mec560_chapter 3_metal forming and shaping processes
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MEM560
EMD5MPL
Chapter 3: Metal Forming and Shaping Processes
Introduction to Nature of Plastics Deformation
• The permanent change in shape of a metallic body as the result of forces acting on its surface
• The strength of metal depend on level/degree of plastic deformation and grain sizes and distribution
• The deformed metal had higher strength because the entanglement of dislocation with grain boundaries and each other
• The higher the deformation, the higher the strength. • Metal with smaller grain size had higher strength. • Effect of plastic deformation Grain be come deformed and elongated Grain become intact but mass continuity is maintained.
Introduction to Nature of Plastics Deformation
Hot and cold working process
•Hot working Plastic deformation that occurs above recrystallization temperature Process involved:Extrusion , welding, Forging, Drawing, and Rotary piercing •Cold working Plastic deformation that is carried out at room temperature Process involved : Bending , rolling, extrusion, forging, Shearing, Drawing, etc •Warm working Plastic deformation that is carried out at intermediate temperature, compromise of cold and hot working
Advantages of Hot working process
• Eliminate the effect of strain hardening - new grain of metal
grow from the just deformed grains • High strength material- small grain is obtained after hot
working which provide better strength • Reduced defect- Blow hole sand pores disappear by welding
action under high pressure and temperature or when they are reduced in size.
• There is increase in ductility- hence larger deformation can be carried out at single stage
• During hot working, metal strength is low, hence, less force is adequate for causing deformation - Large component can be deformed using machines for reasonable size.
Disadvantages of Hot working
• Undesirable reactions between the metal and the surrounding atmosphere - scaling or rapid oxidation of the work piece
• Less precise tolerances- due to thermal contraction and warping from uneven cooling
• Uneven grain structure- Grain structure may vary throughout the metal for various reasons
• Expensive process- Requires a heating unit of some kind such as a gas or diesel furnace or an induction heater
Advantages of cold working
• More economical process- no additional features (heater) required
• Good surface finish and dimensional control – no oxidation or scaling occur
• Reduces waste as compared to machining- eliminates with near net shape methods
• Low production time- economical for large production
Disadvantages of cold working
• Greater force is required – metal is formed at room temperature and solid state
• Expensive tooling- Heavier and more powerful equipment and stronger tooling are required
• Complex process - Metal surfaces must be clean and scale-free
• Only suitable for large volume productions- Due to the large capital costs required to set up a cold working process
• Metal is less ductile - Intermediate anneals may be required to compensate for loss of ductility that accompanies strain hardening
Example of cold working
Products
• What type of process???
• Forging
Forging
Forging is a method of shaping metals and alloys into parts of useful shape.
Using compressive force applied through various die and tooling.
May be carried out at room temperature or elevated temperature
Forged parts had good strength and toughness as the metal flow in a die and material’s grain structure can be controlled.
Forged parts are suitable for highly stressed and critical applications
May be carried out at room temperature, warm or elevated temperature
Subjected to additional finishing operation such as machining and heat treatment
Characteristics of forged parts
Forged parts had good strength and toughness
as the metal flow in a die and material’s grain structure can be controlled.
Schematic illustration of a part made by three different processes showing grain flow. (a) Casting (b) Machining form a blank (c) Forging.
Each process has its own advantages and limitations regarding external and internal characteristics, material properties, dimensional accuracy, surface finish, and the economics of production.
Types of Forging
• Open die forging
• Close die forging
• Precision forging
• Upset die forging
• Coining
Open die forging
Also called Upsetting or flat die forging The simplest forging operation Very versatile- from small to very large sizes parts (275
metric tons) The process start by placing a solid work piece in
between two flat dies and reduced the height by compressing it
Open die forging
•
(a) Schematic illustration of a cogging operation on a rectangular bar. Blacksmiths use this process to reduce the thickness of bars by hammering the part on an anvil.
(b) Reducing the diameter of a bar by open-die forging
(c) The thickness of a ring being reduced by open-die forging.
Closed-die forging
Also called as Impression-die and drop forging The process start as a work piece is placed in between two
shaped dies. The work piece will takes the shape of die cavity while
being forged between two separate dies. Process usually done at elevated temperature to lower the
force and accomplish ductility
Flash
Standard terminology for various features a forging die
Preforming operation in closed die
forging
• Used to distribute the material properly into various region of blank using simple shape dies with various contour
• Fullering – material is distribute away from an area • Edging- material is gathered into localized area • Blocking – parts is formed into rough shape using blocker die • Finishing – give the forged parts the final shape • Trimming – removal of flash
Precision forging
Also known as flashless forging Use to reduced the number of finishing process
required and to diminish flash occurrences Typical products- gear, connecting rods, turbine
blades This type of forging produce net shape product but
require high capacity equipment
Precision forging
• Material is placed on top of lower punch and in between two horizontal flat dies.
