Aluminium Extrusion Glossary
(A)
Age Hardening(precipitation hardening)
A process of aging which increases strength and hardness and ordinarily
decreases the ductility. An Age hardening process usually follows speedy
cooling from solution heat treatment temperatures.
Alloy
Material that displays metallic properties and is composed typically of two
or more chemical elements, one being always metal. The properties of alloy
are usually different from those of its components.
(B)
Bar
Bar is a solid section that is relatively long in comparison to its
cross-sectional dimensions. It has a symmetrical cross-section which can be
square or rectangular (excluding flattened wire) with corners that are sharp
round corners.
Billet
Billet is a cast bar that can be solid semi-finished round, square
or rectangular. Billets are produced in different diameters, lengths and
sizes for use in extrusion process.
(C)
Cable Sheathing
Cable sheathing is the technique of extruding tube around another product,
like an insulated cable; the cable acting as a moving mandrel.
Core
Core is a mandrel that is fixed in relation to the die which manufactures
hollow or semi-hollow sections. For example in a typical bridge die, the
mandrel is integral with the bridge.
(D)
Die
Die is a unit of press tooling that has one or more machined openings to
produce the desired extruded parts or sections.
Drawing
Drawing can reduce both wall thickness as well as outside diameter of
tubing. It is basically a cold working process where an extruded tube bloom
is elongated by pulled it through a tapered die or series of tapered dies. A
mandrel ascertains the inside diameter.
(E)
Extrusion
Extrusion process is the conversion of billets into lengths of uniform
cross-section by the method of forcing plastic metal via a die orifice of
the required cross-sectional outline.
Electrical Conductivity
Electrical conductivity is the capacity of a material for conducting or
permitting the flow of an electric current.
(F)
Finishing
Finishing is basically a secondary operation that is applied to extrusions
for improving the product dimensionally or inducing a change in the surface
condition (etching) or color (powder coating, anodizing, etc).
(G)
Grain
Grains are individual crystals that make up the crystalline structure of
metal.
(H)
Heat Treatment
Heat treatment is the sequence of steps comprising heating and subsequent
fast or slow cooling of aluminum. This helps to change its physical or
mechanical properties or to stabilize its dimensions.
Hollow dies
Hollow dies can take variety of forms such as bridge, porthole, and spider
dies. A popular variety is the pancake form, which costs less and is easy to
make. Extruded sections manufactured on such type of die have more than one
seam or longitudinal weld lines, this is due to the metal flow around the
supports for holding the stub mandrel.
(I)
Inclusions
Inclusions are impurities like, flux, oxides, refractories, etc. They get
trapped in the metal in an ongoing solidification process.
Ingot
Ingots are melted for making cast logs; these are then cut to pieces
for the production of extrusion billets.
(L)
Lubricant
Lubricant is the liquids or semi-solids like oil, kerosene, grease, lard,
fat, soap, tallow and wax that is used on metal for reducing friction and
binding during the extruding operations.
(M)
Mandrel
Mandrel is the projection, that is fixed or floating, placed in the die
opening. It forces the metal to flow around it. An extrusion's wall
thickness is ascertained by the difference in the diameters of the mandrel
and die aperture.
Maximum Speed
Maximum speed is the fastest practical rate for extruding.
Metal Flow
Metal flow is the fashion in which the metal moves in the container as well
as through the extrusion die.
(N)
Natural Aging
It is spontaneous aging at room temperature of a supersaturated solid
solution
(O)
Orientation (laying out)
It is the positioning of die openings for the best shape and consequent
flow distribution.
(P)
Plastic
Plastic is the property of a metal that permits it to deform
non-elastically wit hout having any rupture.
(Q)
Quench
Quench is the quick cooling of metal from above the critical range in a
quenching medium. It is generally oil or water, but often air.
(R)
Ram
Ram and stem are generally interchangeable terms that describes extensions
of the main cylinder in the extrusion press. It is basically the component
that applies force against a dummy block.
Reduction Ratio (extrusion ratio)
Reduction ratio is ascertained by the cross-sectional area of the billet or
container divided by cross-sectional area of the combined die openings.
(S)
Solid Dies
Solid die is a steel disk that has more than one orifice or aperture of
similar cross-sectional area and contour as of the desired product. It is
via this the metal is forced. These dies are generally used where non hollow
shapes are needed.
Stepped Extrusion
Stepped extrusion is a process that is similar to a conventional extrusion
process. However here the extrusion press is stopped as soon as the billet
is partially extruded. The split dies are subsequently removed and replaced
with dies having a larger opening or orifice. Extrusion is then again
resumed.
