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Structural Performance Analysis and Optimization of Machine Tool Bed

Author: HeZuo
Tutor: WangQiFu
School: Huazhong University of Science and Technology
Course: Mechanical Engineering
Keywords: Bed Static & dynamic characteristics Thermal characteristics Modal analysis Finite element Structural optimization
CLC: TG659
Type: Master's thesis
Year: 2011
Downloads: 207
Quote: 2
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Abstract

With the development of Numerical Control machine tools to the high-speed, high precision and high efficiency, higher machining capability and lighter weight are necessarily required. As the key component of machine tools, the bed’s structure performance will directly influence the processing performance. The structure performance contains the static & dynamic characteristics and the thermal characteristics. Improving the dynamic characteristics of the bed will reduce the vibration of the bed. This thesis studies the structural performance of a vertical milling machine bed and its structural optimization based on modal analysis.In order to research the static characteristics of the bed, the geometric model of the bed is created in CATIA and simplified efficiently in SpaceClaim. After importing the model to ANSYS, the finite element model is established for static analysis. The result of static analysis of the bed indicates that it is extremely high in the static stiffness and intensity of the bed, and foundations are provided to lighten it.In order to overcome the disadvantages of static design of the bed, to raise its dynamic characteristics, the weakness of the structure is studied based on the modal analysis of the bed. Five schemes of improving the bed are proposed based on unit structures & rib walls theory. It finally find that scheme four’s natural frequency is quite high and its weight is lightest relatively. The influences of the diameter of sand hole and the thickness of rib walls to the natural frequencies of the bed are researched on the base of previous work. Finally, the scheme six is released which is 16.76 percent lighter and the first frequency is 35.32 percent higher than the original one. It illustrates that the natural frequency can be raised, the weight can be reduced and the material can be saved by choosing the appropriate unit structures and rib walls.In order to control the thermal deformation of the bed, it studies the impact of the temperature rise on the bed. Based on analyzing the heat source and boundary conditions of the bed, the finite element model of the bed’s temperature field is constructed. After the calculation accomplished, the bed’s temperature field dedicate that the temperature rise is extreme low. Through exerting the ststic & thermal load and calculating the heat-structure coupling, it is verified that the major deformation of the bed comes from the thermal deformation. It also indicates that the slide guides have a high steering precision. Combined with the thermal deformation characteristics of the bed, several measures are offered to reduce the thermal deformation and compensate the thermal error.

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