• The upper die will compress the material to take the required shapes and the dies will prevent any flash from forming
Precision forging
• Requirement of precision forging : Special and complex die Precise control of blank volume and shape Accurate positioning of blank in die cavity
Advantages
Near net
shape parts
Save material
Simple
process
Reduce process
Reduce scrap
Save money
Increase
productivity
Stronger and
tougher
Versatile
Coining
• Use to make coin, jewelry and medallion
• The process starts as the blank or slug is coined (compress in high pressure) in a completely close die cavity.
• The pressure required is 5-6 times the strength of metal to produce fine details
• Marking- engraving the coining parts with letter and number
• Sizing- impart the desired dimensional accuracy with little or no change in part size
(a) Schematic illustration of the coining process. The earliest coins were made by open-die forging and lacked precision and sharp details. (b) An example of a modern coining operation, showing the workpiece and tooling. Note the detail and superior finish that can be achieve in this process.
Upset forging
• An upset forging operation to form a head on a bolt or similar hardware item The cycle consists of: (1) wire stock is fed to the stop, (2) gripping dies close on the stock and the stop is retracted, (3) punch moves forward, (4) bottoms to form the head.
Extrusion
• A process of pushing a material through a die for the purpose of reducing or changing it’s cross section area
• type of extrude material- plastic, metal, alloy.
• Typical product – railing for sliding doors, window frames, tubing with various cross section, aluminum ladder frame, structural and architectural shape parts, gear, bracket, coat hanger.
• Advantages – economical for large production, low tooling cost, can be done both cold and hot extrusion
• There are three type of extrusion – (i) direct extrusion (ii) indirect extrusion and (iii) hydrostatic extrusion
Direct extrusion
• Also call forward extrusion
• A billet is place in a chamber and force through a die opening by hydraulically driven stem
• The dummy block protect the tips of pressing stem.
• This process usually done in hot working
Indirect extrusion
• Also called reverse , inverted or backward extrusion
• The dies move forward to unextruded billet
• Had no billet-container friction, thus normally used for high friction material (e.g : high strength steel)
Hydrostatic extrusion
• The billet is smaller in diameter than the chamber filled with fluid
• The pressure is transmitted to the fluid by the ram
• The fluid pressure help improved formability and thus extruded the parts with less friction
Impact Extrusion
Impact extrusion process involve inserting a metal blank inside a vertical/ horizontal dies and the punch quickly impacted the metal blank .
The reasons are : Impact extrusion is perform at higher speed and
shorter strokes compared to conventional extrusion making it a much faster process
Very thin parts are possible to be produced on impact extruded parts as the punches impart the work part rather than simply applying pressure to it.
High speed characteristic of impacting, permit larger reduction and high production rate, making it an important commercial process.
Impact Extrusion
Drawing
• A process of reducing the cross section of a
long rod or wire by pulling it through a die (draw die)
• Typical parts- wire, rod , shaft for power transmission machine, blank for bolt and rivet, electrical wiring cables,welding electrodes
Tube drawing
Tube sinking- Process of reducing the diameter or wall thickness of seamless tube or pipe after the internal tube had been produced by some other process such as extrusion. No mandrel is use in this operation. The limitation is lack of control over inside diameter and wall thickness of tube.
Using fixed mandrel – Using a fixed long support bar to establish inside diameter and wall thickness of tube/pipe. The limitation of this process is it restrict the length of tube that can be drawn
Using floating plug- using a removable plug in which shape is design so that it finds a natural position in the reduction zone of die.
Comparison of extrusion and drawing
Extrusion Drawing
Raw Material Billet Rod, wire or tube
Process The process can be
done both hot work
and cold work
There is a container
(chamber) to place the
raw material
Process of forcing billet
through a die
Drawing can only done cold
work.
The raw material passes
through the die only.
In drawing, rod, wire or tube is
pulled through the die or set of
dies in tandem
Product Solid and hollow products
can be produced
Section, channel, curtain
rail, architecture parts
solid cross-sectional is produced in
drawing
If tube – reduce diameter or
thickness using internal
mandrels
Wire, tube
Rolling process
• Process of reducing the thickness or changing the cross section of long workpiece by compressive force applied through a set of rolls.
• Suitable for almost 90% of metal in the form of slab, billet and bloom.
