Compiled & Edited
By
Sivaraman Velmurugan
Notice to the Reader
This presentation contains information obtained from authen...
 A piece of metal whose thickness is between 0.006(0.15 mm)
and 0.25 inches(6.35 mm).
 Anything thinner is referred to ...

 Sheet metal is a metal formed into thin and flat pieces. It is one
of the fundamental forms used in metalworking, and ...

 The most common sheet metal
used in automotive to make
bodies is steel. It is reasonably
cheap and easy to press into
...
 There are three types of steel
used in the automotive body and
only two are commonly used.
 The first type which is us...

 Boron steel is developed using boron as an
alloying element in developing Ultra High-
strength Steel (UHSS).
 Once be...

 Also called plain-carbon steel, is the
most common form of steel because of
its price is low while it provides materia...

 Mild steel has a relatively low
tensile strength, but its cheap
and malleable; surface hardness
can be increased by ca...
 Carbon steels which can successfully
undergo heat treatment have a content in
the range of 0.3-1.7% by weight.
 Medium...
 6111 aluminum and 2008 aluminum alloy are
extensively used for external automotive body
panels, with 5083 and 5754 used...
 2000 series(2008,2036) – alloyed with copper, can be
precipitation hardened to strengths, comparable to
steel. Formerly...

Sheet Metal Working & Process
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Sheet Metal Forming Process
Large g...
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Sheet Metal Working & Process
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Stresses in Metal Forming
 Stresse...
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Sheet Metal Working & Process
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Material Properties in Metal Formin...
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Sheet Metal Working & Process
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Process Classification
 Bulk Defor...
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Sheet Metal Working & Process
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Bulk Deformation Process
Characteri...
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Sheet Metal Working & Process
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Rolling Forging
Extrusion
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Sheet Metal Working & Process
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Sheet metalworking
Forming and rela...
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Sheet Metal Working & Process
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Sheet Metal Working & Process
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Material Behavior in Metal Forming
...
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Sheet Metal Working & Process
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Flow Stress
 For most metals at ro...
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Sheet Metal Working & Process
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Average Flow Stress
 Determined by...

Sheet Metal Working & Process
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Stress-Strain Relationship
 Averag...
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Sheet Metal Working & Process
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Temperature in Metal Forming
 Any ...
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Sheet Metal Working & Process
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Cold Working
 Performed at room te...
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Sheet Metal Working & Process
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Advantages of Cold Forming
 Better...
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Sheet Metal Working & Process
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Disadvantages of Cold Forming
 Hig...
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Sheet Metal Working & Process
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Warm Working
 Performed at tempera...
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Sheet Metal Working & Process
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Advantages and Disadvantages of War...
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Sheet Metal Working & Process
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Hot Working
 Deformation at temper...
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Sheet Metal Working & Process
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Why Hot Working
Capability for subs...
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Sheet Metal Working & Process
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Advantages of Hot Working
 Workpar...
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Sheet Metal Working & Process
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Disadvantages of Hot Working
 Lowe...
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Sheet Metal Working & Process
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Isothermal Forming- A Type of Hot F...
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Sheet Metal Working & Process
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Strain Rate Sensitivity
 Theoretic...

Sheet Metal Working & Process
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What is Strain Rate?
 Strain rate ...
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Sheet Metal Working & Process
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Evaluation of Strain Rate
 In most...
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Sheet Metal Working & Process
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Effect of Strain Rate on Flow Stres...
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Sheet Metal Working & Process
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Strain Rate Sensitivity
 (a) Effec...
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Sheet Metal Working & Process
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Effect of Temperature on Flow Stres...
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Sheet Metal Working & Process
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Observations about Strain Rate Sens...
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Sheet Metal Working & Process
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Friction in Metal Forming
If the co...
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Sheet Metal Working & Process
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Friction in Metal Forming
 In most...
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Sheet Metal Working & Process
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Lubrication in Metal Forming
 Meta...
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Sheet Metal Working & Process
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Considerations in Choosing a Lubric...
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 Bending
 Shearing
 Blanking
 Punching
 Trimming
 Parting
 Slitting
 Lancing
 Notching
 Perforating
 Nibbling...