(T)
Tensile Strength
Tensile strength is the maximum tensile stress which a material can
withstand without breaking when load is gradually and uniformly applied.
Tongue
Tongue is that component of a die base metal which is surrounded by the
aperture except at one end.
(W)
Water Stain
Water stain is a superficial etching of the surface that happens from
prolonged contact with moisture in limited air space. These stains are
generally white or gray in appearance.
Plastic and Rubber Extrusion Glossary
(A)
Abrasion Resistance
Abrasion resistance refers to the exceptional ability for withstanding
repeated scraping, wearing and rubbing which could remove material from its
surface.
Additives
Additives refer to extremely diverse group of specialty chemicals which are
generally mixed or incorporated into plastic formulations both during
processing, or applied to the outside surfaces of finished products after
the end of processing operation. The basic aim is to alter the behaviour of
plastics during processing for imparting properties that would be useful to
the end products.
Adiabatic
Adiabatic refers to the process in which there is no addition or removal of
heat.
Anneal
Anneal is the process to remove or prevent stress from plastic by applying
a controlled cooling process.
(B)
Blow Moulding
Blow moulding is the process that is used for producing hollow
thermoplastic shapes. It is divided into two categories extrusion and
injection blow moulding. It is typically used for making items like plastic
bottles.
Barrier screws
Barrier screw is the place where a second flight (barrier), that has a
larger radial clearance as compared to a normal flight, separates the solid
bed from melt in a compression section. Barrier screws comes with a higher
melting capacity than any conventional screw. Bond strength: Bond strength
is the measure of force needed to separate objects or materials that are
bonded together.
(C)
Coefficient of Thermal Expansion
Coefficient of thermal expansion refers to the quantum of change in
dimension of a material relative to its temperature change.
Cord
Cord is an extruded section that has a circular profile, they are joined
for making O Rings or seals.
Co-extrusion
Coextrusion is the process where parts are typically blow-moulded using a
layer of more than two different materials. This process is perfectly suited
for recycled materials. High quality plastic can be used outside and
recycled plastic are used inside.
(D)
Dissipation
Unused or lost energy
(E)
Elastomer
A material that at normal temperature temperature stretches under low
stress condition to at least double its length and then goes back to the
original length as soon as the stress is released.
(F)
Flexural Strength
The ability of the plastic to resist bending stresses.
Formulation
The mixture of two or more raw ingredients before a final product is made.
FEP
FEP is the shorter version of Fluorinated ethylene propylene.
(G)
Granulating
The process of size-reduction using a machine for cutting or chopping
plastic into smaller parts in order to prepare them for recycling.
Gasket
Gasket is a flexible sealing device that is applied for providing a seal
between two or more surface. Gaskets can be punched out of sheet or even a
strip material for providing a simple seal or they can be extruded into a
complicated shape for more challenging applications. Gaskets can be made out
of many materials but rubber or softer plastic (e.g. PVC ) is preferred.
(H)
Hose
Hose is the generic term used for tubular profile that comes with a
reinforcement for providing extra flexibility and pressure resistance.
(N)
Natural Rubber
Natural rubber offers a wide range of hardnesses. They are strong
(naturally self-reinforcing) and offers very good resistance. They have a
comparatively low maximum temperatures (75°C - continuous, 100°C-
intermittent). Disadvantage is in the form of poor ozone resistance, and a
propensity for perishing in open air.
NBR(Nitrile Based Rubber)
NBR is a copolymer formed by butadiene and acrylonitrile (ACN). It is of
low cost: Temperature Range: -40° to +225° F. They offer high
tensile strength. Other properties include excellent tear, abrasion, and
compression set resistance. Additionally they offer excellent aging
properties when put under severe operating conditions.
(P)
Purging
Purging is the process of cleaning of one type of material or color from an
extruder. This done by forcing it out with a new material or color.
Sometimes special purging substances can also be used. Purging is generally
more efficient in case the purging material is more viscous than the
material which is being replaced.
(R)
Reactive extrusion
Reactive extrusion is a technique that uses twin screw extruder as a
continuous reactor for completing chemical reactions.
(S)
Strain
Strain is the technical term that is synonymous with deformation.
(T)
Thermal mechanical analysis (TMA)
In this process a sample is allowed to deform under a static load when the
temperature is being changed. Along with glass transition and softening
points the amount of orientation is also measurable by TMA.
(V)
Vulcanization
Vulcanization is an irreversible process. In this process a rubber or
polymeric compound undergoes a change in its chemical structure (i.e.
Crosslinking), to become thermoset (with improved chemical resistance,
extending elastic properties over a more broad range of temperature).