• Also suitable in rolling plastic, metal powder, ceramic slurry and also hot glass.
Hot rolling and Cold rolling
Hot rolling
• Carried out at elevated (high) temperature.
• The coarse grain, brittle and porous structure of ingot is transform into wrought structure having finer grain which resulted in higher strength and toughness
Cold rolling
• Carried out at room temperature
• Compressed grain be come deformed and elongated, resulted in higher strength and hardness
• Better surface finish as no scaling and oxidation occur
General application of rolling
Rolling plates
• Thickness > 6mm, used for structural applications such as structural support (300mm), boiler and nuclear vessel (150mm), bridges and machinery frames (100-125mm).
Rolling sheet
• Thickness < 6mm, used for coil, automobile and aircraft bodies, appliances, food and beverage container.
Flat rolling
• In flat rolling, a bulk material with thickness H1 is reduced to a thinner thickness of Ho through the force of the rolls mills.
Flat rolling
Shape rolling
• To produce straight and long structural shapes (chanel, I beam, solid bar)
• Formed at high temperature
• Stock of material is fed into a specially designed rolls.
• Might undergo different series of rolls to obtain desired shapes.
Roll forging
• Also known as cross rolling
• To produce tapered shaft, table knife and hand tools.
• The cross section of a round bar is shape by passing it through a pair of rolls with profiles groove.
Skew rolling and Upset forging
• Use to produce steel ball and ball bearing
• Round wire of rod is fed into the roll gap and roughly spherical blank are formed continuously by the action of rotating rolls.
• A shear pieces from round bar (blank) is upset in the headers between 2 dies with hemisphere cavities.
• The balls is then ground and polished in special machinery
Ring Rolling • Use to produce large rings for rocket turbine, jet engine cases, gear wheel
rims and flanges. • A thick ring is expanded into a large diameter thinner ring • The ring is place in between two rolls, one is idle (stationery) and one is
driven (moving). • The thickness is reduced by bringing the rolls closer together as they rotate. • Since the material volume is constant during the plastic deformation
process, the ring reduction resulted in increase in it’s diameter. • The advantages of ring rolling process- short production time, material
saving, close dimensional tolerance, enhance strength part
Thread rolling
Thread rolling is used to form external thread on cylindrical parts.
The parts is rolled in between two dies which is one fixed die and another one is moving die until threading surface are formed all around the rolled parts.
It is usually done in cold working condition and the machine is equipped with special dies that determine the size and form of the thread.
Rolling force
Higher rolls force is undesirable as it can cause deflection and flattening of the roll mill, thus damaging it and effect rolling operation. Roll force can be reduce by : •Reducing the friction on roll workpiece interface •Using smaller diameter roll to reduce contact area •Taking smaller diameter reduction per pass to reduce contact area •Rolling at elevated temperature to lower the strength of material
Part B: Sheet-Metalworking Processes
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
SHEET METALWORKING
1. Cutting Operations
2. Bending Operations
3. Drawing
4. Other Sheet Metal Forming Operations
5. Dies and Presses for Sheet Metal Processes
6. Sheet Metal Operations Not Performed on Presses
7. Bending of Tube Stock
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Sheet Metalworking Defined
Cutting and forming operations performed on
relatively thin sheets of metal
Thickness of sheet metal = 0.4 mm (1/64 in) to 6
mm (1/4 in)
Thickness of plate stock > 6 mm
Operations usually performed as cold working
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Sheet and Plate Metal Products
Sheet and plate metal parts for consumer and industrial products such as
Automobiles and trucks
Airplanes
Railway cars and locomotives
Farm and construction equipment
Small and large appliances
Office furniture
Computers and office equipment
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Advantages of Sheet Metal Parts
High strength
Good dimensional accuracy
Good surface finish
Relatively low cost
Economical mass production for large quantities
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Sheet Metalworking Terminology
Punch-and-die - tooling to perform cutting,
bending, and drawing
Stamping press - machine tool that performs
most sheet metal operations
Stampings - sheet metal products
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Basic Types of
Sheet Metal Processes
1. Cutting
Shearing to separate large sheets
Blanking to cut part perimeters out of sheet metal
Punching to make holes in sheet metal
2. Bending
Straining sheet around a straight axis
3. Drawing
Forming of sheet into convex or concave shapes
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
(1) Just before punch contacts work; (2) punch pushes into
work, causing plastic deformation; (3) punch penetrates into
work causing a smooth cut surface; and (4) fracture is
initiated at opposing cutting edges to separate the sheet
Sheet Metal Cutting
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Shearing, Blanking, and
Punching
Three principal operations in pressworking that cut
sheet metal:
Shearing
Blanking
Punching
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Shearing Operation
(a) Side view of the operation; (b) front view of power
shears equipped with inclined upper cutting blade
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Blanking and Punching
(a) Blanking - sheet metal cutting to separate piece (called a
blank) from surrounding stock, (b) punching - similar to
blanking except cut piece is scrap, called a slug
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Clearance in Sheet Metal Cutting
Distance between punch cutting edge and die cutting
edge
Typical values range between 4% and 8% of stock
thickness
If too small, fracture lines pass each other,
causing double burnishing and larger force
If too large, metal is pinched between cutting
edges and excessive burr results
Burr
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Clearance in Sheet Metal Cutting
Recommended clearance is calculated by:
c = at
where c = clearance (mm); a = allowance (no unit);
and t = stock thickness, (mm)
Allowance a is determined according to type of metal
Example: Given thickness of 5052S Alloy is = 10 mm calculate the
clearance?.
