Common blanking die assemblies are known, for example for producing magnetic laminations and/or magnetic lamination packs for electric motors and generators. These die assemblies usually present a lower part and an upper part. These two parts are mutually aligned by guide columns. The upper and lower parts of the die assembly present corresponding substantially flat portions known respectively as the flat lower portion or die plate and the flat upper portion or punch guide plate or punch stripping plate. With the die assembly open, sheet metal in the form of a strip is fed to the die assembly, to rest on the die plate. The die assembly upper part presents a plurality of punches which project from the punch guide plate during blanking, when the die assembly is closed by the action of the press. The punches then blank the laminations. For blanking purposes, recesses are provided in the die plate in positions corresponding with the punches, to receive said punches in order to implement the blanking operation.
On closing the die assembly, the punches press on the sheet metal in positions corresponding with the portion under which the relative recesses lie. Blanking is then achieved by cutting forces which the punches generate on the sheet metal at the recesses.
Blanking hence enables laminations to be obtained which during production can remain loose or, by means of suitable devices, be stacked together in mutual succession to form lamination packs. These lamination packs also present slots, for example slots to receive magnets, and cooling slots, which define axes parallel to each other and parallel to an axial hole.
The need to produce packs with determined characteristics, for example cavity spiralling, has lead to the creation of blanking die assemblies which enable this to be achieved by rotating the detachment die, in which the pack is formed.
This solution is no longer satisfactory as products produced by blanking have increasingly more complex shapes, for example presenting slots orientated differently from each other. To achieve these product types, the laminations of one and the same pack cannot present the same geometry.