Design of a flexible bio-inspired stretch-forming machine for the fabrication of large radius bends parts

The imitation and application of manipulability and dexterity of human arm have been investigated actively as it can improve the time efficiency and save labor cost greatly. Most of the current studies in this area only focus on recreating the structure of human arm without considering how to use the finger path for forming. In this paper, the authors present a flexible bio-inspired stretch-forming machine (SFM) for the fabrication of parts, which are large and possess large radius bends, with small spring back and smooth surfaces. The flexible bio-inspired SFM was composed by two pairs of finger-inspired jaws in conjunction with six couples of muscle-inspired hydraulic cylinders (the sum of numbers is 60), which only integrates six solenoid types of reversing valves. The path of finger-inspired jaws was planned by setting up the parameters of loading order, stretching direction, and cylinder pull force. The finger-inspired jaws, driven by the muscle-inspired hydraulic cylinders, moved along the given route to realize sheet metal forming. The finite element simulation and experiment results on a series of large radius bends parts formed by the flexible finger-inspired SFM have been reported. The remarkable results are that an effective solution for stretch forming of sheet metal with short free edge has been founded, and an easy control process of stretch forming with finger-inspired jaws has been developed, respectively. This work has an important value in implementation of stretch-forming technology from aircraft to vehicle and building.