3 Fundamentals of press design

298 Sheet metal forming and blanking
outside diameter of the electrical machine [mm]
6
6
singlenotchingdie completeblankingdie
3 6 7
segmentblanks
rotor statorblanks
Fig. 4.6.12 Die engineering methods for electric laminations
progressi edie
no.ofpiecesperyearandtype[parts a]
machine bed. An important element of every notching machine is the
indexing device which is also located on the machine bed. This generates
the required notching pitch, i.e. the number of notches per blank.
The punching radius is selected by adjusting the distance between the
press and the indexing device.
In semi-automatic notching machines,the blanking process is performed
automatically, while feed and discharge are manual processes. The indexing
unit is either mechanically or numerically controlled (Fig. 4.6.14).
The mechanical control device operates with a cam tripping gear and
gears that are exchangeable for obtaining different notching pitches.
When using circular blank diameters between 800 and 1,000 mm, these
low-cost devices achieve a higher output than numerically controlled
systems. In contrast, however, numerically controlled solutions offer
greater flexibility: The notching pitch can be varied as required, making
this type of system ideally suited for more complex notch geometries
such as magnet wheels, pole laminations, rotor rim punchings or segments
(Fig. 4.6.15 below). With the aid of controllable dies, it is possible
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998