Sheet metal processes

ME8351 MANUFACTURING TECHNOLOGY 1
UNIT 4 SHEET METAL PROCESSES
S.BALAMURUGAN
ASSISTANT PROFESSOR
MECHANICAL ENGINEERING
AAA COLLEGE OF ENGINEEERING & TECHNOLOGY

SHEET METAL WORKING OR PRESS WORKING
• It is defined as a chip less manufacturing process by which various
components are made from sheet metal.
• This process is also termed as cold stamping.
• It involves forming and cutting operations performed on metal sheets,
strips, and coils. The surface area-to-volume ratio of the starting metal is
relatively high.
• Tools include punch, die that are used to deform the sheets.
APPLICATIONS
• Car bodies, Aircraft fuselages
• Office furniture appliances
• Fuel tanks, CookwareME 8351 MANUFACTURING TECHNOLOGY -1 S.BALAMURUGAN, AP/MECHANICAL, AAACET

SHEET METAL WORKING
METAL CUTTING
OPERATIONS (Stress
beyond Ultimate strength
of sheet metal)
METAL FORMING
OPERATIONS (Stress
below Ultimate
strength of sheet
metal)
1. BLANKING
2. PUNCHING (PIERCING)
3. NOTCHING
4. PERFORATING
5. SLITTING
6. LANCING
7. SHAVING
1. BENDING
2. DRAWING
3. EMBOSSING
4. FORMING
5. COINING (SQUEEZING)
6. STRETCH FORMING
7. IRONING
ME 8351 MANUFACTURING TECHNOLOGY -1 S.BALAMURUGAN, AP/MECHANICAL, AAACET

BLANKING & PUNCHING
BLANKING
• Sheet metal cutting to separate piece from surrounding stock.
• It is the cutting operation of a flat metal sheet & the part punched out is
known as Blank.
PUNCHING or PIERCING
• Similar to Blanking, except cut piece is scrap, called a slug.
• It is the cutting operation with the help of which holes of various are
produced in the sheet.

FINE BLANKING
• Fine blanking is a specialized form of blanking, there is no fracture zone when shearing.
• It requires the use of three very high-pressure pads in a special press.
• These pads hold the metal flat during the cutting process and keep the metal from
plastically deforming during punch entry.
• The tight hold of the high-pressure plates prevents the metal from bulging or plastically
deforming during the extrusion process.
ADVANTAGES
• It can create 100 percent sheared edges with 90-degree angles.
• Dimensional accuracy often is equal to that obtained with machining.
LIMITATIONS
• It can cause severe tool wear, so premium tool steels with coatings are required.
• The V-ring requires space, more material usually is required to make the part as well.

SLITTING LANCING
• It is the operation of making an
unfinished cut through a limited length
only
• In this operation, there is a cutting of
sheet metal through a small length &
bending this small cut portion
downwards.
PERFORATING
• Similar to piercing, but to produce
holes the punch is not of round shape.
• Multiple holes which is very small &
close together are cut in the sheet.
SHAVING
• Very small amount of material is
removed
• Used for cutting unwanted material
from the periphery of a previously
formed workpiece.

NIBBLING NOTCHING
• It is similar to blanking operation, but
in this full surface of punch does not
cut the metal.
• Metal pieces are cut from the edges
of a sheet.
• It is designed for cutting out flat parts
from sheet metal
• The flat parts ranges from simple to
complex contours
• Used for small quantities

SHEARING
• It is a process of cutting a straight line across a strip, sheet
• Metal is placed between upper punch & lower die.
• Pressure is applied, plastic deformation takes place.
• As the pressure is continued, the fracture or crack start at the cutting edge of the
punch
• As the punch descends further, the small fractures meet & the metal is then sheared.
• Shearing is performed by hand or machines.

METAL FORMING OPERATIONS
• In this operations, no material is removed, no wastage.
• The sheet metal is stressed below the ultimate strength of the metal.
U - BENDING V - BENDING
• It is a metal forming operation in which the straight metal sheet is transformed into a
curved form.
• Sheet metal is subjected to both tensile & compressive stresses.
• U-Bending – Channel Bending
• Die cavity in the form of U shape.
• V-Bending – Wedge shape punch is used.
• The angle of V is Acute or Obtuse.
• Angle Bending – there is a bending of a sheet metal at a sharp angle.

