1. Sanjivani Rural Education Society’s
Sanjivani College of Engineering, Kopargaon-423 603
(An Autonomous Institute, Affiliated to Savitribai Phule Pune University, Pune)
NAAC ‘A’ Grade Accredited, ISO 9001:2015 Certified
Department of Mechanical Engineering
Gujrathi Sonam
Assistant Professor
Sanjivani College of Engineering, Kopargaon
E-mail : gujrathisonammech@sanjivani.org.in
Contact No: 8483874906
Subject :- Manufacturing Process I (MP I)
S.Y. B.Tech. Mechanical
Unit 5- Sheet Metal Working
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Contents
• Types of sheet metal operations
• Types of dies and punches, material for dies and punches,
• Die design for Progressive and Drawing Die, clearance analysis, centre
of pressure, blank size determination (Numerical), strip layout, sheet
utilization ratio (Numerical), methods of reducing cutting forces.
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Introduction
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.
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Metals used in sheet metal working
• Black iron – pans, tanks, cabinets, stove pipes
• Galvanised iron – tanks, buckets, heating ducts, furnace, pans
• Aluminium sheets – aero plane bodies, kitchen wares, doors, windows,
building work, electrical appliances
• Copper sheets – radiators of automobile, heating appliances, components in
chemical plants
• Stainless steel – food containing equipment, dairy equipment, chemical plant
• Tin plates – food containers, containers for cooing oil and ghee, cans
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Introduction
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, aluminum 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.
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Introduction
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.
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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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.
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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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.
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Sheet metal hand tools
• Measuring tools
• Steel rule
• Folding rule
• Circumference rule
• Vernier caliper
• Micrometer
• Thickness gauge
• Sheet metal gauge
• Straight edge
• Steel square
• scriber
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Sheet metal hand tools
• Divider
• Trammel points
• Punches
• Chisel
• Hammers
• Snips or shears
• Pliers
• Stakes
• Groovers
• Rivet set
• Soldering iron
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Sheet Metal Operations
• Shearing
• Bending
• Drawing
• Squeezing
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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shearing
• Shearing is a general name for most sheet metal cutting but in a specific
sense designates a cut in a straight line across a strip, sheet or bar
• This procedure leaves a clean edge on the piece of metal that is sheared or
cut
• 3 basic stages –
• Plastic deformation
• Fracture
• shear
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Shearing operations
• Cutting off – severing a piece from a strip with a cut along a single line
• Parting – it signifies that scrap is removed between the two pieces to part them
• Blanking – cutting a whole piece from sheet metal just enough scrap is left
• Punching – producing circular holes on a sheet metal by a punch or die
• Notching – removing metal to the desired shape from the side or edge of a sheet
or strip
• Slitting – when sheering is conducted between rotary blades the process is
referred to as slitting
• Lancing – makes a cut part way across a strip
• Nibbling – cutting any shape from sheet metal without special tools. Done on
nibbling machine
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Shearing operations
• Trimming – operation of cutting away excess metal in a flange or flash from a
piece
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Bending
• In all metal bends the metal is stressed beyond the elastic limit in tension on
the outside and in compression on the inside of the bend
• There is only one line, the neutral line which retains its original length
• Neutral axis is at a distance of 0.3t – 0.5t from the inside of the bend in most
cases
• 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.
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Bending
• In these operations no material is removed hence there is no wastage
• U bending
• V bending
• Angle bending
• Curling
• Roll bending
• Machine bending
• Edge bending
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Bending
• U bending –
• Also called channel bending
• Die cavity is in the form of U, so component forms the shape of U
• V bending –
• Wedge shape punch is used
• V angle may be acute, 90 degree or obtuse
• Angle bending –
• Bending in sharp angle
• Curling –
• The edge of a sheet metal is curled around
• The punch and die both are made to contain the cavity for cutting partially
• Manufacturing of drums, pots, vessels, pans etc.
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Bending
• Roll bending –
• Large metal sheets are formed into cut section
• Fabrication of large storage tanks, pressure vessel etc
• Machine bending –
• Bending of short pieces
• Lateral movement of the dies are controlled with the vertical movement to form part of
desired shapes
• Edge bending –
• Involves cantilever loading of sheet metal
• Operation is limited to bends of 90 degree or less
• The dies used for wedge bending is called wiping dies so can be designed for bend angles
more than 90 degree
• Used for high production work
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Drawing
• Punch forces a sheet metal blank to
flow plastically into the clearance
between the punch and die
• Finally, the blank takes a shape of
cup
• Application – seamless pots, tubs,
cans and covers; automobile panels,
tops and hoods
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Embossing
• With the help of this operation,
specific shapes or figures are
produced
• It is used for decorative purpose
or giving details like names,
trade marks, specification etc.
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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squeezing
• Quick and widely used way of
forming ductile metal
• The squeezing operations of sizing,
coining, hobbing, ironing etc mostly
used on sheet metal
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Sheet metal joints
• Hems & seams –
• A hem is an edge or border made by folding
• It stiffens the sheet of metal and does away with the sharp edge
• seam is a joint made by fastening two edges together
• Types of hems – 1. single hem 2. double hem 3. wired edge
• Single hem is made by folding the edges of sheet metal over to make it smooth
and stiff
• Double hem is made by folding the edges over twice to make it stiff and smooth
• Wired edge is smooth and very strong
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Sheet metal joints
• Seams –
• Lap seam – lap seam made by lap joint by soldering
• Grooved seam – hooking two single hems together
• Double seam – same as single seam (join a vertical bodies to bottom of various
shape) with the difference that its formed edge is bent upward against the body
• Dovetail seam – used to join flat plate to a cylindrical piece, used in carpentry
• Burred bottom or flanged seam – bottom of the container to its body
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Types of die
• Simple die
• Compound die
• Combination die
• Progressive die
• Transfer die
• Multiple die etc.
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Centre of pressure
• When the irregular shape blank is to be cut, then the summation of shear forces
about the centre line of press ram should not be symmetrical
• Hence bending moment will be introduced in the press ram because of which,
undesirable deflection and misalignment are produced.
• So to avoid this centre of pressure of the shearing action of the die must be
found
• While laying out the punch position on the punch holder, centre line of press
ram should pass through the centre of pressure of the blank
• This centre of pressure is thencentroid/ centre of gravity of the line perimeter of
the blank
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Strip layout
• Layout is the position of workpieces in the strip and their orientation
with respect to each other. This is called a strip layout.
• Factors which affect the strip or stock layout
• Economy of material
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Strip layout
• Direction of material grains
• Burr direction
• Press used
• Die cost
• Production required
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Methods of reducing cutting forces
• For cutting operation it has been assumed that, bottom of the punch and the
top of the die block lie in parallel planes
• Due to this very high punch force is exerted for a very short time on the
material, resulting in shock or impulsive conditions
• Hence to reduce cutting forces and smooth out the shock impact of heavy
loads, following methods are used -
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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Methods of reducing cutting forces
• Shear
• Staggering of punches
Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
