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Introduction
This Article takes an In-depth look at Aluminum Extrusions
You will learn more about topics such as:
History of Aluminum Extrusion
What are Aluminum Extrusions?
Types of Extrusions
Aluminum Profiles
Heatsinks
History of Aluminum Extrusion
Aluminum extrusion, or the extrusion process, owes its
beginnings to three men – Joseph Bramah, Thomas Burr, and
Alexander Dick. Each of them advanced and perfected the process
so that inventors from the industrial revolution could improve
it. Though the goals of these men may not have been to create
aluminum extrusion
, they did take the first steps in developing the extrusion
process.
Joseph Bramah, locksmith, inventor of the
hydraulic press, and originator of extrusion, patented the first metal
extrusion process in 1797. With Henry Maudslay, an engineering
genius, Bramah developed a process for forcing soft metals
through a mold using a hand driven plunger. His reason for using
the process was to create parts for producing unpickable locks.
The initial use of the process led to the creation of other
tools, which marked the beginning of metal extrusion.
Impressed with Bramah‘s extrusion process and his
hydraulic press, Thomas Burr, in 1820, combined the two
inventions to develop a hydraulic press to force metal through a
die. Burr‘s goal was to extrude lead pipe using a faster
and more reliable process. At the time, extrusion was named
"squirting".
The present process of hot extrusion dates back to 1894 when
Alexander Dick melted
non-ferrous metals
to be forced through a die. Though there have been many changes
over the last hundred years, the design and developments of
Dick, Bramah, and Burr remain the foundation for the modern
extrusion process.
The Discovery and Early Uses of Aluminum
Aluminum is the perfect metal for the extrusion process since it
can be extruded either hot or cold. Its high resistance to
chemicals, rust, and corrosion has made it the solution for the
manufacture of many of today‘s products. Though
aluminum
is one of the most common metals on earth, it took centuries for
a process to be developed to make the production of aluminum
practical and affordable.
In ancient times, alum was used for hide tanning, first aid,
fabric dying, pickling, canning, and many other processes. In
its natural state, alum appears as a salt of either potassium
aluminum or ammonium aluminum sulfate. It is still used today as
a supplement to medicines.
Alumina, a form of alum, was discovered in 1825 by Danish scientist
Hans Christian Oersted. Though it was known to exist, the
refining and processing of it was extremely difficult making
aluminum more valuable than gold, which continued until 1887. In
1886, Oberlin college student Charles Martin Hall and French
engineer Paul Heroult, working in different parts of the world,
developed a smelting process for aluminum involving
electrolysis. The Hall-Heroult process made aluminum easily
accessible and brought the price of it down, opening the door
for its mass production. A year after Hall and Heroult‘s
advancements, in 1887, Karl Josef Bayer discovered a chemical
process for extracting aluminum from bauxite. Though the
innovations of these three men are over a hundred years old,
they are still used for the modern production of aluminum.
The sharp rise in the uses and applications of aluminum was
spurred by the first extrusion press in the United States that
was built in Pennsylvania in 1904. Its invention became a major
asset for the growing airplane and automotive industries.
In a twist of history, a Swiss student, Robert Viktor Neher,
developed a method for processing thin sheets of aluminum in
1910. At the time, ballooning was popular, but many balloons
lost air due to the thinness of their fabric. Neher came up with
the idea of
pressing aluminum
so thin that it could be placed over the fabric of the balloon
to close any holes. His discovery led to today‘s aluminum
foil.
During World War Two, aluminum became an essential part of the
war effort and was used to make several of the items soldiers
and sailors used. "Aluminum for the Defense" and "Tinfoil"
drives were held for contributions of aluminum for recycling.
From 1940 until the end of the war, of the 296,000 aircraft
produced, more than half were made with aluminum.
The exploration of space began with a beach ball sized satellite
named Sputnik I launched by the Soviet Union in 1957. The outer
shell of the satellite was covered in an
aluminum alloy
that could withstand the heat and
friction
of launching into space. The use of aluminum for the creation
and manufacture of space vehicles increased the need for
aluminum production.
The modern aluminum can began in 1959 with the Coors Brewing
Company in Colorado. They introduced an all-aluminum, seamless,
two piece can for distribution of their beer. In conjunction
with the new can, Coors instituted a recycling program where
every can returned to the brewery was worth one cent. The soft
drink industry began using aluminum cans in 1964 when Royal
Crown Cola, from Columbus, Georgia, introduced them.
