This document summarizes various sheet metal processes. It discusses sheet metal characteristics and typical forming operations like shearing, bending, drawing, and stretching. It also covers special forming processes such as hydroforming, rubber pad forming, spinning, explosive forming and super plastic forming. The document provides details on sheet metal tools, presses, cutting and forming operations, factors affecting formability and various test methods used to evaluate formability.

1. SHEET METAL PROCESSES
Sheet metal characteristics - Typical shearing operations, bending and
drawing operations – Stretch forming operations –– Formability of sheet
metal – Test methods – Working principle and application of special forming
processes - Hydro forming – Rubber pad forming – Metal spinning –
Introduction to Explosive forming, Magnetic pulse forming, Peen forming,
Super plastic forming.

2. Introduction
 The working of metal thickness from 3mm to 5mm
with hand tools and simple machines into various
forms is known as sheet metal work.
Sheet metals
 Black iron
 Galvanized iron
 Stainless steel
 Brass
 Copper
 Zinc , Aluminium, tin plate and lead.

3.  Sheet metal hand tools:
 1. Measuring tools 2. Straight edge
 3. Steel square 4. Scriber
 5. Divider 6. Trammel points
 7. Punches 7. Chisel
 9. Hammers 10. Snips or shears
 11. Pliers 12. Stakes
 13. Groovers 14. Rivet set and
 15.Soldering iron.
 Measuring tools are steel rule, folding rule,
circumference rule, vernier caliper, micrometer,
thickness gauge and sheet metal gauge.

4.  SHEET METAL CHARACTERISTICS
- Roll Forming: Good surface finish, high production rates, high
tooling cost are produced.
- Stretch Forming: Large parts with shallow contour suitable for low
quantity production, high labor cost, tooling & equipment costs are
produced.
- Drawing: Shallow or deep parts with relatively simple shapes, high
production rates, high tooling & equipment costs are produced.
- Stamping: Variety of operations- punching, blanking, embossing,
bending, flanging and coining, complex shapes formed at high
production rates, tooling & equipment costs are produced.

5. - Rubber Forming :It includes drawing and embossing of simple or
complex shapes sheet surface protected by flexibility of operation.
- Spinning: Small or large axisymmetric parts, good surface finish, low
tooling costs , but labor cost high
- Super Plastic Forming: Complex shapes, fine detail and close
tolerances, forming times are long. Production rate low.
- Peen Forming: Shallow contours on large sheets, flexibility of
operation, equipments costs high & used straightening parts.
- Explosive Forming: Very large sheets with relatively complex
shapes, low tooling costs, but high labor cost, suitable for low
quantity production, long cycle times are produced.
- Magnetic Pulse Forming: Shallow forming, bulging & embossing
operations on relatively low strength sheet, high production rates.

6.  SHEARING OPERATIONS:
 The major operations of sheet metal operations are
 1. Shearing
 2. Bending
 3. Drawing, and
 4. Squeezing.
 Shearing process is cutting a straight line across a strip,
sheet or bar. Three important basic stages
 1, Plastic deformation
 Fracture and
 Shear.

7.  SELECTION OF PRESS:
 The following factor should be considered while
selecting a press for a given workpiece
 Force required to cut the metal
 Die space
 Size and type of die
 Stroke length
 Method of feeding and size of sheet blank
 Shut height
 Type of operation
 Speed of operation

8.  Advantages of press working:
 Material economy
 Reduction of weight and considerable cost reduction of
fabricated parts
 High productivity
 Use of unskilled labour
 High degree of precision
 Uniformity of parts
 Predictable strength characteristics
 Use of less labour
 Possibility of automation

9.  TYPES OF PRESSES;
 1. According to the source of power
 a. Manually operated- Hand, ball of fly presses
 b. Power presses – Mechanical, hydraulic
 2. According to the type and design of frame:
 a. Inclinable, b. straight side c. Gap frame
 d. Horning e. Adjustable bed, f. Open end
 According to the position of frame
 A. Inclinable b. Vertical C Horizontal d. Inclined
 According to the action
 A. Single action b. Double action c. Triple action.

10. PRESSES

11. Mechanically Operated Power Press
or OBI Press(open back inclinable)

12. Inclined Press

13. Inclinable Presss

14.  Arch press: These type of presses are suited for blanking,
bending & trimming used in paint cans forming shovels &
kitchenware.
 Straight side Press: This frame are used both mechanical
and hydraulic presses.
 These presses are high capacity presses with increased
strength and rigidity of the frame.
 Horn press: Mainly used for cylindrical objects
performing seaming, flanging, punching, embossing and
riveting operations.
 Crank driven press: The ram or slide moves up and down
within the guide when the crank rotates.
 Rack and gear driven press: The pinion gear rotates, the
ram connected with rack slides up and down.
 To raise the ram quickly, a quick return motion
mechanism will be incorporated.

