• Design & Manufacturing
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• v.6 no.2
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• pp.70-73
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• 2012

Drill process is usually used to manufacture a industry about processing, Therefore, the burr problem is very significant, The burrs took place when drill process. And then, sometimes, the burrs are often caused of some problems during automatic such as no good quality products and having good surface roughness products. And also, this paper had some experiments using magnesium. Specially, the magnesium is one of the non-ferromagnetic materials. Magnesium has attracted a lot of interest for using the industry. They offer a possible alternative to steel and aluminum in automotive and aero industries to satisfy the lightweight requirement. also, magnesium has good specific strength and absorbs vibration in occurring working process. So, it has good quality of product processing. And then, it is one of the lightest materials being used to electronic product's cases and automotive because of lightweight and miniaturization. But this material has not widely used all of the industry due to its natural property. If the magnesium is contacted water, it will cause the exploration. But, nowadays many of people study magnesium to safe their experiment and to widely use this industry.

• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.51-54
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• 2008

Drill process is usually used to manufacture a industry about processing, Therefore, the burr problem is very significant, The burrs took place when drill process. And then, sometimes, the burrs are often caused of some problems during automatic such as no good quality products and having good surface roughness products. And also, this paper had some experiments using magnesium. Specially, the magnesium is one of the non-ferromagnetic materials. Magnesium has attracted a lot of interest for using the industry. They offer a possible alternative to steel and aluminum in automotive and aero industries to satisfy the lightweight requirement. also, magnesium has good specific strength and absorbs vibration in occurring working process. So, it has good quality of product processing. And then, it is one of the lightest materials being used to electronic product's cases and automotive because of lightweight and miniaturization. But this material has not widely used all of the industry due to its natural property. If the magnesium is contacted water, it will cause the exploration. But, nowadays many of people study magnesium to safe their experiment and to widely use this industry.

• Carbon letters
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• v.23
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• pp.1-8
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• 2017

Polycrystalline diamond (PCD) tools possessing high hardness and abrasive wear resistance are particularly suited for drilling of carbon fiber reinforced plastic (CFRP) composites, where tool life and consistent hole quality are important. While PCD presents superior performance when drilling CFRP, it is unclear how it performs when drilling multi-stack materials such as CFRP-titanium (Ti) stacks. This comparative study aims to investigate drilling of a Ti plate stacked on a CFRP panel when using PCD tools. The first sequence of the drilling experiments was to drill 20 holes in CFRP only. CFRP-Ti stacks were then drilled for the next 20 holes with the same drill bit. CFRP holes and CFRP-Ti stack holes were evaluated in terms of machined hole quality. The main tool wear mechanism of PCD drills is micro-fractures that occur when machining the Ti plate of the stack. Tool wear increases the instability and the operation temperature when machining the Ti plate. This results in high drilling forces, large hole diameter errors, high surface roughness, wider CFRP exit thermal damage, and taller exit Ti burrs.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.12
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• pp.152-158
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• 2001

In this paper, we have developed an electro discharge machine for micro drilling driven by a voice coil actuator. Because the voltage signal of the electro-discharging circuit shows a lot of peaks and valleys, the active type low-pass filtering technique is adopted to get the average of the signal. Since the motion of the voice coil is precisely controlled by the error value between the object voltage value and the measured one, it is possible to prevent the mechanical contact between the rotating electrode and the workpiece and to maintain the appropriate machining conditions during the process. The electro-chemical machining technology was also adopted to make small diameter electrodes. Pure water is used as a dielectric. The machining procedure is performed to verify the feasibility of the developed system. It takes about 10 seconds to drill the ${\phi}m$100${\mu}m$ hole to the 100${\mu}m$ thickness stainless steel plate. The machining time depends on the values of the resister and the capacitor. There may exist the optimal values of time constant and the tendency is displayed In the appendix.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.4 s.181
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• pp.29-36
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• 2006

Micro drilling by high-speed air bearing spindle is very useful manufacturing technology in electronic industry For the design of high speed air bearing spindle, there are considered stability of air bearing spindle, allowable load of air bearing, run out and tooling system design for micro drill's attach and remove. According to suggested details, we designed and manufactured high-speed air bearing spindle and carried out performance estimation such as run out, temperature change in running air bearing spindle, stiffness, chucking torque. Results are follows; Run out was measured under $5{\mu}m$ at air bearing spindle revolution $20,000\sim125,000rpm$. High speed air bearing spindle's temperature rose about $20^{\circ}C$ after 5 minutes from running and then was fixed. Allowable thrust load of spindle was 17kgf. Chucking torque of collet was 15kgfcm.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.2
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• pp.13-19
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• 2010

