• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.1053-1062
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• 1993

The effect of loading speed on soil failure was studied by using a high speed triaxial compression test. Tests were conducted at 0.35-6.2m/s loading speed to compress soil specimens of sandy loam at different moisture contents. The axial stress at fracture increased with increase in loading speed up to certain critical speeds, however they decreased as the speed up to certain critical speeds, however they decreased as the speed increased further. Experiments were also conducted in the field of sandy loam soil with the vibrating tillage tool. Tests were done at 0.33-0.85m/s tractor speed oscillating frequency 13.7hz and oscillating amplitude 59mm. The maximum oscillating velocity of tillage tool was 2.5m/s. It was observed that for the oscillating operation, initially draft slightly increased with increase in forward speed and then it decreased .For the non-oscillating operation, draft increased continuously with increase in forward speed. Approach of studying soil failure in the laboratory test can be related to the field experiments.

• 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.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.2 s.179
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• pp.73-80
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• 2006

High speed machining(HSM) technique is widely used in the appliance, automobile part and mold industries, because it has many advantages such as good quality, low cost and rapid machining time. But it also has problems such as tool breakage, smooth tool path, and so on. In particular, small size end mill is easy to break, so it must be changed before interrupting operation. Generally, the tool life of small size end mill is affected by the milling conditions whose selected parameters are spindle speed, feedrate, and width of cut. The experiments were carried out by full factorial design of experiments using an orthogonal array. This paper shows optimal combination and mathematical model for tool life, Therefore, the analysis of variance(ANOVA) is employed to analyze the main effects and the interactions of these milling parameters and the second-order polynomial regression model with three independent variables is estimated to predict tool life by multiple regression analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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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.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.3
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• pp.26-33
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• 2003

The term 'High Speed Machining' has been used for many years to describe end milling with small diameter tools at high rotational speeds, typically 10,000-100,000rpm. The process was applied in the aerospace industry for the machining of light alloys, notably aluminum. In recent year, however, the mold and die industry has begun to use the technology for the production of components, including those manufactured from hardened tool steels. With increasing cutting speed used in modern machining operation, the thermal aspects of cutting become more and mole Important. It not only directly influences in rate of tool weal, but also affects machining precision recognized as thermal expansion and the roughness of the surface finish. Hence, one needs to accurately evaluate the rate of cutting heat generation and temperature distributions on the machining surface. To overcome the heat generation, we used to cutting fluid. Cutting fluid plays a roles in metal cutting process. Mechanically coupled effectiveness of cutting fluids affect to friction coefficient at tool-workpiece interface and cutting temperature and chip control, surface finish, tool wear and form accuracy. Through this study, we examined the behavior of heat generation in high-speed machining and the cooling performance of various cooling methods.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.3
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• pp.705-712
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• 1995

The wear characteristics and wear mechanisms in TiN coating deposited on high speed steel and alloy tool steel by ion plating were investigated. Pin on V-block wear tester was used for a wear test method. The specimen was composed of three kinds of high speed steel and alloy tool steel which had different hardness by changing the heat treating condition. Three kinds of coating thickness were also applied to each specimen. Microscopic observation of worn surfaces was made by SEM. The scratch test of coating surface by the ion plating showed that critical load to break the coating interface was greater than 50N. The critical load increased with both substrate hardness and coating thickness. The wear resistance of TiN coated high speed steel became 10 times greater than that of non-coated ones. SEM observation showed that leading edge of contact was compressive and trailing edge was under maximum tensile stress and then surface cracking broke out perpendicular to sliding direction.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.172-175
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• 2002

High speed machining is one of the most effective technologies to improve productivity. It can give great advantage for manufacture of die and Moulds. However, when machining of micro groove in high speed machining a severely thermal damage was generated on workpiece and cutting tool. Generally, the cutting fluid is used to improve penetration. lubrication. and cooling effect. In order to rise the performance of lubrication. it contains extreme pressure agents (Cl, S, P). But the environment of work room go bad by those additive. Therefore, the compressed chilly air with oil mist system was developed to replace the conventional cutting fluid system. This paper carried out the tests to evaluate the machinability by the cutting environment in high speed micro groove machining of NAK80 (HrC40). Compressed chilly air with oil mist was ejected on the contact area between cutting edge and workpiece. The effect of this developed compressed chilly air with oil mist system was evaluated in terms of tool life. The results showed that the tool lift of carbide tool coated TiAlN with compressed chilly air mist cooling was much longer than that of the dry and flood coolant when cutting the material.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.12
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• pp.895-900
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• 2015

Most of spindles for machine tool are supported by ball bearings, and there are problems in the limits of high speed and high power as well as the cumbersome maintenance due to the short life time. In order to overcome these problems of the conventional spindles, the high speed spindle with magnetic bearings is developed in this study. Magnetic bearings for 60 000 r/min class high-speed spindle are designed, and high speed spindle with magnetic bearings are fabricated. Based on the running test up to 60 000 r/min, it is verified that the spindle is stably supported by the magnetic bearings, and the magnitude of the unbalance response at 60 000 r/min is less than $3{\mu}m$.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.1-8
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• 2007

The ultra-fine tungsten carbide(WC) powders have been actively used in the cemented carbides industry, because they have excellent mechanical properties such as high hardness, strength, and toughness. In this study, ultra-fine WC-Co alloys powders have been fabricated by thermochemical and thermomechanical process such as spray conversion process or high energy ball milling. The non-coated end-mill which is made of ultra-fine tungsten carbide is investigated by measuring cutting force, tool wear, tool life, and surface roughness profile according to cutting length. The machining test was conducted with high hardened workpiece and their performances are investigated in high speed cutting conditions. Also, the relationship between the machining characteristics and the Co contents are investigated under various high speed cutting conditions.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.63-69
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• 2007

The high speed machining has been widely applied to manufacture dies and machine elements in industrial field. Especially, 5-axis milling has been employed to produce a wide range of turbine blades, impellers and complex molds. In this study, the machining characteristics of injection molds were investigated according to tool tilting angles in 5-axis milling. The cutting force and surface roughness were investigated with various tool tilting angles. When the tool tilting angle was over than 10 degree, the characteristics of cutting force and surface roughness were improved in machining of Al alloy.