• Journal of the Korea Safety Management & Science
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• v.2 no.2
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• pp.117-126
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• 2000

Recently micro deep hole drilling is required in the whole industry. However, micro deep hole drilling has still much difficulty because of the lack of drill rigidity and the interruption of chip. We treated a micro deep hole(diameter 0.35mm, depth 3mm) used in a connector jack pin. Therefore, a surface roughness is very important. In this paper, we studied on the variation of the surface roughness for cutting conditions during micro deep hole drilling of Be-Cu material. Most of all, we tried to drill on CNC for the realization of automatization.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.873-877
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• 2005

The burr of micro drilling and micro cutting on thin metal film is a major obstacle to mass production for micro PCB boards in micro technologies of personal computing and telecom explosion. As the burr affects on the assembling process, it is necessary to study continuously on control or elimination of the burr. In order to get higher valued products, it is also needed to competitive techniques with the high resolution. In this paper, we studied experimentally the burr generation that when it is processed on the copper foil by laser in micro-hole machining. Unlike mechanical machining the burr produced on substrate is a resultants of melt and re-solidification of a melten metal which was heated and treated by laser. And higher laser energy increases the size of burr. Therefor in micro-drilling with laser, it is difficult to reduce the effects of burr for very thin metal sheets. We investigated the stale of the burr and analyzed the laser ablation Cu micro machining with respect to laser intensity and processing time.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.6
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• pp.591-597
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• 2001

Ti alloy is used for essential parts of aircraft for high temperature environment. Although Ti alloy has excellent performance in regard to mechanical properties, it is difficult ot find fatigue cracks by nondestructive ultrasonic inspection due to its two-phase microstructure, which consists of hard alpha and beta phases. Sound energy reflected from microstructural features in the component produces a background inspection noise which is seen even when no defects are present. This noise can inhibit the detection of critical internal defects such as pores cracks or inclusions. To obtain fundamental data on ultrasonic inspection of Ti alloy, ultrasonic testing was performed using a specimen with small drill holes and ultrasonic wave propagation velocites were measured.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.23-28
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• 2002

This paper describes the machining characteristics of the $MoSi_2$ based composites by electric discharge drilling with various tubular electrodes, besides, Hardness characteristics and microstructures of $Nb/MoSi_2$ laminate composites were evaluated from the variation of fabricating conditions such as preparation temperature, applied pressure and pressure holding time. $MoSi_2$ -based composites has been developed in new materials for jet engine of supersonic-speed airplanes and gas turbine for high- temperature generator. Achieving this objective may require new hard materials with high strength and high temperature-resistance. However, With the exception of grinding, traditional machining methods are not applicable to these new materials. Electric discharge machining (EDM) is a thermal process that utilizes a spark discharge to melt a conductive material, the tool electrode being almost non-unloaded, because there is no direct contact between the tool electrode and the workpiece. By combining a nonconducting ceramics with more conducting ceramic it was possible to raise the electrical conductivity. From experimental results, it was found that the lamination from Nb sheet and $MoSi_2$ powder was an excellent strategy to improve hardness characteristics of monolithic $MoSi_2$. However, interfacial reaction products like (Nb, Mo)$SiO_2$ and $Nb_2Si_3$ formed at the interface of $Nb/MoSi_2$ and increased with fabricating temperature. $MoSi_2$ composites which a hole drilling was not possible by the conventional machining process, enhanced the capacity of ED-drilling by adding $NbSi_2$ relative to that of SiC or $ZrO_2$ reinforcements.

• Journal of the Korean Ceramic Society
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• v.40 no.9
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• pp.867-873
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• 2003

$Si_{3}N_{4}$-BN based machinable ceramics were fabricated by hot-pressing at $1800^{\circ}C$ for 2 h under a pressure of 25 MPa. The microstructure, mechanical properties, and machinability were investigated. With increasing h-BN content from 5 vol% to 30 vol%, three point flexural strength decreased from 1000 MPa of monolithic S $i_3$ $N_4$ to 720～400 MPa. The fracture toughness, $K_{IC}$ , was decreased from 7.6 MPaㆍ$m^{1/2}$ of monolithic S $i_3$ $N_4$ to 6.5～4.1 MPaㆍ$m^{1/2}$. The grain size and aspect ratio of $\beta$-S $i_3$ $N_4$ slightly decreased with increasing h-BN content. S $i_3$ $N_4$ monolith could not be machined due to brittle fracture, but S $i_3$ $N_4$-BN based machinable ceramics could be machined without fracture, showing excellent machinability. With increasing h-BN content, the thurst force during cutting and micro-drilling process was decreased.