| Summary: | 碩士 === 國立高雄科技大學 === 機械工程系 === 107 === Conventional turning machining is a common machining method for metal components. Due to the continuous cutting state between the turning tool and the workpiece, the cutting resistance continues to accumulate and increase. Such high cutting resistance tends to cause turning tool loss and reduce its life. In the cutting process of turning hard and brittle materials, workpiece cracking is likely to occur due to high cutting resistance, and turning processing cannot be completed. In order to improve the shortcomings of high cutting resistance caused by the continuous cutting state of conventional turning, ultrasonic vibration cutting technology has been developed, which is characterized by applying micro-vibration to the traditional turning tool, which changes the cutting state from continuous cutting state to intermittent cutting state. It causes the cutting resistance to increase cumulatively only during each vibration cycle, which can make the chip finer and greatly reduce the cutting resistance, which can prolong the tool life and avoid the occurrence of cracking during the turning process of hard and brittle materials.
The main purpose of this paper is to develop an ultrasonic vibration turning tool for the vibration conditions required for ultrasonic vibration turning. The turning tool is composed of a flexible structure of a turning head, some piezoelectric elements, a connecting block and a mass. It forms a one-dimensional ultrasonic vibration turning tool that can be used in multiple directions. The turning tool has two sets of piezoelectric structures for pushing the ultrasonic head of the flexible structure to generate ultrasonic vibration, and can generate normal vibration or tangential vibration according to driving conditions. In the theoretical analysis, the effects of vibration velocity and cutting speed on the cutting effect are derived for ultrasonic vibration machining of tangential, axial and radial vibrations in this study. In the vibration analysis, the static stiffness analysis, modal analysis, harmonic analysis and dynamic stiffness analysis of the turning tool were performed using the finite element analysis software ANSYS to confirm that the performance of the designed ultrasonic vibrating turning tool meets the requirements.
After the actual fabrication and assembly, the prototype of the ultrasonic vibrating turning tool was completed. The dynamic performance of the ultrasonic vibrating turning tool was confirmed by the measurement of the vibration characteristics. In the turning machining test, this research uses two equipments, such as basic CNC machine tool and turning-milling compound CNC machine tool, to install this ultrasonic vibrating turning tool, and use different cutting parameters to carry out cutting experiments of medium carbon steel materials, and compare their surface roughness after material cutting. The experimental results show that ultrasonic vibration turning has a significant effect of improving surface roughness compared to conventional turning. In addition, the vibration state of the machine used in the basic CNC machine tool and the turning-milling compound CNC machine tool is different. Even if the cutting experiment is performed under the same cutting parameters, different surface roughness effects will be produced obviously. Due to the small vibration of the turning-milling compound CNC machine tool, the surface roughness after machining is better than the surface roughness of the basic CNC machine tool.
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