A new system for the piercing process, which has high positioning accuracy and monitoring of the position during piercing, is introduced. When the piercing force on a micropiercing punch is increased in the production of microholes, the tool life becomes shorter. Furthermore, 1 μm becomes relatively large when the product is of microsize, and any difference in the tool position or punch diameter significantly affects the micropiercing. In this study, a nanometric-motion stage is included in the die as a new tooling system, enabling the control of the relative positon between the punch and die at a nanoscale. Different forces and hole conditions are observed in different punch positions, and the die position movements in X, Y, and Z directions are monitored during each micropiercing using the developed system.
In this study, the shrink-fit die is developed for high-strength aluminium alloy hollow extrusions. The metal flow of the extrusion process is analyzed by the finite-element method to investigate the extrusion pressure in the die, which is later used as the applied load in the die structural analysis. Simulation results are compared with experimental results for the billet press. They show fairly good coincidence. In the die structural analysis, the effect of the shrink fitting value on the maximum principal tensile stress and the total strain range of the root of the bridge are investigated, and the optimum shrink fitting value is obtained. In comparison with the porthole die, the extrusion load of the shrink fit die is lower by 15%, and the stress at the root of the bridge is decreased by 38%. Experimental results also show that the die life of the shrink die is improved more than that of the porthole die.
The cost of a forging die is around 20% of the total forging process cost. It is important, for total cost reduction, to improve the forging die life. Recently, the advances in the development of FEM have been marked, contributing to the development of simulation tools that are being effectively applied to the improvement of forging die life. First of all, we describe the approaches for die-life improvement approaches for the cases of fracture and wear by reliability analysis. Then, we introduce the application of those improvement techniques on the two cases.