• Korean Journal of Computational Design and Engineering
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• v.1 no.2
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• pp.150-157
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• 1996

The hob is considered as an effective gear cutting tool for achieving the various gears such as spur gear, helical gear, worm gear and so on. To enhance the productivity and precision of hobs and the competitive ability of domestic CNC hob relieving lathes, a CAM system for CNC hob relieving lathe needs to be realized. In this study, the CAM system is developed based on the personal computer and C language. Besides the automatic generation of CNC data, the developed CAM system has the various capabilities related to the generation of tool path, the cutting simulation for verifying the generated CNC data and forecasting the cutting time, the DNC operation for communicating the CNC data with CNC controller by RS232C port, and the estimation of undercut length for verifying the hob cutting conditions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3175-3184
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• 1994

The high strength and wear-resistant metal bonded diamond wheel was applied to the drilling process of carbon fiber reinforced plastics (CFRP), The helical-feed drilling method was use for the first time to overcome the limit of drilling depth of the conventional drilling process and to improve the dressing of the wheel. The helical-feed drilling method was found effective at high cutting speed without the limit of drilling depth.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.4
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• pp.138-146
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• 1997

The optimal drill helix angle, point angle, and cutting conditions are recommended in the study so as to maximize the drilling performance by investigating the experimental reaults concerning with the state of chip formation, roundness of machined holes, and geometry of projected burr at hole exit, which are examined under the conditions of various helix angles, drill point angles of twist drill, cutting speeds, and feeds in operional parameters. In the easiness of chip escape, the helical type of chip is producted when a helix angle is 30$^{\circ}$, drill point angle 118$^{\circ}$, 140$^{\circ}$and feed is st between 0.1 and 0.15mm/rev. Roundness of machined hole is improved when the helix angle is 37$^{\circ}$, drill point angle is 118$^{\circ}$, and feed is 0.15mm/rev. The height of projected burr at the button of machined hole increases when the drill point angle and helix angle becomes large.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.8
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• pp.164-174
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• 1996

As tools for machining precision componants, end mills and ball end mills are widely used. For the end mills have longer cylindrical shape comparing dianeter, they are liable to deflect when machining and induce geometrical error and deterioration of surface roughness. To improve the stiffness and the sharpness of the cutting edge of end mill, a software for manufacturing end mills are developed. The program predicts the result of helical flute grinding and the configuration of cuting edge which is located in cylindrical surface. Furthermore to facilitate the manufacturing end mills using CNC grinding machine, the setting condition which satisfy the geometrical requirements like tool rake angle and stiffness are obtained.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.9-14
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• 1996

The deflection of an end mill is very important in machining process and cutting simulation because it affects directly workpiece accuracy, cutting force, and chattering. In this study, the deflection of the end mill was studied both experimentally and by using finite element analysis. And the moment of inertia of radial cross sections of tile helical end mill is calculated for the determination of the relation between cross section and rigidity of tile tools. Using tile Bernoulli-Euler beam and and the concept of equivalent diameter, a deflection model is established, which includes most influence from tool geomety parameters. It was found that helix angle attenuates the rigidity of the end mill.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.176-181
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• 1994

As tools for machining precesion componants, end mills and ball end mill are widely used. For the end mill have longer cylindrical shape comparing diameter, they are liable to deflect when machining and induce geometrical error and deterioration of surface roughness. To improve the stiffness and the sharpness of the cutting edge of end mill, a software for manufaturing end mills are developed. The progeam predicts the result of helical flute grinding and the configuration of cutting edge which is located in cylindrical surface. Furthermore to facilitate the manufacturing end mill using CNC grinding machine, the setting conditions which satisfy the geometrical requirments like tool rake angle and stiffness are obtained.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.3
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• pp.63-68
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• 2017

In order to process more complicated and higher-precision parts, generally, an additional axis for a machine tool is needed which was an approach to minimize the cost of tool modification. A table with a rotary reducer that can rotate through the axis of the gear system was employed to a machine tool to achieve the purpose of adding an extra motion axis. In general, the motion of the rotary reducer is driven by a worm/wheel or helical gear system, which is different from the hypoid helical gear structure that used in this research. Reliability of guarantee of high accurancy throughout the whole life cycle is on of the critical factors to evaluate a rotary reducer in this field. In this paper, in order to evaluate life-time of rotary reducer, a low-cost accelerated life test was developed to satisfy the demands of clients.

• The korean journal of orthodontics
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• v.39 no.2
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• pp.95-104
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• 2009

Objective: The purpose of this study was to evaluate the effect of length and shape of cutting flute on mechanical properties of orthodontic mini-implants. Methods: Three types of mini-implants with different flute patterns (Type A with 2.6 mm long flute, Type B with 3.9 mm long and straight flute, Type C with 3.9 mm long and helical flute) were inserted into the biomechanical test blocks (Sawbones Inc., USA) with 2 mm and 4 mm cortical bone thicknesses to test insertion and removal torque. Results: In 4 mm cortical bone thickness, Type C mini-implants showed highest maximum insertion torque, then Type A and Type B in order. Type C also showed shortest total insertion time and highest maximum removal torque, but Type A and B didn't showed statistically significant difference in insertion time and removal torque. In 2 mm cortical bone thickness, there were no significant difference in total insertion time and maximum removal torque in three types of mini-implants, but maximum insertion torque of Type A was higher than two other Types of mini-implants. Conclusions: Consideration about length and shape of cutting flute of mini-implant is also required when the placement site has thick cortical bone.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.12
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• pp.143-152
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• 1997

The deflection of an end mill is very important in machining process and cutting simulation because it affects directly workpiece accuracy, cutting force, and chattering. In this study, the deflection of the end mill was studied both experimentally and by using finite element analysis. And the moment of inertia of cross sections of the helical end mill is calculated for the determination of the relation between geometry of radial cross section and rigidity of the tools. Using the Bernoulli-Euler beam theory and the concept of equivalent diameter, a deflection model is established, which includes most influences from tool geomety parameters. It was found that helix angle attenuates the rigidity of the end mill by the finite element analysis. As a result, the equivalent diameter is determined by tooth number, inscribed diameter ratio, cross sectional geometry and helix angle. Because the relation betweem equivalent diameter and each factor is nonlinear, neural network is used to decide the equivalent diameter. Input patterns and desired outputs for the neural network are obtained by FEM analysis in several case of end milling operations.

• Restorative Dentistry and Endodontics
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• v.36 no.1
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• pp.1-11
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• 2011

Introduction: The aim of this paper is to discuss the mechanical and geometric features of Nickel-titanium (NiTi) rotary files and its clinical effects. NiTi rotary files have been introduced to the markets with their own geometries and claims that they have better ability for the root canal shaping than their competitors. The contents of this paper include the (possible) interrelationship between the geometries of NiTi file (eg. tip, taper, helical angle, etc) and clinical performance of the files as follows; - Fracture modes of NiTi rotary files - Non-cutting guiding tip and glide path - Taper and clinical effects - Cross-sectional area and clinical effects - Heat treatments and surface characteristics - Screw-in effect and preservation of root dentin integrity - Designs for reducing screw-in effect Conclusions: Based on the reviewed contents, clinicians may have an advice to use various brands of NiTi rotary instruments regarding their advantages which would fit for clinical situation.