 Bending is a metal forming process in which a force is applied to
a piece of sheet metal, causing it to bend at an ang...

Press Brake Machine
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Two common bending methods are:
 V-Bending
 Edge bending
 V-Bending - The sheet metal blank is
bent between a V-shaped...

 Edge (or) Wipe Bending - Wipe
bending requires the sheet to be
held against the wipe die by a
pressure pad. The punch ...

Bending Operations
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
Bending Operations
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Shearing
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 Shearing is defined as separating
material into two pa...

Blanking
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 A piece of sheet metal is removed
from a larger piece ...

Fine Blanking
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 A second force is applied
underneath the sheet, d...

Punching Operations
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
Punching Or Piercing
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 The typical punching operation, in
which a...

Blanking & Punching examples
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Trimming
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 Punching away excess material from the perimeter of a ...

Parting
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 Separating a part from the remaining sheet, by punching...

Slitting
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 Cutting straight lines in the sheet. No scrap material...
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Lancing
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 Creating a partial cut in the sheet, so that no materia...

Notching
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 Punching the edge of a sheet, forming a notch in the s...

Perforating
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 Punching a close arrangement of a large number of h...
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Nibbling
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 Punching a series of small overlapping slits or holes ...
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Embossing
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 Certain designs are embossed on the sheet metal.
 Pu...

Shaving
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 Shearing away minimal material from the edges of a feat...
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Cuttoff
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 Cutoff - Separating a part from the remaining sheet, wi...
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Dinking
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 Dinking - A specialized form of piercing used for punch...
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Coining
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 Similar to embossing with the difference that similar o...

Deep Drawing
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 Deep drawing is a metal forming process in which s...

Process overview in deep drawing
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Stretch Forming
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 Stretch forming is a metal forming process in w...
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Roll Forming
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 Roll forming is a continuous bending
operation in ...
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Dies
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 Made up of tool steel and used to cut or shape material.
...
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Simple Die
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 Simple dies or single action dies perform single ope...

Compound Die
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 In these dies, two or more operations may be perfo...

Combination Die
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 In this die also , more than
one operation may ...

Progressive Die
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 A progressive has a series of operations.
 At ...

Progressive Die
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Rolling Defects
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 Wavy edges
 Result from concave roll bending a...

Forging defects
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 Surface crack
 Excessive working at low temper...

Drawing Defects
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 Wrinkling in the flange
 Occurs due to compres...

Drawing Defects
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 Tearing
 High tensile stresses that cause thin...

Defects in Extrusions
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 Surface Cracking / Fir-tree cracking
 Hi...
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Defects in Extrusions
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 Internal Cracking/ Chevron cracking
 Cen...

Mail me – sudhavel@yahoo.com
Questions & Comments
2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 87

2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 88
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Sheet Metal Working & Process

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Roll forming Long parts with constant complex cross-sections; good surface finish; high
production rates; high tooling costs.
Stretch forming
Large parts with shallow contours; suitable for low-quantity production; high
labor costs; tooling and equipment costs depend on part size.
Drawing Shallow or deep parts with relatively simple shapes; high production rates;
high tooling and equipment costs.
Stamping Includes a variety of operations, such as punching, blanking, embossing,
bending, flanging, and coining; simple or complex shapes formed at high
production rates; tooling and equipment costs can be high, but labor costs
are low.
Rubber-pad
forming
Drawing and embossing of simple or complex shapes; sheet surface protected
by rubber membranes; flexibility of operation; low tooling costs.
Spinning Small or large axisymmetric parts; good surface finish; low tooling costs, but
labor costs can be high unless operations are automated.
Superplastic
forming
Complex shapes, fine detail, and close tolerances; forming times are long,
and hence production rates are low; parts not suitable for high-temperature
use.
Peen forming Shallow contours on large sheets; flexibility of operation; equipment costs
can be high; process is also used for straightening parts.
Explosive
forming
Very large sheets with relatively complex shapes, although usually axisymmetric;
low tooling costs, but high labor costs; suitable for low-quantity
production; long cycle times.
Magnetic-pulse
forming
Shallow forming, bulging, and embossing operations on relatively lowstrength
sheets; most suitable for tubular shapes; high production rates;
requires special tooling.

