• Journal of the Korean Society for Precision Engineering
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• v.22 no.9 s.174
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• pp.7-13
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• 2005

• Journal of the Korean Society for Precision Engineering
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• v.22 no.9 s.174
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• pp.20-26
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• 2005

• 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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.53-57
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• 1996

The side burrs and shape distortion resulting from the micromachining of an array of V-shape microgrooves in optical components were experimentally invesigated and a simplified model for their formation is proposed. Burr/shpae distortion should be kept to a minimum level since they degrade the characteristics and performance of these parts. The focus of this study is on the influence of depth of cut and workpiece material. The workpiece materials use were brass, bronze and copper. From the obsevation of the chip shape and burr/shape distortion, the proposed model, that the compressive force at the cutting edge causess the ductile uncut chip material to flow plastically outward toward the free surface to result in a burr, was verified.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.434-438
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• 2003

The shearing process for the sheet metal is normally used in the precision elements such as semi-conductor components. In these precision elements, the burr formation brings a bad effect on the system assembly and demands the additional de-burring process. In this paper, we have developed the desktop-type precision punching system to investigate the burr formation mechanism and present kinematically Punch-die auto aligning methodology, for the purpose of burr unifomizing and minimizing, between the rectangular shaped punch and die. By using the scanning electron microscope, the aligned punching results are compared with the miss-aligned ones. Also, we measured the relative burr heights using the self-designed laser measuring device for insitu self aligning. Since it is hard to get the perfect, so called, burr-free edges during the shearing process, we introduced the ultrasonic do-burring machine. The de-burring operation was carried out by a novel do-burring method, the reversal flow resistance method, under different machining loads and abrasive types. The final do-burring results show the validity of our punching do-burring system pursuing the burr-free punched elements.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.867-875
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• 2004

In order to inspect burr geometry and hole quality in micro-drilling processes, a cost-effective method using an image processing and shape from focus (SFF) methods on the machine tool is proposed. A CCD camera with a zoom lens and a novel illumination unit is used in this paper. Since the on-machine vision unit is incorporated with the CNC function of the machine tool, direct measurement and condition monitoring of micro-drilling processes are conducted between drilling processes on the machine tool. Stainless steel and hardened tool steel are used as specimens, as well as twist drills made of carbide are used in experiments. Validity of the developed system is confirmed through experiments.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.12 s.177
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• pp.198-204
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• 2005

For precise micro V-grooving, ultrasonic elliptical vibration cutting (UEVC) is proposed using two parallel piezoelectric actuators, which are energized by sinusoidal voltages with a phase difference of 90 degrees. Experimental setup is composed of stacked PZT actuators, a single crystal diamond cutting tool, and a precision motorized xyz stage. It is found that the chip formed in the process of UEVC is discontinuous because of the periodic contacts and non-contacts occurring between the tool and workpiece. It is experimentally observed that the cutting force in the process of UEVC significantly reduces compared to the ordinary non-vibration cutting. In addition, the creation of burr during UEVC is significantly suppressed, which is attributable to the decrease in the specific cutting energy.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.52-56
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• 2006

Punching tools like an electrodes are made by milling or etching or EDM. These methods had time consuming, low efficiency and air pollution. So, we have developed a shearing device which counter punching method for burrless cutting of micro wire. Using the straightened SUS304 wire with $200{\mu}m$ diameter, we confirmed the tendency of the shear plane for punch tools. It was impossible to completely remove the bun in the shearing process. In order to minimize the burr size and fine shear plane, we have accomplished the various experiment conditions such as the U-groove, the effect of the counter punch, shear angle and clearance. The results of the experiments show that indentation, slip plane and bent shape were related to the shear angle and clearance.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.107-110
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• 2003

The sheet metal shearing process is normally used in the precision elements such as semi-conductor components. In precision elements, burrs usually reduce the quality of machined parts and cause interference, jamming and misalignment during assembly procedures and because of their sharpness, they can be safety hazard to personnel. Furthermore, not only burrs are hard to predict and avoid, but also deburring, the process of removing burrs, is time-consuming and costly. In order to get the burr-free parts, therefore, we developed the precise burr measuring system using the laser. Using the X-Y precious table, we used vertical measuring method. Through the laser measurement system, we gain the minute analog signal, so this signal was amplified by the electric circuit. Finally, we gained the realtime burr data using A/D converter, PC. By introducing the novel laser measuring method which employing vertical measurement mechanism, we could get fast and precious burr data. Through the experiments, the accuracy of the developed system is proved. The burr height measured during the punching process can be used for automatic deburring and in-situ aligning.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.7
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• pp.70-75
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• 2004

The shearing process for the sheet metal is normally used in the precision elements such as a lead frame of IC chips. In these precision elements, the burr formation brings a bad effect on the system assembly and demands the additional deburring process. In this paper, we developed the small size precision punching system to investigate burr formation mechanism and to present kinematically punch-die aligning methodology between the rectangular shaped punch and die. The punch is driven by an air cylinder and the sheet metal is moving on the X-Y table system which is driven by two stepping motors. The whole system is controlled by microprocessor and is communicated with each other by RS232C serial communication protocol. Punching results are measured manually using the SEM photographs and are compared aligning result with miss aligning one.