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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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S. Suryakumar, ME, IITH ME2230: Manufacturing Processes – 1 2
• Shearing
• Punching
• Bending
• Deep drawing
• Hydroforming
Sheet Metal Operations
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S. Suryakumar, ME, IITH ME2230: Manufacturing Processes – 1 3
Shearing
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S. Suryakumar, ME, IITH ME2230: Manufacturing Processes – 1 4
• 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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S. Suryakumar, ME, IITH ME2230: Manufacturing Processes – 1 5
Dynamics
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S. Suryakumar, ME, IITH ME2230: Manufacturing Processes – 1 6
Blanking / Punching
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Engineering Analysis: Clearance
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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
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Clearance
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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
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• 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
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Sheet-metal Cutting Operations
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(a) Slotting, (b) perforating, (c) notching & seminotching
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Shaving and Fine Blanking
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• 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
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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
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• 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
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Bending Analysis
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Bending Analysis
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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
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Flanging, Hemming, Seaming, and Curling
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S. Suryakumar, ME, IITH ME2230: Manufacturing Processes – 1 23
Deep Drawing
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S. Suryakumar, ME, IITH ME2230: Manufacturing Processes – 1 25
Hydroforming
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Have a nice day!