Published in: Engineering

Sheet Metal Working & Process

  1. 1. Compiled & Edited By Sivaraman Velmurugan Notice to the Reader This presentation contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to compile & edit reliable data and information, but the author cannot assume responsibility for the validity of all materials or the consequences of their use. The authors have attempted to trace the copyright holders of all material reproduced in this compilation and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let me know so I may rectify in any future presentation.
  2. 2.  A piece of metal whose thickness is between 0.006(0.15 mm) and 0.25 inches(6.35 mm).  Anything thinner is referred to as a foil and thicker is considered as a plate.  Sheet thickness is generally measured in gauge. Greater the gauge number, thinner the sheet of metal.  Sheet metal can be cut, bent and stretched into nearly any shape.  Generally two types of operations are performed- forming and cutting. What is Sheet Metal? 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 2
  3. 3.   Sheet metal is a metal formed into thin and flat pieces. It is one of the fundamental forms used in metalworking, and can be cut and bent into a variety of different shapes.  Countless everyday objects are constructed by this material.  Thicknesses can vary significantly, although extremely thin sheets are considered as foil or leaf, and sheets thicker than 6 mm (0.25 in) are considered as plate.  Sheet metal forming is a grouping of many complementary processes that are used to form sheet metal parts. What is Sheet Metal? 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 3
  4. 4.   The most common sheet metal used in automotive to make bodies is steel. It is reasonably cheap and easy to press into shape to make body parts.  The next best is aluminum. It is lighter but harder to bend into tight shapes without cracking. It is also harder to weld in mass production. What metals are used in automotive? 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 4
  5. 5.  There are three types of steel used in the automotive body and only two are commonly used.  The first type which is used by Volvo™ is boron steel which is stronger than the other two types of steel.  The two types commonly used are:  Mild and low-carbon steel  Higher carbon steel Steel and it’s types.. 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 5
  6. 6.   Boron steel is developed using boron as an alloying element in developing Ultra High- strength Steel (UHSS).  Once bent, it can’t be straightened and it requires replacement if damaged.  Boron steel are also sensitive to heat and it weakens when it’s heated rapidly.  Because of its sensitivity to heat, it can’t be galvanized. Therefore, corrosion protection is crucial and essential after welding. More on Boron Steel… 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 6
  7. 7.   Also called plain-carbon steel, is the most common form of steel because of its price is low while it provides material properties that are acceptable for many applications, more so than iron.  Contains approximately 0.05-0.3% carbon making it malleable and ductile. More on Mild and Low-Carbon Steel… 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 7
  8. 8.   Mild steel has a relatively low tensile strength, but its cheap and malleable; surface hardness can be increased by carburizing. Note: Carburizing is a heat treatment process in which iron or steel absorbs carbon liberated when the metal is heated in the presence of carbon bearing material, such as charcoal or carbon monoxide with the intent of making the metal harder. More on Mild and Low-Carbon Steel… 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 8
  9. 9.  Carbon steels which can successfully undergo heat treatment have a content in the range of 0.3-1.7% by weight.  Medium carbon steel :- approximately 0.3- 0.59% carbon content. (Balances ductility and strength and has good wear resistance).  High-carbon steel :- 0.6-0.99% carbon content. (Very strong).  Ultra-high-carbon steel :- 1.0-2.0% carbon content. (Steels that can be tempered to great hardness). More on Mild and Low-Carbon Steel… 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 9
  10. 10.  6111 aluminum and 2008 aluminum alloy are extensively used for external automotive body panels, with 5083 and 5754 used for inner body panels.  Hoods have been manufactured from 2036, 6016, and 6111 alloys.  Truck and trailer body panels have used 5456 aluminum.  Automobile frames often use 5182 aluminum or 5754 aluminum formed sheets, 6061 or 6063 extrusions Aluminum and it’s types… 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 10
  11. 11.  2000 series(2008,2036) – alloyed with copper, can be precipitation hardened to strengths, comparable to steel. Formerly referred as duralumin, they were once the most common aerospace alloys, but were susceptible to stress corrosion cracking and are increasingly replaced by 7000 series in new designs.  5000 series(5083,5754,5456,5182) – alloyed with magnesium.  6000 series(6111,6016,6061,6063) – alloyed with magnesium and silicon, are easy to machine, and can be precipitation hardened, but not to the high strengths that 2000 and 7000 can reach. Aluminum and it’s types… 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 11
