Page 47 - Module DMV20173

3.0 SHEET METAL PROCESSES

the sheet; (c) Cracks on the outer surface of an aluminum strip bent to an angle of

90°.

Figure 3.18 (a) Cracks (b) No cracks (c) Cracks at an angle of 90
o

c. Bending allowance

1. The bend allowance is the length of the neutral axis in the bend and is used
to determine the length of the blank for a part to be bent.

d. Bending force

1. The bending force for sheets and plates can be estimated by assuming that
the process is one of the simple bending of a rectangular beam.

e. Anisotrophy

1. Anisotropy of the sheet is another important factor in bendability.
2. Cold rolling results in anisotropy by preferred orientation or by mechanical

fibering due to the alignment of any impurities, inclusions, and voids that may
be present.

3.3.2 PRESS BRAKE FORMING

1. Sheets or narrow strips that are 7 m or even longer usually are bent in a
press brake.

2. Fig 3.19 (a) through (e) shows the schematic illustrations of various bending
operations in a press brake, and (f) shows the schematic illustration of a
press brake.
3. The process can be automated easily for low-cost, high-production runs.

BPLK 79 DMV 20173