was carried out like the cutting process of skilled machinist.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.1
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• pp.22-28
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• 1995

Micro Drills have found ever wider application. However micro drilling is a machining to integrate the difficult machinablities such as tool stiffness, position control and revolution accuracy, and is known to cost and time consuming. So, this study aimed to practice ultraminiature drilling(0.05 .phi. ) wiht simple component, if possible. System is developed as the three modules : feed drives, spindle and monitoring part. The dynamics of measured current signals from the spindle of Micro Hole Drilling machine are investigated to establish the criteria of stepfeed mechanism. Cutting experiments identify the relationship of spindle rpm, feed rate and tool life. The smaller drill diameter is, the more suitable cutting condition have to be selected because of chip packing.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.3 s.168
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• pp.15-20
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• 2005

This paper describes the PCB drilling using an ultra high-speed air bearing spindle system and micro drill. For this research, we have developed the ultra high-speed air bearing spindle of 125,000 rpm and made an experiment for the application possibility in the PCB drilling. In order to estimate the drilling performance, we have investigated the size and damage of drilled hole, and the wear of drill at 90,000rpm. Results are as follows; we have confirmed the possibility in the PCB drilling of air bearing spindle. In case of micro-drilling PCB at $0.1mm\sim0.3mm$, the increase in the number of drilling has resulted in a bigger size of holes and also a bigger size of damage. It has been found that the wear of micro drill tends to concentrate in the main cutting edge.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.12
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• pp.171-178
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• 2002

With increasing the needs for micro and precision parts, micro machining technology using micro tools has been studied to fabricate a small part with high density such as electronics, optics, communications, and medicine industry more than before. Though these micro tools have developed rapidly, it is difficult to apply them to micro fabrication technologies, because of the inherent manufacturing. In this study, micro tools (WC) to produce micro structures and parts were manufactured by cylindrical grinding machine employing ELID (Electrolytic In-process Dressing) technique and the micro tools are fabricated as square shape with the dimension less than 100${\mu}{\textrm}{m}$. With the micro tools on the same machine, characteristics of micro grooving and drilling are evaluated. Also we compare normal micro machining with ultrasonic micro machining on the vibration table. It is confirmed that the developed micro tools are fully applicable to micro grooving, micro drilling and free form cutting.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.12
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• pp.46-53
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• 1996

Micro drilling is one of the most important machining types and its necessity becomes more and more increasing in the whole field of industry. Micro drilling, however, has few the case of practical application, because it requests high techniques : manufacturing micro drill, treating chip, producting precise hole shape and progressing machining effeciency. Micro drilling has a technical problem: drill breakage from the lack of drill rigdity and the interuption of chip. It is, therefore, essential to select the proper cutting conditions and the step fed for the method solving the lack of rigidity and the interruption of chip. Especially, step feed is very efficient to avoid the breakage of drill, but bring about reducing of cutting efficiency. The study on step feed must be requested more than the present in the near future. The purpose of this paper is to investigate experimentally about cutting conditions which affect on tools and round errors and to estimate about the effect of step feed as well as optimal step feed size to solve the breakage of drill.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.264-268
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• 2003

Recently reduction of industrial products in size and weight has been increased by application of micro-drills in gadgets of high precision and a great interest of a micro-drilling has been raised. Due to the lack of tool stiffness and the chip packing, the micro-drilling requires not only the robust tool structure which has not affected by vibration but also effective drilling methods designed to prevent tool fracture from cutting troubles. This paper presents an optimum design shape of a 0.15 mm micro-drill associated with a new manufacturing process to improve the production rate and to lengthen the tool life and suggestions on the micro-drilling characteristic properties associated with the tool life and workpiece quality.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.1 no.1
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• pp.109-116
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• 2002

Resently, reduction of industrial products in size and weight has increased by the application of micro-drill for gadgets of high precision and gave rise to a great interest in a micro-drilling. Due to the lack of tool stiffness and the chip packing, micro-drilling requires not only the robust tool structure which has not affected by the vibration, but also the effective drilling methods designed to prevent tool fracture from cutting troubles. Firstly, this paper presents a new manufacturing process of micro-drill for improving the product rate and an optimum shape of micro-drill for lengthening the tool life, and secondly suggests between tool life and drilling torque acquired in the inprocess monitoring system.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.3
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• pp.133-140
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• 2004

Recently reduction of industrial products in size and weight has been increased by application of micro-drills in gadgets of high precision and a great interest of a micro-drilling has been raised. Due to the lack of tool stiffness and the chip packing, the micro-drilling requires not only the robust tool structure which has not affected by vibration but also effective drilling methods designed to prevent tool fracture from cutting troubles. This paper presents an optimum design shape of a 0.15 mm micro-drill associated with a new manufacturing process to improve the production rate and to lengthen the tool life and suggestions on the micro-drilling characteristic properties associated with the tool life and workpiece quality.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.3 s.96
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• pp.47-52
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• 1999

Theoretical and experimental studies on burr formation and deburring in many manufacturing processes have been actively pursued. Though micro-drilling has become more important in the production of precision parts such as PCB, air bearing, camera and nozzle, most studies on drilling burr formation have focused on the conventional drilling process. This paper describes burr formation process and the effect of cutting conditions such as spindle speed, feedrate and drilling depth per one step on burr formation in drilling A6061 with drills of diameter 1.0mm and 0.6mm. Experimental results showed that burr with cap were formed at relatively low feedrates, while petal burrs with several large burr fragments were formed at high feedrates. Burr height appeared to increase at the hight feedrates and lower spindle speeds. The effect of final cutting depth on burr height was negligible.