Sheet metal wo rking

Prepared By:
Nikunj Patel
(ID No: 2017PMT5480)

What is sheet metal ?
 Sheet metal is metal formed by an industrial process
into thin, flat pieces.
 It is one of the fundamental forms used in
metalworking and it can be cut and bent into a variety
of shapes.
 Countless everyday objects are fabricated from sheet
metal.
 Thicknesses can vary significantly; extremely thin
sheets are considered foil or leaf, and pieces thicker
than 6 mm (0.25 in) are considered plate.

Foil
 A foil is a very thin sheet of metal, usually made by
hammering or rolling.
 Foils are most easily made with malleable metals, such
as aluminium, copper, tin, and gold.
 Foils usually bend under their own weight and can be
torn easily.
 For example, aluminium foil is usually about 1/1000
inch (0.03 mm), whereas gold can be made into foil
only a few atoms thick, called gold leaf.

Plate
 When sheet metal pieces thicker than 6 mm (0.25 in)
are considered plate.
 It is thicker than foil. So you can have more strength
then foil and used for industrial purpose, where
strength are needed.

Sheet metal thickness in mm and
gauge
 In most of the world, sheet metal thickness is
consistently specified in millimeters.
 In the US, the thickness of sheet metal is commonly
specified by a traditional, non-linear measure:-
GAUGE
 The larger the gauge number, the thinner the metal.
Commonly used steel sheet metal ranges from 30
gauge to about 7 gauge.
 Gauge differs between ferrous metals and nonferrous
metals such as aluminum or copper.

Application of Sheet metal
 Aluminum is also a popular metal used in sheet metal
due to its flexibility, wide range of options, cost
effectiveness, and other properties.
 The four most common aluminium grades available as
sheet metal are 1100-H14, 3003-H14, 5052-H32, and
6061-T6.
 Grade 1100-H14 is commercially pure aluminium,
highly chemical and weather resistant. It is ductile
enough for deep drawing and weldable, but has low
strength. It is commonly used in chemical processing
equipment, light reflectors, and jewelry.

Application of Aluminium
 Grade 3003-H14 is stronger than 1100. It is often used
in stampings, spun and drawn parts, mail boxes,
cabinets, tanks, and fan blades.
 Grade 5052-H32 is much stronger than 3003. Common
applications include electronic chassis, tanks, and
pressure vessels.
 Grade 6061-T6 is a common heat-treated structural
aluminium alloy. It is weldable, corrosion resistant,
and stronger than 5052. It is used in modern aircraft
structures.

List of process of sheet metal working for
non-ferrous metal and alloy
Bending
Curling
Decambering
Deep drawing
Expanding
Hydro-forming
Perforating
Punching
Roll forming
Rolling
Spinning
Stamping
Water jet cutting
Wheeling

Commonly used processess are:
 Bending
 Curling
 Deep drawing
 Punching
 Roll forming
 Rolling

Bending
 Bending is a manufacturing process that produces a V-
shape, U-shape, or channel shape along a straight axis
in ductile materials, most commonly sheet metal.
 Typical products that are made like this are boxes such
as electrical enclosures and rectangular ductwork.

Bending Process
 In press brake forming, a work piece is positioned over
the die block and the die block presses the sheet to
form a shape.
 When bending is done, the residual stresses cause the
material to spring back towards its original position,
so the sheet must be over-bent to achieve the proper
bend angle.
 The amount of spring back is dependent on the
material, and the type of forming.

Bending Process
 When sheet metal is bent, it stretches in length.
 The bend deduction is the amount the sheet metal will
stretch when bent as measured from the outside edges
of the bend.
 The bend radius refers to the inside radius.
 The formed bend radius is dependent upon the dies
used, the material properties, and the material
thickness.

Types of Bending
 Air bending
 Bottoming
 Coining
 Three-point bending
 Folding
 Wiping
 Rotary bending
 Roll bending
 Elastomer bending
 Joggling

Calculations for Bending
Lf = flat length of the sheet
BA = bend allowance
BD = bend deduction
R = inside bend radius
K = K-Factor, which is t / T
T = material thickness
t = distance from inside face to the neutral line[6]
A = bend angle in degrees (the angle through which the
material is bent)

Formula for bending
Bend allowance:

Advnatage of Bending
 Bending is a cost effective process when used for low to
medium quantities.

Curling
 Curling is a sheet metal forming process used to form
the edges into a hollow ring.
 Curling can be performed to eliminate sharp edges and
increase the moment of inertia near the curled end.
 Other parts are curled to perform their primary
function, such as door hinges.

Curling Operations
 In the curling operation, the flare, or burr, should
always be turned away from the die.
 This will help prolong the life of the die by avoiding
unnecessary damage due to scratching.
 The stroke of the die must be as long as the curl.
 Curling is often performed as part of a high
production, multiple operation progressive forming.