  12. 12.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 12 Sheet Metal Forming Process Large group of manufacturing processes in which plastic deformation is used to change the shape of metal workpieces.  The tool, usually called a die, applies stresses that exceed the yield strength of the metal  The metal takes a shape determined by the geometry of the die.
  13. 13.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 13 Stresses in Metal Forming  Stresses to plastically deform the metal are usually compressive  Examples: rolling, forging, extrusion  However, some forming processes  Stretch the metal (tensile stresses)  Others bend the metal (tensile and compressive)  Still others apply shear stresses (shear spinning)
  14. 14.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 14 Material Properties in Metal Forming  Desirable material properties:  Low yield strength  High ductility  These properties are affected by temperature:  Ductility increases and yield strength decreases when work temperature is raised  Other factors:  Strain rate and friction
  15. 15.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 15 Process Classification  Bulk Deformation Process  Rolling  Forging  Extrusion  Wire and bar drawing  Sheet Metalworking  Bending  Deep drawing  Cutting  Miscellaneous processes
  16. 16.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 16 Bulk Deformation Process Characterized by significant deformations and massive shape changes "Bulk" refers to workparts with relatively low surface area - to - volume ratios. Starting work shapes include cylindrical billets and rectangular bars  Rolling - compression process to reduce the thickness of a slab by a pair of rolls.  Forging - compression process performing between a set of opposing dies.  Extrusion - compression process squeezing metal flow a die opening.  Drawing - pulling a wire or bar through a die opening.
  17. 17.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 17 Rolling Forging Extrusion
  18. 18.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 18 Sheet metalworking Forming and related operations performed on metal sheets, strips, and coils. High surface area-to-volume ratio of starting metal, which distinguishes these from bulk deformation. Often called pressworking because presses perform these operations. Parts are called stampings : Usual tooling: punch and die. Forming on metal sheets, strips, and coils. The process is normally a cold working process using a set of punch and die.  Bending - straining of a metal sheet to form an angle bend.  Drawing - forming a sheet into a hollow or concave shape.  Shearing - not a forming process but a cutting process.
  19. 19.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 19
  20. 20.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 20 Material Behavior in Metal Forming  Plastic region of stress-strain curve is primary interest because material is plastically deformed.  In plastic region, metal's behavior is expressed by the flow curve : σ =Kϵn where K = strength coefficient; and n = strain hardening exponent.  Flow curve based on true stress and true strain.
  21. 21.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 21 Flow Stress  For most metals at room temperature, strength increases when deformed due to strain hardening.  Flow stress = instantaneous value of stress required to continue deforming the material : Yf =Kϵn where Yf = flow stress, that is, the yield strength as a function of strain.
  22. 22.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 22 Average Flow Stress  Determined by integrating the flow curve equation between zero and the final strain value defining the range of interest where Ȳf = average flow stress; and  = maximum strain during deformation process n K Y n f   1 _ 
  23. 23.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 23 Stress-Strain Relationship  Average flow stress in relation to  Flow stress Yf  Yield strength Y Temperature in Metal Forming For any metal, K and n in the flow curve depend on temperature  Both strength (K) and strain hardening (n) are reduced at higher temperatures.  In addition, ductility is increased at higher temperatures.
  24. 24.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 24 Temperature in Metal Forming  Any deformation operation can be accomplished with lower forces and power at elevated temperature  Three temperature ranges in metal forming:  Cold working  Warm working  Hot working
  25. 25.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 25 Cold Working  Performed at room temperature or slightly above,  Many cold forming processes are important mass production operations,  Minimum or no machining usually required,  These operations are near net shape or net shape processes.
  26. 26.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 26 Advantages of Cold Forming  Better accuracy, closer tolerances  Better surface finish  Strain hardening increases strength and hardness  Grain flow during deformation can cause desirable directional properties in product  No heating of work required
  27. 27.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 27 Disadvantages of Cold Forming  Higher forces and power required for deformation  Surfaces of starting work must be free of scale and dirt  Ductility and strain hardening limit the amount of forming that can be done  In some cases, metal must be annealed before further deformation can be accomplished  In other cases, metal is simply not ductile enough to be cold worked
