Abstract
To establish the dynamic model of machine tool structure is an important means to assess the performance of the machine tool structure during the cutting process. It is necessary to study the dynamics of the machine tools in different configurations for the sake of analyzing the dynamic behavior of the machine tools in the entire workspace. In this paper, a robust approach is presented to build an efficient and reliable dynamic model to evaluate the position-dependent dynamics of the twin ball screw (TBS) feed system. First, the TBS feed system is divided into several components, and a finite element (FE) model is built for each component. Second, the Craig-Bampton method is proposed to reduce the order of the substructures. Third, a multipoint constraints (MPCs) method was introduced to model the mechanical joint substructures of the TBS system, and the spring-damper element (SDE) is employed to connect the condensation nodes. Finally, a series experimental tests and full-order FE analysis are conducted on the self-designed TBS worktable in the four positions to validate the effectiveness of the proposed dynamic model. The results show that the proposed approach evaluates accurately the position-dependent behavior of the TBS system.
Highlights
twin ball screw (TBS) feed system is widely employed in gantry precision CNC machine tools with high rigidity, high stability and high control bandwidth
The results showed that the proposed dynamic substructuring method based on multipoint constraints (MPCs) joint model can accurately and quickly predict the dynamic characteristics of TBS feed system
To further validate the proposed method, a series of dynamic experiments were conducted on a self-designed TBS worktable depicted in Fig. 1(a), the worktable is bolted to the base
Summary
TBS feed system is widely employed in gantry precision CNC machine tools with high rigidity, high stability and high control bandwidth. References [29,30,31] showed several method to use the MPCs to a reduced order model of machine tools These substructuring methods do not consider the TBS feed system, which limits the accurate prediction of the position-dependent dynamic behavior of the machine tool equipped with the TBS system. A dynamic substructuring method with position flexible coupling of the substructures is presented, which considers mechanical joint models for each direction. Considering the mechanical joints among the substructures, MPCs model approach based spring-damper element (SDE) is used to couple the flexible substructures. The results showed that the proposed dynamic substructuring method based on MPCs joint model can accurately and quickly predict the dynamic characteristics of TBS feed system
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