• Journal of the Korean Society for Precision Engineering
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• v.34 no.3
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• pp.161-166
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• 2017

Inconel 718, a typical ultraheat-resistant alloy, is recognized as a useful component in aircraft parts owing to its high-temperature strength and good chemical stability. Although many studies have been conducted to determine the proper drill shape to overcome the poor machinability when drilling into Inconel 718, most have involved a cutting process program known as AdvantEdge, as an experimental approach requires much time and money. In this study, our purpose is to optimize the drill shape for efficient drilling by conducting a trust force and temperature analysis using AdvantEdge. In order to achieve this purpose, the reliability of the results of the analysis was verified and by applying design of experiment an analysis of the geometric parameters of the drill shape considering the thrust force and temperature was conducted.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.146-152
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• 1997

This paper deals with a study of striker type impact hammer drill for improving the drilling performance. The study was performed through a numerical simulation of the impact hammer mechanism, an experimental comparison of the numerical simulation results and an optimization of the impact mechanism. The numerical model of the impact hammer drill takes into account the striker motion and the effects of the pressure in the cylinder as well as the friction acting on the striker. The equation of motion is solved with the pressure equation in the cylinder and the friction force. At the moment of impact, an ideal impact model that uses restitutiion codfficient is used to calculate the sudden change of the striker motion. The impact force numerically simulated shows a good agreement with the experimental results and thus, the validity of the numerical model is proven. Based upon the proposed model, an optimization was performed to improve the impact force of the hammer drill. The objective function is to maximize the impact force and the design variables are striker mass, frequency of piston, bit guide mass, cylindrical diameter and dimensions of the mechanism components. Each design variable and some other conditions that are essential to maintain normal operation of the hammer drill are considered as constraints. The optimized result shows remarkable improvement in impact force and an experimental proof was investigated.

• Journal of KSNVE
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• v.7 no.4
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• pp.669-679
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• 1997

This paper deals with a study of striker type impact hammer drill for improving the drilling performance. The study was performed through a numerical simulation of the impact hammer mechanism and an experimental comparison of the numerical simulation results was followed. Optimization of the impact mechanism was also performed. The numerical model of the impact hammer drill takes into account the striker motion and the effects of the pressure in the cylinder as well as the friction acting on the striker. The equation of motion is solved with the pressure equation in the cylinder including the friction force. The friction is considered as a combination of Coulomb friction and viscous damping friction. At the moment of impact, an ideal impact model that uses restitution coefficient is used to calculate the sudden change of the striker motion. The numerically simulated impact force shows a good agreement with the experimental result and thus, the validity of the numerical model is proven. Based upon the proposed model, an optimization was performed to improve the impact force of the hammer drill. The objective function is to maximize the impact force and the used design variables are striker mass, frequency of piston, bit guide mass, cylindrical diameter and dimensions of the mechanism components. Each design variable and some other conditions that are essential to manitain normal operation of the hammer drill are considered as constraints. The optimized result show a remarkable improvement in impact force and an experimental proof was investigated.

• Journal of Periodontal and Implant Science
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• v.52 no.5
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• pp.411-421
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• 2022

Purpose: In this study, we aimed to evaluate the degree of heat generation when a novel drill design with an irrigation slot was used with metal sleeve-free (MF) and metal sleeve-incorporated (MI) surgical guides in an environment similar to that of the actual oral cavity. Methods: A typodont with a missing mandibular right first molar and 21 bovine rib blocks were used. Three-dimensional-printed MF and MI surgical guides, designed for the placement of internal tapered implant fixtures, were used with slot and non-slot drills. The following groups were compared: group 1, MI surgical guide with slot drill; group 2, MI surgical guide with a non-slot drill; and group 3, MF surgical guide with a slot drill. A constant-temperature water bath at 36℃ was used. The drilling was performed in 6 stages, and the initial, highest, and lowest temperatures of the cortical bone were measured at each stage using a non-contact infrared thermometer. Results: There were no temperature increases above the initial temperature in any drilling procedure. The only significant difference between the non-slot and slot groups was observed with the use of the first drill in the MI group, with a higher temperature in the non-slot group (P=0.012). When the heat generation during the first and the second drilling was compared in the non-slot group, the heat generation during the first drilling was significantly higher (P<0.001), and there was no significant difference in heat generation between the drills in the slot group. Conclusions: Within the limitations of this study, implant-site preparation with the surgical guide showed no critical increase in the temperature of the cortical bone, regardless of whether there was a slot in the drill. In particular, the slotted drill had a cooling effect during the initial drilling.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4359-4364
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• 2012