CURLING
• In this operation, the edge of a sheet
metal is curled around.
• The punch & die are made to contain
the cavity for cutting partially.
• After the operation, punch moves up,
& work piece is ejected out with the
help of plunger.
• Used for manufacturing of Drums,
Pots & Vessels, Pans.
ROLL BENDING
• Large sheet metal parts are formed
into curved sections
• Sheet passes between the rolls, the
rolls are brought towards each
other to a configuration that
achieves the required radius of
curvature on the work piece.
• Used for making large storage
tanks, pressure vessel, structural
shapes.

BENDING IN A 4 SLIDE MACHINE
• Used for bending short pieces
• The lateral movement of the dies are
controlled with the vertical die
movement to form the part of desired
shapes.
EDGE BENDING
• It involves cantilever loading of
sheet metal
• Pressure pad is used to hold the
work piece
• Punch forces the work piece to
yield & bend over the edge of the
die
• Die – Wiping die
• Due to pressure pad, wiping die
are more complicated & costly
than the V-die.
• Used for high production work

DRAWING
• In this operations, punch forces a
sheet metal blank to flow plastically
into the clearance between the
punch & die.
• The blank takes a shape of cup.
• Drawing = Height < Half Diameter
• Deep Drawing = Height > Half the
diameter
EMBOSSING
• Used for decorative purpose.
• Used to give details like names,
trade marks, specifications on
the sheet metal.
• Specific shapes or figures are
produced on the sheet metal.

DEEP DRAWING - CUPPING
• It is a process of making the cup-shaped parts from a flat sheet-metal
blank.
• To provide necessary plasticity for working, the blank is first heated & then
placed in position over the die.
• To achieve the desired size & wall thickness, the process can be done with
a series of smaller dies.
• Deep Drawing = Height > Half the diameter

DEFECTS IN DEEP DRAWING/ DRAWING
WRINKLING IN FLANGE & CUP WALL – This is like ups & downs or waviness that is
developed on the flange. In flange, this is due to small holding force. In wall, this defect
is due to insufficient holding force,
TEARING - It is a crack in the cup, near the base, happening due to high tensile
stresses causing thinning and failure of the metal at this place. This can also occur due
to sharp die corner.
EARING - The height of the walls of drawn cups have peaks and valleys called as
earing. This is due to Anisotropy of the material.
SURFACE SCRATCHES - Usage of rough punch, dies and poor lubrication cause
scratches in a drawn cup.

REDRAWING & REVERSE DRAWING
• In redrawing, punch is always in
contact with the same side of the
cup.
• In reverse redrawing, the inner
side of the original cup becomes the
outer side.
• The punch will come in contact with
the surface other than that in the
deep drawing process.

COINING(SQUEEZING)
• Like Cold forging operation except
that the flow of the material occurs
only at the top layers & Not in the
entire volume
• High pressure is applied on the
blank from both ends.1600 Mpa.
• The punch & Die have Engraved
Details required on both sides of the
final object.
• Used for making coins, medals,
ornamental parts.
FORMING
• In forming operation, sheet metal
is stressed beyond its yield point
so that it takes a permanent set &
retains the new shape.
• The shape of the die & punch
surface reproduced without any
metal flow.

IRONING
• It involves thinning & lengthening
of the wall material by generating
compressive stress between the
die & Punch.
• The clearance is finer than the
drawing operation.
• Up to 50% thinning can be
obtained in a single Ironing
operation

SPRING BACK OR ELASTIC RECOVERY
• The total deformation imparted to a
workpiece will be the sum of elastic
deformation & plastic deformation.
• At the end of a metal working operation,
when the pressure on the metal is
released, there is an elastic recovery by
the material & the total deformation will get
reduced a little.
• This phenomenon is called as Spring
Back.
• To compensate for spring back, the
cold deformation must always be
carried out beyond the desired limit
by an amount equal to the spring
back.
• It depends on yield point,
High yield point – High Spring back

COMPENSATION FOR SPRING BACK
• OVER BENDING
– The work piece is slightly overbent.
– Over bending is done by setting the bending die &
punch at smaller angle than required.
– When it springs back, it will achieve proper bend
angle.
• BOTTOMING
– The work piece is subjected to high localized
compressive stresses.
– This results in high compressive strains in metal that
set most of the metals past yield point – Spring back
avoided.
• STRETCH FORMING
– It strains the metal beyond elastic limit to give work
piece a permanent set. – Prevents the metal from
spring back.
• IRONING
– Using wiping dies
– To iron the bend effectively, the distance between the
punch & die should be kept less than the material
thickness.

