• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.02a
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• pp.260-265
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• 2002

In micro hole punching process, it is very difficult to align punch with die hole. Misalignment can cause a falling-on in hole quality and breakage of punch and die. Micro punching using soft die plate without a die hole has a big advantage because it is not necessary to align punch with die hole and to consider die clearance. Soft die plates are made by polymers or hard rubbers which are softer than metals. In this study, several micro punching experiments are conducted. Micro punching test with some materials shows that micro hole punching is feasible with some soft die plates. Through the section shape obtained by mounting and polishing, the punched hole quality is measured and the shapes of burr and dome we studied.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10b
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• pp.179-188
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• 2003

The objective of our study is to investigate the micro fabric ability by conventional metal forming processes. In the present investigation, micro hole punching was studied. We tried to control punching process at the micro level and scaled down the standard blanking condition for $25{\mu}m$ hole fabrication. To accommodate this, tungsten carbide tooling sets and micro punching press were carefully designed and assembled meeting accuracy requirements for $25{\mu}m$ hole punching. With our developments, 100, 50, and $25{\mu}m$ holes were successfully made on metal foils such as brass and stainless steel of 100, 50, and $25{\mu}m$ in thickness, respectively, and hole sizes and shapes were measured and analyzed to investigate fabrication accuracy. Shear behavior during micro punching was also discussed. Our study showed that the conventional punching process could produce high quality holes down to $25{\mu}m$.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.02a
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• pp.239-244
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• 2002

In this study, we developed the manufacturing technology of micro-hole and micro-shaft for micro punching system using micro electrical discharge machining and micro electro chemical machining. Micro punching dies of tungsten carbide with $55\;{\mu}m\;and\;110\;{\mu}m$ diameter and $250\;{\mu}m$ depth were made by micro electrical discharge machining. The form accuracy and surface roughness of die hole were pretty good and it was shown that the punched hole quality was fine. WC micro-shaft with $30\;{\mu}m$ diameter was made by the multistep micro electro chemical machining. The developed technologies can be effectively used in precision manufacturing of micro punching die and mass production of micro-shaft.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.213-216
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• 2001

A micro hole punching system was developed and micro holes of 100m in diameter were successfully made on brass sheets of loom in thickness. A micro punch made of tungsten carbide was designed to withstand the punch load, considering the buckling and the bending moment due to possible misalignment error. The punch was fabricated by the grinding process with diamond wheel. The die was designed considering the punch load and fabricated by micro electrodischarge machining process. In this system the stripper is designed to guide punch tip to minimize the possible misalignment. The punch was installed on a vertical stepper and the die was mounted on an X-Y translation unit. The precision motion controller controlled all motions of the micro hole punching system. In this study technical difficulties and solutions in the micro hole punching process were also discussed.

• Transactions of Materials Processing
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• v.13 no.3
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• pp.190-204
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• 2004

The objective of this study is to develop a highly accurate micro tool alignment system applicable to the micro machining technology. In a specific application such as micro hole punching, radial clearance between micro tools is order of a few micron. Under this micron scale tool clearance, accuracy of tool alignment is very important for ensuring hole quality. In the present study, a two-way image acquisition system was developed, which can produce overlapped image of both micro tools that face each other, and applied to the tool alignment in the micro punching. Also, to meet alignment accuracy of tools within $1\mu\textrm{m}$, the cross correlation image processing algorithm was employed. With this system, $25\mu\textrm{m}$ punching tools with $1\mu\textrm{m}$ radial clearance could be accurately aligned.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.386-390
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• 2003

As a trial of application of hydrostatic pressure in micro fomring, burr-free punching has been conducted by means of hydro-mechanical procedure. Even though it is in beginning stage, result of the hydro-mechanical punching is promising. Hydrostatic pressure helps delay fracture initiation and makes it possible to get clean shearing surface. Without any burr on both side of sheet, smooth holes are archived as intended. To verify the significance of hydro-mechanical punching, conventional punching is performed under similar conditions and relatively larger portion of fracture surface is detected in the punching hole. Despite the quality of sidewall is not good enough, it might be possible to make the hole shaped upright, reduce the roll-over radius and minimize the fracture surface by optimizing process parameters.

• Transactions of Materials Processing
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• v.12 no.4
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• pp.314-319
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• 2003

In the micro hole punching, the size and shape of burr and burnish zone are very important factors to evaluate quality of micro holes which depend on punch-die clearance, strain rate, workpiece material and etc. To get micro holes with small burr and wide burnish zone for industrial demands, not only the parametric study but also a study on fracture behavior in shear band are necessary. In this study, 100 $\mu$m, 25 $\mu$m micro holes in diameter were fabricated on brass (Cu63/Zn37) and SUS 316 foils as aspect ratio 1:1, and the characteristics of micro holes was investigated comparing with those of macro holes over several mm by scanning electron microscopic views and section views. Like macro hole, micro hole is also composed of 4 portions, rollover. burnish zone, fracture zone and burr, and it shows similar fracture behavior in shear band. But by high strain rate (10$^2$∼10$^3$s$^{-1}$ ) condition unlike that of macro hole fabrication and by the increment of relative grain size in the direction of the workpiece thickness, fracture zone is not observed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.230-235
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• 2003

In the micro hole punching, the size and shape of burr and burnish zone are very important factors to evaluate quality of micro holes which depend on punch-die clearance, stain rate, workpiece material and etc. To get micro holes with small burr and wide burnish zone for industrial demands, not only the parametric study but also a study on fracture behavior in shear band are necessary. In this study, 100 $\mu\textrm{m}$, 25 $\mu\textrm{m}$ micro holes in diameter were fabricated on brass (Cu63/Zn37) and SUS 316 foils as aspect ratio 1:1, and the characteristics of micro holes was investigated comparing with man holes over several mm by scanning electron microscopic views and section views. Like macro hole, micro hole is also composed of 4 portions, rollover, burnish zone, fracture zone and it shows similar fracture behavior in shear band, but？ by high strain rate (10$^2$∼ 10$^3$s$\^$-1/) unlike macro hole fabrication and increment of relative grain size several different results are shown.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.3
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• pp.61-67
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• 2004

In micro hole punching process the burr occurs inevitably, but the burr must be minimized in order to improve the quality and accuracy of the product. In this study, magnetic field-assisted polishing technique is applied to remove the burr which exists in nozzles for ink-jet printer head and proved to be a feasible for deburring by experiment. The deburring characteristics of sheet metals was investigated changing with polishing time and magnetic abrasive size. After the deburring, the burr size has remarkably reduced and roundness of the hole also has improved.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.329-333
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• 2003

In micro hole punching process the burr occurs inevitably, but the burr must be minimized in order to improve the quality and accuracy of the product. In this study, magnetic field assisted polishing technique is applied to remove the burr which exists in nozzles for ink-jet printer head and proved to be a feasible for deburring by experiment. The deburring characteristics of sheet metals was investigated changing with polishing time. After the deburring, the burr size has remarkably reduced and roundness of the hole also has improved.