• 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.

• 한국정밀공학회지
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• 제25권7호
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• pp.39-46
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• 2008

High precision machining technology has become one of the important parts in the development of a precision machine. Such a machine requires high speed on a large workspace as well as high precision positioning. For machining systems having a long stroke with ultra precision, a dual-stage system including a global stage (coarse stage) and a micro stage (fine stage) is designed in this paper. Though linear motors have a long stroke and high precision feed drivers, they have some limitations for submicron positioning. Piezo-actuators with high precision also have severe disadvantage for the travel range, and the stroke is limited to a few microns. In the milling experiments, the positional accuracy has been readily achieved within 0.2 micron over the typical 20 mm stroke, and the path error over 2 micron was reduced within 0.2 micron. Therefore, this technique can be applied to develop high precision positioning and machining in the micro manufacturing and machining system.

• 대한금속재료학회지
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• 제48권7호
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• pp.651-659
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• 2010

When high-speed interrupted cutting is carried out for die and mold steels with high hardness, CBN tools manifested a significantly longer wear life than carbide, ceramic, or cermet tools in an experiment of face milling characteristics. In addition, it was also found that they secured a stable surface roughness within a range of 1.6 S~6.3 S, an acceptable range for precision machining for polished machining parts. And it makes them acceptable in the precision machining field, except in industries where very high machining accuracy is required. In the high hardness interrupted cutting, it was advantageous to perform a negaland treatment and a honning treatment on the tools' cutting edge to extend tool life and surface roughness. Also, severe crater development was found on the sloped face in CBN tools following high-speed machining. This caused the cutting edge to be weakened and damaged, and ultimately resulted in a shorter tool life. Finally, as a result of EDX mapping inspection, Cr component was detected evenly on the entire crater wear area, which can be included only in STD 11.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1418-1423
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• 2004

High speed machining experiment on the heat-treated mold steel(STAVAX and CALMAX of hardness HRc 53) is carried using TiAlN coated ball endmill. Tool life and wear characteristics under the various machining parameters and cooling methods are investigated. Effect of cooling method on life and wear of the tool was compared. For most cases, tool life was not determined by the amount of wear but by th chipping on the cutting edge. It is found that tool manufacturer's cutting parameters generally agrees with the results of this experiment.

• 한국초전도ㆍ저온공학회논문지
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• 제19권2호
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• pp.19-24
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• 2017

Cryogenic milling which is a combined process of low-temperature treatment and mechanical milling was applied to fabricate high critical current density $(J_c)MgB_2$ bulk superconductors. Liquid nitrogen was used as a coolant, and no solvent or lubricant was used. Spherical Mg ($6-12{\mu}m$, 99.9 % purity) and plate-like B powder (${\sim}1{\mu}m$, 97 % purity) were milled simultaneously for various time periods (0, 2, 4, 6 h) at a rotating speed of 500 rpm using $ZrO_2$ balls. The (Mg+2B) powders milled were pressed into pellets and heat-treated at $700^{\circ}C$ for 1 h in flowing argon. The use of cryomilled powders as raw materials promoted the formation reaction of superconducting $MgB_2$, reduced the grain size of $MgB_2$, and suppressed the formation of impurity MgO. The superconducting critical temperature ($T_c$) of $MgB_2$ was not influenced as the milling time (t) increased up to 6 h. Meanwhile, the critical current density ($J_c$) of $MgB_2$ increased significantly when t increased to 4 h. When t increased further to 6 h, however, $J_c$ decreased. The $J_c$ enhancement of $MgB_2$ by cryogenic milling is attributed to the formation of the fine grain $MgB_2$ and a suppression of the MgO formation.

• 한국생산제조학회지
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• 제18권3호
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• pp.261-269
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• 2009

Micro end-milling process is applied to fabricate precision mechanical parts cost-effectively. It is a complex and time-consuming job to select optimal process conditions with high productivity and quality. To improve the productivity and quality of precision mechanical parts, micro end-mill wear and cutting force characteristics should be studied carefully. In this paper, high speed machining experiments are studied to construct the optimum process design as well as the mathematical modeling of tool wear and cutting force related to cutting parameters in micro ball end-milling processes. Cutting force and wear characteristics under various cutting conditions are investigated through the condition monitoring system and the design of experiment. In order to construct the cutting database, mathematical models for the flank wear and cutting force gradient are derived from the response surface method. Optimal milling conditions are extracted from the developed experimental models.

• 한국공작기계학회논문집
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• 제10권5호
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• pp.17-24
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• 2001

Recently, the requirements for high precision and efficiency machining are gradually increased to raise international competitiveness at the industrial fields of die and molds. This trend had made effects on the industrial fields in Korea and which needs fur studying of high precision and efficiency machining. This study is to investigate the effects of the non-out of end mill in the external cylindrical machining operated by solid carbide end mills with Al-alloy in high speed machining center relating to high spindle revolution and frost fred per minute on the dimensional precision, roundness of workpiece. From the results of experimentations followings are obtained; when Al-alloy is processed by the external cylindrical cutting of end milling through the high speed revolution, if the spindle revolution is higher relating to radial depth of cut, feed per tooth in very lower situation, finally, productivity can be raised because high precision and quality products are machined high efficiently.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.32-36
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• 2002

High-speed movement and high-precision machining are the two most important requirements of present machine tool structures to reduce machining time and to increase the precision of products in various industrial fields such as semiconductor, automobile, and mold fabrication. The high speed operation of machine tools tue usually restricted not only by the low stiffness but also by the low damping of machine tool structures, which induces vibration during high speed machining. If the damping of machine tool structures is low, self induced or regenerative vibrations are bound to occur at high speed operation because the natural frequencies of machine tool structures can not be increased indefinitely. Therefore, the high damping capacity of a machine tool structure is an important factor for high speed machine tool structures. Polymer concrete has high potential for machine tool bed due to its good damping characteristics. In this study, a polymer concrete bed combined with welded steel structure i.e., a hybrid structure was desisted and manufactured for a high-speed gantry-type milling machine through static and dynamic analyses using finite element method. Then the dynamic characteristics were tested experimentally.

• 제어로봇시스템학회논문지
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• 제2권4호
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• pp.351-361
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• 1996

A variable structure controller is developed for an AC servo motor used in CNC milling machines. The designed controller is implemented as an outer loop controller to a factory designed motor-servopack system. The robustness parameter is tuned for a fast response when the speed tracking error is large, while it is tuned for small oscillations when the speed tracking error is small. The designed controller is installed on a CNC machine using a PC. Cutting experiments show improved performance over the factory-designed controller.

• 한국정밀공학회지
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• 제19권4호
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• pp.154-160
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• 2002

Powder metallurgy(P/M) process has been used for the production of high performance high-speed steels. P/M high speed steel has more uniform and fine microstructure than those of conventional wrought products. Therefore, it offers distinct advantages over conventional tool steels. The superior uniformity of composition and fine microstrucure lead to excellent toughness and less distortion during heat treatment, which in turn can reduce total grinding costs and provides other benefits, such as uniform hardness and increased tool life. From these reasons, milling, hole machining, broaching, and gear manufacturing tools are major applications of P/M high-speed steels. In this research, we evaluated tool wear of flat endmill which is made of P/M high-speed steel from the view point of cutting tool performance.