CLEARANCE – METAL CUTTING
• In metal cutting operations, Blanks are produced by Shearing
• The shape of punch is similar to die opening except that it is smaller on each side.
• The difference in dimensions between die & punch is known as Clearance.
• In shearing operation, both tensile & compressive stress act on the metal. The
material is stretched beyond elastic limit.
• Stress is high at the cutting edges of the punch & die, leads to material cracking
from the edges.
• If Clearance is correct, - Cracks from punch & die will meet
• If Clearance is incorrect
• Too small – cracks do not meet, A ragged edge – Burr formed
• Too large – Excessive disc shape deformation.

CLEARANCE – METAL CUTTING
PIERCING OPERATION
Requirement – The hole in the sheet metal is
to be accurate & the slug is wastage.
• The punch is made to the hole size.
• The die opening is obtained by adding
clearance to the punch size.
BLANKING OPERATION
Requirement – Blank is the desired part
• Die opening is made to the Blank size.
• The punch size is obtained by subtracting
the clearance from die opening size.
• Due to spring back effect, the dimension of
the parts gets deviated.
• Due to cold welding, the slug material get
stick with the surface.
• To avoid this, clearance will be provided

CLEARANCE PROBLEM
Find the total pressure, dimensions of tools to produce a washer of 5.5cm
outer diameter with 2.5cm diameter hole, from a material of 4 mm
thickness, having shear strength of 350 N/mm2.
GIVEN DATA – D = 5.5 cm, t = 4mm, d = 2.5 cm, Ʈs = 350 N/mm2.
• The production washer consists of two operations.
• Blanking – Outside diameter, Piercing – Inner hole
• Blanking pressure or Force Fb = π D t Ʈs = 241.902 × 103 N
• Piercing pressure or Force Fp = π d t Ʈs = 109.955 × 103 N
• Total pressure or Force required FT = Fb + Fp = 351.857 × 103 N
Calculating the Dimensions of Tool
Clearance as 5% of thickness on one side,
Blanking die diameter = 55 mm
Blanking Punch diameter= 55 – 2(5% of thickness)= 55 – 2(0.05 × 4) = 54.6mm
Piercing punch diameter = 25 mm
Piercing die diameter = 25 + 2(5% of thickness) = 25 + 2(0.05 × 4) = 25.4mm

CUTTING FORCES IN SHEARING OPERATION
MAXIMUM FORCE REQUIRED TO CUT THE MATERIAL
• Fmax = Shear Area × Shear strength = A × Ʈs
• If the part is a circular blank, then Shear Area = 𝜋 D t
• If the part is a rectangular blank, then Shear Area = 2(L + b) t
• Actual cutting force F =
𝐹 𝑚𝑎𝑥
× 𝐾 ×𝑡
𝐾 ×𝑡+𝐼
• I – Shear on punch or die
• K – Percentage of penetration
• The distance which the punch enters into the stock to cause rupture is called
penetration.

BENDING OF SHEET METAL
• Bend Allowance – The length of the bend area which is more than blank length
before bending is known as Bend Allowance.
• Bend Allowance, B = α (r + k)
• Bend Angle = α, Bend Radius = r, K Factor = K =
𝒕
𝑻
• K factor is a ratio between the distance from the neutral bend line to the inside
bend radius and the material thickness.
• Developed length = L1 + L2 + B

