7/23/2019 L21 - Sheetmetal

1/28

MECH152-L21 (1.0) - 1

Sheet Metalworking

7/23/2019 L21 - Sheetmetal

2/28

MECH152-L21 (1.0) - 2

Cutting Operations

Shearing by two sharp cutting edges.Plastic deformation penetration fracture

7/23/2019 L21 - Sheetmetal

3/28

MECH152-L21 (1.0) - 3

Shearing, Blanking and Punching

Shearing - Cutting on sheet-metal withstraight edges.

Blanking - Cutting sheet-metal with a closed

contour.Punching - Making holes on sheet-metal.

7/23/2019 L21 - Sheetmetal

4/28

MECH152-L21 (1.0) - 4

Sheet-metal Cutting

c = atc = clearance

a allowance

t thickness

Blanking!

Blanking punch dia. Db- 2c

Blanking die dia. Db

Punch

"ole punch dia. Db

"ole die dia. Db+ 2c#.$%to &.%

7/23/2019 L21 - Sheetmetal

5/28

MECH152-L21 (1.0) - 5

Sheet-metal Cutting

Small clearance

'arge clearance

Cutting force StL

S Shear strength of sheet-metalt Sheet-metal thickness

L 'ength of cutting edge

or, Cutting force #.(TtL

T = )ltimate tensile strength of sheet-metal

7/23/2019 L21 - Sheetmetal

6/28

MECH152-L21 (1.0) - 6

Sheet-metal Cutting Operations

Cut-off

Parting

Slotting Perforating *otching + Seminotching

7/23/2019 L21 - Sheetmetal

7/28

MECH152-L21 (1.0) - 7

Sheet-metal Cutting Operations

ine blanking -

close tolerances

and smooth

edges in one

step.

rimming - Cutting operation to remoe e/cess metal

Shaing - Shearing with ery small clearance to obtain

accurate dimensions., secondary or finishing operation.

7/23/2019 L21 - Sheetmetal

8/28

MECH152-L21 (1.0) - 8

Bending

0- bending 1dge - bending

7/23/2019 L21 - Sheetmetal

9/28

MECH152-L21 (1.0) - 9

Bending 2nalysisBA = 2 A( R + Kbat ) / 360

whereBA bending allowance,A bend angle,R bend radius, tstock thickness,Kba = stretch factor.

or 34 $t,Kba #.55 6 for 3$t,Kba #.%.

Spring back,

where 27 include angle of sheet-metal part

27b include angle of bending tool

w width of sheet-metal

Bending force D die opening dimension

Kbf = &.55 0-bending

Kbf = #.55 edge bending

b

b

A

AASB

=

D

TwtKF

bf

$

=

7/23/2019 L21 - Sheetmetal

10/28

MECH152-L21 (1.0) - 10

Bending 2nalysis

Spring back

8ie-opening

dimension

7/23/2019 L21 - Sheetmetal

11/28

MECH152-L21 (1.0) - 11

Bending Operations

Straight flanging Stretch flanging Shrink flanging

"emming Seaming Curling

7/23/2019 L21 - Sheetmetal

12/28

7/23/2019 L21 - Sheetmetal

13/28

MECH152-L21 (1.0) - 13

8rawing

c Clearance

Db blank diameter

Dp Punch diameter

Rd die corner

radiusRp Punch corner

radius

F drawing force

Fh holding force

MECH152L21(10)14

7/23/2019 L21 - Sheetmetal

14/28

MECH152-L21 (1.0) - 14

8eep 8rawing

9nitial step bending of edge straightening of side wall

hinning and drawing final cup shape

7/23/2019 L21 - Sheetmetal

15/28

MECH152L21(10)16

7/23/2019 L21 - Sheetmetal

16/28

MECH152-L21 (1.0) - 16

8rawing 2nalysis

> Blank diameter can be calculated from the conseration of

olume based on the final olume of the part.

> 9f the limits on the drawing ratio, reduction and thickness-

to-diameter ratio are e/ceeded, the blank must be drawn in

steps or haing annealing between the steps.

> Process optimi?ation!

@ Punch and die corner radii

@ friction

@ depth of draw =per step