• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.911-914
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• 1997

This Experiment was carried out for bur minimization in drilling. New drill geometries are proposed to minimize the burr formation in drilling operation. Three types of drills are made, champer, round and step drill. The burr formed in first cutting by front cutting edge ca be removed in second cutting by the cutting edges in chamfer, round edge and step. New burrs are formed by second cutting and can be minimized according to the change of drill geometry like, chamfer size and angle, corner radius in round drill and step size and angle in step drill. To measure the burr formed in drilling, laser sensor is used.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.139-144
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• 1991

Chip flow angle is one of the important factors to be determined for the scheme of Chip Control. Up to now, however, a dependable way to predict the chip flow angle in practical cutting has not been established satisfactorily. In this paper a rather simple theoretical prediction of chip flow angle is tried based on some already widely confirmed hypotheses. The developed equation of chip flow angle contains the parameters of depth of cut d, feed rate f, nose radius $r_{n}$ side cutting edge angle $C_{s}$, side rake angle .alpha.$_{s}$ and back rake angle .alpha.$_{b}$. Theoretical results of chip flow angle given by this study bas been shown in a good agreement with experimental ones.s.s.s.s.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.581-584
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• 2003

The austenitic STS 304 stainless steel was turned to clarify the effects of tool geometry on the tool wear. The wear of TiN-TiCN-TiC-TiAlN coated tungsten carbide tool was the smallest, exhibiting larger wear in the order of Si-Al-O-N ceramic, TiN coated tungsten carbide, TiN-TiCN-TiN coated tungsten carbide, TiC-TiN cermet and M20 tungsten carbide tools at the same cutting conditions. The S-type tool of M20 with large approach angle showed the longest tool life of all tools used in this tests due to preventing the groove wear of the side cutting edge. The wear of the S-type tool with the rake angle of 15$^{\circ}$became smaller than with that of -5$^{\circ}$, but the tool with the nose radius of 0.8mm did not perform much better with increasing the rake angle.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.3
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• pp.83-90
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• 2004

This paper proposes a tool path generation method for machining impellers with 5-axis machining center. The shape of impeller is complex, being composed of pressure surface, suction surface and leading edge, and so on. The compound surface which is made of ruled surface such as pressure surface and suction surface and leading edge such as fillet surface, makes the tool path generation much complicated. To achieve efficient roughing, cutting area is divided into two region and then tool radius of maximum size that do not cause tool intereference is selected for shortening machining time. In finishing, accuracy is improved using side cutting for blade surface and point milling for leading edge.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.2
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• pp.228-236
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• 2002

In this study, the carbon steels, SM20C were machined with the tungsten carbide tipped circular saw to clarify the cutting-off characteristics in terms of tool wear. The results show that an improved performance in view of both the tool wear and the cutting efficiency was obtained by using oil base cutting fluid at the cutting speed of 100m/min with the feed of 0.06mm/tooth. The rake angle of 10$^{\circ}$ , clearance angle of 8$^{\circ}$ , nose radius of R0.1mm, and end cutting edge champer of 0.1mm$\times$25$^{\circ}$ are believed as the best tool geometries. The tool wear decreases due to using the saw of the disk of STS5 and the tool material of P30.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.930-933
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• 2000

Experimental study was conducted for finding the characteristics of machining precision according to the change of feedrate when ball endmilling of semisphere shape. The values of tool deflection and cutting force were measured simultaneously by the systems of eddy-current sensor and dynamometer. The machining precision was analyzed by roundness values, which were deeply relating with tool deflection and forces. the roundness was decreased in down-milling than in up-milling for each feedrate. As the cutting edge is moved to radius direction on the tool path, the tool deflection and the cutting force were seemed to be decreased. As the tool path was moved downward, the values of roundness, cutting force and tool deflection were obtained better ones. When compared the values of roundness, cutting force and tool deflection for different feedrate, the best machining accuracy was obtained at feed rate of 90mm/min in down-milling.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.2
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• pp.23-30
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• 2008

As a basic machining process, turning is a widely used machining process in which a single-point cutting tool removes material from the surface of a rotating material. A common method of evaluating machining performance is to measure the surface roughness. In a turning operation, it is important to select cutting conditions for achieving high cutting performance. As a rule, cutting conditions can be classified into feed rate, depth of cut and insert radius. While cutting process even though cutting conditions are optimized, the average roughness can be deterioration due to wear of the cutting tool edge. In this study, the aim is to maintain the average roughness even though the cutting condition is irregularly changing within the predictable range due to the working environment. First, the surface roughness model influenced by cutting conditions is constructed based on the experimental results in a turning operation, Second, applying the sliding mode control theory to the turning operation model which is composed of the surface roughness model and the motor transfer function, the surface roughness is closed to the desired value. Finally, the effectiveness of this approach is demonstrated through the computer simulation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.9
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• pp.1520-1530
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• 1997

Machining pressed compacts of ceramic and WC-Co materials can be the most cost effective way of forming the bodies prior to sintering when the required number of pieces is small. In this study, in order to clarify the machinability for turning, the $Si_3N_4$ and the WC-Co green compacts unsintered were machined under different cutting conditions with various tools. Absorbing chips by vacuum hose decreases tool wear. The tool wear becomes larger in the order of the ceramic, CBN and cemented carbide tools in machining the $Si_3N_4$ green compacts. In machining the WC-Co green compacts, the tool wear becomes larger in the order of the ceramic, cemented carbide and CBN tools. The land of cutting edge does not affect tool wear. When machining with cemented carbide tool, the tool wear i equal cutting length is nearly identical in spite of the increase of cutting spee, and the roughness of machined surface was the best in the cutting speed of 90 m/min. The tool wear decreases with the increase of rake angle and relief angle and with the decrease of nose radius. The machined surfaces become worse with the increase of feed rate and depth of cut, and with the decrease of rake angle and relief angle. The tool wear is not affected by the feed and depth of cut.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.119-124
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• 1996

End milling operation is very important in machining precision components. Deterioration of surface roughness and surface geometry will cause more process for surface finishing. According to the feed rate and the cutting edge geometry, the cusp which is geometrically uncut surface is determined. To reduce the cost for dinishing operation after end milling, the cusp must be remaianed in small size as possible. Due to the cylindrical type of the end mill, tool deflection is one of the main problems in surface generation. The cutting resistance and the rigidity of the end mill will determine the size of tool deflection. One more important factor which deteriorate surface quality comes from the error in manufacturing end mills. Run-out of end mill which is the difference of the radius of each cutting edges will produce the difference of the cusp size in every rotation of end mill. These three major factors to the surface quality will be analized and the result will be compared with experimental ressult.

• Structural Engineering and Mechanics
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• v.73 no.6
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• pp.631-640
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• 2020

Using backup plate is one of the most commonly used methods to decrease drilling-induced delamination of composite laminates. It has been shown that, the size of the delamination zone is related to the vertical element of cutting force named as thrust force. Also, direct control of thrust force is not a routine task, because, it depends on both drilling parameters and mechanical properties of the composite laminate. In this research, critical feed rate and thrust force are predicted analytically for delamination initiation in drilling of composite laminates with backup plate. Three common theories, linear elastic fracture mechanics, classical laminated plate and mechanics of oblique cutting, are used to model the problem. Based on the proposed analytical model, the effect of drill radius, chisel edge size, and backup plate size on the critical thrust force and feed rate are investigated. Experimental tests were carried out to prove analytical model.