• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.3
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• pp.268-273
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• 2011

In light guide panels, the PMMA sheet that is used in liquid crystal displays plays an important role in scattering the incident light and requires very fine machining as the sheet is directly related to the optical characteristics of the panels. High speed end milling(HSE) and high speed shaping(HSS) processes that are widely adopted and applied to the precise machining of light incident plane through vibration-assisted HSS for increasing the optical quality by minimizing the above-mentioned problems. The cutting tool and the tool post presented in this paper are designed by the authors to increase the magnitude of the cutting stroke by adopting the resonant frequency without weakening the stiffness and to reduce vibrations during even high speed feeding. The dynamic haracteristics of thecutting tool and the tool post are evaluated through simulation and experiment as well. The results reveal very appropriate dynamic characteristics for vibration-assisted HSS.

• Design & Manufacturing
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• v.17 no.2
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• pp.15-21
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• 2023

In this study, a diamond turning machine and a laser-assisted machining module were utilized for the complex combined cutting of aspheric shapes and fine patterns on the surface of high-hardness brittle material, silicon. The analysis of material's form accuracy and corrective machining was conducted based on key factors such as laser output, rotational speed, feed rate, and cutting depth to achieve form accuracy below 1 ㎛ and surface roughness below 0.1 ㎛. The cutting condition and corrective machining methods were investigated to achieve the desired form accuracy and surface roughness. The rotational speed of the spindle and the linear feed rate of the diamond turning machine were varied in five stages for the cutting condition test. Surface roughness and form accuracy were measured using both a contact surface profilometer and a non-contact surface profilometer. The experimental results revealed a tendency of improved surface roughness with increased rotational speed of the workpiece, and the best surface roughness and form accuracy were observed at a feed rate of 5 mm/min. Furthermore, based on the cutting condition experiments, corrective machining was performed. The experimental results demonstrated an improvement in form accuracy from 0.94 ㎛ to 0.31 ㎛ and a significant reduction in the average value of the surface roughness curve from 0.234 ㎛ to 0.061 ㎛. This research serves as a foundation for future studies focusing on the machinability in relation to laser output parameters.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.3
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• pp.28-35
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• 2013

Micro electrical discharge machining (EDM) as a non-contact machining process is very effective for micromachining with a thin electrode because of its low machining reaction force. The micro-electrode machining device has the advantage of maintaining high precision through the whole processes and uses a feeding wire in the thin electrode tool manufacturing process. This study describes the design and evaluation of a micro-electrode machining device using optical photo-interrupter. The electrode was fabricated by reverse electrical discharge machining. The performance of designed system was evaluated to measure tension force according to feed speed of wire. This system for micro electrode fabrication proves the feasibility in the micro-EDM process of the micro holes and parts for industrial applications.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.3
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• pp.5-12
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• 2003

In order to reduce the lead-time and cost, many useful methods have been applied to rapid prototyping (RP) in recent years. But cutting process is still considered as one of the effective RP methods that have been developed and currently available in the industry. It also offers practical advantages in aspects of precision and versatility. However, traditional 3-axis NC machining has some inherent limitations such as the restriction of tool accessibility and the complex setup. In this work, a new rapid prototyping system with high speed 5-axis machining of plastics has been developed to overcome those limitations. And cutting experiments were conducted to determine the design factors of the system and the cutting conditions of plastics. The architecture of developed system is described in detail and the successful application examples are presented.

• Journal of Industrial Technology
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• v.19
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• pp.1-7
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• 1999

This is the pre-study to pile up the basic technique for the electro-discharge machining in the field of micro-drilling. The machined chips are flowed out from the machining area by the flow arisen from the high speed rotation of the electrode. The cylindrical shape electrode, whose diameter is 0.5mm, is clamped by the three point clamping type clamper and the clamper is attached at the front shaft of the high speed rotating DC motor. The current for machining is controlled by pulse width modulation technique and the machining conditions such as frequency and duty ratio are changed to find out the effect of the variables for machined results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.06a
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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.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.206-210
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• 2003

Machining of deep holes with conventional boring bars frequently induce chatter vibration because of their low dynamic stiffness which is defined as the product of static stiffness and damping of conventional boring bar materials. In addition, the specific stiffness ($E/{\rho}g$) of boring bars is more important than the static stiffness to increase the fundamental natural frequency of boring bars in high speed machining. Therefore, boring bar materials should have high static stiffness and high damping as well as high specific stiffness. The best way to meet requirements is to employ fiber reinforced composite materials for high speed boring bars because composite materials have high static stiffness, high damping and high specific stiffness compared to conventional boring bar materials. In this study, the dynamic characteristics of carbon fiber epoxy composite boring bars were investigated. From the metal cutting test, it was found that the chatter was not initiated up to the ratio of length to diameter of 10.7 at the rotating speed of 2,500 rpm.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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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.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.223-226
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• 2002

To maximize the productivity in machining molds and dies, machine tools should operate at high speeds. However, the productivity of mold manufacturing has not increased significantly because CNC milling machines have massive slides, which do not allow rapid acceleration and deceleration during the frequent starts/stops encountered in machining molds and dies. This paper presents the use of composites for these slides to overcome this limitation. The vertical and horizontal slides of a large CNC machine were constructed by bonding high-modulus carbon-fiber epoxy composite sandwiches to welded steel structures using adhesives. These composite structures reduced the weight of the vertical and horizontal slides by 34% and 26%, respectively, and increased damping by 1.5 to 5.7 times without sacrificing the stiffness. Without much tuning, this machine had a positional accuracy of $\pm5\mu\textrm{m}$ per 300 m of the slide displacement.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.33-33
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• 2003