• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1803-1806
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• 2003

Metalworking fluids (MWFs) are fluids used during machining and grinding to prolong the lift of the tool, carry away debris, and protect the surfaces of work pieces. These fluids reduce friction between the cutting tool and the work surface. reduce wear and galling, protect surface characteristics, reduce surface adhesion or welding and carry away generated heat. Workers can be exposed to MWFs by inhaling aerosols (mists) and by skin contact with the fluid. Skin contact occurs by dipping the hands into the fluid, splashes, or handling workpieces coated with the fluids. The amount of mist generated (and the resulting level of exposure) depends on many factors. To reduce the environmental pollution wastes and the potential health risks associated with occupational exposures to MWFs, it is required to establish optimum MWFs supply method and condition with minimum quantity in all over the mechanical machining field including high-speed type heavy cutting process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.886-889
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• 2000

This paper describes the machining characteristics of the MoSi$_2$-based composites by electric discharge drilling with various tubular electrodes. MoSi$_2$-based composites has been developed in new materials for jet engine of supersonic-speed airplanes and gas turbine for high- temperature generator. By combining a nonconducting ceramics with more conducting ceramic it was possible to raise the electrical conductivity. In drilling by EDM, the dielectric flushed down the interior of the rotating tube electrode, in order to facilitate the removal of machining debris from the hole. Various metal-coated tubular electrodes of which core are copper and brass are used to know the effect of coating material on machinability of ED drilling.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.8
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• pp.139-145
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• 1996

Tapping is one of the most widely used machining operations. There are several methodes of producing external screw threads, e.g. turning, milling with single or multiple cutter, rolling, and grinding, but the methods available for cutting enternal threads are less numerous, and for threads in small holes, tapping is employed almost exclusively. In this study, the tap with the various geometry has been developed in order to tap special workmaterial at considerably higher cutting speed than that of the conventional HSS tap. The experimental tests are run with various cutting speed by using a piezo type tool dynamometer to measure tapping torque. Tapping torque is affected by the design of the tap, which seems to be due to internal friction and shearing of the metal. It is clarified that the process of chip formation strongly depends on rake angle, relief angle, angle of twist.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1162-1165
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• 2003

Contouring errors are important especially for high speed and precision machining. Since the contouring errors of a machine tool affect the error of a machined part directly, it is necessary to find the contouring errors by some relevant tests. In this study, contouring errors are obtained by performing circular tests with a grid plate. Various error sources are diagnosed by a least square method.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.1
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• pp.123-133
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• 1996

From the experimental study of wire-cut Electric Discharge Machining of alloyed tool steel and tungsten carbide, the characteristics such as cutting speed, surface roughness has been observed and evaluated for various conditions. Cutting speed is improved as peak discharge current and wire tension become increased, and gap voltage and spark cycle decreased. Surface roughness can be better when peak discharge current and gap voltage become smaller, or spark cycle and wire tension become larger. Secondary cut is recommended to obtain high precision and good quality.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1745-1748
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• 2005

According to the demand of the high productivity, the interest of manufacturing skills is growing in industrial society. Especially the high speed spindle in machining center becomes important these days. The exchange time of the tool in machining center usually calls T-T(tool to tool) time. Detailly explaning, It is influenced by the unclamping time. Affecting factors of the unclamping time are various(the hydraulic system, drawbar mass, a flow meter, disc spring, a piston diameter, pipe diameters, and so on). In this study, we could find factors that decrease the unclamping time and verify it for softwares.(AMESim $4.0^{(R)}$ & visual Nastran $4D^{(R)}$)

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.168-173
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• 2005

Composite material is combined with two or more chemical ingredient and different components. FRP has been widely used for the structure of aircraft, ships, automobiles, sporting goods and other machines because of their high specific strength, high specific stiffness and excellent fatigue strength. Recently, the development of machine tool and cutting tool greatly relies on high speed process to satisfy high precision, high efficient machining, shortened process time to maximize material removal rate (MRR) through high cutting speed and feed speed. The research molded CFRP, GFRP as stacking sequence methods of two direction (orientation angle $0^{\circ}\;and\;0^{\circ}/9^{\circ}$) hand lay-up, drilled molded plates using cemented carbide drill and examined chip shapes, surface roughness properties.

• Journal of Welding and Joining
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• v.28 no.3
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• pp.42-48
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• 2010

Polycarbonate (PC) and Acrylonitrile Butadiene Styrene (ABS) were welded by a combination of a diode laser and a CNC machining center. Laser beam delivered through the transparent PC and was absorbed in an opaque ABS. Polymers were melted and joined by absorbed and conducted heat. Experiments were carried out by varying working distance from 44mm to 50mm for the focus spot diameter control, laser input power from 10W to 25W, and scanning speed from 100 to 400mm/min. The weld bead and cross-section were analyzed for weld quality, and tensile results were presented through the joint force measurement. With focus distance at 48mm, laser power with 20W, and welding speed at 300mm/min, experimental results showed the best welding quality which bead size was measured to be 3.75mm. The shear strength at the given condition was $22.8N/mm^2$. Considering tensile strength of ABS is $43N/mm^2$, shear strength was sufficient to hold two materials. A single process was possible in a CNC machining system, surface processing, hole machining and welding. As a result, the process cycle time was reduced to 25%. Compared to a typical process, specimens were fabricated in a single process, with high precision.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.35-36
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• 2006

In Nd:YAG laser welding, evaluation methods of welding flaw are various. But, the method due to fume shape is difficult to classification of welding flaw. The Nd:YAG laser process is known to have high speed and deep penetration capability to become one of the most advanced welding technologies. At the present time, some methods are studied for measurement of fume shape by using high-speed camera and photo diode. This paper describes the machining characteristics of SM45C carbon steel welding by use of an Nd:YAG laser. In spite of its good mechanical characteristics, SM45C carbon steel has a high carbon contents and suffers a limitation in the industrial application due to the poor welding properties. In this study, fume shape was measured by infrared thermal camera that is non-contact/non-destructive thermal measurement equipment through change of laser generating power, speed, focus. Weld was performed on bead-on method. Measurement results are compared as two equipments. Here, two results are composed of measurement results of fume quantities due to fume shape by infrared thermal camera and inspection results of weld bead include weld flaws by ultrasonic inspector.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.18-21
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• 2003

Fused Deposition Modeling (FDM) parts are made by piling up thin layers that cause the stair stepping effect at the surface of FDM parts. This effect brings about poor surface roughness of the part and requires additional post machining such as manual finishing that is detrimental to the part geometry and time consuming. Determining optimal build orientation for FDM parts can be one solution to minimize the post machining. However, by using the CAD model, calculating the optimal build orientation is impractical due to heavy computing process. In order to calculate the optimal build orientation with high speed. the surface roughness model based on measured data and interpolation is newly developed in this research. Also. the genetic algorithm (GA) is applied for acquiring reliable solution. Finally, It is verified from the test that the presented approach is very efficient for reducing the additional post machining process fer FDM parts.