Stacking with cylindrical spots in lamination of stamped electrical steel sheets

Abstract The rotors and stators of motors (or generators) as well as the cores of transformers are produced by progressive stamping coupled with stacking. Failure in stacking leads to rotor/stator/core misalignment during winding or loss of lamination after crashes. Proper embossing depth of cylindrical spots and clearance between the punch and die are essential for achieving high-quality lamination. In this work, the proper embossing depth was determined and the effect of the punch/die clearance on stacking quality was investigated. Three electrical sheets with various iron losses (H470, H600, and H1300) were used. The sheet thickness was 0.5 mm. The punch/die clearance ranged from 1% to 4% of the sheet thickness. DEFORM 2D was used for the finite element analysis. The piercing test shows that the proper embossing depths for the H1300, H600, and H470 sheet metals are 0.39, 0.37, and 0.36 mm, respectively. The draft angle of the joined interface increases with punch/die clearance. A small clearance is favorable for the stacking with cylindrical spots. Poor stacking occurs when the clearance is larger than 4% of the sheet thickness.