• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.9
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• pp.1359-1367
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• 2001

Improvement of machine tool accuracy is an essential part of quality control in manufacturing process. Among of all the errors of a particular machine tool, the thermal errors of the spindle have a notably significant effect on machining accuracy and have a direct influence upon both the surface finish and geometric shape of the finished workpiece. Therefore, this paper proposed new measurement method for thermal errors of the spindle in machine tools. The thermal errors are measured by a ball bar system instead of capacitance sensor system. The novel measurement method using ball bar system is more efficient, easier to use than conventional measurement system. And also the ball bar system is possible to measure both geometric errors and thermal errors at the same time.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.7
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• pp.275-286
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• 2001

The research presents an analytical theory to calculate the characteristics of the bal bearing with waviness in its rolling elements considering the centrifugal force and gyroscopic moment of bal. The effects of centrifugal force and gyroscopic moment are introduced to the kinematic constraints and force equilibrium equations. and the waviness of rolling elements is modeled by sinusoidal function to calculate the contact force at each ball. The numerical solutions of governing equation of berating due to waviness are calculated by using the Newton-Raphson method. The accuracy of the research is validated by comparing the contact force. contact angle in case of considering the centrifugal force and gyroscopic moment of bal and the contact force and vibration frequencies in cases of considering waviness with the prior researches respectively. It investigates the stiffness, contact force. displacement and vibration frequencies of the ball bearing considering not only the centrifugal force and gyroscopic moment of ball but also the waviness of the rolling elements.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1814-1819
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• 2005

This paper describes the development of a Stewart platform-based robot force sensor with distinctive structure of ball joints. The number of ball joints is only a half of the similar style sensors, so it is possible to reduce size and weight of the sensor. The structure of ball joint is described and discussed. Furthermore, we use strain gauges, but not liner voltage differential transformers, as sensing elements, in order to reduce size and weight of the sensor. It is also proposed that beams are replaced with pipes as sensing elements of the sensor. The ball joints and sensing elements with pipes can effectively reduce the error of the sensor. A geometric analysis model is also proposed. The external force and its moment can be measured with this model. Moreover, the performance of this sensor was tested. The test results conducted to evaluate the sensing capability of the sensor is reported and discussed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.2
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• pp.46-51
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• 2011

This study result is obtained by flow analysis according to opening and shutting angle of ball valve. As opening and shutting angle becomes larger, vortex flow becomes smaller and flow rate becomes increased. And the pressure drop is shown to be smaller at the inlet and outlet of ball. As this angle becomes larger, mass flow rate becomes increased. Its rate becomes increased abruptly in case of opening and shutting angle at more than $60^{\circ}$.This analysis result can be applied usefully with no leak at pipe system field by the optimum control of mass flow rate according to opening and shutting of ball valve.

• Advances in concrete construction
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• v.15 no.4
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• pp.287-301
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• 2023

Hockey games attracts many fans around the world. This game requires a specific type of ball and a stick for controlling the motion and trace of the ball. This control of motion involves hitting the ball which is a direct intensive dynamic loading. The impact load transferred directly to the hand of the player and in the professional player may cause long term medical problems. Therefore, dynamic motion of the stick should be understood. In the current study, we analyze the dynamic motion of a hockey stick under impact loading from a hockey ball. In doing so, the stick geometry is simplified as a beam structure and quasi-2D relations of displacement is applied along with classical linear elasticity theory for isotropic materials. The governing equations and natural boundary condition are extracted using Hamilton's principle. The final equations in terms of displacement components are solved using Galerkin's numerical method. The results are presented using indentation and contact force values for variations of different parameters.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.1
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• pp.177-183
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• 1994

The ball-end milling process is widely used in the die/mold industries, and it is very suitable for the machining of free-from surfaces. However, cusps(or scallops) remaining at the machined part along the cutter paths require anothe finish process such as polishing or grinding. In this study, a high sped micro ball-end milling method has been suggested for the finish of free- form surfaces. A new tool path which makes the geometrical roughness of workpiece be constant through the machined surface has been developed. In the high speed machining of micro ball-end muling experimets, the developed tool paths have been successfully applied. And it was concluded that the surface roughness from this finish cuts of micro ball-end milling process was acceptable.

• Korean Journal of Applied Biomechanics
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• v.13 no.2
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• pp.175-183
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• 2003

The purpose of this study was to analyze the kinetic energy of putter head and ball movements during the process of impact. Highly skilled 5 golfers(less than 1 handicap) participated in this study and the target distance was 3 m. Movements of ball and putter head were recorded with 2 VHS video cameras(60 Hz, 1/500 s shutter speed). Small control object($18.5{\times}18.5{\times}78.5\;cm$) was used in this sdtuldy. Analyzing the process of impact, putter was digitized before 0.0835 s and after 0.0835 s of impact. Ball was digitized 0.1336 s after impact. The results showed that the maximum speed was appeared at Impact and prolonged for a while. Contact point of the club head was within 0.7 cm to the z axis. After contacting the club head, the ball was moved above the ground level(slide) and returned to the ground with sliding and rolling. After contacting the ground, the speed of ball was relied on the surface of the ground. During impact, 70% of kinetic energy of club head has been transferred to the ball.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.03a
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• pp.25-29
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• 1998

One of the crucial problems that must be solved in a computerised unmanned machining environments requires the development of algorithm in order to predict the reliable cutting conditions on surface roughness. This paper is to develop the mathematical models for choosing the suitable cutting conditions and assist a comprehensive understanding of its machinability properties for cutting process by Ball End Mill. The mathematical equations developed to predict the surface results. It has been found that theoretical results obtained from the empirical equations agree with the experimental results of surface roughness.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.5
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• pp.354-361
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• 2016

Parallel robots are usually used for performing pick-and-place motion to increase productivity in high-speed environments. The present study proposes a high-speed parallel robot and a control approach to improve the tracking performance for the purpose of handling a solar cell. However, the target processes are not limited to the solar cell-handling field. Therefore, a delta-type parallel manipulator is designed, and a ball joint structure is specifically proposed to increase the allowed angle that would meet the required workspace. A control algorithm considering the synchronization between multiple joints in a closed-chain mechanism is also suggested to improve the tracking performance, where the tracking and synchronization errors are simultaneously considered. In addition, a prototype machine with the proposed ball joint is implemented. A satisfactory tracking performance is achieved by applying the proposed control algorithm, with a cycle time of 0.3 s for a 0.1 kg payload.

• Tribology and Lubricants
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• v.11 no.5
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• pp.184-189
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• 1995

The antiwear performance of dialkyl 3, 5-di-t-butyl 4-hydroxy benzyl phosphonates was investigated using a four ball wear test machine. Diethyl 3, 5-di-t-butyl 4-hydroxy benzyl phosphonate (DEP) and dibutyl 3,5-di-t-butyl 4-hydroxy benzyl phosponate (DBP) among them showed excellent antiwear performances compared with conventional additives, ZDDP and TCP as the bulk oil temperature and the sliding velocity increased. The surface analysis through an optical microscopy was conducted for tribological studies.