Determine the developed length of the part for the
diagram
To calculate the developed length for bending, external dimensions should
be converted into internal dimensions.
• Developed length = L1 + L2 + B
• The inside bend radius r = 3.2 – 2.3 = 0.9 mm
• Length L1 = 76 – (2.3 + 0.9) = 72.8 mm
• Length L2 = 115 – (2.3 + 0.9) = 111.8 mm
• Bend Allowance, B = α (r + k), α = 90° = 90° ×
π
180
rad =
𝝅
𝟐
rad
Assume K Factor = K =
𝒕
𝟑
=
𝟐.𝟑
𝟑
= 0.766
Bend Allowance B = α (r + k) =
𝝅
𝟐
× (0.9 × 0.766) = 2.617 mm
Developed Length = 72.8 + 111.8 + 2.617 = 187.217 mm

DIE DETAILS & ACCESSORIES
• DIE SET – It is an assembly, it contains a lower
shoe, upper shoe & guide posts, Bushings
• DIE – female part of a complete tool for
producing work in a press
• DIE BLOCK – It contains die cavity
• PUNCH – It is the male part of the die, Actuated
by the Ram
• LOWER SHOE – Mounted on the bolster plate
of a press. The die block is mounted on the
lower shoe.
• UPPER SHOE – Upper part of the die set &
contains guide post bushings.
• PUNCH PLATE – Punch Retainer – Fits over
the punch body & holds it in proper position
• BACK UP PLATE – Pressure plate – to reduce
the excessive pressure on the punch holder
• STRIPPER PLATE – Used to strip the metal
strip from the punch or die. Guides the metal
sheet
• KNOCKOUT – It is a mechanism, used for
freeing the work piece from die. Operated by
Ram.

DIE MATERIALS
SHEET METAL FORMING PROCESS - Die & Punch
MECHANICAL PROPERTIES
– Strong - to hold the force
– Hardness - Dimensional stability, Wear resistance
– Toughness - Impact load
OTHER PROPERTIES
– Suitable for fabrication - machinability
– Cheap & availability
• White cast iron - Hard & brittle - cheaper - cheaper
• Cast iron - Hard & brittle - Low toughness
• Cast steel - moderate strength, rigidity, hardness
• Moderate toughness - High cost
• Wrought iron - High toughness, less rigidity

TYPES OF DIESAccording to the method of press operation
• CUTTING DIE - used to cut the metal - blanking
dies , perforating dies , notching dies , trimming ,
shaving and nibbling dies
• FORMING DIE - change the appearance of the
blank without removing stock. - Bending, drawing
and squeezing dies
According to the method of operation
SIMPLE DIE
• If only one operation is performed in One Stroke
and at One Stage is called as Simple Die.
COMPOUND DIE
• If more than one cutting operation is performed
in one stroke and at one stage called as
Compound Die.
• Ex: Washer.
• One component is produced for stroke.
production rate is high.
• Both of the methods of reducing the punch force.
The force required for compound die will be
higher.

PROGRESSIVE DIE
• In this, more than one cutting
operation will be performed in one
stroke but at different stages.
• Punched out sheet is progressing from
one stage to another stage for completing
the punching operations so that Blanking
will be the last operation.
• One component is produced for stroke.
Production rate is same as that of
compound die.
• In addition, either by providing the shear
or by staggering the punches
methodology, the force required will be
reduced.
• In addition, because the operation is
performed at different stages, the design
and manufacturing of punch and die
combination is easier.

TYPES OF DIE
TRANSFER DIE
• It is same as that of Progressive die, but the
blanking will be the 1st operation so that
the blank produced in the 1st stage is
travelling from one to another stage for
completing punching operations.
COMBINATION DIE
• If more than one Cutting and Forming
operations are combined together and
performing one stroke at one stage is
called Combination Die.
• Blanking combined with Deep drawing
• Punching combined with Deep drawing
• Blanking combined with bending etc.

