1. Sheet Metalworking

2. Cutting Operations Shearing by two sharp cutting edges.
Plastic deformation penetration fracture

3. Shearing, Blanking and Punching
Shearing - Cutting on sheet-metal with straight edges.
Blanking - Cutting sheet-metal with a closed contour.
Punching - Making holes on sheet-metal.

4. Sheet-metal Cutting 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
0.25 to 1.5

5. Sheet-metal Cutting Small clearance Cutting force = StL
S = Shear strength of sheet-metal
t = Sheet-metal thickness
L = Length of cutting edge
or, Cutting force = 0.7TtL
T = Ultimate tensile strength of sheet-metal
Large clearance

6. Sheet-metal Cutting Operations
Cut-off
Parting
Slotting Perforating Notching / Seminotching

7. Sheet-metal Cutting Operations
Fine blanking -
close tolerances and smooth edges in one step.
Trimming - Cutting operation to remove excess metal
Shaving - Shearing with very small clearance to obtain accurate dimensions., secondary or finishing operation.

8. Bending
V- bending Edge - bending

9. Bending Analysis BA = 2  A( R + Kbat ) / 360
where BA = bending allowance, A = bend angle, R = bend radius, t = stock thickness, Kba = stretch factor.
For R< 2t, Kba= 0.33 ; for R 2t, Kba= 0.5.
Spring back,
where A’ = include angle of sheet-metal part
A’b = include angle of bending tool
w = width of sheet-metal
Bending force D = die opening dimension
Kbf = V-bending
Kbf = edge bending

10. Bending Analysis
Spring back
Die-opening
dimension

11. Bending Operations Straight flanging Stretch flanging Shrink flanging
Hemming Seaming Curling

12. Bending Operations Channel bending U-bending air-bending
Offset-bending Corrugating Tube forming

13. Drawing c = Clearance Db = blank diameter Dp = Punch diameter
Rd = die corner radius
Rp = Punch corner
radius
F = drawing force
Fh = holding force

14. Deep Drawing Initial step bending of edge straightening of side wall
Thinning and drawing final cup shape

15. Drawing Analysis Drawing ratio,  2.0 where Db = blank diameter
Dp = punch diameter
t = thickness of the starting blank
Reduction,  0.5
Thickness to diameter ratio,  1%
Drawing force, , max. at 1/3 stroke.
Holding force,
Holding pressure may be set at of the yield strength
T = Tensile strength, Y = Yield strength, Rd = die corner radius

16. Drawing Analysis
Blank diameter can be calculated from the conservation of volume based on the final volume of the part.
If the limits on the drawing ratio, reduction and thickness-to-diameter ratio are exceeded, the blank must be drawn in steps or having annealing between the steps.
Process optimization:
Punch and die corner radii
friction
depth of draw (per step)
material characteristics

17. Other Drawing Operations
Redrawing
Reverse drawing
r, 40%-45% first draw
r, 30% second draw
r, 16% third draw
Drawing without blank holder,

18. Drawing Defects a) Wrinkling in flange - small holding force
b) Wrinkling in the wall - insufficient holding force, wrinkling initially occurring on the flange.
c) Tearing - high stress, sharp die radius
d) Earing - anisotropy of the material
e) Surface scratches - Die or punch not having a smooth surface, insufficient lubrication

19. Other Sheet-metal Operations
Ironing - squeezing and drawing in conjunction
Corning & Embossing - to produce surface details
Lancing - combination of cutting and forming

20. Other Sheet-metal Operations
Rubber forming processes:
Guerin process - low cost, small volume, pressure up 10 MPa.
Hydroforming - Higher pressure, up to 100 MPa.

21. Components of a punch and die for blanking operation
Dies
Components of a punch and die for blanking operation

22. Dies
Progressive dies and final part

23. Press Press are driven mechanically or hydraulically. crankshaft
Knuckle joint
eccentric
Press are driven mechanically or hydraulically.

24. Stretch Forming
Stretching and forming with a die at the same time.

25. Roll Forming
Similar to the the rolling process but working on sheet-metal or tubes.

26. Spinning Conventional spinning
Shear spinning - thinning and bending occur at the same time.

27. Spinning
Tube spinning - similar to shear spinning but working on a tube.

28. High Energy Forming Explosive forming Electrohydraulic forming
Electromagnetic forming

29. Tube Bending Stretch bending Drawing bending Compression bending
R/D  3.0 with mandrel
R/D  1.5 without mandrel