Drawing and Bending Process

-Dinesh Kumar R Ad-hoc Faculty Dept. of Production Engg NIT-Trichy

Drawing

Process of forming flat piece of metal into a hollow by means of punch and die cavity

Two Stress:– Circumferential Compressive stress- flange– Tensile Stress – Wall area

Types of Drawing Process

1. Shallow Drawing - Depth of cup formed is (h<d/2) upto half the

diameter2. Deep drawing - Depth greater than diameter (h>d)3. Moderate drawing - between half and full

(d/2<h<d) diameter (not normally done)

Necking

Necking is a mode of tensile deformation where relatively large amounts of strain localize disproportionately in a small region of the material 

The resulting prominent decrease in local cross-sectional area provides the basis for the name "neck".

a form of plastic deformation associated with ductile materials, often metals or polymers.

Ironing

 Ironing is a process to reduce the wall thickness of parts. Typically ironing should not exceed a depth of 30% of the material thickness.

Uniform thickness occurs Purely tensile process

Drawing Ratio

ratio of the maximum blank diameter that can be safely drawn into a cup without flange to the punch diameter

Drawing Ratio=Diameter of Blank/Diameter of cup formed from same blank

Deep Drawing

Blanking

Deep Drawing

Redrawing

Ironing

Doming

Necking

Seaming

Relatively complex 3

dimensional shapes can be

made out of sheet metal!

Examples of Deep Drawing

Bending

Beyond yield strength but below the ultimate tensile strength

Placed on die and bent using a simple punch.

Bending Mechanism

Spring-back

Roll Bending/ Forming

Used for bending boilers, cylindrical pressure vessels, and any other curved structure

Flexible adjustments

PICTURE FRAMES

Tube Bending and Forming

Work-piece Pressure Bar Clamp

* Internal filling is sometimes necessary to prevent collapse.

Tube Bending and Forming

Additional Operations

Beading- sheet metal bent into cavity

Flanging- edge bending of sheet metal

Bulging- tubular expansion

The End…!!!