COMPOUND DIE PROGRESSIVE DIE
Cutting dies, only cutting operations are
carried out.
These dies are follow on dies as it has number
of stations to perform operations
It performs one or more cutting operations
during one stroke of press at one station only.
It performs one or more operations during
one stroke of press at different locations
Slower in operation Faster in operations than compound die
Small strips are used Long strips are used
It increases material handling cost It reduces material handling cost
Final component is formed by simultaneously
performing more than one cutting operation
with each stroke.
Final component is obtained by gradual
progressing the sheet metal strip
Washer is produced by simultaneous blanking
& piercing operation at one station
Washer is produced by blanking operation at
one station & piercing operation at other
station
Larger parts can be blanked in a smaller press Larger parts cannot be blanked in smaller
press

STRETCH FORMING OPERATIONS
• The sheet is clamped at ends & stretched over the die so as to achieve
Plastic State & permanent deformation.
• This process strains the metal beyond the elastic limit, to give the work
piece a permanent set.
FORM BLOCK METHOD
• The two edges of the metal sheet are gripped
firmly & stretched by using a form block.
• By providing pressure on these pistons, the jaws
can be pulled away & tensile forces are applied on
the sheet.
• At the same time, the cylinders can be moved in
guides along a pre-determined path to stretch the
sheet along the contour of the form.
MATING DIE METHOD
• The jaws are mounted on two sides which are
moved apart horizontally for providing tensions
to the sheet.
• The form is attached to the raw of a hydraulic
press which moves upwards.
• The combinations of these two movements
enables the required forming of the sheet.

STRETCH FORMING OPERATIONS

FORMABILITY OF SHEET METAL
SHEET METAL FORMABILITY – It is defined as the ability of the sheet metal
to undergo the desired shape change without failure, such as by necking or
tearing.
The formability depends upon sheet metal characteristics
• ELONGATION – Large uniform elongation is desirable for good formability
• GRAIN SIZE – It affect the mechanical property & influence the surface
appearance of the formed part. Coarser grains – Rough Surface. Small
grain size provide better formability.
• THICKNESS OF THE SHEET – Larger Thickness provide large
formability. A thick blank may not bend as easily around small radius
without cracking.
• TENSILE STRENGTH – the tensile strength & yield strength must not be
high, too much required to forming the material.

ERICHSEN TEST
• A sheet metal specimen is
clamped over a flat die with a
circular opening & a load of
1000kg.
• Specimen – 90mm wide
• A 20mm diameter steel ball is
then hydraulically pressed into
the sheet until a crack appears
on the specimen.
• Distance d = Erichsen Number
TENSILE TEST
• This test is used to evaluate formability.
• It determines the important properties.
• Elongation %
• Ultimate strength
• Yield Strength
• Total elongation at fracture
• Used for stretching & Drawing
operations
• Radial crack – Poor Drawing ability
• Circular crack – Good drawing
ability

FORMING LIMIT DIAGRMS
• Blank sheet is marked with a grid of circles(2.5 – 5mm)
• The blank is then stretched over a punch, until the grid pattern deforms
where necking & tearing occur.
• The deformed circles are measured in the failed region, that is the major
strain & minor strain are obtained.
• The sheet is after stretching, the original circle deformed into ellipse shape.
• 10 data points are considered.
• EXAMPLE
• Original circle diameter – 4mm
• After punch stretch diameter
• Major Ellipse Dia – 5mm
• Minor Ellipse Dia – 3.2mm
• Major strain = ((5-4)/4)×100 = 25%
• Minor strain = ((3.2-4)/4)×100 = - 20%

SPECIAL FORMING PROCESS
• Forming process is performed by pressing the form tool over the sheet or
blank to produce the required shape
• Form tool is operated by Hydraulic cylinder
• If the form tool is operated by any other method except hydraulic cylinder, in
the forming process, then the process are called as Special Forming
Process.
• HERF – HIGH ENERGY RATE FORMING
• HERF - The processes developed to form metals using large amounts of
energy applied in a very short time.
• Explosive Forming
• Electro Hydraulic Forming
• Magnetic forming
• Hydro forming
• Rubber Pad forming
• Peen forming
• Metal spinning
• Roll forming
• Press Brake forming
• Super Plastic Forming
• Explosive forming
• Magnetic Pulse forming

HYDRO FORMING or HYDRO MECHANICAL FORMING
ADVANTAGES OF HYDROFORMING:
• Tooling can be changed rapidly because only
punch & draw ring are required.
• Sharp corners on inner radius are also possible.
• The complex shape can be manufactured.
• Rapid process – Mass production
MATERIALS
• Carbon steel
• Aluminum, Copper
• Brass, High Strength Alloys