15. Types of Cutting Dies
1.Progressive Dies

16. Compound Dies

17. Blanking

18. Piercing

19. CUTTING OPERATIONS

20.  Cutting Operations:
 Blanking: The operation of cutting a flat shape from the
sheet metal.The metal punched out is called as blank &
metal that is left out is scrap.
 Punching or Piercing: The operation of producing the
hole on the workpiece by a punch. The punching, the
metal removed is called as scrap,& metal that is left out
called as workpiece.
 Shearing: Metal is cut along a single line usually a
straight line.
 Parting : metal is cut simultaneously along two parallel
lines or any other two lines which can balance each other
Notching: metal pieces are cut from the edge of a sheet,
strip or blank
 Trimming:

21.  Forming operations:
 (a) Bending: The operation of forming the metal between
a suitably punch & a forming block. The include angle on
the tools is usually smaller than that to be produced to
allow for the spring back of the metal forming.
 (b) Drawing : the operation consists of a punch forcing a
sheet metal blank to flow plastically into the clearance
available between the punch and die surfaces.
 Squeezing : The metal caused to flow to all portions of a
die cavity under the action of compressive force.
 Embossing : The press of producing required shapes on
sheet metal blanks by means of punches and dies.
 Nibbling: the operation of cutting any shape from sheet
metal without special tools. The required shape of profile
is connected in the form of templates in nibbling
machine.

22. PHASES IN SHEARING

23. SHEARING OPERATION - BENDING
TYPES OF BENDING OPERATION
- Angle Bending

24. - Angle Bending
- Roll Bending

25. - Roll Forming
If the edges are formed to a desired shape in the form of bend is
made on the sheet metal
- Seaming
The process of providing lock between the two edges of the
different work metal.
SHEARING OPERATION - DRAWING
- Deep Drawing
Length of the part drawn is deeper then width.
- Box Drawing
Length of the part drawn is lesser then width

26. STRETCH FORMING OPERATION
Stretching is the process of stressing the work blank beyond its elastic limit
by moving a form block towards the blank.
FORM BLOCK METHOD

27. FORM BLOCK METHOD
MATING DIE METHOD

28. SPECIAL FORMING PROCESSES
1.0 HYDRO FORMING
1.Hydro Forming
2. Rubber Pad Forming
3. Metal Spinning
4. Explosive forming
5.Magnetic pulse forming
6. Peen forming
7. Super plastic forming
a) Hydro Mechanical forming
b) Electro Hydraulic Forming

29. 1) Hydro mechanical Forming

30. b) Electro Hydraulic Forming

31. 2.0 RUBBER PAD FORMING

32.  Punch is called male die and upper pattern is called
female parts is just move and touch on the work.
 The force is applied gradually increased on the blank
through rubber die.
 The blank holder ring is used to distribute uniform
pressure thought out the blank.
 The required shape is formed on the sheet metal
between male and female parts.
 The retainers are placed on both sides of the rubber
pad.
 Function of retainers to apply hydrostatic pressure on
the blank and prevents sideward motion.
 The rubber pad is released by moving upward. The
completed shell is stripped out from the punch.

33.  Advantages:
 Process is more economical
 Tooling cost is less
 Many required shapes can be formed in one rubber pad
 There is no need of lubricants
 No thinning metal blank take place
 Tool setting time is less
 Deeper shells can be drawn
 Limitations
 Rubber pads will wear out rapidly
 Sharp corners cannot be made accurately.

34. RUBBER HYDROFORMING PROCESS

35.  Force is applied on the blank through a pressurized
liquid behind the rubber pad.
 The force is used to form the sheet metal into the
required shape.
 Rubber act as a seal between pressure forming chamber
 And blank. Due to application of hydrostatic pressure
over the blank is formed into required shape.
 Hydro forming presses, the hydraulic pressure energy is
directly applied over the surface of the blank.
 Rubber pad forming press, the pressure is applied over
the surface of the blank by the rubber pad which is
operated by hydraulic ram.

36. 3.0 METAL SPINNING
a) Manual Spinning
b) Power Spinning
Applications: Ash trays, flower pots, lamp shades, missile and radar units

37.  Form block is mounted on the head stock of the spinning
lathe. The blank is tightly held between form block and
tail stock spindle.
 The required contour surface is made on the form block
 The pressure is applied by the roller type forming tool
which is placed on the tool post of the spinning lathe.
 The required shape is gradually formed by continuous
application of pressure by the roller.
 During spinning process, some stretching and thinning
of material take place.
 Spinning speed varies with size, design, type of metal and
thickness sheet metal.
 Al, copper, brass and stainless steel can be spin in the
spinning process. The lubricants of grease, linseed oil
and bees wax are used.

