3 Fundamentals of press design

352 Sheet metal forming and blanking
the position of the inside contours relative to the outside contour. The
blanking burr on the inside contours is located on the opposite side to
that of the outside contour. The compound progressive die also permits
forming operations such as bending, offsetting, drawing, etc. in the consecutive
stations (Fig 4.7.21 and 4.7.22). Compared to complete blanking,
parts produced using this method exhibit generally larger dimensioned
tolerances and lower flatness.
In the case of transfer dies, the part is not held in the scrap web. The
blanks are transported from one workpiece station to the next by
means of a gripper rail, which is frequently coupled to the press (cf.
Fig. 4.4.24 or as illustrated in 4.7.22, by means of a transverse feeder).
Die systems
In fine blanking technology, the dies belonging to the various die types
are subdivided into “moving punch” and “fixed punch” systems.
The system making use of a moving punch is used mainly for complete
blanking dies in the production of small to medium-sized parts
with few inner forms (Fig. 4.7.23).The blanking plate 2 is mounted in the
upper die-set 16 on the die block. For the purpose of positioning, it is
positioned and fastened and additionally supported by the base plate 14,
piercing punch retaining plate 10, back-up plate 8 and holding ring 9.
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998
Fig. 4.7.21
Two-station compound
progressive fine blanking die:
1 st station: semi-piercing from
below and hole punching,
2 nd station:embossing the cylindrical
countersinks at the inside
hole, blanking the slots and outside
contour.
Tooling system ”fixed punch”, fourcolumn
steel frame with ball gibs,
active elements are constructed
and coated in segments