  28. 28.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 28 Warm Working  Performed at temperatures above room temperature but below recrystallization temperature  Dividing line between cold working and warm working often expressed in terms of melting point:  0.3Tm, where Tm = melting point (absolute temperature) for metal
  29. 29.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 29 Advantages and Disadvantages of Warm Working  Advantages  Lower forces and power than in cold working  More intricate work geometries possible  Need for annealing may be reduced or eliminated  Disadvantage  Workpiece must be heated
  30. 30.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 30 Hot Working  Deformation at temperatures above the recrystallization temperature  Recrystallization temperature = about one-half of melting point on absolute scale  In practice, hot working usually performed somewhat above 0.5Tm  Metal continues to soften as temperature increases above 0.5Tm, enhancing advantage of hot working above this level
  31. 31.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 31 Why Hot Working Capability for substantial plastic deformation - far more than is possible with cold working or warm working Why?  Strength coefficient (K) is substantially less than at room temperature  Strain hardening exponent (n) is zero (theoretically)  Ductility is significantly increased
  32. 32.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 32 Advantages of Hot Working  Workpart shape can be significantly altered  Lower forces and power required  Metals that usually fracture in cold working can be hot formed  Strength properties of product are generally isotropic  No strengthening of part occurs from work hardening  Advantageous in cases when part is to be subsequently processed by cold forming
  33. 33.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 33 Disadvantages of Hot Working  Lower dimensional accuracy  Higher total energy required, which is the sum of  The thermal energy needed to heat the workpiece  Energy to deform the metal  Work surface oxidation (scale)  Thus, poorer surface finish  Shorter tool life  Dies and rolls in bulk deformation
  34. 34.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 34 Isothermal Forming- A Type of Hot Forming When highly alloyed metals such as Ti and Nickel alloys are heated to hot temp and bring in contact with cold tooling, the heat radiates from the metal to tooling. This result in high residual stresses and temp variation over metal and hence irregular material flow occurs during forming, causing cracks. In order to avoid this problem, both metal and tooling are heated to same temp. However, this causes reduction in tooling life. ** Mostly, Forging is performed through this process
  35. 35.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 35 Strain Rate Sensitivity  Theoretically, a metal in hot working behaves like a perfectly plastic material, with strain hardening exponent n = 0  The metal should continue to flow at the same flow stress, once that stress is reached  However, an additional phenomenon occurs during deformation, especially at elevated temperatures:  Strain rate sensitivity
  36. 36.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 36 What is Strain Rate?  Strain rate in forming is directly related to speed of deformation v  Deformation speed v = velocity of the ram or other movement of the equipment  Strain rate is defined:  Where = true strain rate; and h = instantaneous height of workpiece being deformed h v  .  
  37. 37.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 37 Evaluation of Strain Rate  In most practical operations, valuation of strain rate is complicated by  Workpart geometry  Variations in strain rate in different regions of the part  Strain rate can reach 1000 s-1 or more for some metal forming operations.
  38. 38.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 38 Effect of Strain Rate on Flow Stress  Flow stress is a function of temperature  At hot working temperatures, flow stress also depends on strain rate  As strain rate increases, resistance to deformation increases  This is the effect known as strain-rate sensitivity
  39. 39.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 39 Strain Rate Sensitivity  (a) Effect of strain rate on flow stress at an elevated work temperature  (b) Same relationship plotted on log-log coordinates Strain Rate Sensitivity Equation where C = strength constant (analogous but not equal to strength coefficient in flow curve equation), and m = strain-rate sensitivity exponent m f CY ε=
  40. 40.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 40 Effect of Temperature on Flow Stress  The constant C, indicated by the intersection of each plot with the vertical dashed line at strain rate = 1.0, decreases  And m (slope of each plot) increases with increasing temperature
  41. 41.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 41 Observations about Strain Rate Sensitivity Increasing temperature decreases C and increases m  At room temperature, effect of strain rate is almost negligible  Flow curve alone is a good representation of material behavior  As temperature increases  Strain rate becomes increasingly important in determining flow stress