Since its beginnings in the late 19th Century,
aluminum
has become a vital necessity to many industries from household
products to airplanes and cars. It is hard to imagine modern
society without it.
What are Aluminum Extrusions?
Aluminum extrusions
are linear products valued for their high strength-to-weight
ratio and the low cost of the extrusion process. Aluminum can be
extruded either hot or cold. Extrusion produces strong and
lightweight shapes of varying angles, beams, channels, and
profiles as well as different sizes of tubing. Complex designs
can be produced with precision tolerance to interlock with
channels and other aluminum structures. Since aluminum is strong
and resistant to extreme temperature variances and rust, it has
become the first choice for the construction and building
industries.
Aluminum extrusion can be hot, warm, or
cold. The selection of the appropriate process depends on how the
fabricated piece will be used and the type of product. Of the
three processes, hot extrusion is the most extensively used
since final products tend to have greater strength and
tolerance. Warm extrusion is performed at above room temperature
while cold extrusion is done at room temperature or slightly
below. All three processes involve forcing aluminum through a
die.
All extrusion processes involve shaping using a die in the form
of the cross section. Dies are thick, circular disks with one or
several openings that create the profile. They are made from
steel that is heat treated to withstand the pressure and
temperature of hot aluminum. When raw aluminum is forced through
the die, it takes 100,000 to 125,000 psi to push it through.
Though there is a limitless number of die shapes, they all fall
into three basic types: solid, semi-hollow, and hollow. Solid
dies produce shapes with no openings in the middle while hollow
dies have one or many openings and semi-hollow dies are nearly
hollow.
The life of an
aluminum die
depends on its original design since the buildup of pressure and
heat can produce a great deal of wear. Dies need to be able to
withstand uneven pressure and control the amount of heat. Over
time, dies wear out. Fortunately, the low cost of the extruding
process makes up for the expense of replacing them. Profile
design, tolerance settings, and adjustments for the types of
alloys can significantly help in extending a die‘s use.
The feedstock for the
extrusion process
is referred to as a billet or log, which can be square or
circular. It is forged by taking pure aluminum and combining it
with other metals to form an alloy. The combined metals are
smelted to remove impurities. The molten mixture is poured into
a form where it is placed under high pressure to remove any air
or gases and to align the molecules. The final result is a solid
block of aluminum ready for extrusion.
During
extrusion, the billet is heated to temperatures of 800 to 925° F
above the recrystallization temperature to keep it from
hardening, which makes it easier to push through the die. Once
heated, it is moved to the loader where a thin film of
lubricant, which can be oil or graphite for cool extrusions and glass
powder for hot ones, is added to keep it from sticking to the
equipment before being placed in the cradle.
The ram pushes the billet crushing it against
the die. As the molten aluminum is forced through, liquid nitrogen
cools it, which helps to increase the life of the die. As the
extrusion exits the die, it is pushed to the lead out table and
puller, which guides it down the table. As the extrusion is
pulled, it cools. At the desired length, the extrusion is cut
and placed on the cooling table. After it cools, it is stretched
to increase its hardness. The final step of the process is to
cut the fully processed extrusion to the desired length. In some
cases, there may be a need for extra finishing, buffing, or
trimming. Those processes depend on the requirements of the
final product.
In cold extrusion, the part is formed by moving the aluminum
through the die at room temperature. The necessary force to move
it through the die has to exceed the strength of the aluminum to
ensure proper deformation. Cold extrusion produces parts with
close tolerance, high strength, and requires minimal
finishing. Though there are several methods of cold extrusion, for most
manufacturers, there are three basic types – forward or direct,
backward or indirect, and upsetting.
For forward or direct cold extrusion, the ram forces the billet
through the die. The billet is placed in a heavily walled
container
for the ram to force it forward. With backward or indirect cold
extrusion, the metal moves upward into the descending die, which
requires greater pressure. Upsetting cold extrusion is normally
a part of backward or forward cold extrusion and performed at
right angles to the workpiece or billet.