Tools used for Curling
 The curling die is designed to curl a material of
specific thickness.
 Dies are generally made of hardened tool steel because
of the amount of wear caused by the operation.
 Their smooth, rounded cavities are often lapped and
polished to help curl the material uniformly.

Deep drawing
 Deep drawing is a sheet metal forming process in
which a sheet metal blank is radially drawn into a
forming die by the mechanical action of a punch.
 It is thus a shape transformation process with material
retention.
 The process is considered "deep" drawing when the
depth of the drawn part exceeds its diameter. This is
achieved by redrawing the part through a series of
dies.

Deep drawing process
 The total drawing load consists of the ideal forming load
and an additional component to compensate for friction in
the contacting areas of the flange region and bending
forces as well as unbending forces at the die radius.
 The forming load is transferred from the punch radius
through the drawn part wall into the deformation region
(sheet metal flange). In the drawn part wall, which is in
contact with the punch, the hoop strain is zero whereby the
plane strain condition is reached.



Deep drawing process
 The thinnest part thickness determines the maximum
stress that can be transferred to the deformation zone.
Due to material volume constancy, the flange thickens
and results in blank holder contact at the outer
boundary rather than on the entire surface.
 The maximum stress that can be safely transferred
from the punch to the blank sets a limit on the
maximum blank size (initial blank diameter in the
case of rotationally symmetrical blanks).

Deep drawing
 An indicator of material formability is the limiting
drawing ratio (LDR), defined as the ratio of the
maximum blank diameter that can be safely drawn
into a cup without flange to the punch diameter.
Determination of the LDR for complex components is
difficult and hence the part is inspected for critical
areas for which an approximation is possible. During
severe deep drawing the material work hardens and it
may be necessary to anneal the parts in controlled
atmosphere ovens to restore the original elasticity of
the material.

Deep drawing force requirement
 Softer materials are much easier to deform and
therefore require less force to draw. The following is a
table demonstrating the draw force to percent
reduction of commonly used materials.

Tools used for Deep drawing
 Punches and dies are typically made of tool steel,
however cheaper (but softer) carbon steel is
sometimes used in less severe applications.
 It is also common to see cemented carbides used
where high wear and abrasive resistance is present.
 Alloy steels are normally used for the ejector system to
kick the part out and in durable and heat resistant
blankholders.

Punching
 Punching is a metal forming process that uses a punch
press to force a tool, called a punch, through the
workpiece to create a hole via shearing.
 The punch often passes through the work into a die. A
scrap slug from the hole is deposited into the die in the
process. Depending on the material being punched
this slug may be recycled and reused or discarded.
Punching is often the cheapest method for creating
holes in sheet metal in medium to high production
volumes.

Punching
 When a specially shaped punch is used to create
multiple usable parts from a sheet of material the
process is known as blanking. In forging applications
the work is often punched while hot, and this is called
hot punching.
 Slugging- It is the operation of punching in which
punch is stopped as soon as the metal fracture is
complete and metal is not removed but held in hole.

Punching Process
 Punch tooling (punch and die) is often made of
hardened steel or tungsten carbide. A die is located on
the opposite side of the workpiece and supports the
material around the perimeter of the hole and helps to
localize the shearing forces for a cleaner edge. There is
a small amount of clearance between the punch and
the die to prevent the punch from sticking in the die
and so less force is needed to make the hole.

Punching
 The amount of clearance needed depends on the
thickness, with thicker materials requiring more
clearance, but the clearance is always less than the
thickness of the workpiece. The clearance is also
dependent on the hardness of the workpiece. The
punch press forces the punch through a workpiece,
producing a hole that has a diameter equivalent to the
punch, or slightly smaller after the punch is removed.

Punching process
 All ductile materials stretch to some extent during
punching which often causes the punch to stick in the
workpiece. In this case, the punch must be physically
pulled back out of the hole while the work is
supported from the punch side, and this process is
known as stripping.
 The hole walls will show burnished area, rollover, and
die break and must often be further processed. The
slug from the hole falls through the die into some sort
of container to either dispose of the slug or recycle it.

Punching characteristics
 Punching is the most cost effective process of making
holes in strip or sheet metal for average to high
fabrication.
 It is able to create multiple shaped holes
 Punches and dies are usually fabricated from
conventional tool steel or carbides.
 Creates a burnished region roll-over, and die break on
sidewall of the resulting hole.
 It's quick.

