Transcript Slide 1

• Extrusion is a manufacturing process where a
material, often in the form of a billet, is pushed
and/or drawn through a die to create long
objects of a fixed cross-section.
• Hollow sections are usually extruded by
placing a pin or mandrel in the die. Extrusion
may be continuous (producing indefinitely long
material) or semi-continuous (repeatedly
producing many shorter pieces).
• Some materials are hot drawn while others
may be cold drawn.
• The feedstock may be forced through the die by various
methods: by an auger, which can be single or twin screw,
powered by an electric motor; by a ram, driven by
hydraulic pressure (for steel alloys and titanium alloys for
example), oil pressure (for aluminum ) or in other
specialised processes such as rollers inside a perforated
drum for the production of many simultaneous streams
of material.
• Commonly extruded materials are copper (pipe for
plumbing), aluminium (various extrusion profiles for
tracks, frames, rails, mullions), steel (rod, track),
titanium (aircraft components, including seat tracks,
engine rings, structural parts), rubber (tire tread and
sidewalls), and a multitude of plastics (pipes, rods,
rails, seals).
• Aluminium extrusions are made from solid
aluminium cylinders called billets, which are
continuously cast from molten aluminium.
• Billets are available in a wide variety of
alloys, pretreatments and dimensions,
depending upon the requirements of the
manufacturer.
• The extrusion process involves aluminium metal
being forced through a die with a shaped
opening. This is made possible by preheating
the billet to 450-500°C and then applying a
pressure of between 500 and 700 MPa
(equivalent to the pressure found at the bottom
of a 60km high water tank!).
• The heated and softened metal is
forced against the container walls and
the die by a hydraulic ram, the only exit
is the geometric cross-section of the
die opening, and the metal is squeezed
out.
• The extrusion leaves the die at a
temperature of around 500°C and the
exit temperature is carefully controlled
in order to achieve specified
mechanical properties, a high quality
surface finish and good productivity.
The Press
• The press supplies the force necessary to squeeze the
billet through the extrusion die.
It consists of:
• The container where the billet is put under pressure.
• The main cylinder with the ram for pushing the billet into
the container and through the die.
• The front platen giving counter support to the die
package.
• The main columns fixing the front platen and the cylinder
together.
• The die is supported by a series of back dies or backers
and bolsters for transferring the main press load to the
front platen.
The principle of an extrusion press
An extruded component
• Applications
Aluminium extrusions are used throughout
the construction industry, particularly in
window and door frame systems,
prefabricated houses/building structures,
roofing and exterior cladding and curtain
walling. Extrusions are also used in road
and rail vehicles, airframes and marine
applications.
• Steel and titanium extrusions use glass powder
as a lubricant. This process was invented in
France, in 1935 by Mr Séjournet. This solution
was patented throughout the world and helped
launch industrial steel extrusion. The process
was later applied to titanium.
• Plastic extrusion commonly uses plastic chip,
which is heated and extruded in the liquid state,
then cooled and solidified as it passes through
the die. In some cases (such as fibre reinforced
tubes) the extrudate is pulled through a very
long die, in a process called pultrusion.
• Extrusion has found a great application in food
processing. Various products like pastas,
breakfast cereals, and ready to eat snacks are
now manufactured by extrusion. Softer foods
such as meringue have long been piped using
pastry bags.
• Extrusion simulation tools help to understand
extrusion process and to optimize development
of tools and products.
From "http://en.wikipedia.org/wiki/Extrusion"
Extrusion Moulding
• Extrusion Moulding is a manufacturing process used to make
pipes, hoses, drinking straws, curtain tracks, rods, and fibres.
• The machine used to extrude materials is very similar to an injection
moulding machine. A motor turns a screw which feeds granules of
plastic through a heater. The granules melt into a liquid which is
forced through a die, forming a long 'tube like' shape. The shape of
the die determines the shape of the tube. The extrusion is then
cooled and forms a solid shape. The tube may be printed apon, and
cut at equal intervals. The pieces may be rolled for storage or
packed together. Shapes that can result from extrusion include Tsections, U-sections, square sections, I-sections, L-sections and
circular sections. One of most famous products of extrusion
moulding is the fiber optic.
• From "http://en.wikipedia.org/wiki/Extrusion_Moulding"
Impact Extrusion
• A commonly used to make collapsible
tubes such as toothpaste tubes, cans
usually using soft materials such as
aluminum, lead, tin. Usually a small shot of
solid material is placed in the die and is
impacted by a ram, which causes cold flow
in the material.
Hydrostatic extrusion is a form of impact extrusion, uses
a fluid hydrostatic pressure instead of a mechanical ram.
