Preshearing influences on sheet-bulk metal forming of aluminum gear

Shear-cutting methods are more efficient than machining methods for preparing billets from sheet metal. In this study, several shearing methods were applied to prepare semi-finished billets for sheet-bulk metal forming of duplex gears. The influences of shearing features such as fracture, roll over, and grain flow lines on subsequent forming were analyzed. The results indicated that conventional blanking billets with imperfect shapes in the fracture zone could cause defects in the duplex gear in the sheet-bulk metal forming (SBMF) stage. To avoid imperfect shapes in the fracture zone, five types of clean shear-cut billets were prepared. Different roll over values and grain flow lines were achieved for the five billets. SBMF analysis using the clean shear-cut billets indicated that grain flow lines had a major influence on the material flow in subsequent forming. Among the preformed billets, the semi-finished billets produced through backward closed die shearing provide symmetrical grain flow lines, which results in superior symmetry of the outer tooth filling.