Geometry for Punching
 The workpiece is often in the form of a sheet or roll.
Materials for the workpiece can vary, commonly being
metals and plastics. The punch and die themselves can
have a variety of shapes to create an array of different
shaped holes in the workpiece. Multiple punches may be
used together to create a part in one step.
 Extruded holes with the punch and die used to create
them. No pilot hole was used on the left.
 Usually, the punch and die are close to the same
dimensions, creating a sheared edge when they meet. A
punch that is significantly smaller than the die can be used
to produce an extruded hole where the punch displaces the
punched material to the sides, forming a tube
perpendicular to the punched sheet.

Related processs
 Other processes such as stamping, blanking,
perforating, parting, drawing, notching, lancing and
bending operations are all related to punching.

Roll forming
 Roll forming, also spelled rollforming, is a type of
rolling involving the continuous bending of a long
strip of sheet metal (typically coiled steel) into a
desired cross-section.
 The strip passed through sets of rolls mounted on
consecutive stands, each set performing only an
incremental part of the bend, until the desired cross-
section (profile) is obtained.
 Roll forming is ideal for producing constant-profile
parts with long lengths and in large quantities.

Roll forming process
 A variety of cross-section profiles can be produced, but
each profile requires a carefully crafted set of roll tools.
Design of the rolls starts with a flower pattern, which
is the sequence of profile cross-sections, one profile for
each stand of rolls. The roll contours are then derived
from the flower pattern profiles. Because of the high
cost of the roll sets, computer simulation is often used
to develop or validate the roll designs and optimize the
forming process to minimize the number of stands
and material stresses in the final product.


Roll forming
 Roll-formed sections may have advantages over
extrusions of a similar shapes. Roll formed parts may
be much lighter, with thinner walls possible than in
the extrusion process, and stronger, having been work
hardened in a cold state. Parts can be made having a
finish or already painted. In addition, the roll forming
process is more rapid and takes less energy than
extrusion.[

Process of Roll forming
 Roll forming is, among the manufacturing processes,
one of the simplest. It typically begins with a large coil
of sheet metal, between 1 inch (2.5 cm) and 20 inches
(51 cm). in width, and 0.004 inches (0.10 mm) and
0.125 inches (3.2 mm) thick, supported on an uncoiler.

Roll forming
 The strip is fed through an entry guide to properly
align the material as it passes through the rolls of the
mill, each set of rolls forming a bend until the material
reaches its desired shape. Roll sets are typically
mounted one over the other on a pair of horizontal
parallel shafts supported by a stand(s). Side rolls and
cluster rolls may also be used to provide greater
precision and flexibility and to limit stresses on the
material. The shaped strips can be cut to length ahead
of a roll forming mill, between mills, or at the end of
the roll forming line.

Rolling Process
 In metalworking, rolling is a metal forming process in
which metal stock is passed through one or more pairs of
rolls to reduce the thickness and to make the thickness
uniform.
 The concept is similar to the rolling of dough. Rolling is
classified according to the temperature of the metal
rolled.
 If the temperature of the metal is above its
recrystallization temperature, then the process is known
as hot rolling. If the temperature of the metal is below its
recrystallization temperature, the process is known as
cold rolling.

Rolling
 In terms of usage, hot rolling processes more tonnage
than any other manufacturing process, and cold
rolling processes the most tonnage out of all cold
working processes.
 Roll stands holding pairs of rolls are grouped together
into rolling mills that can quickly process metal,
typically steel, into products such as structural steel,
bar stock, and rails. Most steel mills have rolling mill
divisions that convert the semi-finished casting
products into finished products.

Hot Rolling
 Hot rolling is a metalworking process that occurs above the
recrystallization temperature of the material. After the
grains deform during processing, they recrystallize, which
maintains an equiaxed microstructure and prevents the
metal from work hardening.
 The starting material is usually large pieces of metal, like
semi-finished casting products, such as slabs, blooms, and
billets. If these products came from a continuous casting
operation the products are usually fed directly into the
rolling mills at the proper temperature. In smaller
operations the material starts at room temperature and
must be heated. This is done in a gas- or oil-fired soaking
pit for larger workpieces and for smaller workpieces
induction heating is used.

Hot rolling
 As the material is worked the temperature must be
monitored to make sure it remains above the
recrystallization temperature. To maintain a safety
factor a finishing temperature is defined above the
recrystallization temperature; this is usually 50 to 100
°C (90 to 180 °F) above the recrystallization
temperature. If the temperature does drop below this
temperature the material must be re-heated before
more hot rolling.

Cold Rolling
 Cold rolling occurs with the metal below its recrystallization
temperature (usually at room temperature), which increases
the strength via strain hardening up to 20%.
 It also improves the surface finish and holds tighter
tolerances. Commonly cold-rolled products include sheets,
strips, bars, and rods; these products are usually smaller than
the same products that are hot rolled.
 Because of the smaller size of the workpieces and their greater
strength, as compared to hot rolled stock, four-high or cluster
mills are used. Cold rolling cannot reduce the thickness of a
workpiece as much as hot rolling in a single pass.

