Design of a novel robotic arm with non-backlash driving for friction stir welding process

Application of industrial robots in the field of manufacturing has increased over the years due to their advantages of large workspace, good flexibility and low cost. Industrial robots are trying to replace machine tools for heavy load manufacturing, for instance, friction stir welding (FSW). However, the stiffness of industrial robots is weak which affects the manufacturing precision seriously as well as driving backlash. This paper presents a novel robotic arm with non-backlash that used for FSW process. First, the structure of the robot and how to eliminate the backlash of the robot are introduced. Secondly, a semi-analytical method based on strain energy and the equivalent stiffness of bars obtained by finite element analysis (FEA) is proposed for calculating the overall stiffness of the robot, and the effectiveness of the method is verified through the integrated FEA results. Finally, a FANUC S900iB/400 robot that used for FSW is selected as a representative of industrial robots to be compared, the stiffness of the robot presented in this paper is better than the FANUC robot, which is beneficial to improve the welding quality.