Size effects of the cavity dimension on the microforming ability during coining process

With the miniaturization of the parts, the size effects occur in microforming processes. To investigate the effect of die cavity dimension on the microforming ability of the billets, the coining tests have been carried out with pure aluminum using groove width from 40 to 120 μm at the temperature of 400 °C. The experimental results show that the microforming ability decreases with the increasing of ratio L/b when the ratio L/b is less than 0.5, and the microforming ability increases with increasing of the ratio L/b when the ratio L/b is larger than 0.5. These phenomena might be analyzed from the viewpoint of multi-grain structure of billet. Following that, the isothermal microforming processes of microgears are carried out, and the successful manufacture of the microgears indicates that the billet can fill a very small die cavity completely.