• Journal of the Korean Society for Precision Engineering
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• v.22 no.4
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• pp.68-75
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• 2005

This paper presents a new method for the optimization of feed rate in sculptured surface machining. A NC verification model based on Z-map was utilized to obtain chip load according to feed per tooth. This optimization method can regenerate a new NC program with respect to the commanded cutting conditions and the NC program that was generated from CAM system. The regenerated NC program has not only the same data of the ex-NC program but also the updated feed rate in every block. The new NC data can reduce the cutting time and produce precision products with almost even chip load to the feed per tooth. This method can also reduce tool chipping and make constant tool wear.

• Journal of Korean Society for Quality Management
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• v.26 no.4
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• pp.51-64
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• 1998

Mean shifts may be found in tool wear in machining, drawing, stamping and moulding operations, which make the process quality level deteriorate over time. In such situations, it is necessary to reset or readjust the manufacturing process at regular time basis or by inspection to prevent defective items produced. Although the deterioration rate may be assumed to be linear in a production cycle, there are many cases where the rate varies after resetting due to the variation of tool characteristics or by using the resharpened tools. In such cases, the deterioration rate should not be assumed to be a deterministic constant but a random variable. This paper is to find an optimal resetting period and quality level for such production processes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.801-805
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• 2000

This paper presents a new method of tool path optimization. A NC verification model based Z-map was utilized to obtain chip load in feed per tooth. This developed software can regenerate a NC program from cutting condition and the NC program that was generated in CAM. The regenerated NC program has not only all same data of the ex-NC program but also the new feed rates in every block. The new NC data can reduce the cutting time and manufacture precision dies with the same chip load in feed per tooth. This method can also prevent tool chipping and make constant tool wear. This paper considered the effects of acceleration and deceleration in feed rate change.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.482-487
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• 2001

Leaf type foil bearings have been used successfully in many aerospace applications such as air cycle machines, turbocompressors and turboexpander. These applications are characterized by light loads, constant speeds and low to moderate temperatures. But, as system on start-up or shutdown, sliding contact between the shaft and foil surfaces cause wear. So, in present study, to understand pressure-flow characteristics and deformation of foil bearing, flow/structure interaction analysis was used. and using this method, 2D and 3D calculation was peformed for shape of foil bearing to know circumferential direction flow and leakage flow characteristics of axial direction.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.5
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• pp.1149-1157
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• 1995

The research for variation of coolant film thickness and separating force has been investigated following the examination for friction profile of work roll and roughness change of strip surface in rolling mill producting actual commercial products. The obtained results are as follows ; (1) Coolant film thickness in cold rolling has been increased relative to the circumferential velocity of work roll, and formation of coolant films has decreased with the smaller diameter of work roll. (2) Separating force is related to the formation of coolant film, and large separating force is needed to the formation of coolant film but it is constant after formation of appropriate film. (3) Wear and roughness alleviation of work roll is larger in bottom-roll than in top-roll on cold surface is larger in the direction of width than in roll direction, and changes of roughness and strip surface hardness rarely occurred after 3 passes.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.4
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• pp.136-142
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• 1996

Automatic monitoring of cutting process is one of the most important technology in machining. AE sensing technology has been applied to monitoring process and proved to be effective in detecting tool abnor- malities such as tool wear and fracture. In this experimental study. AE signals were detected from the tool holder for continuous and interrupted cutting, which obtained from changing workpice material configuration, under control of constant cutting speed from CNC lathe. From statistical and frequency analysis, the AE signals were analyzed to obtaining the characteristics of continuous and interrupted cutting conditions and tool failure. The Kurtosis values decreased but RMS voltages increased as the cutting speed increased, in both continuous and interrupted cutting. RMS voltage is suddenly increased but Kurtosis value is suddenly decreased when tool failure condition. Power spectrum density of AE signals when tool failure reaches extreme value around 0.065 cycles/ .mu. m.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.190-195
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• 1998

This paper reports on the theoretical and expetimental study of the vane and cam ring motions in a variable displacement vane pump which is already used widely in various industrial and automotive applications. Dynamic equations of vane and cam ring motion and flow continuity equations are derived and then solved simultaneously using the numerical method. Vane detachment cause the pressure tipples, noise, wear in cam ring, and decrease the volumetric efficiency. Consequently, Vane detachment occurs due to excess compression in the pumping chamber, and it can be reduced by adjustment of design parmeters.

• Journal of the Korean Society of Costume
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• v.53 no.6
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• pp.101-115
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• 2003

The purpose of this study is to define women's classic tailored suits surviving, despite current millennial impulses tend toward disintegration in style. Through documentary study, the reason which women had chosen the mannish tailored suits instead of sumptuous dresses in the 20th century beginnings is considered carefully. Also, examining the process of transition of women's classic suits makes it possible to infer the aesthetic characteristics of them. According to study, women had began to wear tailored suits acquiring physical comfort and the equality of the sexes. In the early stage, women imitated men's tailored suits in order to show seriousness, intelligent, capability for social success. However, in accordance with the advance of women's social position women modified it to suits themselves to present intrinsic feminity as well as masculine values. By staying the basic form, classic tailored suits have undergone constant internal changes in relation to sexuality. The aesthetic properties of women's classic tailored suits can be inferred as moderation, dualism, and versatility. In conclusion, the credibility with own authority and the evolutionary character inhering in the classic tailored suits could explain the continuity of them.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.31-35
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• 1996

The cross section of the circular rod type workpiece to be cut in the band saw machine is variable at every moment in the sawing process. When the cutting feed rate is fixed to the constant speed, the cutting edges of the band saw teeth are also variabl eat any moment, so this causes the wear of the land saw teeth and the deterioration of the quality in the surface roughness. In this study, to work out this kind of problem basically, the mean cutting force of a tooth in the band saw was estimated by using the workpiece which was smaller than the interval of each tooth, i.e. band saw pitch, in the thickness. Then the static cutting forces were predicted by appling the mean cutting forces referred above to the mechanistic cutting force model which were analyzed through the geometric profile of a band saw tooth.

• Journal of Korean Society for Quality Management
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• v.15 no.1
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• pp.76-81
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• 1987

Past treatment of the single machine maintenance problem has shown that preventive maintenance may be desirable for equipment for which failures are caused at least partially by wear-out factors. In all previous treatment, however, the size of the maintenance-repair crew has been held constant and the optimal maintenance period has then been determined. This paper suggests a simultaneous solution for the maintenance-repair crew size and the optimal maintenance period. The optimal maintenance period is seen to shift as the size of the maintenance-repair crew varies.