With warm extruding, the billet is heated to temperatures
ranging between 800° F to 1800° F. The ideal range is
1000° F to 1330° F. In either case, these temperatures
are below the recrystallization temperature, which enhances the
ductility of the billet while keeping it solid. Less force is
required with warm extruding to move the billet through the die.
A crucial part of the
extrusion process
is the maintenance of the temperature for both the billet and
the die. Controlling the billet feed and exit temperature
improves the quality of the final product. In many situations,
the operator is responsible for ensuring the temperature is
correct and determining the quality of the finished product.
With closed looped systems, the control of the profile
temperature is electronically controlled to keep it consistent
and increase extrusion speed.
Leading Manufacturers and Suppliers
Types of Extrusions
Extrusion is a part of so many industries that it is not
possible to create a complete list of every one of its types.
The descriptions below contain a very general overview of the
various kinds of extrusion and their use. A more complete set of
information can be found at the various
manufacturer‘s websites.
Aluminum extrusion profiles can be divided into standard common
profiles such as corners, duct, square and round, T, U, and Z.
All extrusion manufacturers have these profiles on hand and
immediately available or dies to form them. They come in a wide
range of sizes and lengths.
The second group of aluminum profiles are complex and intricate
shapes that require special dies and tooling. These can include
profiles with screw attachments, specialty corner profiles,
handles, handrails, and transition strips with shanks. Unlike
the standard aluminum profiles, complex profiles are special
ordered and may require the engineering of a die to match the
requirements of the profile.
A common use of complex profiles is as accents for architectural
structures and decorative pieces to highlight the features of a
project. The beauty of the extrusion process is the ability to
produce shapes and profiles that fulfill the needs of any
application.
Aluminum Angles
The standard
extruded aluminum angle
is a L-shaped part with two legs that are formed by bending the
extrusion to a 90 degree angle. Aluminum is an ideal metal for
the manufacturing of this long, narrow shape because of its high
strength-to-weight ratio and corrosion resistance. The legs of
the angle are either equal or unequal and have sharp corners.
The bent L-shape extends the length of the material creating
horizontal and vertical flat surfaces that add strength to the
unit in both directions. L-shaped components are used as
structural support. In the building industry, they are referred
to as aluminum angle irons or aluminum angle bars.
Aluminum Beams
Aluminum beams
are large, oblong pieces of metal, constructed from aluminum
alloys, and are used as horizontal support in building
construction. Aluminum beams are a preferred alternative to
steel, which is stronger but heavier and wood is lighter but
weaker. Structural Aluminum is used for beams because of its
light weight, which makes it easier to install. Structural
aluminum is weather resistant, doesn't corrode quickly, is able
to withstand high and low temperatures, and doesn't rust when
exposed to water. Aluminum beams last longer without any need
for maintenance or upkeep and come in different shapes including
unequal or equal I beams, the most commonly used, unrounded and
C-shaped channels, H beams, and T beams.
Aluminum Channels
One of many extruded aluminum shapes is
aluminum channels, which are smooth, linear, and narrow. Channels provide
support framing for roll formed products and are ideal for
engineering and structural applications such as light building
frames, frame extensions, light poles, lighting fixtures, window
frames, car bumpers, hardware joints and boat dock ladders. They
have high electrical conductivity and are good heat conductors
and reflectors, making them ideal for heat transfer and heat
shields. Industries that use aluminum channels include
construction, industrial
manufacturing
, shipping, automotive, aerospace, medical and automotive.
Aluminum Extruded Tubing
Aluminum extruded tubing
tubing is a hollow linear aluminum product that is typically
cylindrical, however aluminum square tubing and aluminum
rectangular tubing is also manufactured for specialty
applications such as aluminum downspouts and building supplies.
Aluminum tubing may also have rectangular, square or round
cross-sections. Formed during extrusion processes, aluminum
tubing may be hot extruded, cold extruded or warm extruded, all
of which extrude aluminum through a die, although at various
temperatures.
Aluminum Extruders
The term "aluminum extruders" refers to both the machines and the manufacturers that
fabricate aluminum products via the extrusion process. Aluminum
extrusion is a popular process because of aluminum’s many
attributes, which include flexibility, recyclability,
durability, high structural strength and a comparably low weight
that makes it cheaper to ship and perfect for use with
applications with weight restrictions and sensitivities. In
addition, it remains strong in cold temperatures in which other
metals would become brittle and break, it is non-toxic and
non-magnetic, it conducts electricity and it responds incredibly
well to alloying.
