• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.22 no.2
• /
• pp.268-274
• /
• 2013

Electric discharge machining drill (EDM-drill) is an efficient process for the fabrication of micro-diameter deep metal hole. As there is non-physical contact between tool (electrode) and workpiece, EDM-drill is widely used to machine the hard machining materials such as high strength steel, cemented carbide, titanium alloys. The electro-thermal energy forces the electrode to wear out together with the workpiece to be machined. The electrode wear occurs inside of a machining hole. and It causes hard to monitor the machining state, which leads the productivity and the quality to decrease. Thus, this study presents a methodology to estimated the electrode wear amount while two coefficients (scale factor and shape factor) of the logarithmic regression model are evaluated from the experiment result. To increase the accuracy of estimation model, the linear transformation method is adopted using the differences of initial electrode wear differences. The estimation model is verified through experiment. The experimental result shows that within minute error, the estimation model is able to predict accurately.

• Geomechanics and Engineering
• /
• v.8 no.4
• /
• pp.477-493
• /
• 2015

In rock drilling, the most important characteristic to clarify is the wear of the drill bits. The reason that the rock drill bits fail with time is wear. In dry sliding contact adhesive wear deteriorates the materials in contact, quickly, and is the result of shear fracture in the momentary contact joins between the surfaces. This paper aims at presenting an overview of the assessment of WC/Co cemented carbide (CC) tricone bit in rotary drilling. To study wear of these bits, two approaches have been used in this research. Firstly, the new bits were weighted before they mounted on the drill rigs and also after completion their useful life to obtain bit weight loss percentage. The characteristics of the rock types drilled by using such this bit were measured, simultaneously. Alternatively, to measure contact wear, namely, matrix wear a micrometer has been used with a resolution of 0.02 mm at different direction on the tricone bits. Equivalent quartz content (EQC), net quartz content (QC), muscovite content (Mu), coarseness index (CI) of drill cuttings and compressive strength of rocks (UCS) were obtained along with thin sections to investigate mineralogical properties in detail. The correlation between effective parameters and bit wear were obtained as result of this study. It was observed that UCS shows no significant correlation with bit wear. By increasing CI and cutting size of rocks wear of bit increases.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.5 no.2
• /
• pp.38-45
• /
• 1996

This study was focused on the prediction of the approprite tool life by clarifying the correlation between progressive drill wear and AE signal. on drilling SM45C the following results have been obtained; RMSAE, AE CUM-CNTS had a tendency to increase slowly according to wear size, at 1000rpm, 150mm/min However, these increased suddenly in the range of 0.20~0.22mm wear, about 102 holes and had a tendency to go up and down until the drilling was impossible. The sudden increase of AE signals shows that something is wrong and it is closely connected with drill wear and chipping. It also makes the working surface bad From the above results, AE signals could be used to monitor the drill's condition and to determine the right time to change tools.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2000.11a
• /
• pp.888-891
• /
• 2000

Drilling is one of the most important operations in machining industry and usually the most efficient and economical method of cutting a hole in metal. From automobile parts to aircraft components, almost every manufactured product requires that holes are to be drilled for the purpose of assembly, creation of fluid passages, and so on. It is therefore desirable to monitor drill wear and hole quality changes during the hole drilling process. One important aspect in controlling the drilling process is drill wear status monitoring. With the monitoring, we may decide on optimal timing for tool change. The necessity of the detection of tool wear, fracture and the abnormal tool state has been emphasized in the machining process. Accordingly, this paper deals with the cutting characteristics of the hot-rolled high strength steels using common HSS drill. The performance variables include drill wear data obtained from drilling experiments conducted on the workpiece. The results are obtained from monitoring of the cutting force and Acoustic Emission (AE) signals, and from the detection of the abnormal tool state with the computer vision system.

