| Summary: | 碩士 === 國立中興大學 === 機械工程學系所 === 106 === This study investigated the thermal displacement characteristics of two domestic 5-axis large gantry type CNC machining center with different structures, mainly affecting the temperature variation and thermal deformation of the entire machine structure due to environmental temperature changes. In the experimental measurement section, multiple critical temperature measurement points are placed on the machine, and the non-contact eddy current displacement meter is used to obtain the instantaneous thermal displacement. Based on the experimental measurements, a multi-physics simulation model was constructed.
In order to achieve more flexible thermal balance technology to temperature control of the key points of the machine structure, this study attempts to use small cooling water blocks for temperature control on the beam. The study based on the multiple physical coupled thermal displacement model established, the temperature value of the measured point and the corresponding cutting point thermal displacement input neural network are used for learning and training, and a neural network model for effectively predicting the temperature variation and thermal deformation of the machine structure is established respectively. Through the neural network model, multiple cooling water blocks are placed on the beam area of machine tools, adjust the cooling point parameters of multiple cooling water blocks to control the temperature distribution of the key structural positions of the machine, and then achieve the control of the thermal displacement of the cutting point and the bending degree of the beam.
The temperature of the beam is unevenly distributed due to the change of the ambient temperature was observed from the side-mounted model, which causes the thermal displacement of the x-axis of the tool tip to change the most. Use fan and cooling water block to improve the x-axis of the tool tip point and the bending degree of the beam. The Box-in-box model is also caused by the variation of the ambient temperature of the beam, which makes the temperature distribution of the beam structure uneven, resulting in the largest thermal displacement change of the z-axis of the tool tip point. The cooling water block is used to improve the bending degree of the beam, and it is easier to improve the z-axis thermal displacement of the tool tip point under compensation. The follow-up verification experiment was carried out on the side-mounted model, and the parameters obtained by the simulation were improved. In the fan experiment, the x-axis thermal displacement amount of the tool tip point was improved by about 10%, and the cooling water block was used to improve the x-axis thermal displacement amount of the tool tip point about 45%.
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