• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.627-628
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• 2006

High speed milling process is emerging as an important fabrication process benefits include the ability to fabricate micro and meso-scale parts out of a greater range of materials and with more varied geometry. It also enables the creation of micro and meso-scale molds for injection molding. Factors affecting surface roughness have not been studied in depth for this process. A series of experiments has been conducted in order to begin to characterize the factors affecting surface roughness and determine the range of attainable surface roughness values for the high speed milling process. It has previously been shown that run-out creates a greater problem for the dimensional accuracy of pans created by high speed milling process. And run-out also has a more significant effect on the surface quality of milled parts. The surface roughness traces reveal large peak to valley variations. This run-out is generated by spindle dynamics and tool geometry. In order to investigate the relationship between tool alignment errors and surface roughness the scallop generating mechanism in the ball-end milling with tool alignement errors has been studied and simulated. The results indicate that tool alignment errors have no significant effects ell the dimension of scallops in for flat planes.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.1
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• pp.30-40
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• 2010

The hard disk is one of the most frequently used storage in IPTV sep-top box. It has large storage capacity and provides fast I/O speed compared to its price whereas it causes high power consumption due to mechanical characteristics of spindle motor. In order to play streaming data in the set-top box, spindle motor of hard disk keeps active mode and it causes high power consumption. In this paper, We propose an offset-buffering and multi-mode spin-down method to reduce power consumption for streaming data playback. The offset-buffering inspects the user's viewing pattern and performs buffering based on the analysis of viewing pattern. So, it can maintain the status of spindle motor as idle mode for long time. Besides, it can reduce power consumption by spinning down according to offset-buffer size. The experimental result shows that proposed offset-buffering and multi mode spin-down method is about 28.3% and 12.5% lower than the full-Buffering method in terms of the power consumption and spin-down frequency, respectively.

• Tribology and Lubricants
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• v.39 no.1
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• pp.28-34
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• 2023

Because of their cleanliness, low friction, and high stiffness, aerostatic bearings are used in numerous applications. Aerostic bearings that use porous materials as means of flow restriction have higher stiffness than other types of bearings and have been successfully applied as guide bearings, which have high motion accuracy requirements. However, the performances of porous bearings exhibit strong nonlinearity and can vary considerably depending on design parameters. Therefore, accurate prediction of the performance characteristics of porous bearings is necessary or their successful application. This study presents a porous bearing design and performance analysis for a spindle used in wafer polishing. The Reynolds and Darcy flow equations are solved to calculate the pressures in the lubrication film and porous busing, respectively. To verify the validity of the proposed analytical model, the calculated pressure distribution in the designed bearing is compared with that derived from previous research. Additional parametric studies are performed to determine the optimal design parameters. Analytical results show that optimal design parameters that obtain the maximum stiffness can be derived. In addition, the results show that cross-coupled stiffness increases with rotating speed. Thus, issues related to stability should be investigated at the design stage.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.429-433
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• 1997

High-speed and high-precision are trendy at present in the development of machine tools which are required for various fields of industry such as semiconductor, automobde, mold fabricat~on and so on. High damping capacity of the structure is an iniportant factor to ohtain precise products without vibration during manufacturing caused by rapid trarisportatm and rotation of spindle unit Resin concrete have high potential for machine tool bed due to its good damping characteristics. In this study, the statlc and dynamic characteristics of the machine tool bed were analysed. Also, the hybrid machine tool bed, made of steel base and polyester resin concrete material, was manufactured and its good dynamic characteristics were proved experimentally.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.2
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• pp.121-126
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• 2013

Precision machine tools for high dignity cutting are needed for efforts to improve machining accuracy. However, there are many factors to improve machining accuracy. This study investigated how machining accuracy changes when variation and unbalance amount in rotational speed domain is decreased. Machining accuracy of initial machine tools depends on manufacturing and assembly of parts such as bearing. And then, vibration and noise vary with volume of unbalance amount when it is rotation, so it effects unbalance amount. Also vibration and noise increased by unbalance shorten spindle's life and it especially makes worse boring accuracy. Therefore, this study studied the change of roundness and cylindricity of workpiece when it decreases variation and unbalance in rotational speed domain.

• Transactions of the Society of Information Storage Systems
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• v.7 no.1
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• pp.25-30
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• 2011

In the last couple of years, the flexible optical disk(FOD) system that consists of a thin polycarbonate(PC) film of 95 ${\mu}m$ thick, a rigid stabilizer, and a high speed spindle motor has been spot-lighted as the next-generation optical system for archival use of digital data. The air film between the rotating disk and stabilizer provides a means for damping out the lateral disk vibrations. However, its damping-capability drops significantly as the rotational speed of the disk exceeds a specific limit and, eventually, the disk vibration propagates inward causing the whole span of the disk exhibits large vibration amplitudes. Based on the numerical simulations as well as the experimental results, the present work aims to evaluate the damping coefficient of the air-film near the outer region of the disk where the capillary type orifices are applied to the edge of the curved stabilizer.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1338-1343
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• 2007

High-efficient machining, which means cutting a part in the least amount of time, is the most effective tool to improve productivity. In this study, a new feed optimization method based on the cutting power regulation was proposed to realize the high-efficient machining in turning process. The cutting area was evaluated by using the Boolean intersection operation between the cutting tool and workpiece. And the cutting force and power were predicted from the cutting parameters such as feed, depth of cut, spindle speed, specific cutting force, and so on. Especially, the reliability of the proposed optimization method was validated by comparing the predicted and measured cutting forces. The simulation results showed that the proposed optimization method could effectively enhance the productivity in turning process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.9
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• pp.960-966
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• 2007

High-efficient machining, which means to machine a part in the least amount of time, is the most effective tool to improve productivity. In this study, a new feed optimization method based on virtual manufacturing was proposed to realize the high-efficient machining in turning process through the cutting power regulation. The cutting area was evaluated by using the Boolean intersection operation between the cutting tool and workpiece. And the cutting force and power were predicted from the cutting parameters such as feed, depth of cut, spindle speed, specific cutting force, and so on. Especially, the reliability of the proposed optimization method was validated by comparing the predicted and measured cutting forces. The simulation results showed that the proposed optimization method could effectively enhance the productivity in turning process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.923-928
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• 1997

An MCP (Microchannel Plate) is a secondary electron multiplier to detect and amplify electrons. An MCP has many rnicrochannels whose diameters range from 10 to 100pm and whose lengths range from 40 to 100times of the diameter. Each microchannel of the MCP amplifies electrons over IOOOtimes by the secondary electron emission. Even though MCPs have high performance for electron amplification, the application of MCPs is limited to high performance electronic equipments because of their high fabricating cost and the limit of increasing their size due to the conventional fabrication process. Therefore, in this work, microchannels of the MCP are manufactured by micro-drilling to reduce the cost of the MCP and to increase their size. Alumina green body with epoxy binder was machined for fabricating microchannels using a high speed air turbine spindle and micro-drills with diamond grinding abrasives. Then alumina MCP was fabricated through the sintering of the machined alumina green body.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.4
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• pp.1-8
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• 2004

Various controllable parameters of an experiment have influence on grinding process. In order to get good products with a high quality, these parameters should be considered whether each parameter has relations to the quality. This paper describes the use of the design of experiments to minimize geometric error in surface grinding. Controllable parameters for the design of experiments were selected as spindle speed, table speed, depth of cut and grain size. From the experimental results, a degree of influence between these parameters and the geometric error was evaluated. An optimal set of grinding conditions was obtained by means of analysis of variance(ANOVA).