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 2001.12a
• /
• pp.74-77
• /
• 2001

One of the most important technology in PA(Factory Automation) is to construct the diagnostic system for manufacturing process. To improve the productibility in the factory, the state of tools such as bite, drill, endmill should be monitored continuously. In this study, fuzzy logic was used to check the wear of drill in drilling process. The input variables to construct the fuzzy rules are cutting force and the rate of cutting force's change. The experiment was done with the fixed spindle speed and feed rate in cutting condition.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.3 s.168
• /
• pp.15-20
• /
• 2005

This paper describes the PCB drilling using an ultra high-speed air bearing spindle system and micro drill. For this research, we have developed the ultra high-speed air bearing spindle of 125,000 rpm and made an experiment for the application possibility in the PCB drilling. In order to estimate the drilling performance, we have investigated the size and damage of drilled hole, and the wear of drill at 90,000rpm. Results are as follows; we have confirmed the possibility in the PCB drilling of air bearing spindle. In case of micro-drilling PCB at $0.1mm\sim0.3mm$, the increase in the number of drilling has resulted in a bigger size of holes and also a bigger size of damage. It has been found that the wear of micro drill tends to concentrate in the main cutting edge.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.21 no.3
• /
• pp.77-85
• /
• 2022

In this study, to diagnose the grinding state of a micro drill bit, a sensor attachment location was selected through random vibration analysis of the grinding unit of the micro drill-bit grinding system. In addition, the vibration data generated during the drill bit grinding were collected from the grinding unit for the grinding wheels under the steady and worn conditions, and data feature extraction and dimension reduction were performed. The wear of the micro-drill-bit grinding wheel was diagnosed by applying KNN, a machine-learning algorithm. The classification model showed excellent performance, with an accuracy of 99.2%. The precision, recall and f1-score were higher than 99% in both the steady and wear conditions.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.11 no.9
• /
• pp.833-836
• /
• 2001

One of the most important technology in Factory Automation and Unmanned Automation is to construct the diagnostic system for manufacturing process. To improve the productivity in cutting process, the state of tools such as bite, drill, endmill should be monitored continuously. In this study, fuzzy logic was used to check the wear of drill in drilling process. The input variables to construct the fuzzy rules are cutting force and the rate of cutting force's change. The experiment was done with the fixed spindle speed and feed rate in cutting condition. The proposed algorithm is verified by comparing Fuzzy wear with real wear measured.

• Journal of Korean Institute of Industrial Engineers
• /
• v.39 no.3
• /
• pp.149-155
• /
• 2013

Electric discharging machining (EDM) is commonly adopted to machine the precise and tiny part when it is difficult to meet the productivity and the tolerance by the conventional cutting method. The die-sinking EDM method works well to machine the micro-parts and the perpendicular wall of die and mould, whereas EDM drilling, called super drill, is excellent to machine the deep and narrow hole regardless the material hardness and the hole location. However, the electrode wear is rapid compared to the conventional cutting tool and makes it difficult to control the electrode feeding and to machine precisely. This paper presents an efficient method to estimate the electrode wear using hole pass-through experiment while the stochastic method is used to compensate for the estimation model. To validate the proposed method, the commercial EDM drill machine is used. The experiment result shows that the electrode wear amount can be predicted very precisely.

• Tribology and Lubricants
• /
• v.39 no.1
• /
• pp.13-20
• /
• 2023

Large drill bits may face high hardness ore and high working pressure when working. To optimize the use effect of large drill bits and prolong the use time, it is necessary to add a layer of pressure-resistant, wear-resistant, and low-friction coating on the surface of the drill bit. In this study, CoCrNiAlTi high-entropy alloy coatings and CoCrNiAlTi (70 wt%)-TiC (30 wt%) composite coatings are successfully prepared on Q235 steel by plasma spraying. The CoCrNiAlTi (70 wt%)-TiC (30 wt%) coating consists of FCC solid solution and a small amount of TiC phase. The effect of TiC on the composition phase, microhardness, and elastic modulus of HEA coating is studied by X-ray diffractometer (XRD) and microhardness tester. The effect of TiC on the friction and wear properties of HEA coatings is investigated using a wear tester. By improving the process parameters, the metallurgical bonding between the coating and the substrate is well combined, and a coating without pores and cracks is obtained. The experimental results confirm that the microhardness, elastic modulus, and wear resistance of CoCrNiAlTi-TiC composite coating are better, and the friction coefficient is lower.