Abstract
The effective way to improve the position accuracy of rotary table of ultra-heavy vertical milling lathe is to reduce or even eliminate the clearance of mechanical transmission structure. In this paper, a useful method for eliminating the gear clearance of C axis of heavy duty machine tool is proposed based on dual servo motor driving system. The principle of double gear anti-backlash is explained and the process of clearance elimination is determined by adjusting the driving torques of the two motors. The dynamic model of the driving system of the dual servo motor is established, so as to find the non-linearity of the clearance, wear and tooth clearance in the drive system. According to the dynamic model and simulation results, the master-slave control parameters of the dual servo motor system are optimized in order to eliminate the clearance and improve the accuracy of the dual drive C-axis. Experiments are carried out to verify the validity of the proposed anti-backlash method. The experimental result also shows that the indexing accuracy of the table has been improved by more than 50% under different working conditions.
Highlights
With the development of the manufacturing industry, computer numerical control (CNC) machine tools are toward the goal of high reliability and high precision, and for industry, such as aviation, aerospace, shipping, and energy, higher requirements are put forward for the manufacturing precision of related parts, especially the super large parts
The processing of super-large parts is mainly completed on the ultra-heavy duty machine tool [1], and the indexing ability of the rotary table determines the precision level of the workpiece [2]
The development of the C-axis indexing feed system of CNC machine tools is mainly divided into the following stages [4]
Summary
With the development of the manufacturing industry, computer numerical control (CNC) machine tools are toward the goal of high reliability and high precision, and for industry, such as aviation, aerospace, shipping, and energy, higher requirements are put forward for the manufacturing precision of related parts, especially the super large parts. In view of the above problems, the current ultra-heavy machine tools mainly adopt the dual servo motor to achieve the C-axis rotation and indexing feed function. The dual servo motor adopts the master-slave control function, with the independent drive chain to eliminate the tooth side clearance [11,12,13,14] This kind of transmission structure can meet the power demand of the ultra-heavy machine tool, and use the control means to eliminate the lateral clearance of gear teeth of the transmission mechanism and improve the positioning accuracy. In view of the characteristics of ultra-heavy duty vertical machine tool’s rotating table bearing large load, this paper designed a two-servo motor driven table, and analyzed the principle and process of eliminating the gear tooth clearance when C-axis indexing positioning. The feasibility and superiority of the presented method were demonstrated by the experiments
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