| Summary: | 碩士 === 國立中興大學 === 機械工程學系所 === 105 === The design of the advanced turning center machine tools is becoming more and more complicated due to the increasing demand on function, cutting speed and cutting quality. The requirement for high rigidity, light weight and thermal stability of the machine tool is increasing, while for a both fast tapping and heavy duty cutting a stable and long term high processing accuracy are needed to be achieved. In the past, most machine tool designers elaborated static and modal analyses in the machine structural design, and relied on the empirical guideline for the cooling system design and compensation techniques for mitigating thermal errors of the machine tools. In recent years, however, emerging numbers of advanced machine tool manufacturers have been applying multi-physics analysis to assist the design and development of the machine utilized for and thermal stability optimizations such as the Thermo-Friendly design concept. Therefore, the development of the analysis and optimal design ability that combines the structural rigidity, dynamic characteristics and thermal deformation stability is essential to the competitiveness of modern machine tool designers.
In this thesis, experimental and numerical studies of the heat transfer and thermal deformations for a real computer numerical control (CNC) horizontal turning center were conducted. In the simulation section, a multi-physics model based on the fluid dynamics, heat transfer and thermo-elasticity of the spindle head region including the structure and air flow inside the enclosure was established using a finite element method software (ANSYS Fluent). Experimental measurements of the spindle head temperature and the cutting point deformation are used to verify and correct the simulation model of the basic case.
The results of the analyses thus provide the insights for the thermal characteristics of the machine. The simulation model in conjunction with an optimization analysis was thus used for improving the thermal error, for the machine with the information of critical locations and parameters for temperature monitoring and control that corresponds to the Thermal Balance concept. Based on the analyzed results, the design of the cooling fan circulation of the spindle head region was proposed and experimentally tested. It is shown that the appropriate design for the location of the fan can effectively improve the thermal deformation of the spindle head and therefore improve the precision of machining.
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