Design and construction of a compact high energy rate forming (HERF) hammer

High speed forming is receiving increasing attention due to high rate of production, smaller-size equipment, improved quality of the products and economic reasons. It is also preferred to manufacture parts which cannot be produced by other methods because of size and material characteristics. However, high speed forming requires specially designed equipment and techniques. High Energy Rate Forming (HERF) hammers operate at forming speeds between 5 and 22 m/s.The aim of this study is to design and construct a compact prototype HERF hammer which uses two-cylinder internal combustion to produce forming energy and a mechanical re-cocking mechanism. Therefore, it can be considered as a new type of HERF hammer in the literature. It?s a compact prototype having a capacity of 100 J and 12 m/s forming speed. The performance characteristics of the HERF hammer were compared with conventional hydraulic and mechanical presses. For this purpose, forging and blanking operations were carried out on three different materials (aluminum, St37 and AISI 304) using these presses.The results of open die cylindrical forging operations show that the barreling effect is reduced by increasing punch speed. The blanking load and energy values for all of the materials under investigation were significantly reduced at HERF hammers. From the microstructural analyses of the blanked surfaces, formation of adiabatic shear band was observed at higher strain rates. The surface quality of the blanks are also much better at HERF hammers showing less dishing and lower surface roughness. The corrosion test results indicate that the resistance to corrosion of the blank surfaces increased with increasing punch speed.