| Spiral bevel gears are one of basic mechanical units that transmit motion between concurrent axes. Thanks to the great merits of the transmission, such as the big overlap ratio, the high loading capacity, the high transmitting efficiency, the stability, the small noises, and so on, they are widely used in automotive vehicle, planes, machine tools and all kinds of machines. Now CNC machines using in machining spiral bevel gears mainly depend on importation. The imported machine tools not only the price being high, but being locked. Although there have been several domestic producing CNC machines using in machining spiral bevel gears, but its machining efficiency and precision have huge difference with foreign product. This paper takes the YK20100 CNC spiral bevel gear grinding machine as the research object, aiming at improving its machining efficiency and precision, the dynamic characteristics of main components and composite structure were investigated by finite element analysis, testing experiment.The main research works and conclusion are listed as follows:1,Based on grinding theory and spiral bevel gear processing method, the YK20100 CNC spiral bevel gear grinding machine be in working conditions is analyzed. When spiral bevel gear that its diameter is 1 meter was processing, the vertical direction maximum grinding force on column and bed is worked out, and carries out static finite element analysis for column and bed under maximum force, which lays foundation for the further structure optimization. Results show: the top of the column and protruding of the bed have the maximum deformation, and the bottom supporting of components have the maximum stress.2,The modal analysis is carried out for column and bed by ANSYS software, at the same time, the preceding six steps natural frequencies and mode shape of the structure are obtained which lay a foundation for the study of composite structure and optimization design. The preceding six steps natural frequencies of column respectively are 118.85Hz, 137.46Hz, 210.05Hz, 256.34Hz, 273.47Hz and 328.09Hz, and the preceding six steps natural frequencies of bed respectively are 370.45Hz, 391.20Hz, 456.21Hz, 543.08Hz, 600.66Hz and 626.71Hz.3,Based on the modeling principle and method of bolted joint and guide joint, dynamic model of spring-damper element is built and characteristic parameters of the bolted joint are calculated. Further, the effect of the number and diameter of bolts to the dynamic characteristics of the machine is studied. The result shows that: regarding to the bolted joint, it's more useful to enhance the machine's dynamic characteristics by increasing the number of the bolts than increasing the diameter of the bolts under the same pre-tightening force.4,In view of the optimization design of column and the bed, it adopts unit structure theory. Based on the selected optimal types of the unit structure, the relationship between the diameter of hole and thickness of reinforcing plates and the lower steps natural frequencies is studied. Also, the relationship between the frame sizes of column and bed and the lower steps natural frequencies is studied. The variation law is obtained between the frame sizes and the lower steps natural frequencies can be used in structure design.5,The modal analysis for the original and optimized composite structures are carried out by ANSYS software, comparing with the preceding steps frequencies and discovering that the dynamic characteristics of the optimized composite structure improve a lot. The preceding four steps natural frequencies respectively increased 27.1%, 20.5%, 58.6%, 16.7% compared with original composite structures. Besides, discovering the joint parts have great effect on the dynamic characteristics of whole machine. Results show: only improves the dynamic characteristics of components and joints doesn't improve, dose the whole machine improve little.6,In order to verify the correctness of establishing method for finite element model of joint parts, carrying out harmonic response analysis for composite structure under the same condition as testing. Then, confirming characteristic parameters of the bolted join by comparing with the analysis and test results. |
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