38. 4).EXPLOSIVE FORMING PROCESSES
- Stand off operations
The explosive charge is located at some distance away from the blank
and energy is transmitted through some fluid medium such as water.
- Contact Operations
The explosive charge is directly located over the blank.
AEROSPACE COMPONENTS

39.  Explosive forming process is used for blanking, cutting
expanding, coining, embossing, flanging, power
compacting, drawing and sizing operations etc.
 Various forms such as rod, sheet granules, liquid, stick etc
 Contact operation:
 Explosive charge is directly located over the blank.
 This operation is mainly used for welding, hardening,
compacting and cutting process.
 Advantages:
 Less capital investment
 Presses are not required
 Only one die is enough to form the sheet metal
 Required shapes of components are formed in one stroke
 Large and complex shapes can also be handled.

40. 5.0 MAGNETIC PULSE FORMING PROCESS

41.  Advantages:
 This process is carried out with uniform rate of forming
 The surface finish of the process is excellent
 Time of operation is less as compared to conventional
process
 Disadvantages:
 Non conducting materials are not processed without aid
of conducting materials
 It is limited for sheet metal forming process not an
forming bulk material.
 Applications:
 Producing bulging of tube, shrinkage of tube, attaching
tube, forming a torque joint forging of structural joints,
instrument gear assembly, embossing and sizing of cups

42. 6.0 PEEN FORMING PROCESS

43.  Peen forming is a process of well established surface
cleaning. In this process, a stream of metal shots is
blasted against the surface of the blank to be made into
required shape.
 A stream of small ball is suddenly forced with very high
velocity against the surface of the blank.
 Used to form irregular contour surfaces of al sheet and
plates.
 The length of contour of the blank to be formed may be
larger.
 Advantages:
 Complex contour can be produced easily
 Does not require any die and punch

44.  Disadvantages:
 It requires longer time for forming the required shape
 It requires additional devices for forming out metal
shots
 Applications:
 Used in producing specific portions on crankshaft,
connecting rods and gears.
 It is used for producing honeycomb panels like aircraft
wings and large tubular shapes.

45. 7.0 SUPER PLASTIC FORMING PROCESS
a) Loading
b) Forming
c) Forming
d) Release

46.  SPF is valuable tool for the fabrication of complex parts
used in the aircraft and automobile industries.
 SPF of sheet metal has been used to produce very
complex shapes and integrated structures and lighter
and stronger than the assemblies they replace
 SPF process, the material is heated to the SPF temp
within a sealed die. Inert gas pressure is then applied, at
a controlled rate forcing the material to take the shape
of the die pattern.
 The flow stress of the material during deformation
increases rapidly with increasing strain rate
 Super plastic alloy can be stretched at higher temp by
several times of their initial length with out breaking.

47.  SPF process: Consists in hot forming up to 1000 celsius
super plastic alloys by using an inert gas pressured up to
50 bars.
 Combined with diffusion bonding, this process allows
honeycomb structures made of several sheets in a single
operation.
 Loading: The blank is loaded in the form die. The hot
press heats the die and the blank pressure to the material
super plastic temp
 Forming: Once the temp is reached, it is accurately
controlled, the gas pressure slowly inflates the blank.
 The gas keeping inflating the part to fit the die.
 The material at the super plastic temp can allow up to
500% elongation.

48. BASIC SHEARING OPERATION
1.0 Cutting operations
(a) Blanking

49. BASIC SHEARING OPERATION
1.0 Cutting operations

50. BASIC SHEARING OPERATION
1.0 Cutting operations

51. BASIC SHEARING OPERATION
2.0 Forming operations
(a) Bending
(b) Drawing
(c) Sequeezing
(d) Embossing
(e) Nibbling
It is an operation of cutting any shape from sheet metal
without special tools. It is done on a nibbling machine.

52. FORMABILITY OF SHEETMETAL
Formability = f(f1, f2)
F1 = Material Variables - ductility
F2 = Process Variables – stress system, lubrication, die design etc
Law 1 – Process of fracturing
Ductility of the same material is lower if the section size is large.
Law 2 –Law of geometrical Similitude
1 Blank are geometrically similar to dimension, thickness, width etc.
2 Unit strain at corresponding locations are identical
3 Forces required directly proportional to the square of the thickness
.
4 Consumption of work proportional to the cube of its thickness.

53. FORMABILITY TEST METHOD
1 Formability tests for bulk deformation
Elastic deformation and Plastic deformation
2 Formability test for elastic plastic deformation
1) Tensile test
a) Stretch forming - local thinning
b) Drawing operation – Lower punch by thinning under bi-axial stresses.
2) Simulative tests
a)Erichsen test – Stretchability based on erichsen number
b)Olsen test
c) Swift test - based on blank to punch diameter- drawing ratio
d) Fukui test – both assessed - based on formability index

54. FORMABILITY TEST METHOD
3) Full scale forming test