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manoeuvrable and can be used
to cut complex curves.
BANDSAW
FIGURE VII.2
2,5 to 8 mm 1,8 t
55°
t
3° to 0°
THE CHARACTERISTICS OF A BAND SAW FOR ALUMINIUM ARE AS FOLLOWS:
• E (thickness) =
Diameter of flywheel
1000
• Width = 10 to 30 mm
• Tooth pitch = 2.5 to 8 mm; two teeth must always be in action
• Lubricant = tallow or soluble oil.
SAW - MILLING OR CIRCULAR
FIGURE VII.3
25°
h
p
d
t
–
3
t
–
3
t t
60° 60°
d: draw of 8°
over 1 mm of width
94
ALUMINIUM IN COMMERCIAL VEHICULES CHAPTER VII FABRICATION 94 | 95
2.3.3. Fluid jet
Metals, including aluminium
alloys, can be cut using water
jets bearing abrasive particles
(PASER process) at high pressures
(3000 bars and over). Granules
of garnet, corundum or other
very hard minerals are used.
The advantage of this process is
that it does not affect the metallurgical
condition of the product
and is very versatile.
Its performance is also excellent,
and in aluminium, thicknesses
between 1 and 100 mm can be
cut at rates of 3500 mm/min
down to 30 mm/min for the larger
thickness.
Water jet cutting (SAG)
95
EUROPEAN ALUMINIUM ASSOCIATION
2.3.4. Plasma
There are two plasma cutting
techniques (Figure VII.4):
• traditional plasma, with a draft
of some 6°,
• water VORTEX plasma, with
a very small cutting draft, of the
order of 2°.
Compared to traditional plasma,
water VORTEX plasmas facilitate
greatly increased cutting speeds
and reduce nuisance factors such
as smoke, noise, ozone discharge.
The process requires substantial
amounts of power however.
The plasma is formed in a special
torch, and an inert gas (usually
argon or nitrogen) moving at
great speed is dissociated under
the effect of an electric arc to
attain the plasma state.
Owing to its high cutting speed
(several metres per minute), its
quality and precision of cut and
suitability for automation, a plasma
cutting machine can be a
highly profitable investment,
even for short production runs.
2.3.5. Laser cutting
This process is mainly used in the
automotive industry.
More information can be found
in the Aluminium Automotive
Manual (www.eaa.net/aam).
Note:
The width of the heat affected
zone is less than 1 mm whatever
the alloy and for all thicknesses.
However cracking is sometimes
observed in the short transverse
dimension (Figure VII.5) that can
attain a depth of some 2 mm.
Whatever the thickness of the
product, machining off 2 mm of
material will restore the metal's
original qualities.
This is obviously unnecessary if
the cut pieces are intended for
use as welding blanks.
PLASMA TECHNIQUES
FIGURE VII.4
+ +
-
Cooling
water
Electrode
Plasmagen gas Plasmagen gas
Electrode
Water cone
Vortex water inlet Plasma column
Plasma in vortex Plasma in free air
-
FIBRE ORIENTATION
FIGURE VII.5
Direction of rolling
Transverse direction
Longitudinal direction
short transverse
direction
Copper
96
ALUMINIUM IN COMMERCIAL VEHICULES CHAPTER VII FABRICATION 96 | 97
2.4. Edge rolling
This shaping technique requires
no special equipment for aluminium.
The rollers must of
course be clean and have
smooth surfaces.
2.5. Bending
For multiple folds, holes should
be used to mark the crossover
points of the fold lines to avoid
causing cracks when the folds
are made.
Aluminium does not require any
special bending tools, and conventional
table bending
machines or presses are perfectly
adequate provided the working
parts of the tooling are free from
unacceptable irregularities.
The bending radii to be observed
as a function of the thickness are
given in standard EN485-2.
2.6. Non-machinable faces
As with bending, one worthwhile
precaution is to remove all
score marks from the edges
caused by cutting so as to prevent
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