Transcript Chapter 11

Chapter 11
Mechanical and Other Methods of
Change of Form
Forming
• This is another way to get metal to flow
into a desired shape.
• Not a gentle process
• Sometimes described as a “bulk
deformation process”, which involves a lot
of force.
• Can be performed with hot or cold metals
Some terms associated with
Mechanical forming
• Billet the piece being formed.
• Ram or Punch is the moving part that
delivers the blow.
• Die is the tool with the cavity through
which the billet is formed.
• Reference figures 11-2, 3, & 4.
There are 7 processes of Forming
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Forging
Extrusion
Rolling
Bending
• Drawing
• Spin Forming
• High-energy-rate
forming.Explosive and
Magneforming
Forging
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First recorded use of forging was
around 5000 B.C.
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Hand
Drop
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Several methods are common
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Different patterns on each side
Heading
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Use of dies
Coining
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Reduces size of billet
Closed
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Press between flat plates
Cogging
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Mechanized Black Smith
Open
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Black Smith
Upset to form nail or screw heads
Swaging
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Tubing size reduction
Hand Forging
• This is what the
Blacksmiths did.
• Still around
• Some horse shoes are
hand forged.
Drop Forging
• Simplest form.
• Raise a massive weight and let it fall.
• Mechanized form of a Blacksmith’s
hammer.
• Reference figure 11-6
Two basic forging machines
• Presses
• Hammer
Metals used in a Press Machine
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Aluminum
Magnesium
Beryllium Alloys
Bronzes
Brass
• Exert forces up to
75,000 tons (670
meganewtons.
• Slow enough to let
metal flow
Hammer machines
• Raise a massive weight and let it drop.
• Power hammers add to gravity with
pneumatics or hydraulics.
• Can be vertical or horizontal.
• Horizontal uses two opposed hammers
(counterblow hammers) that work together.
• Produce much less vibration.
Metals used in Hammer
Machines
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Copper
Alloys
Steel
Titanium
Refractory Alloys
Presses and Hammers can be
used in many ways
• Open Forging,
pressing the billet
between two flat plates
to reduce thickness
• Cogging, reduces
thickness with small
increments by
hydraulic pneumatic,
or mechanical means.
• Closed forging, uses
dies to form or fill die,
makes flashing.
• Coining, used in
making coins.
• Heading, used in
making nails.
• Swaging, reduces
tubular billets uses 2
to 4 dies
Lubricants for Forging
• Lubricants improve the flow of the
materials in to the die.
• Also help it flow out of the die.
• Cold forging lubes are mineral oils, soap,
silicones, and low friction lubes like
polytetrafluorethene. Teflon.
• Hot forging lubes are graphite, molybdenum
disulfide, or powdered glass
Pressures involved in forging
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Depends on metal
Area of metal
Temperature being forged
amount of deformation being exerted for
each stroke
Hydroforming
• Has one die
• Top is covered with a rubber sheet.
• Oil or water fills the dam that has the rubber
cover.
• An even pressure of the fluid is pumped
into the dam and forms the piece.
• Reference figure 11-12
Extrusion
• Developed in the late 18th century.
• Compared to squeezing tooth pastes from a
tube.
• This also can be done hot or cold.
• Involves the use of a ram or piston as well
as a cylinder extrusion die.
Extrusion is divided into five
major parts
• Direct, cold metal
being forced through a
die, done vertically.
• Indirect, used in
smaller batches where
the ram is part of the
die.
• Hydrostatic, like direct
but liquid fills
between ram and part.
• Impact, impact for
making hollow
containers.
• Hollow, some obstacle
is part of the die
design, aluminum is
hollow extruded to
make tubes.
Rolling
• Developed in the late 16th century
• One of the most used process in today’s
industry.
Rolling uses
• Bend rods or sheets
into curved surfaces.
• Change the grain
structure of cast bars
or sheets
• Form billets into
structural shapes such
as flanges, funnels
channels, or railroad
rails
• Produce tapers or
threads on rods
• Straighten bent sheets,
rods or tubing.
More rolling uses
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Threads
Gears
Ball bearings
Straightening
Bending
Tubing
I beams
Rolling
• Hot versus Cold
– Hot leads to softer product
– Cold leads to harder products
Factors affecting Rolling
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Material being rolled
Material of the roller
The shape being rolled
Size of the stock being rolled
Size of the rollers
Power Requirements
Bending
• On of the most basic processes available.
• Mostly used on flat sheets, plate, extrusions,
rods, and tubing stock.
Bending
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Punch and dies
Wiping
Hinged braking
Press braking
Air bending
Beading
Flanging
• Dimpling
• Hemming and
seaming
• Tube flaring
• Tube bending
• Roll forming
Bending methods used
• Continuous roll
bending, three rollers
curving sheet metal
distance of the bottom
rollers sets curvature.
• Punch and dies,
similar to forging.
• Wiping die, slides a
moveable die across
an extended piece of
• Metal bending around
a mandrel.
• Hinged braking, used
for one of a kind
bends, uses fingers to
support the bend.
• Press braking,
extension of the punch
and die for complex
shapes
Contin…
• Air bending, no
defined cavity or die.
Free hand operation.
Bicycle handle bars
are made this way.
• Beading, forming a
rolled edge.
• Flanging, piece of an
object that protrudes at
90 degrees
• Dimpling, formation
of a cylindrical flange
at a location other than
the end.
• Hemming and
Seaming, folding sheet
metal and pressing it
back.
• Seaming, joining two
edges.
Still more...
• Tube flaring, bend is
less than 90 degrees.
• Tube bending, uses
two ways to prevent
collapse inner core
substance or outer
constraint to keep
sides of the tubing
from spreading apart.
• Roll forming, used to
form seamless gutters.
Drawing
• Primary process in forming wire and
metallic thread.
• In drawing the billet is pulled through the
die.
• Pressure is used on the output side rather
then the input side.
• Most used lubricant is soap.
Spin forming
• A process that deforms a disk of metal
material around a mandrel.
• Used for making cymbals.
• Has some limitations
• Not very practical.
• Used for simple low production parts
• Reference figures 11-53 & 54
High energy rate methods
• Explosion forming is the use of explosives
that range from a .38 caliber blank to sticks
of dynamite.
• Metal is placed in a sealed container and the
air pressure of the explosion forces the
metal into the die forming the piece.
• Underwater explosions are also used, in this
case the water pressure forms the metal.
Die materials for explosion
forming
• Do not have to be extremely high strength.
• Aluminum alloys, Steel, Zinc alloys,
reinforced concrete, wood, or even plastics
can be used.
High-energy-rate methods
• Magneforming based on the principles that
poles repel each other.
• High energy capacitor flows energy through
a coil and forms the a magnetic field, since
the the poles are the same they repel each
other.
• The coil is mounted to the frame so the
metal is the only thing that moves and
forms to the die.
Magneforming
• Some metals may be painted before
magneforming.
• Used in making toys and aircraft.
• Reference figures 11-62 & 63