me2030_20160331- metal forming- stamping

8/18/2019 ME2030_20160331- Metal Forming- Stamping

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S. Suryakumar, ME, IITH ME2230: Manufacturing Processes – 1 1

ME2030: Manufacturing Processes – 1

Metal Forming: Sheet Metal Operations


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• Shearing

• Punching

• Bending

• Deep drawing

• Hydroforming

Sheet Metal Operations


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Shearing


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• Shearing is a process for cutting sheet metal to size out of a

larger stock such as roll stock. Shears are used as the

preliminary step in preparing stock for stamping processes.

• Material thickness ranges from 0.125 mm to 6.35 mm (0.005

to 0.250 in). The dimensional tolerance ranges from ±0.125mm to ±1.5 mm (±0.005 to ±0.060 in).

• The shearing process produces a shear edge burr, which can

be minimized to less than 10% of the material thickness. The

burr is a function of clearance between the punch and the die

(which is nominally designed to be the material thickness),

and the sharpness of the punch and the die.

Shearing


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Dynamics


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Blanking / Punching


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Engineering Analysis: Clearance



c = at

c = clearance

a = allowance

t = thickness

Blanking:

Blanking punch dia. = Db- 2c

Blanking die dia. = Db

Punch

Hole punch dia. = Db

Hole die dia. = Db+ 2c

Clearance



Clearance



The force required for shearing is:

F = S*t*L; where

S: shear strength of the sheet metal

t: sheet thickness

L: length of the cut edge

The shear strength S can be estimated by:

S = 0.7 * UTS;where

UTS: the Ultimate Tensile Strength

The above formula does not consider other factors such as friction

Force Required



• A round disk of 150-mm diameter is to be blanked

from a strip of 3.2-mm, half-hard cold rolled steel

whose shear strength = 310 MPa. Determine (a) the

appropriate punch and die diameters, and (b)

blanking force.

Example



Sheet-metal Cutting Operations



(a) Slotting, (b) perforating, (c) notching & seminotching



Shaving and Fine Blanking



• Bending is defined as the straining of metal around a straight axis. During

this process, the metal on the inside of the neutral axis is compressed,while the metal on the outside of the neutral axis is stretched.

Bending

α = bend angle

w = width of sheet

R = bend radius

t = sheet thickness

α′ = 180° - α, “included” angle



Two common bending methods are:

– V-bending

– Edge or wipe bending.

In V-bending the sheet metal blank is bent between a V-shaped punch and

die. The figure below shows a front view and isometric view of a V-bending

setup with the arrows indicating the direction of the applied force:

Types of Bending



• Edge or wipe bending (conducted in lab) involves cantilever loading of the

material. A pressure pad is used to apply a Force to hold the blank against the die,while the punch forces the workpiece to yield and bend over the edge of the die.

The figure below clearly illustrates the edge (wipe)-bending setup with the arrows

indicating the direction of the applied force (on the punch):

Types of Bending



Bending Analysis



Springback is defined as the increase in included angle of the

bent part relative to the included angle of the forming tool after

the tool is removed.

After springback:

• The bend angle will decrease (the included angle will increase)

• The bend radius will increase

Bending Analysis



Flanging, Hemming, Seaming, and Curling


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Deep Drawing


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Hydroforming


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Have a nice day!

me2030_20160331- metal forming- stamping

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