  42. 42.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 42 Friction in Metal Forming If the coefficient of friction becomes too large, a condition known as STICKING occurs. Sticking in metal working is the tendency for the two surfaces in relative motion to adhere to each other rather than slide. When Sticking Occurs? The friction stress between the surfaces becomes higher than the shear flow stress of the metal thus causing the material to deform by a shear process beneath the surface rather than slip at the surface. Sticking is a prominent problem in forming operations, especially rolling.
  43. 43.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 43 Friction in Metal Forming  In most metal forming processes, friction is undesirable:  Metal flow is reduced  Forces and power are increased  Tools wear faster  Friction and tool wear are more severe in hot working
  44. 44.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 44 Lubrication in Metal Forming  Metalworking lubricants are applied to tool-work interface in many forming operations to reduce harmful effects of friction  Benefits:-  Reduced sticking, forces, power, tool wear  Better surface finish  Removes heat from the tooling
  45. 45.  Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 45 Considerations in Choosing a Lubricant  Type of forming process (rolling, forging, sheet metal drawing, etc.)  Hot working or cold working  Work material  Chemical reactivity with tool and work metals  Ease of application  Cost
  46. 46.   Bending  Shearing  Blanking  Punching  Trimming  Parting  Slitting  Lancing  Notching  Perforating  Nibbling  Embossing  Shaving  Cutoff  Dinking  Coining  Deep drawing  Stretch forming  Roll forming Sheet Metal Working & Process 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 46
  47. 47.   Bending is a metal forming process in which a force is applied to a piece of sheet metal, causing it to bend at an angle and form the desired shape. Bending 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 47
  48. 48.  Press Brake Machine 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 48
  49. 49. Two common bending methods are:  V-Bending  Edge bending  V-Bending - The sheet metal blank is bent between a V-shaped punch and die.  Air bending - If the punch does not force the sheet to the bottom of the die cavity, leaving space or air underneath, it is called “air bending”. Bending Types 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 49
  50. 50.   Edge (or) Wipe Bending - Wipe bending requires the sheet to be held against the wipe die by a pressure pad. The punch then presses against the edge of the sheet that extends beyond the die and pad. The sheet will bend against the radius of the edge of the wipe die. Bending Types 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 50
  51. 51.  Bending Operations 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 51
  52. 52.  Bending Operations 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 52
  53. 53.  Shearing 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 53  Shearing is defined as separating material into two parts.  It utilizes shearing force to cut sheet metal.
  54. 54.  Blanking 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 54  A piece of sheet metal is removed from a larger piece of stock.  This removed piece is not scrap, it is the useful part.
  55. 55.  Fine Blanking 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 55  A second force is applied underneath the sheet, directly opposite the punch, by a "cushion".  This technique produces a part with better flatness and smoother edges.
  56. 56.  Punching Operations 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 56
  57. 57.  Punching Or Piercing 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 57  The typical punching operation, in which a cylindrical punch pierces a hole into the sheet.
  58. 58.  Blanking & Punching examples 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 58
  59. 59.  Trimming 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 59  Punching away excess material from the perimeter of a part, such as trimming the flange from a drawn cup.
  60. 60.  Parting 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 60  Separating a part from the remaining sheet, by punching away the material between parts.
  61. 61.  Slitting 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 61  Cutting straight lines in the sheet. No scrap material is produced.
  62. 62.  Lancing 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 62  Creating a partial cut in the sheet, so that no material is removed. The material is left attached to be bent and form a shape, such as a tab, vent, or louver.
  63. 63.  Notching 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 63  Punching the edge of a sheet, forming a notch in the shape of a portion of the punch.
  64. 64.  Perforating 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 64  Punching a close arrangement of a large number of holes in a single operation.
  65. 65.  Nibbling 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 65  Punching a series of small overlapping slits or holes along a path to cut-out a larger contoured shape.
  66. 66.  Embossing 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 66  Certain designs are embossed on the sheet metal.  Punch and die are of the same contour but in opposite direction.