In this study, we carried out finite element analysis for drill bit design on ground boring. We verified analysis between drill bit analysis results and experiment results of test machine. From the study, the results expect that time and cost reduction for experiment using finite element analysis for determination on drill bit geometry and material property.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.2
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• pp.36-44
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• 2000

In this paper drill shape and cutting conditions for environmentally conscious dry drilling of A319 Al-alloy are studied by experimental method. The experiment is planned with Taguchi's method that is based on the orthogonal array of design factors. The result is summarized as follows (1) Drill geometry optimization can increase the number of holes in dry drilling and also large helix angle and large point angle are desirable in dry drilling. (2) It is found that cutting conditions that is cutting speed and feed rate are closely related to the drill geometry(3) For dry drilling of Al-alloys drill shape and cutting conditions are selected and tested by experimental method. But it is found that the perfect dry drilling is difficult because of the machining characteristics of Al-alloys and so new machining method such as minimal lubricant application is required.

• Journal of The Korean Society of Grassland and Forage Science
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• v.23 no.2
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• pp.107-114
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• 2003

Growth characteristics and seed productivities of orchardgrass "Hwabsung 2 Ho" cultivated for seed production were examined in the NLRI from 2000 to 2002. The experimental design was a split-plot arrangement with three replications. The main-plots were three drill widths of 15, 30 and 45cm, and subplots were four nitrogen application levels of 45, 90, 135 and 180kg/ha in early spring. Lodging was less in 45cm of drill width than in 15 and 30cm and was not severe by 90kg per ha of nitrogen including 45cm of drill width. Number of panicles per $1\m^2$ was tended to be more in 15cm of drill width than in 30 or 45cm. Among 45cm of drill widths. 45kg per ha of nitrogen had most numerous panicles. Panicle length, number of 1st branch, weight of 1,000 grain, and germination of 30 or 45cm of drill width showed better characters than that of 15cm. Seed yield was not statistical different among the treatments but was some more in 30cm of drill width, and was tended not to be different among nitrogen levels. Therefore, considering lodging tolerances, seed yield components, and mechanizations, treatment with 45cm of drill width including 45kg per ha of nitrogen in early spring was better than other treatments for orchardgrass seed production.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.264-268
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• 2003

Recently reduction of industrial products in size and weight has been increased by application of micro-drills in gadgets of high precision and a great interest of a micro-drilling has been raised. Due to the lack of tool stiffness and the chip packing, the micro-drilling requires not only the robust tool structure which has not affected by vibration but also effective drilling methods designed to prevent tool fracture from cutting troubles. This paper presents an optimum design shape of a 0.15 mm micro-drill associated with a new manufacturing process to improve the production rate and to lengthen the tool life and suggestions on the micro-drilling characteristic properties associated with the tool life and workpiece quality.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.3
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• pp.133-140
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• 2004

Recently reduction of industrial products in size and weight has been increased by application of micro-drills in gadgets of high precision and a great interest of a micro-drilling has been raised. Due to the lack of tool stiffness and the chip packing, the micro-drilling requires not only the robust tool structure which has not affected by vibration but also effective drilling methods designed to prevent tool fracture from cutting troubles. This paper presents an optimum design shape of a 0.15 mm micro-drill associated with a new manufacturing process to improve the production rate and to lengthen the tool life and suggestions on the micro-drilling characteristic properties associated with the tool life and workpiece quality.

• Journal of Technologic Dentistry
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• v.40 no.1
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• pp.1-8
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• 2018

Purpose: The purpose of this study is to evaluate the trueness and fitness of machined prostheses according to drill radius setting in CAD software. Methods: For this study, standard abutment were replicated in Type IV stone. The stone abutment were scanned using a dental scanner. The CAD design software was designed using scanned abutment data. When designing, the drill radius was set to 0.3 mm and 0 mm, respectively, and saved. The saved design data was milled using a milling machine (n=13). The inner surface of the milled crown was scanned. The trueness and fitness were measured using the inner scan data of prostheses. Independent t-tests were performed to identify significant differences in each data. Results: Trueness values of the data saved with 0.3 mm and 0 mm drill radius were $18.9{\pm}2.3{\mu}m$ and $19.1{\pm}0.9{\mu}m$, respectively. There was no statistically significant difference between the groups. Fitness values of the data saved with 0.3 mm and 0 mm drill radius were $65.5{\pm}0.8{\mu}m$ and $33.8{\pm}1.0{\mu}m$, respectively. There was a statistically significant difference between the groups (p<.05). Conclusion : Setting the drill radius is important to produce clinically good fit prostheses.