Due to the rapid spread of mobile handheld devices, industrial demands for micro-scale holes with a diameter of even smaller than $10{\mu}m$ in sapphire/silicon wafers have been increasing. Holes in sapphire wafers are for heat dissipation from LEDs; and those in silicon wafers for interlayer communication in three-dimensional integrated circuit (IC). We have developed a sapphire wafer driller equipped with a 532nm laser in which a cooling chuck is employed to minimize local heat accumulation in wafer. Through the optimization of process parameters (pulse energy, repetition rate, number of pulses), quality holes with a diameter of $30{\mu}m$ and a depth of $100{\mu}m$ can be drilled at a rate of 30holes/sec. We also have developed a silicon wafer driller equipped with a 355nm laser. It is able to drill quality through-holes of $15{\mu}m$ in diameter and $150{\mu}m$ in depth at a rate of 100holes/sec.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.6
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• pp.638-643
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• 2013

Laser beam machining (LBM) is fast, contactless and able to machine various materials. So it is used to cut metal, drill holes, weld or pattern the imprinted surface. However, after LBM, there still leave burrs and recast layers around the machined area. In order to remove these unwanted parts, LBM process often uses electrochemical etching (ECE). But, the total thickness of workpiece is reduced because the etching process removes not only burrs and recast layers, but also the entire surface. In this paper, surface coating was performed using enamel after LBM on metal. The recast layer can be selectively removed without decreasing total thickness. Comparing with LBM process only, the surface quality of enamel coating process was better than that. And edge shape was also maintained after ECE.

• Design & Manufacturing
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• v.2 no.5
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• pp.39-42
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• 2008

The Paper discussed the effects of working electric current and pulse when using super hardend alloy drill as corona electrode. The discharge effect can be obtained very precisely in the ranges of 1A - 2A in working current. $12{\mu}s-14{\mu}s$ in dis charge pulse on time width and $8{\mu}s-10{\mu}s$ in discharge pulse off time.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.435-440
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• 2000

In this study, we aims to develop the machining technology for the ultra precision surface and profile accuracy. For this purpose, we construct the electrolytic in process grinding system (ELID grinding) and apply to the cylindrical and internal grinding. Through the various machining experiments such as SCM steel., ceramics, tungsten carbide etc., we have obtained nanometer surface roughness. And we have applied this mirror grinding technique to hydraulic manual valve and mold core of mini disk optical pick-up base. For the development of fine mechanical part machining technology, e have made multi fiber optical connector using fine grinding technology. And constructed micro drilling system with process monitoring system which is possible to drill 50${\mu}{\textrm}{m}$ diameter hole.

• Journal of Korean Neurosurgical Society
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• v.58 no.6
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• pp.571-577
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• 2015

Direct removal of beak-type ossification of posterior longitudinal ligament at thoracic spine (T-OPLL) is a challenging surgical technique due to the potential risk of neural injury. Slipping off the cutting surface of a high-speed drill may result in entrapment in neural structures, leading to serious complications. Removal of T-OPLL with an ultrasonic osteotome, utilizing back and forth micro-motion of a blade rather than rotatory-motion of drill, may reduce such complications. We have applied the ultrasonic osteotome for posterior circumferential decompression of T-OPLL for three consecutive patients with beak-type OPLL and have described the surgical techniques and patient outcomes. The preoperative chief complaint was gait disturbance in all patients. Japanese orthopedic association scores (JOA) was used for functional assessment. Scores measured 2/11, 5/11, 2/11, and 4/11 for each patient. The ventral T-OPLL mass was exposed after posterior midline approach, laminotomy and transeversectomy. The T-OPLL mass was directly removed with an ultrasonic osteotome and instrumented segmental fixation was performed. The surgeries were uneventful. Detailed surgical techniques were presented. Gait disturbance was improved in all patients. Dural tear occurred in one patient without squeal. Postoperative JOA was 6/11, 10/11, 8/11, and 8/11 (recovery rate; 44%, 83%, 67%, and 43%) respectively at 18, 18, 10, and 1 months postoperative. T-OPLL was completely removed in all patients as confirmed with computed tomography scan. We hope that surgical difficulties in direct removal of T-OPLL might be reduced by utilizing ultrasonic osteotome.