Aluminum Shapes
Aluminum shapes are linear aluminum products highly valued in a
wide spectrum of structural applications due to aluminum's high
strength-to-weight ratio and the cost effectiveness of the metal
extrusion process. Aluminum is one of the most recent metals to
be used in industrial manufacturing processes with just over a
hundred years of usage in industrial and commercial
applications. However,
aluminum shapes
have a far longer service life than most metal extruded shapes
and are therefore embraced. Standard aluminum shapes include
beams, trim caps, rods, angles, bars and channels, all of which
are available in a wide range of configurations and sizes.
Aluminum Tubing
Aluminum extruded tubing is a hollow linear cylindrical, square,
round, or rectangular tubing manufactured for uses such as
downspouts and building supplies. Tubing can be formed using
either hot, cold, or warm extrusion methods.
Extruded tubing
has a wide variety of applications, which include mining
equipment, hardware joints, fluid and gas transport, light
building frames, structural applications, lighting fixtures and
light poles. As with other extruded products, aluminum tubing is
an excellent heat conductor or reflector, is flexible, and has a
high strength-to-weight ratio.
Extruded Aluminum
Extruded aluminum
is an inexpensive and versatile product with possible uses that
spread far and wide across the industrial and manufacturing
worlds. Extruded aluminum is used the most by the industrial,
automotive and construction industries. Shapes like rods,
profiles, tubing, channels, trim and angles also contribute to
products used in architecture, aerospace, commercial furniture,
marine vehicle manufacturing, public transportation, structure,
mining, medicine, military and more.
Extruded Aluminum Tubing
Extruded aluminum tubes
are extruded products that are used for a variety of
applications, especially those where lightweight and corrosion
resistance are required. There are two main types of structural
aluminum tubing. The first splits the aluminum tube and reseals
it under high temperature and pressure conditions. The resealing
is also facilitated by metallurgical welds. The seam is also
created during this process and in some cases can be seen by the
naked eye. Tubes made with this method are not ideal for the
transportation of gasses or liquids under high pressure because
of the possible breakage or leak of the seam.
Fabricated Aluminum Extrusions
Fabricated aluminum extrusions
refer to the different forms, shapes and sizes that aluminum can
be extruded into. The general process involves heating up a
piece of aluminum and passing it through a shaped opening in a
die. The emerging aluminum product takes on the shape of the
opening in the die and it is then cooled, straightened, and cut.
Using a different die opening causes a change in shape of the
emerging piece of aluminum. There are several forms of
fabricated aluminum extrusions namely: aluminum angles, beams,
channels, bars, plates, sheets, pipes, tubes, and gratings.
Structural Aluminum
Structural aluminum
goes through post forming treatments to make it light weight,
durable, and corrosion resistant for high-strength applications.
Since pure aluminum is too soft for structural applications, it
has to be alloyed with magnesium, silicon, zinc, copper,
zirconium, chromium, or manganese. The most common aluminum
alloy is 6061-T6, which is a combination of aluminum, manganese
and silicone.
Structural aluminum is more costly to produce but has a faster
manufacturing process and low labor costs. Other benefits of
structural aluminum are its cleanness and aesthetically pleasing
appearance that can be painted or
finished
. It is commonly used by marine, automotive, engineering and
construction industries to produce machine bases, building
framing, cryogenic vessels, piping, bridges, and industrial
machinery. Regardless of its strength, it can be easily formed
into several shapes such as
castings
, forgings, wire, rod, bar, and flat rolled sheets or plates.
T-Slot Aluminum Extrusion
T-slot aluminum extrusion
is a structural fabricated die that utilizes an engineered
cross-sectional profile that is both strong and versatile.
Aluminum extrusion in itself is a technique used to transform
aluminum alloy into objects with a definitive cross-sectional
profile for a wide range of uses. A t-shaped extrusion process
makes most of the aluminum’s unique combination of physical
characteristics. The malleability allows it to be easily
machined and cast. Using aluminum allows for one third the
density and stiffness of steel so the resulting products offer
strength and stability, particularly when alloyed with other
metals.
