An in-situ incremental microforming system for three-dimensional shell structures of foil materials

The aim of the present study is to establish micromachining technology for micro-electro-mechanical-system parts such as various three-dimensional body shell structures for micro-robots, various micro-devices, and facilities. For this purpose, the authors developed a CNC-incremental sheet metal forming system for foil materials as a microfactory cell. Using this system, they formed a 600 μm long micro-car body shell without dies in a scanning electron microscopic field of view. The principle of this flexible sheet metal forming system is called incremental forming by hammering. Small increments of sheet metal bending and bulging deformation are generated by hammering. Repeated step-by-step cycles result in variously shaped shell structures without dies. The tip of the hammer is 10 μm in diameter. The system is installed in the vacuum chamber of a commercial scanning electron microscope (SEM) and controlled in the microscopic field of view. The deformations of very thin sheet metals or foils are directly observed on a microscopic scale. To realize these systems, small actuators, such as piezoelectric actuators, small linear sensors, and an X–Y stage driven by ultrasonic linear motors, are selected. The resolution of the positioning system for the sheet material is 0.2 μm. The hammer is installed at the end of the beam, and the beam (handle) is resonantly oscillated by a piezoelectric actuator. The displacement of the hammer is detected by a displacement sensor. As a result, this flexible sheet microforming system transfers a three-dimensional shape to sheet or foil materials directly from the designing (virtual) space. In-situ observation in the SEM field of view contributes to the analysis of the local deformation and to the optimization of the forming processes.