Abstract:

Objective The single-station needling machine has low preform production efficiency. The existing linear double-station needling robot equipment occupies a large space, and both double stations are equipped with external rotary axes, ausing system programming difficult. A linear/rotary hybrid switching double-station needling robot system was proposed, with the function of automatic preform changing for efficient needling of large-size quasi-rotary composite preforms. The design of the double-station needling robot is aimed at automatic change of preforms while ensuring that the equipment occupies a small space with the reduced use of external rotary axes to ensure convenient programming of the system.

Method The mechanical structure design, design of quasi-rotary preforms mold and needling process, control system design, motion simulation and experimental verification of the double-station needling robot system were carried out. The double-station involved needling station and a layup station. The motor on the needling station was linked to a 6-joint mechanical arm, and system had only one external rotation axis. Within the rated load range of the robot arm, the number of needles of the needling robot effector was increased and the carrying capacity of the CNC rotary table was further improved to meet the needling molding of large-size preforms.

Results The double-station needling robot consisted of a 6-joint mechanical arm, a needling robot effector, and a double-station working platform. The robot arm controller model was Kawasaki E02/7.5 kW with rated end load of 50 kg. The needling robot effector had 25 needles using a TK13500EL CNC rotary table with a maximum allowable inertia of 19 kg/m² and a maximum allowable driving torque of 1 430 N·m. The experimental results demonstrated that the double-station needling robot system was able to fabricate successfully quasi-rotary composite preforms. The actual needling trajectories in the experiment were highly consistent with the simulated needling trajectories. In the system, the bearing capacity of the CNC rotary table was improved and the number of needles in the needling robot effector was increased to 25ss, which met the need for needling of large-size preforms, and the needling efficiency was double folded. The system facilitated the automatic preform changing, enabling the workers and needling robot to efficiently cooperate in production. The downtime of the robot after the needling of each unit layer was shortened from the existing 1 h to 1 min., and the needling production efficiency had been greatly improved. In addition, the linear/rotary hybrid switching method made it possible for the double-station working platform to occupy a small working space with a compact structure, providing enough distance between the raw material laying station and the robot needling station, ensuring the safety of raw material laying personnel.

Conclusion This paper presented a linear/rotary hybrid switching double-station needling robot system for efficient manufacturing of large-size quasi-rotary composite preforms. By increasing the carrying capacity of the CNC rotary table and the number of needles of the needling robot effector to 25, the system can achieve needling of quasi-rotary preforms with a height of 1.5 m and a diameter of 1 m. The needling trajectory on the surface of the experimentally prepared preform was highly consistent with the simulated needling trajectory, and the needling efficiency was double folded by virtue of the increase in the number of needles. The setting of double-stations made the automatic change of preforms possible, and the workers and the needling robot could efficiently collaborate in production, which greatly improved the efficiency of needling production. The linear/rotary hybrid switching method made the double-station working platform occupy a small working space with a compact structure. In the double-station, only the external rotary axis on the needling station was linked to the 6-joint mechanical arm. The system was relatively simple and the programming was convenient.

Key words: double-station, preform, robot, needling, special-shape curved surface composite material