Fabrication of superplastic microtubes using dieless drawing process

Abstract

Microtube is commonly used and required, particularly as micro components in micro-system technologies (MST) and micro electromechanical systems (MEMS). In this paper, fabrication process of microtube using superplastic dieless tube drawing was studied experimentally. Superplastic material used is Al-78Zn alloy tube with outer diameter of 2 mm and wall thickness of 0.5 mm. A high-frequency induction heating apparatus with air cooling nozzle was used for the dieless drawing. In the experiment of single pass dieless drawing, the effect of drawing conditions such as forming temperature, distance between heater and cooler and tensile speed on deformation profile, was clarified. Furthermore, in three-pass dieless drawing, a microtube with outer and inner diameters of 343 μm and 161 μm respectively can be fabricated successfully. In addition, from the experimental results and fundamental principles, it is confirmed that the ratio of inner to outer tube diameters maintains a constant value during dieless drawing. In other words, the geometrical similarity with the minimization of dimension is satisfied in this process. Finally, it is found that the surface roughness of microtube maintains a constant value in the dieless drawing process. © 2008 The Japan Society for Technology of Plasticity.