• Korean Journal of Materials Research
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• v.18 no.12
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• pp.635-639
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• 2008

In this paper, experimental studies of the regrinding of tungsten carbide (WC-Co) tools for high-speed machining were conducted. Regrinding and a subsequent evaluation test were carried out for a flat endmill tool with diameters of 10 mm and 3 mm using a CNC five-axis tool grinder and a CNC three-axis machining center. Tool wear on the two types of endmill tools increased as the cutting length increased, and the tool wear was not influenced by the regrinding state. In case of the micro endmill with a tool diameter of 3 mm, the effective regrinding time was determined for a flank wear threshold of 0.3 mm considering the tool life according to cutting length. The tool lives of the 10 mm and 3 mm endmill tools were increased by 80% and 72%, respectively. This conclusion proves the Feasibility of the recycling of tungsten carbide materials in the high-speed machining of high-hardened materials for industrial applications.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.1 s.94
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• pp.182-190
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• 1999

The objective of this study is to develop an analysis scheme in order to predict regrinding due to tool wear in shearing process. The analysis of material now and fracture in shearing process should precede the prediction of tool wear. Thus the developed FE-program to analyze shearing process is used. In order to predict tool wear, the wear model is reformulated as an incremental form and then the wear depth of tool is calculated at each deformation path. Because the regrinding of shearing tool is determined on the basis of allowable size of burr, the analysis of shearing process is iteratively performed using the worn profile of tool. To show the effectiveness of the scheme the simulation result is compared with experimental one.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.489-490
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• 2013

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1999.06a
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• pp.201-206
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• 1999

The influence of surface preparation methods after plasma cutting on the quality of welding zone is investigated. For comparison. three types of welded specimens are prepared by machining(YM), plasma cutting with light regrinding(WPG) and without regrinding(WP), by using three kinds of materials, carbon steel(S45C), stainless steel(Type304) and aluminum alloy (6061-T6). Nondestructive examination, hardness test, microstructure examination, and fracture toughness test are performed. The results show that there is no appreciable reduction in hardness or fracture toughness in WP specimens. But a little difference in heat affected gone size is observed.

• Korean Journal of Materials Research
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• v.19 no.12
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• pp.661-666
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• 2009

Froth flotation has been carried out in order to produce roasting-molybdenite concentrate from molybdenite ore in the Shin-yeomi mine. In our study, roasting-molybdenite (Mo 0.43%) from Shin-yeomi mine was recovered by varying the conditions of regrinding time, dosage of collector and alkalinity. Liberation and flotation efficiency more were effective at regrinding time of six minutes than at single grinding. Mo recovery curves increased considerably as dosage of kerosene increased, whereas Mo grade curves decreased gradually. The separation efficiency of molybdenite was effective when the dosage of collector (kerosene) was adjusted to 300 g/t. The molybdenite concentrate was agglomerated in the range of pH 5-7 and its separation efficiency increased to pH 9-10. The concentrate of 49.5% Mo grade ($MoS_2$, 82.6%) with 81.5% recovery from Shin-yeomi molybdenite ores was obtained under conditions of 20% pulp concentration, 300 g/t kerosene 325 g/t frother (AF65), 2.5 kg/t depressant ($Na_2SiO_3$), pH 9-10 and four cleaning times. In the future, a trial run that can separate up to 50% Mo grade from Shin-yeomi molybdenite ores will be performed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.1
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• pp.8-13
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• 2016

The micro drill bit automatic regrinding in-line system is a system that refurbishes drill bits used in a PCB manufacturing process. This system is able to refurbish drill bits with a minimum size of ø0.15-0.075mm that have previously been discarded. Beyond the conventional manual cleaning process using ultrasound, this system adopts a water jet cleaning system, making it capable of cleaning drill bits with a minimum size of ø0.15-0.075mm. This paper analyses various contact pressures applied to the surface of drill bits depending on the shooting pressure of the cleaning device and fluid velocity in order to optimize the nozzle location and to detect structural instability caused by the contact pressures.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.9
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• pp.68-74
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• 1999

The influence of surface preparation methods after plasma cutting on the quality of weld zone was investigated. For comparison, three types of welded specimens were prepared by machining (WM), plasma cutting with light regrinding (WPG) and without regrinding (WP), by using three kinds of materials, carbon steel (SM45C), stainless steel (STS304) and aluminum alloy (A6061-T6). Nondestructive examination, hardness test, microstructure examination, and fracture toughness test were performed. The results showed that there was no appreciable reduction in hardness or fracture toughness in WP specimens. But a little difference in heat affected zone size was observed.

• Journal of the Korean Ceramic Society
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• v.36 no.11
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• pp.1150-1155
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• 1999

• Journal of the Korean Ceramic Society
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• v.32 no.2
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• pp.147-154
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• 1995

Abnormal grain growth behavior of BaTiO3 ceramics with controlling of particle size distribution of calcined powder was investigated. The particle size distribution was controlled by changing the calcining temperature or by using of classification and regrinding process. With broadening of the normallized size distribution in calcined powder, it showeda normal grain growth behavior in sintered body due to an increase of volume fraction of seed grain in the calcined powder. It was supposed that the seed grains could easily contact each other for the rapid grain growth during sintering process and resulted in fast switching-over from abnormal to normal grain growth stage.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.1063-1067
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• 1997

A study of carbide step drill cutting ability is highly progessing the step drill with more then twice diameter rate is so difficult in regrinding and very easy to damage during machining. As the machining of step drill for closed hole is occur to breakage at small diamter poistion, so it is very difficult to machinine. Thue, in this experiment, We investance roundness and surface roghness by machining distance and were identifid that the first distance, 5~10m, was fine with 7 .mu.m but the arround of 15m was happened so much alternation. And we were indentified that after 20m was happend statable machining. The surface roughness was happened the same conditions. So application of stwp drill we think that the selection of cutting conditions need lots consideration and the study of step drill's diameter ratio ratio is carred out.