Investigation on stability of robotic rotary ultrasonic edge milling component with poor rigidity

The poor rigidity of large composite material components in the helicopter has an important impact on robotic milling stability. Based on the machining stability of robotic edge trimming process, a method for calculating the component overhang is proposed in this paper. Firstly, the stability model of robotic longitudinal-torsional ultrasonic milling component (RCUM-LT) with poor rigidity is established by machining dynamics analysis. Then, the influence mechanism of variables such as ultrasonic vibration energy, workpiece overhang, and edge thickness on the stability region of robotic edge milling is explored emphatically. The calculation results show that the intake of ultrasonic energy suppresses robotic milling chatter effectively. As a result, the stability region of RCUM-LT is increased by 361.79%. In addition, the smaller the component overhang, the better the stability of edge milling will be. The effect of component thickness on RCUM-LT stability is the combined action result of modal property and dynamic milling force. Considering the influence of three variables on the stability region comprehensively, a reasonable boundary curve of the adsorption position is achieved according to RCUM-LT stability model. It provides technical support for realizing robotic edge milling composite material with high efficiency and stability. Finally, the verification experiments are carried out for stability lobes and optimal overhang length. The results show that the experimental results of RCUM-LT stability are in good agreement with the theoretical prediction. With the adsorption method proposed by this study, the surface roughness and its consistency of machined surface are significantly improved.