RUBBER PAD FORMINGMARFORM PROCESS
• Sheet metal is pressed between a die & rubber
block
• By the application of pressure, the rubber & sheet
metal are driven into the die & confirms to its shape
by forming block.
• Force is applied with the help of Hydraulic cylinder.
• Used for Bending & Drawing operations
• The retainers are used to apply essential hydrostatic
pressure on the blank & prevent sideward motion.
ADVANTAGES
• Less Tooling cost
• Time required for tool setting is less
• Thinning of metal blank does not take place.
• Formed parts does not have any wrinkles.
DISADVANTAGES
• Difficult to produce sharp corners
• Rubber pad will wear out at faster rate
APPLICATIONS – Rectangular cups, Spherical
Domes, Shell with parallel & Tapered walls

SPINNING
• Used for making Axi-Symmetrical Cup Shaped Parts.
• Force is applied on the rotating Blank is held against the form block so as to
get shape of the form block.
• In a conventional spinning operation the work is essentially formed by bending.
• There is usually not much change in the thickness of the sheet metal.
• The diameter of the work in conventional spinning must be large enough to account for the
size of the final part.
• Shear spinning involves forming the work over the mandrel, causing metal flow within the
work.
• This metal flow will act to reduce the thickness of the work as it is formed.
• The initial diameter of the work can be smaller in shear spinning.
• Shear spinning of some materials will be conducted at elevated temperatures.

SPINNING PROCESS

TUBE SPINNING
• Tube spinning is performed on cylindrical parts.
• It is similar to shear spinning in that metal flow occurs within the work.
• This metal flow acts to reduce the thickness of the metal.
• While using tube spinning to reduce the thickness of the tube, the tube's
length will be increased.
• This manufacturing process can be performed externally with the tube over a
mandrel or internally with the tube enclosed by a die.

TUBE BENDING OPERATION
STRAIGHT BENDING
• The work piece, in this case a tube is clamped by
its ends.
• An axial pulling force applied to the pipe as it is
pulled towards and over the template radius so
that the tube is bent by plastic deformation.
ADVANATGES - Bending without pressing forces in
the material
DISADVANTAGES - Thinner wall thicknesses
required.
COMPRESSION BENDING
• The work piece, in this case a tube pressed by a
pressure bar [1] against the fixed form block [2].
• The wipe shoe [3] is pressed against and drawn
along the radius of the block so as to bend the
tube along its contour by plastic deformation.
• Bending core [4] is used but it’s usually done
without it, thus giving an oval cross section in the
bent area.
ADVANTAGES - Cheap method, Simple tools
DISADVANTAGES - The tube can get deformed -
Limited to certain pipe sizes.

TUBE BENDING OPERATIONDRAW BENDING
• The work piece or pipe held by clamps [1] to a rotary bending die [2].
• Just behind the clamp enclosing the tube is a sliding pressure die [3] and a stationary
wiper [4].
• When bending, the pipe is rotated along with the rotary bending die around its outline,
while the follower works as a support for the forces that occur when the pipe
undergoes plastic deformation.
• An articulated bending core [5] prevents cross section deformation.
R/D < 3.0, WITH MANDREL
R/D < 1.5, WIHTOUT MANDREL

EXPLOSIVE FORMING - HERF
• Use of explosive charge to form sheet metal into a die cavity.
• Explosive charge causes a shock wave whose energy is transmitted to force part
into cavity.
• Explosive forming: (1) setup, (2) explosive is detonated, and (3) shock wave forms
part and plume escapes water surface.
• To avoid adiabatic compression & heating of the entrapped air, the air present in the
space will be evacuated. (Vaccum Line – To avoid Air Cushion effect)
• Applications: large parts, typical of aerospace industry.
According to the placement of the explosive, the operations are divided.
STAND OFF OPERATION – Used for Forming.
The charge is located some distance away from the workpiece & the energy is
transmitted through a fluid medium like water.
CONTACT OPERATION – Welding, Hardening, Compacting the powder metals
The explosive is in direct contact with the work piece & the explosive energy acts
directly on the metal ME 8351 MANUFACTURING TECHNOLOGY -1 S.BALAMURUGAN, AP/MECHANICAL, AAACET