  67. 67.  Shaving 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 67  Shearing away minimal material from the edges of a feature or part, using a small die clearance. Used to improve accuracy or finish. Tolerances of ±0.025 mm are possible.
  68. 68.  Cuttoff 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 68  Cutoff - Separating a part from the remaining sheet, without producing any scrap.  The punch will produce a cut line that may be straight, angled, or curved.
  69. 69.  Dinking 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 69  Dinking - A specialized form of piercing used for punching soft metals. A hollow punch, called a dinking die, with beveled, sharpened edges presses the sheet into a block of wood or soft metal.
  70. 70.  Coining 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 70  Similar to embossing with the difference that similar or different impressions are obtained on both the sides of the sheet metal.
  71. 71.  Deep Drawing 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 71  Deep drawing is a metal forming process in which sheet metal is stretched into the desired shape.  A tool pushes downward on the sheet metal, forcing it into a die cavity in the shape of the desired part.
  72. 72.  Process overview in deep drawing 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 72
  73. 73.  Stretch Forming 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 73  Stretch forming is a metal forming process in which a piece of sheet metal is stretched and bent simultaneously over a die in order to form large bent parts.
  74. 74.  Roll Forming 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 74  Roll forming is a continuous bending operation in which a long strip of sheet metal is 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.
  75. 75.  Dies 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 75  Made up of tool steel and used to cut or shape material.  Simple die  Compound die  Combination die  Progressive die
  76. 76.  Simple Die 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 76  Simple dies or single action dies perform single operation for each stroke of the press slide.  The operation may be one of the cutting or forming operations.
  77. 77.  Compound Die 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 77  In these dies, two or more operations may be performed at one station.  Such dies are considered as cutting tools since, only cutting operations are carried out.
  78. 78.  Combination Die 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 78  In this die also , more than one operation may be performed at one station.  It is different from compound die in that in this die, a cutting operation is combined with a bending or drawing operation, due to that it is called combination die.
  79. 79.  Progressive Die 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 79  A progressive has a series of operations.  At each station, an operation is performed on a work piece during a stroke of the press.
  80. 80.  Progressive Die 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 80
  81. 81.  Rolling Defects 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 81  Wavy edges  Result from concave roll bending and  Thinner along its edges than at its center  Cracks  Result from poor material ductility  Convex roll bending  Severe conditions cause center split  Alligatoring  Defects in the original cast material  Only surface of work is deformed
  82. 82.  Forging defects 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 82  Surface crack  Excessive working at low temperatures  High sulphur concentration  Crack at flash  More prevalent for thinner flash  Penetrates to work  Internal cracks  Secondary tensile stresses  Cold shuts  Lubricant residue
  83. 83.  Drawing Defects 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 83  Wrinkling in the flange  Occurs due to compressive buckling in the circumferential direction (blank holding force should be sufficient to prevent buckling.  Wrinkling in the wall  Takes place when a wrinkled flange is drawn into the cup or if the clearance is very large, resulting in a large suspended (unsupported) region.
  84. 84.  Drawing Defects 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 84  Tearing  High tensile stresses that cause thinning and failure of the metal in the cup wall.  If the die has a sharp corner radius.  Earring  When the material is anisotropic  Varying properties in different directions.  Surface scratches  If the punch and die are not smooth  If the lubrication of the process is poor.
  85. 85.  Defects in Extrusions 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 85  Surface Cracking / Fir-tree cracking  High friction or speed.  Sticking of billet material on die land.  Material sticks, pressure increases, product stops and starts to move again.  produces circumferential cracks on surface, similar to a bamboo stem.(bambooing).
  86. 86.  Defects in Extrusions 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 86  Internal Cracking/ Chevron cracking  Center of extrusion tends to develop cracks of various shapes.  Center-burst, and arrowhead  Center cracking:  Increases with increasing die angle.  Increases with impurities.  Decreases with increasing R and friction.
  87. 87.  Mail me – sudhavel@yahoo.com Questions & Comments 2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 87
  88. 88.  2/17/2016 Compiled & Edited by SIVARAMAN VELMURUGAN 88

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