Page 49 - Module DMV20173

3.0 SHEET METAL PROCESSES

Figure 3.20 (a) Bead forming with a single die. (b) Though (d) Bead forming

b. Flanging

1. This is a process of bending the edges of sheet metals, usually to 90°.
2. In shrink flanging, the flange is subjected to compressive hoop stresses
which, if excessive, can cause the flange periphery to wrinkle.

3. The wrinkling tendency increases with decreasing radius of curvature of
the flange.
4. In stretch flanging, the flange periphery is subjected to tensile stresses
that, if excessive, can lead to cracking along the periphery.

5. Fig 3.21 shows various flanging operations. (a) Flanges on flat sheet. (b)
Dimpling. (c) The piercing of sheet metal to form a flange. In this
operation, a hole does not have to be pre-punched before the punch
descends. Note, however, the rough edges along the circumference of the
flange. (d) The flanging of a tube. Note the thinning of the edges of the

flange.

BPLK 81 DMV 20173