• EXPLOSIVES – That undergo rapid
chemical reaction during which heat &
large quantities of gaseous products are
produced.
• Solid – TNT(Trinitro Toluene), Liquid (Nitro
Glycerin), Gas (Oxygen & Acetylene
mixture)
ADVANTAGES
• Only one die required (male or female),
reduces tooling cost
• Complex shapes can be produced.
• Smoothness of the contour can be
controlled.
• Cheap alternative to Superplastic Forming
DISADVANTAGES
• High skilled operators required
• Only viable for low production volumes.
• Handling explosives requires great care
and safety precautions
EXPLOSIVE FORMING - HERF
APPLICATION
• Sheet metal panels, Tubing
• Housings, Jet engine parts,
Missile nose cones, Ducts

ELECTRO – HYDRAULIC FORMING- HERF
• This forming, Converts the Electrical Energy into
mechanical energy in a liquid medium.
• Shock waves & Pressure produced by Electric
spark in a liquid.
• High voltage electrical energy is discharged from a
capacitor into a thin wire suspended between the
two adjustable electrodes.
• This setup immersed in water.
• This system vaporizes the water, starts converting
the electrical energy into hydraulic energy.
• The generates shock waves forces the metal
against the die.
ADVANTAGES
• Tooling cost is low
• Complex shapes can be produced
DISADVANTAGES
• Not suitable for the materials having low ductility like Titanium alloys
• The energy produced for forming is less, hence it is necessary to repeat the
operations several times to obtain the desired shape.
APPLICATIONS
Used for forming of tubular shapes – Aerospace industries

https://www.quia.com/jg/1961543list.html
• Sheet metal is deformed by mechanical force of an electromagnetic field
induced in the work part by an energized coil- Presently the most widely
used HERF process.
• APPLICATIONS: tubular parts.
• Electromagnetic forming diagram
• Setup in which coil is inserted into tubular work part surrounded by die
• formed part.
ELECTRO MAGNETIC FORMING - HERF

SUPER PLASTIC FORMING
SUPER PLASTICITY
• Ability of the material to
undergo extreme elongation at
the proper temperature &
strain rate.
• A very high tensile
elongations, ranging from two
hundred to several hundred
percent.
• Formed by applying gas
pressure(Argon) between
sheet & die surface, causing
the sheets to stretch & fill the
die cavity.
STEP 1 – The material is heated to SPF temperature with in a sealed die.
Titanium – 900°C, Aluminium – 450° -520°C
STEP 2 – Inert gas pressure is applied at a controlled rate, to force the material to
take the shape of the die pattern.
STEP 3 - The flow stress of the material during deformation increases rapidly with
increasing strain rate.
STEP 4 – Formed Part.

SUPER PLASTIC FORMING
MATERIALS DEVELOPED FOR SUPER
PLASTIC FORMING
• Bismuth – Tin (200% Elongation)
• Zinc – Aluminium, Titanium (Ti-6Al-V)
• Aluminum (2004,2419,7475), Aluminum
– Lithium Alloys
ADVANTAGES
• It can form large & complex shape
components in one operation only.
• Less tooling cost
• The components does not suffer Spring
back effect.
• This process eliminates unnecessary
joints & rivets
DISADVANTAGES
• Forming rate is low
• Some materials must not be
superplastic at service temperatures.
APPLICATIONS
• Automotive body panels
• Window frames, Seat
Structures

PEEN FORMING(SHOT PEENING)
• The peen forming process not requires any die and forming press.
• During the operation blanks are clamped over simple form blocks.
• The ball forced by compressed air or rotating blade.
• The ball is having high velocity directly imping the sheet metal to the form of
block.
• There is repeated force by sheet metal get the require form block shape.
• The numerous small balls is having diameter of 2.5 mm size cast- steel ball
blast against the metal surface.
• The ball discharged from the rotating wheel or by air blast from nozzle.
• The balls travelling speed of 60 m/s.
• The residual stress are induced to the compressive surface which improve the
fatigue strength of sheet metal.
ADVANTAGES
• Tooling cost will be low
• The compound curvatures are easily produced
• Die less forming, So that require minimum lead time
APPLICATIONS
• Provide smoothing and complex curvature of aircraft
wings
• Large tubular shapes, Military air craft

Sheet metal processes

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