• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.04a
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• pp.22-31
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• 1991

Machining with boring bars frequently induce chatter vibration because of the low stiffness and damping of cantilever shape of boring bars. To increase stiffness and damping, a carbon fiber epoxy composite boring bar was designed, manufactured and tested. The natural frequency of the carbon fiber epoxy composite boring bar in the free-free end condition was incerased more than 50% over that of the steel boring bar, and the damping of the carbon fiber epoxy composite boring bar was also increased 450%. The fundamental natural frequency of the carbon fiber epoxycomposite boring bar in the cantilever beam condition was found to be increased 20-30% over that of the steel boring bar in overhang length range 140-200mm. In machining S45C tapered workpieces, the limit of the overhang length of the steel boring bar was about 170mm in cutting speed 140m/min.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.1
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• pp.78-83
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• 1996

This paper presents the characteristics of surface roughness and cutting force in ultraprecision cutting of aluminium alloy using natural diamond tools whose edge radii are smaller than those of tools made of other materials. The feed rate and depth of engagement were set to be a micrometer order. After measuring the surface roughness of machined surface and cutting force for each cutting condition, the relations between the surface quality and its condition were investigated qualitatively. If the feed rate was under a certain limit, the machined surface quality was deteriorated unexpectedly. This is supposed to have happened due to vibration leading its condition to abnormal one. In a certain situation the machined surface roughness by a natural diamond tool was inferior to that made by a carbide tool whose cutting edge radius is larger. This is supposed to be caused by not normal machining but burnishing effect.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1996.03a
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• pp.18-23
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• 1996

The Job of Milling in the Local Skill Contest in 1996 was to assemble parts into a complete whole of the parts number 1, 3, 4 worded by Milling Machine and the parts number 2 worked by Machining Center. In the parts of Milling Machine, the Job was to work 45$^{\circ}$angle working, T-slot, dovetail, the correct position drilling, rimming, boring, etc. In the Machining Center, there were the way of calculation of point of contact of 'R' contour curved line and lots of working elements. So, it was possible to work the parts and assemble them within the time limit only through the program to be made out in the way to shorten working hours.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.95.5-95
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• 2002

Tool condition monitoring is recognized important in CNC machining processes since the excessive wear or breakage of tool has to be noticed immediately in an automated manufacturing system to keep the quality and productivity. In this research, as an economic way of detecting the status of tool change, the wavelet transform has been applied to the measurement of spindle motor current. The energy of a specific level shows the difference between a normal tool and worn one. By setting a limit on the change of energy, it is possible to notify the time to inspect the tool.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.18 no.35
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• pp.9-16
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• 1995

The degeneration of tool in material removal processing machinery can be characterized by wear, deflection, chattering and any failure in tool or in the material In be processed. In the previous studies, first three of them are analyzed as a preventive maintenance strategy in quality control area. The last of them, any failure, is analyzed as a preventive maintenance strategy in reliability area. In this research, we propose a simple integrated mathematical model which minimizes the cost of machinery failures and producing defects. We determine the optimal wear limit of tool by considering the percent defects. cost, the preventive maintenance cost, and the corrective maintenance cost.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.3
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• pp.149-156
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• 2003

The estimation of fatigue limit for the component with complicated shape is difficult than of standard fatigue specimen, due to complex test equipment. So, we substitute maximum principle stress from FEM results for fatigue limit diagram made by standard fatigue specimen. Then we can estimate endurance safety of component with high trust. The static stress analysis, the nonlinear contact stress analysis and the model analysis for turbine blade is performed by ANSYS ver. 5.6. the comparison of maximum static stress around hole with maximum contact stress between pun and hole can make the cause of fracture for turbine blade clear. The difference of fatigue limit between fatigue test by standard specimen and in-service mechanical components is due to surface roughness and machining condition etc. In in-service mechanical components, Goodman diagram has to consider surface roughness for failure analysis. To find fracture mechanism of torison-mounted blade in nuclear plant. This study performs the static stress, the nonlinear contact stress and the modal analysis on torison-mounted blade with finite element method and makes the estimation for safety of turbine blade.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.9
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• pp.125-132
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• 2002

We use a compound-cam twin arm structure and random tool access method to achieve a faster ATC (Automatic Tool Changer) system for the accurate position and rotation control of a tool magazine and an exchange am. Based on the data obtained from various sensors, it is possible to follow the sequence of commands in each control step for an exchange arm. However, it is not so easy to reduce the exchange time of the system because of the slow responses of the sensors and execution mode delays of PLC (Programmable Logic Controller) scan time. In this paper, we propose a new programmed limit-switch position control method to obtain the shortest possible delays for the random tool access method and compound-cam twin arm structure. With some experimental results, we have achieved below 0.9sec tool exchange time with the proposed method.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.10
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• pp.847-852
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• 2016

In this paper, important design parameters for parallel kinematic robots are defined, paying special attention to machining errors which may cause kinematic errors at the end effector of a robot. The kinematic effects caused by each design parameter, as well as their upper/lower limits, are analyzed here. To do so, we have developed a novel software program to compute kinematic errors by considering its defined design parameters. With this program, roboticists designing parallel kinematic robots can understand the important design parameters for which upper/lower allowances have to be strictly controlled in the design process. This tactic can be used for the design of high-speed, parallel kinematic robots to reduce the design/manufacturing costs and increase kinematic precision.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.1
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• pp.9-15
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• 2019

This study focused on the application of ELID mirror-surface grinding technology to the manufacture of off-axis asymmetric large-area reflecting mirrors made of BK7 glass. The size of the parts, such as asymmetric large-area mirrors or lens, made form-accuracy or roughness especially hard to measure after machining because of the measuring range limit of measurement devices. In this study, the ELID grinding system has been set up for mirror-surface machining experiments manufacturing off-axis asymmetric lenses. A measuring method using a reference workpiece has been suggested to measure the form-accuracy and roughness. According to the experimental results, even when using only a reference workpiece, it is confirmed that the surface roughness was 8 nmRa and form-accuracy was 80 nmRMS, with a best fit asymmetric radius when using a grinding wheel of #8,000. It is found that the accuracy of large-area parts could be estimated by the proposed process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.10a
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• pp.71-76
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• 2001

In the surface measurement system using touch probe, probe radius compensation is a key factor for accuracy. In this paper we investigate methods for compensating probe radius so that the surface equation for an "unknown surface" can be efficiently derived. The developed algorithm derives the surface equation by the iterative procedure of estimation, verification, and modification . Since the procedure is applied only for the surface region exceeding the tolerance limit, an accurate surface equation can be obtained with less computation and measurement point. The validity and effectiveness of the algorithm was tested by numerical simulations. The results convinced us that the develop algorithm can be used for surface measurement and tool path planning for NC machining.