Types of Rolling
 Roll bending
 Roll forming
 Flat rolling
 Ring rolling
 Structural shape rolling
 Controlled rolling
 Forge rolling

Defect in Rolling
 Flatness and shape
 Profile
 Draught
 Surface defect types:
Lap
Mill shearing
Rolled in scale
Scabs
Seams
Silver

Decambering
 Decambering is the metalworking process of removing
camber, or horizontal bend, from strip shaped
materials. The material may be finite length sections
or continuous coils. Decambering resembles flattening
or levelling processes, but deforms the material edge
(left or right) instead of the face (up or down) of the
strip.

Expanding
 Expanding is a process of cutting or stamping slits in
alternating pattern much like the stretcher bond in
brickwork and then stretching the sheet open in
accordion-like fashion.
 It is used in applications where air and water flow are
desired as well as when light weight is desired at cost
of a solid flat surface.
 A similar process is used in other materials such as
paper to create a low cost packing paper with better
supportive properties than flat paper alone.

Hemming and Seaming
 Hemming and seaming are two similar metalworking
processes in which a sheet metal edge is rolled over onto
itself.
 Hemming is the process in which the edge is rolled flush
to itself, while a seam joins the edges of two materials.
 Hems are commonly used to reinforce an edge, hide
burrs and rough edges, and improve appearance.
 Seams are commonly used in the food industry on
canned goods, on amusement park cars, and in the
automotive industry.

Hyrdoforming
 Hydroforming is a process that is analogous to deep
drawing, in that the part is formed by stretching the
blank over a stationary die.
 The force required to do so is generated by the direct
application of extremely high hydrostatic pressure to
the workpiece or to a bladder that is in contact with
the workpiece, rather than by the movable part of a die
in a mechanical or hydraulic press.
 Unlike deep drawing, hydroforming usually does not
involve draw reductions.

Ironing
 Ironing is a sheet metal forming process that
uniformly thins the workpiece in a specific area.
 This is a very useful process when employed in
combination with deep drawing to produce a uniform
wall thickness part with greater height-to-diameter
ratio.
 One example of ironing can be found in the
manufacture of aluminum beverage cans, which are
actually pressed from flat sheets of thicker material.



Laser cutting
 Sheet metal can be cut in various ways, from hand
tools called tin snips up to very large powered shears.
With the advances in technology, sheet metal cutting
has turned to computers for precise cutting. Many
sheet metal cutting operations are based on computer
numerically controlled (CNC) laser cutting or multi-
tool CNC punch press.


Laser cutting
 CNC laser involves moving a lens assembly carrying a beam
of laser light over the surface of the metal.
 Oxygen, nitrogen or air is fed through the same nozzle
from which the laser beam exits. The metal is heated and
burnt by the laser beam, cutting the metal sheet. The
quality of the edge can be mirror smooth and a precision of
around 0.1 mm (0.0039 in) can be obtained. Cutting speeds
on thin 1.2 mm (0.047 in) sheet can be as high as 25 m (82
ft) per minute. Most laser cutting systems use a CO2 based
laser source with a wavelength of around 10 µm; some more
recent systems use a YAG based laser with a wavelength of
around 1 µm.

Photochemical perforating
 Photochemical machining, also known as photo
etching, is a tightly controlled corrosion process which
is used to produce complex metal parts from sheet
metal with very fine detail.
 The photo etching process involves photo sensitive
polymer being applied to a raw metal sheet.
 Using CAD designed photo-tools as stencils, the metal
is exposed to UV light to leave a design pattern, which
is developed and etched from the metal sheet.

Spinning
 Spinning is used to make tubular (axis-symmetric)
parts by fixing a piece of sheet stock to a rotating form
(mandrel).
 Rollers or rigid tools press the stock against the form,
stretching it until the stock takes the shape of the
form.
 Spinning is used to make rocket motor casings, missile
nose cones, satellite dishes and metal kitchen funnels.

Stamping
 Stamping includes a variety of operations such as
punching, blanking, embossing, bending, flanging,
and coining; simple or complex shapes can be formed
at high production rates; tooling and equipment costs
can be high, but labor costs are low.
 Alternatively, the related techniques repoussé and
chasing have low tooling and equipment costs, but
high labor costs.

Water Jet Cutting
 A water jet cutter, also known as a waterjet, is a tool
capable of a controlled erosion into metal or other
materials using a jet of water at high velocity and
pressure, or a mixture of water and an abrasive
substance.

Sheet metal wo rking

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Sheet metal wo rking