This is useful for making parts out of materials such as
Molybdenum, Tungsten that are relatively hard to extrude
using normal extrusion methods.
•Extrusion Coating/Lamination
•
•
•
•
In extrusion coating and lamination, resin is melted and formed into thin hot
film, which is coated onto a moving, flat substrate such as paper, paperboard,
metal foil, or plastic film. The coated substrate then passes between a set of
counter-rotating rolls, which press the coating onto the substrate to ensure
complete contact and adhesion.
Extrusion laminating, also called sandwich laminating, is a process related to
extrusion coating. However, in this case, the extrusion coated layer is used as
an adhesive layer between two or more substrates. A second layer is applied to
the extrusion coating while it is still hot and then the sandwich is pressed
together by pressure rolls. The extrusion coated layer may also serve as a
moisture barrier.
In film lamination, a fabricated film is adhered to a moving substrate by
application of heat and pressure. Film lamination methods include hot roll,
belt, flame, calender lamination and sheet extrusion; each type providing a
different combination of heat and pressure. The laminated film can add a
functional surface to a substrate, or be used between two substrates to stick
them together.
Substrates that can be coated with polyolefins include paper, paperboard,
biaxially-oriented polypropylene (BOPP), biaxially-oriented nylon (BON),
polyester and other plastic films, metal foil, fabrics, glass fiber mat, metal sheet
and flexible foams.
Lamination with Film Substrates
• Hot Roll/Belt Lamination
• Hot roll and belt lamination use heat and pressure as their means of
bonding. The Dow Chemical Company's (Dow) adhesive films to
your desired substrate. As shown below, the adhesive film and
substrate are drawn onto heated rollers where the materials are
heated and pressed together. The heat activates the adhesive film,
creating a bond when pressed against the substrate material. Hot
roll and belt lamination of Dow's engineered adhesive films allow for
continuous in-line lamination and an even distribution of adhesive.
• With your needs in mind, Dow has developed a portfolio of products
that bond to a variety of substrate materials. Dow's adhesive films
are composed of thermoplastic polymers that allow them to be
reheated and molded in subsequent operations.
Flame Lamination
• Flame lamination is often used to bond film and/or fabric to soft
polyurethane foams. The process, shown below, involves the
passing of the soft foam over an open flame, which creates a thin
layer of molten polymer. The film and/or fabric are quickly pressed
against the foam while it is still in the molten state. The strength of
the bond depends upon the film, fabric and foam selected and the
processing conditions (i.e., gas type, flame height and spread, foam
burn-off and nip pressure).
• Flame lamination is a continuous process that, depending on the
equipment, adheres fabric or film to one or both sides of the foam in
a single pass. Using The Dow Chemical Company's (Dow)
engineered adhesive films in your flame lamination process will
provide an opportunity for an even distribution of adhesive.
Calender Lamination
• Calender lamination of The Dow Chemical Company's
(Dow) engineered adhesive films allows for continuous
in-line lamination and provides an opportunity for an
even distribution of adhesive. Calender lamination,
similar to hot roll lamination, uses a heated three-roll
stack to heat and activate Dow's adhesive films. The
adhesive film and substrate, shown below, are drawn
into a stack of heated rolls where the film is heated,
activated and applied to the substrate. Material selection
is critical in providing a strong, long-lasting bond
between the film and the substrate. That's why we
encourage you to STICK WITH US™ and work with
Dow's adhesive films team for your dry adhesive needs.
Sheet Extrusion
• Thermoplastic polymers are often extruded into a sheet
for subsequent forming/processing. The Dow Chemical
Company's (Dow) engineered adhesive films allow for inline lamination and even distribution of adhesive in your
extrusion process. The polymer sheet, shown below, is
extruded and then brought into contact with the adhesive
film. The residual heat from the extruded sheet activates
the adhesive. The strength of the bond depends upon
material selection and processing conditions. That's why
when you STICK WITH US™ Dow will work with you to
determine the best combination of materials for your
processing conditions
Profile Extrusion
• Profile and pipe extrusion is normally carried out using a
single screw extruder which melts and conveys the
pellets through an annular die. Under vacuum (pressure
sizing is less common), the profile/pipe is then formed by
cooling in a water bath with its outside diameter
dimension controlled by a calibration sleeve. The
profile/pipe is continually taken away from the die head
by a haul-off and then cut to size.
• Profiles and pipes can vary in diameter with
corresponding increases in wall thickness. Processing
pellets into pipes and profiles for such a large range of
sizes presents different extrusion challenges. However,
basic pipe extrusion requirements hold good for most
sizes.