• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.32-36
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• 2002

High-speed movement and high-precision machining are the two most important requirements of present machine tool structures to reduce machining time and to increase the precision of products in various industrial fields such as semiconductor, automobile, and mold fabrication. The high speed operation of machine tools tue usually restricted not only by the low stiffness but also by the low damping of machine tool structures, which induces vibration during high speed machining. If the damping of machine tool structures is low, self induced or regenerative vibrations are bound to occur at high speed operation because the natural frequencies of machine tool structures can not be increased indefinitely. Therefore, the high damping capacity of a machine tool structure is an important factor for high speed machine tool structures. Polymer concrete has high potential for machine tool bed due to its good damping characteristics. In this study, a polymer concrete bed combined with welded steel structure i.e., a hybrid structure was desisted and manufactured for a high-speed gantry-type milling machine through static and dynamic analyses using finite element method. Then the dynamic characteristics were tested experimentally.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.404-409
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• 2004

To maximize the productivity in machining molds and dies, machine tools should operate at high speeds. During the high speed operation of moving frames or spindles, vibration problems are apt to occur if the machine tool structures are made of conventional steel materials with inferior damping characteristics. However, self-excited vibration or chatter is bound to occur during high speed machining when cutting speed exceeds the stability limit of machine tool. Chatter is undesirable because of its adverse effect on surface finish, machining accuracy, and tool life. Furthermore, chatter is a major cause of reducing production rate because, if no remedy can be found, metal removal rates have to be lowered until vibration-free performances is obtained. Also, the resonant vibration of machine tools frequently occurs when operating frequency approaches one of their natural frequencies because machine tools have several natural frequencies due to their many continuous structural elements. However, these vibration problems are closely related to damping characteristics of machine tool structures. The polymer concrete has high potential for machine tool bed due to its good damping characteristics with moderate stiffness. This paper presents the use of polymer concrete and sandwich structures to overcome vibration problems. Also, co-cure bonding method for functional part mounting was exhibited experimentally, by which manufacturing time and cost for polymer concrete bed will be remarkably reduced.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.113-116
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• 2003

To maximize the productivity in machining molds and dies, machine tools should operate at high speeds. During the high speed operation of moving frames or spindles, vibration problems are apt to occur if the machine tool structures are made of conventional steel materials with inferior damping characteristics. However, self-excited vibration or chatter is bound to occur during high speed machining when cutting speed exceeds the stability limit of machine tool. Chatter is undesirable because of its adverse effect on surface finish, machining accuracy, and tool lift. Furthermore, chatter is a major cause of reducing production rate because, if no remedy can be found, metal removal rates have to be lowered until vibration-free performances is obtained. Also, the resonant vibration of machine tools frequently occurs when operating frequency approaches one of their natural frequencies because machine tools have several natural frequencies due to their many continuous structural elements. However, these vibration problems are closely related to damping characteristics of machine tool structures. This paper presents the use of polymer concrete and sandwich structures to overcome vibration problems. The polymer concrete has high potential for machine tool bed due to its good damping characteristics with moderate stiffness. In this study, a polymer concrete bed combined with welded steel structure i.e., a hybrid structure was designed and manufactured for a high-speed gantry-type milling. Also. its dynamic characteristics were measured by modal tests.

• 한국공작기계학회논문집
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• 제15권1호
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• pp.39-48
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• 2006

In this paper, polymer composites based sandwich structures like beams and plates are optimised by using parametric study. The structures are composed of fibre reinforced composites for facial material and resin concrete and PVC foam for core materials. The stacking sequences and thickness of the composites are controlled as major parameters to find out the optimal condition for machine tool components. For the plate structure of machine tool bed composites-skined sandwich structure which has several ribs are proposed to enhance bending stiffnesses in two major directions at the same time. Dynamic robustness of a machine tool structure is investigated using modal analysis. From the results optimal configuration and materials for high precesion machine tools are proposed. And the plate was made of fiber reforced composite material and PVC foam.

• 한국기계가공학회지
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• 제5권4호
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• pp.72-78
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• 2006

Inherent in machine tool structures are the vibrations which are generated by rotating parts such as motors, spindles and chucks. The vibrations not only hurt the precision machining but also damage the structures, and become more serious with time. Many of the old machine tools show severe vibrations for the desired accuracy of the modern industries. It is too much of a waste, however, to get rid of them as scraps. There have been many researches in order to suppress the vibrations of old machine tool structures using the tool post which utilizes actuators to compensate the existing vibrations and using the dampers or absorbers attached to some critical parts. In this paper, the dynamic properties are analyzed to obtain the natural frequencies and mode shapes of a machine tool structure which reflect the main reasons of the biggest vibrations under the given operating conditions. And the feasibility of improving the stability of the structure has been investigated with minor design changes and expenses. The result of the study shows that simple changes based on proper system identification can considerably improve the stability of the machine tool structure.

• 대한기계학회논문집
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• 제7권2호
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• pp.138-144
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• 1983

To evaluate the dynamic characteristics of machine tool system, the system is modelled as a closed-loop system composed of cutting process and improved machine tool structures. The proposed machine tool structure model is constructed in consideration of energy transfer through the system. A new methodology to identify the machine tool dynamics by adopting impulse response and impulse cutting techniques is also proposed. It is shown that the methodology is successfully applied to a machine tool system to identify its dynamic characteristics employing the improved model.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.189-196
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• 2001

Machine tools of high-speed and high-precision are required for various fields of industry such as semiconductor, automobile, mold fabrication and so on. Light-weight machine tool structure is essential for reduction of production time through rapid transportation. Also, high damping capacity of the structure is required to obtain precise products without vibration during manufacturing. Composite materials have high potential for machine tool structures due to its high specific stiffness and good damping characteristics. In this study, the design and the manufacture of a hybrid machine tool structure using composite materials was attempted and the damping capacity was investigated experimentally.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.638-643
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• 1993

The three dimensional finite element models for the basic deflection of linear motion guides and ball screws were developed. Form the comparison of the results calculated by the finite element method with those by the experiment, it was proved that the modeling method might be applied to real machine tool structures. Form the structural analysis of the headstock of the machine tool, it was found that the static stiffness was calculated within 6.5% error

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.199-202
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• 2003

The dynamic characteristics of composite tool bars depend on the clamping conditions such as clamping force, stiffness and surface characteristics of clamping parts as well as the basic structures. Therefore, in this work, the effects of clamping part conditions on the dynamic characteristics of cantilever type composite machine tool structures with clamped joint were investigated because the cantilever type machine tool structures are ideal cases for composite application to increase the natural frequency and damping of structures. New design of the clamping part was developed in order to improve shear properties of the clamping part and dynamic characteristics of composite tool bars. From FE analysis and Impulse response tests, dynamic characteristics were obtained with respect to the clamping part conditions of the new design.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.261-265
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• 2002

In the machining tool avoid vibration problem have an effect on high precision as well as statical and thermal characteristics. Therefore overcome this problem is essential to advance of machine tool and machining skill. Even though vibration arises owing to a variety of causes, in this paper vibration analysis of column as a major part of machine tool structures is presented. At this procedure vibration analysis applied to mode synthesis method using a attachment mode .