3 Fundamentals of press design

270 Sheet metal forming and blanking
a c
b
d
e f
Fig. 4.5.3 Examples of favorable part arrangement in the sheet metal strip
utilize the remaining scrap for other workpieces (Fig. 4.5.4). If scrap
skeletons or webs have become deformed during the initial blanking
process, they must go through a straightening machine before further
processing (cf. Sect. 4.8.3).
T, L and U-shaped workpieces are ideally produced in alternatively
reversed manner (top to tail) (Fig. 4.5.3 e, f and Fig. 4.5.5). It is important
to remember when blanking top to tail that the straight strip bends
within the strip plane if subjected to unilateral stress and stretched during
the blanking process, or if unilateral tensions are released. This
applies in particular to soft, thick sheet material. In these cases, it may
be more practical to blank using a multiple punch arrangement for the
simultaneous production of several workpieces rather than using the
top to tail arrangement (Fig. 4.5.4).
Occasionally, it is possible to improve material utilization by blanking
another usable component b from the main piece a, as demonstrated
in Fig. 4.5.6. Figure 4.5.6c illustrates the two parts assembled. The
multiple arrangement of workpieces is often economical (Fig. 4.5.7). In
the interests of optimum material savings, web or skeleton widths
should be kept as narrow as possible (Table 4.5.1). The designations on
the blanking strip are indicated in Fig. 4.5.8. It is important to remem-
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998
Fig. 4.5.4
Utilization of scrap pieces