• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.367-370
• /
• 1997

Linear motors can drive a linear motion without intermediate gears, screws or crank shafts. Linear motors can successfully replace ball lead screw in machine tools because they have a high velocity, acceleration and good positioning accuracy. On the other hand, linear motors emit large amounts of heat and have low efficiency. In this paper, the thermal behavior of a synchronous linear motor with high velocity and force is analyzed. To improve the thermal characteristics of the linear motor, structure of linear motor and cooler is changed. Some effects of an integrated cooler, an U-cooler and a thermal symmetrical cooler are presented.

• International Journal of Precision Engineering and Manufacturing
• /
• v.6 no.3
• /
• pp.8-12
• /
• 2005

The positioning system for an ultra precision machine tool must be accurate to the order of a nanometer. Various feed drive devices have been proposed to achieve this resolution; currently, most attention is directed towards hydrostatic lead screws and friction drives. It has been reported that a positioning resolution accurate to an angstrom can be achieved using a twist-roller friction drive. Therefore, we manufactured an ultra precision positioning system driven by a twist-roller friction drive and assessed its performance when defining problems and finding solutions. Our study showed that the twist-roller friction drive is mechanically suitable for ultra precision positioning, but some considerations are required to obtain a higher resolution.

• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.2
• /
• pp.21-27
• /
• 1998

NC machining of large screw which is usually used as a part in an extruder for injection molding is done on 3-axis turning machine, and it is very time-consuming process. Not only in machining but in preparing part program for a NC machine, it requires very long time because the shape of the screw is not easy to model when using an existing general CAD/CAM software even though it is workstation level software. In addition, tool path generation procedure for NC turning for screw shape is also very tedious one because large amount of data for cutter location point must be produced and there is no specific CAM software for the machining. In this paper. development of a CAM system for screw machining which saves the role of CAD software by use of menu driven data input system for various screw shapes is introduced.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.1503-1507
• /
• 2003

A general vibration phenomenon of a rigid-body supported by springs can be viewed as a small repetitive screw displacement. From this view, a multi-directional vibration absorber can be designed by use of screw theory and transfer matrix method. In this paper, the basic equations of motion for a multi-body system have been expressed in terms of screws using transfer matrix method and a simple approach to the design of a multi-degrees-of-freedom absorber has been presented. In order to illustrate the methodology, an example for the design of a 2-DOF active absorber which is capable of absorbing vibration of a rigid body excited by 3-DOF external force has been presented.

• Steel and Composite Structures
• /
• v.7 no.1
• /
• pp.35-52
• /
• 2007

The cold formed light-gauge profiled steel sheeting can offer considerable shear resistance acting in the steel building frame. This paper conducted the full-scale test on the shear behavior of stressed skin diaphragm using profiled sheeting connected by the self-tapping screws. A three-dimensional finite element model that simulates the stressed skin diaphragm was developed. The sheet was modeled using thin element model while the supporting members were simulated using beam elements. Fasteners were represented in the numerical model as equivalent springs. A joint test program was conducted to characterize the properties of these springs and results were reported in this study. Finite element model of the full-scale test was analyzed by use of the ANSYS package, considering nonlinearity caused by the large deflection and slip of fasteners. The experimental data was compared with the results acquired by the EUR formulas and finite element analysis.

• Clinics in Shoulder and Elbow
• /
• v.6 no.1
• /
• pp.80-84
• /
• 2003

We report a patient with an anterior dislocation of the shoulder with uncommon bucket handle type fracture of the anterior glenoid fossa with intact glenoid labrum. The fracture fragment was displaced into the posterior aspect of the glenohumeral joint resulting in prevention of reduction of the shoulder. Excellent fixation was obtained with suture anchors and bioabsorbable interfragmentary screws. This allowed stable range of motion exercises, optimizing the patient's functional outcome.

• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.3
• /
• pp.123-130
• /
• 2002

Linear motors can drive a linear motion without intermediate gears, screws or crank shafts. Linear motors can successfully replace ball lead screw in machine tools because they have a high velocity, acceleration and good positioning accuracy. On the other hand, linear motors emit large amounts of heat and have low efficiency. In this paper, heat sources of a synchronous linear motor with high velocity and force measured and analyzed. To improve the thermal characteristics of the linear motor, an insulation layer with low thermal conductivity is inserted between cooler and machine table. Some effects of the insulation layer are presented.

• Proceedings of the KSME Conference
• /
• 2000.04a
• /
• pp.375-380
• /
• 2000

The purpose of this study is to verify the relations with the fatigue life and stress distribution on the screw thread for thoracic and lumbar spine. These screws are now developed for Korean in this research group. The fatigue life of single screw was found longer than that of up-left-screw, but shorter than that of up-right-screw. The fatigue life of screw used was associated with the angie between bending and thread direction. In the case of upper left and right screw were fractured in the region of one pitch and two pitch of the thread valley from the shank of pedicle screw, respectively.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1999.10a
• /
• pp.3-10
• /
• 1999

One of the important considerations in designing a machine tool is the durability. In this study, a durability estimation systems for horizontal machining centers is developed to evaluate the effects of structural specification and driving conditions on the durability. All loads such as weights, inertia forces, cutting force and so on, are automatically transferred from the upper elements to the lower elements by the force flows which can be derived from the structural code of horizontal machining centers. And the external loads applied to the motion elements such as bearings, LM guides, ball screws and so on, are determined by the equilibrium conditions of force and moment. Especially, the durability of horizontal machining center is estimated based on the lifes of motion elements operating under the desired driving conditions.

• Journal of the Korean Arthroscopy Society
• /
• v.2 no.2
• /
• pp.173-176
• /
• 1998

Isolated posterior cruciate ligament injuries are rare and their management is controversial. But, there is general concept that a bony avulsion of posterior cruciate ligament should be repaired. The treatments for the bony avulsion of posterior cruciate ligament were conservative treatment, open reduction and internal fixation and arthroscopic fixation. We report 2 cases of posterior cruciate ligament avulsion fractures, which were arthroscopically reduced and stabilized with cannulated screws and Kirschner wires, and introduce the arthroscopic fixation technique.