Solution: c = at
c = (0.045) x (10)
c = 0.45 mm WRONG!
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Sheet Metal Groups Allowances
Metal group a
1100S and 5052S aluminum alloys, all
tempers
0.045
2024ST and 6061ST aluminum alloys; brass,
soft cold rolled steel, soft stainless steel
0.060
Cold rolled steel, half hard; stainless steel,
half hard and full hard
0.075
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Punch and Die Sizes
For a round blank of diameter Db:
Blanking punch diameter = Db - 2c
Blanking die diameter = Db
where c = clearance
For a round hole of diameter Dh:
Hole punch diameter = Dh
Hole die diameter = Dh + 2c
where c = clearance
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Die size determines
blank size Db
Punch size
determines hole
size Dh
c = clearance
Punch and Die Sizes
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Purpose: allows slug or blank to drop through die
Typical values: 0.25 to 1.5 on each side
Angular Clearance
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Cutting Forces
Important for determining press size (tonnage)
F = S t L
where S = shear strength of metal (Mpa); t = stock
thickness (mm), and L = length of cut edge (mm)
Example: Determine the tonnage requirement for the blanking operation given
thickness = 4mm, Diameter = 150mm and that the stainless steel has a yield
strength = 275 MPa, shear strength = 450 MPa, and tensile strength = 650 MPa.
Solution: F = StL
t = 4 mm
L = 150mm x = 471 mm
F = 450(4.0)(471) = 847,800 N 86 Tonnes
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
(a) Straining of sheet metal around a straight axis to take a
permanent bend, (b) metal on inside of neutral plane is
compressed, metal on outside of neutral plane is stretched
Sheet Metal Bending
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Types of Sheet Metal Bending
V-bending - performed with a V-shaped die
Edge bending - performed with a wiping die
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
(1) Before bending,
(2) after bending
Application notes:
Low production
Performed on a
press brake
V-dies are
simple and
inexpensive
V-Bending
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
(1) Before bending, (2) After bending
Application notes:
High production
Pressure pad required
Dies are more complicated and costly
Edge Bending
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Stretching during Bending
If bend radius is small relative to stock thickness,
metal tends to stretch during bending
Important to estimate amount of stretching, so final
part length = specified dimension
Problem: to determine the length of neutral axis of
the part before bending
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Springback
Increase in included angle of bent part relative to
included angle of forming tool after tool is removed
Reason for springback:
When bending pressure is removed, elastic
energy remains in bent part, causing it to
recover partially toward its original shape
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Springback results in a decrease in bend angle and an
increase in bend radius: (1) during bending, work is forced to
take radius Rt and angle b' of the bending tool, (2) after
punch is removed, work springs back to R and ‘
Springback
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Die opening dimension D for (a) V-die, (b) wiping die
Die Opening Dimension
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Drawing
Sheet metal forming to make cup-shaped, box-shaped,
or other complex-curved, hollow-shaped parts
Sheet metal blank is positioned over die cavity and
then punch pushes metal into opening
Products: beverage cans, ammunition shells,
automobile body panels
Also known as deep drawing (to distinguish it from
wire and bar drawing)
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
(a) Drawing of
cup-shaped part: (1)
before punch contacts
work, (2) near end of
stroke
(b) Starting blank and
drawn part
Deep Drawing of Cup
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Clearance in Drawing
Sides of punch and die separated by a clearance c
given by:
c = 1.1 t
where t = stock thickness
In other words, clearance is about 10% greater than
stock thickness
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Shapes other than Cylindrical
Cups
Each of the following shapes presents its own unique
technical problems in drawing
Square or rectangular boxes (as in sinks)
Stepped cups
Cones
Cups with spherical rather than flat bases
Irregular curved forms (as in automobile body
panels)
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Other Sheet Metal Forming on
Presses
Other sheet metal forming operations performed on
conventional presses can be classified as
Operations performed with metal tooling
Operations performed with flexible rubber tooling
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Ironing
Achieves thinning and elongation of wall in a drawn cup:
(1) start of process; (2) during process
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Creates indentations in sheet, such as raised (or
indented) lettering or strengthening ribs: (a) Punch and
die configuration during pressing; (b) finished part with
embossed ribs