Aluminum Trim
Aluminum trim is long, thin, narrow extrusions used for
automotive designs, decorative architecture, screen printing,
indoor and outdoor lighting, and construction and engineering
projects. It is weather resistant, impervious to high and low
temperatures, and corrosion and rust resistant.
Trim manufacturers use all three of the different fabrication
methods. Over the past few years, aluminum trim has found wide
use in the automotive industry due to its light weight, which
helps to lower the overall weight of vehicles to increase gas
mileage. Most of the vehicles produced since 2012 have used
aluminum trim
for interior and exterior accents, instead of heavier, more
expensive metals like steel and chrome.
In addition to being lightweight and inexpensive, aluminum trim
is flexible and can be extruded in a variety of shapes, have
finishes applied, and holds its shine. Interior trim for
vehicles is small with detailed surface patterns or textures.
With the help of the right finish, aluminum trim can look
luxurious while saving manufacturers production costs.
In architecture, aluminum trim is used most often to create
exterior accents on both residential and commercial buildings.
Trim used in buildings as an aesthetic accent has a secondary
processing of powder coating to provide extra water and
corrosion resistance
. Possible defects in aluminum trim include surface cracking,
internal cracking, surface lines, and pipe, which can be
prevented during the die design phase.
Aluminum Profiles
Aluminum profiles are the shape of extruded aluminum products
and include trim caps, rods, angles, bars, and channels, which
is a small portion of the wide range of configurations and sizes
that
aluminum profiles
can take. Profiles can be hot, cold, or warm extruded through a
die that has the shape of the profile. There are standard
profile designs that are generally used, or profiles can be
custom designed for special applications. The most common alloys
used in the fabrication of profiles are 6061, 6063 and 1100
aluminums.
The profile plays a critical part in the extrusion process. The
billet or log forced through the die emerges in a shape, which
is referred to as the profile. The design of the profile is
created during the design phase where its dimensions and shape
are determined. Over the many years that extrusion has been
used, a wide range of profiles have been developed that are
either hollow, solid, or semi-hollow.
Prior to production, the profile is carefully selected to fit
its application. Its shape is forged into the die to precisely
match its design requirements. Once the profile is approved and
the die cast, it is applied to the application process and the
product or part is produced.
Heatsink
A
heatsink
is a metallic device that absorbs thermal energy, or heat, from
another object using thermal compounds known as thermally
conductive materials. Heat is absorbed from the object at a
relatively high temperature and transferred to the heatsink,
which has a larger heat capacity. Extruded heatsinks are a
thermal energy solution for both low and high volumes and are
used in refrigeration, heat engines, cooling medical devices,
lasers
, and CPUs.
Heatsink applications are used by production processes that
require efficient heat dissipation such as the electronic,
military, medical equipment, industrial manufacturing,
appliance, and LED lighting industries. Extruded heatsinks vary
in design by length, noise level, speed, width, style, height,
and weight. Other forms of heatsinks, that are not extruded, are
stamped, bonded, or folded, which have higher production costs.
Extruded heatsinks are made from aluminum alloys 6061 and 6063.
The most common design is a flat
aluminum base
with vertical radiating fins to increase surface area. Three
things are required for the transfer of thermal energy: a heat
source, a thermal compound, and a heatsink. Heat sources must
have a high temperature and be thermally bonded to the base of
the heatsink by a thermal compound for the heat transfer to
occur. Thermal compounds are a paste-like substance made of
particles of silver, which has a very low thermal resistance.
Once bonded,
heat transfer
brings the heat source into thermal equilibrium as the heatsink
lowers its temperature.
Extruded heat sinks can be passive or active. Active heat sinks
use a power source such as
integrated fans
with directed fins that direct airflow patterns in order to help
to increase the surface area of the heatsink. Passive heatsinks
do not use any mechanical components. Heat is dissipated through
convection or transfer of heat through a liquid or gas caused by
molecular motion.
Heatsinks are a major part of the computer age and the most
important component for computer efficiency. Computer processors
are capable of completing multiple operations rapidly, which
generates a great deal of heat. To control the heat, a heatsink
transfers keeping the computer from overheating. Without the
dispersal of heat by a heatsink, computers would shut down
causing thousands of dollars of damage. Every computing device
has some form of heatsink for protection and optimal
performance.
Leading Manufacturers and Suppliers
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