• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.33-37
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• 2009

Finite-element methods are used to study non-adhesive, frictionless rough contact of elastic and plastic solids. Roughness on spherical surfaces is realized by self-affine fractal. True contact area between the rough surfaces and flat rigid surfaces increases with power law under external normal loads. The power exponent is sensitive to surface roughness as well as the curvature of spherical geometry. Surface contact pressures are analyzed and compared for the elastic and plastic solids. Distributions of local contact pressure are shown dependent on the surface roughness and the yield stress of plastic solids.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.255-259
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• 2001

The spring constant of a micro coil spring was measured by uniaxial tensile test. The inner diameter of it is $35{\mu}m$ and the pitch size is about $23{\mu}m$. A suing constant measurement system was developed. It consists of control units, load cell units, linear stages and several specially designed jigs and fixtures. Load and displacement are measured using a commercial load cell of 1000g capacity and a magnetic scale of $0.5{\mu}m$ resolution. In this study, a method to measure the spring constant of micro coil spring is presented and the relationship between misalignment of specimen and measurement error is discussed.

• Transactions of Materials Processing
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• v.12 no.2
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• pp.128-133
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• 2003

In this study, the momentum conservation type punching mechanism for micropunching system was developed to avoid the punch failure in the misaligned status between the punch and die. The punching energy can be precisely controlled by the falling height of the projectile mass and the intermediata mass, which contacts with the punch, transmit the energy to the punch with the same contact condition. The potential energy of the projectile mass is converted to kinetic energy at the light weight punch that the projection speed into the sheet metal workpiece can be accelerated. The butt formation characteristics for the alignment condition and for the projection speeds are investigated to verify the feasibility of the proposed punching mechanism.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.76-79
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• 2003

Glass molding is an advantageous method to manufacture glass micro optical components. However, it is difficult to make tungsten carbide core for glass molded micro optics way. We have developed novel method to fabricate tungsten carbide core for glass molding of glass micro optical components. Silicon masters were fabricated by micro machining. Tungsten Carbide cores were fabricated by forming, sintering and coating. Finally we fabricated glass molded V-groove with pitch of 192$\mu\textrm{m}$ and glass microlens way with lens diameter of 36∼225$\mu\textrm{m}$ by the present method.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.381-385
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• 2003

This paper presents the fabrication possibility of the micro actuator which uses a micro-thermal bubble, generated by a micro-heater under pulse heating. The micro-actuator is consist of three plate. The lower plate includes the channel and chamber are fabricated on high processability silicon wafer by the DRIE(Deep Reactive ion Etching) process. The middle plate includes the chamber and diaphragm, and the upper plate is the micro-heater. The micro-heater designed non-uniform width and results in periodic generation of stable single bubbles in D.I water. The single bubble appears precisely on the narrow part of the micro-heater and control is recorded.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.371-376
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• 2003

The hot embossing process has been mentioned as one of major nanoreplication techniques. This is due to its simple process, low cost, high replication fidelity and relatively high throughput. As the initial step of quantitating the embossing process, simple parametric study about embossing time have been carried out using high-resolution masters which patterned by the DRIE process and laser machining. Under the various embossing time, the viscous flow of thin PMMA films into microcavities during Compression force has been investigated. Also, a study about simulating the viscous flow during embossing process has planned and continuum scale FDM analysis was applied on this simulation. With currently available test data and condition, simple FDM analysis using FLOW3D was made attempt to match simulation and experiment.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.377-380
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• 2003

Recently, demand of digital products with optoelectronic device is increasing rapidly. A microlens array is applied to improve optical efficiency on optoelectronic device, and it is usually fabricated by photolithography and reflow process after planarization layer coating process. UV molding process is more suitable for mass production of high quality microlens array than photolithography and reflow process. In the present study, microlens array was fabricated on the simulated optoelectronic device with planarization layer by aligned UV molding process. The shape of replicated microlens was measured, and the section image of molded part was examined.

• Transactions of Materials Processing
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• v.18 no.2
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• pp.144-149
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• 2009

Recently, the monitoring technology of machining process is very important to improve productivity and quality in manufacturing filed. Such monitoring technology has been performed to measurement using vibration signal, acoustic emission signal and tool dynamometer. However, micro machining is limited small-scale parts machining because micro tool is very small and weakness to generate signal in micro machining process. Therefore, this study has efficient sensing technology for real monitoring system in micro machine that is proposed to supplement a disadvantage of single-sensor by multi sensor. From experimental result, it was evaluated tool wear and cutting situation according to repetitive slot cutting condition and changing cutting condition, and it was performed monitoring spindle rpm and condition according to compare acceleration signal with current signal.

• Transactions of Materials Processing
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• v.18 no.2
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• pp.166-171
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• 2009

In this paper, a basic study on micro cutting process with SM20C at low temperature environment was performed. In macro cutting fields, the cryogenic cutting process has been applied to cut the refractory metal but, the serious problem may be generated in micro cutting fields by the cryogenic environment. However, if the proper low temperature is applied to micro cutting area, the cooling effect of cutting heat is expected. Such effect can make the reduction of tool wear and burr formation. For verifying this possibility, the micro cutting experiment at low temperature was performed and SEM images were analyzed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.452-457
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• 2003

As a fundamental study on developing elements with micro shape, micro mold parts machining and experiment of injection molding using it were performed. The ultra precision micro machining system with high functionality was fabricated, and utilized in the machining of micro parts. By using this machining system and micro end-mill tool, a micro circle column structure of high aspect ratio, diameter 60 $\mu\textrm{m}$, height 500 $\mu\textrm{m}$, was fabricated. And a micro lens molds were fabricated by using ball end-mill tool of 300 $\mu\textrm{m}$ diameter and diamond fly-cut tool of 150 $\mu\textrm{m}$ radius. A micro injection molding machine, which is clamping force 1.75 ton, injection capacity 2.8cc, was fabricated for injection molding experiment using micro molds. The injection molding experiment was performed by using the injection molding machine, micro cylinder structures and lens molds. This paper introduces these micro machining system and injection molding machine and demonstrates examples of injection molding using fabricated molds.