Embossing
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
(1) Before
and (2) after
Guerin Process
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Advantages of Guerin Process
Low tooling cost
Form block can be made of wood, plastic, or other
materials that are easy to shape
The same rubber pad can be used with different form
blocks
Process attractive in small quantity production
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Dies for Sheet Metal Processes
Most pressworking operations are performed with
conventional punch-and-die tooling
Custom-designed for the particular part
The term stamping die is sometimes used for high
production dies
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Components of a punch and die for a blanking operation
Punch and Die Components
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Components of a
typical mechanical
drive stamping
press
Stamping Press
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Types of Stamping Press Frame
Gap frame
Configuration of the letter C and often referred to
as a C-frame
Straight-sided frame
Box-like construction for higher tonnage
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Gap Frame
Press
Gap frame press for
sheet metalworking
(photo courtesy of BCN
Technology Services)
Capacity = 1350 kN
(150 tons)
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Press Brake
Press brake
(photo courtesy
of Strippit, Inc.)
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
CNC Turret Press
Computer
numerical
control turret
press (photo
courtesy of
Strippit, Inc.)
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Straight-sided frame
press for sheet
metalworking (photo
courtesy of BCN
Technology Services)
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
CNC Turret Press Parts
Collection of
sheet metal
parts produced
on a turret press,
showing variety
of hole shapes
possible (photo
courtesy of
Strippit Inc.)
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Power and Drive Systems
Hydraulic presses - use a large piston and cylinder to drive the ram
Longer ram stroke than mechanical types
Suited to deep drawing
Slower than mechanical drives
Mechanical presses – convert rotation of motor to linear motion of ram
High forces at bottom of stroke
Suited to blanking and punching
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Operations Not Performed on
Presses
Stretch forming
Roll bending and forming
Spinning
High-energy-rate forming processes
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Sheet metal is stretched and simultaneously bent
to achieve shape change
Stretch Forming
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Large metal sheets
and plates are
formed into curved
sections using rolls
Roll Bending
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Continuous bending process in which opposing rolls
produce long sections of formed shapes from coil or
strip stock
Roll Forming
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Spinning
Metal forming process in which an axially symmetric
part is gradually shaped over a rotating mandrel
using a rounded tool or roller
Three types:
1. Conventional spinning
2. Shear spinning
3. Tube spinning
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
(1) Setup at start of process; (2) during spinning; and
(3) completion of process
Conventional Spinning
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
High-Energy-Rate Forming
(HERF)
Processes to form metals using large amounts of
energy over a very short time
HERF processes include:
Explosive forming
Electrohydraulic forming
Electromagnetic forming
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Explosive Forming
Use of explosive charge to form sheet (or plate)
metal into a die cavity
Explosive charge causes a shock wave whose
energy is transmitted to force part into cavity
Applications: large parts, typical of aerospace
industry
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
(1) Setup, (2) explosive is detonated, and (3) shock
wave forms part and plume escapes water surface
Explosive Forming
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Electromagnetic Forming
Sheet metal is deformed by mechanical force of an
electromagnetic field induced in the workpart by an
energized coil
Presently the most widely used HERF process
Applications: tubular parts
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
(1) Setup in which coil is inserted into tubular workpart
surrounded by die; (2) formed part
Electromagnetic Forming
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Bending of Tube Stock
Dimensions and terms for a bent tube: D = outside
diameter, R = bend radius, t = wall thickness
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Bending of Tube Stock
Stretch bending of tube: (1) start of process and (2)
during bending
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
Bending of Tube Stock
Draw bending of tube: (1) start of process and (2)
during bending
TEST Information
TEST 1 • 21/10/2015 (Exam Hall Level 8) • 9.00 PM– 10 PM • Chapter 1,2 and 3
TEST 2 • 02/12/2015 (Exam Hall Level 8) • 9.00 PM– 10 PM • Chapter 4,5 and 6
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