Technical information

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Die casting
Die casting of metal is a method
of production that produces
strong parts, a high quality fin-
ish and a lot of integrated func-
tionality. With zinc the parts are
ready for use immediately after
leaving the moulding room. For
aluminium the remains from
the stub will, generally, need
to be shaped. The parts are
normally rolled to remove burrs and soften the edges.
Die casting of aluminium
Aluminium is moulded at high pressure, which requires the tooling
to have exact tolerances and good sealing surfaces to contain the
material being moulded which has a consistency like water. There
are advantages to die cast aluminium parts, such as a high strength
to weight ratio. The most common aluminium alloy used by Fager-
hult is AlSi8Cu3.
Another advantage of aluminium is that it can be readily recycled.
Recycling uses a fraction of the energy required to manufacture
virgin material.
Die cast aluminium is used in parts such as outer and inner caps,
continuous couplers and various types of bracket.
Die casting of zinc
Zinc is a corrosion-resistant material with good mechanical
properties. The main dierence between zinc and aluminium is
the weight: zinc is 2.5 times heavier, but has inferior heat resist-
ant properties and a lower creep strength. The advantages of zinc
are that it is easier to mould, melts at a lower temperate and is
therefore gentler on the tool. A properly made zinc tool can handle
close to 1 million cycles with good quality results and high repeti-
tion precision.
With zinc it possible to produce thin products with a high finish
on the surfaces, important for the treatment of visible surfaces
such as chrome or nickel-plating. The parts are usually ready for use
immediately following die casting with no further shaping required
except, occasionally, for rolling.
The areas of application are the same as for aluminium, but zinc
is better suited for applications which require a significantly higher
measurement tolerance or finer requirements for the surfaces.
Extrusion
Extrusion is a process that can
be done with both aluminium
and plastic. The method is
cost-eective and provides op-
tions for integrating functions
and fine detail. It is possible to
combine extruded plastic and
aluminium parts.
Extrusion of aluminium
The material, which at the start is called bloom, is heated and
moulded at great force through a profile tool. Depending on the size
of the profile and capacity of the machine, it may be necessary or
desirable to manufacture several profiles at the same time. However
a single profile is more usual.
Following moulding the profile is stretched, causing it to straight-
en. The material is then tempered in a furnace; in this state, the
profiles are normally a good 6 metres in length. Cross-cutting, shap-
ing and anodising are additional processes that can be performed if
required.
Anodising involves adding a protective oxide layer to the surface
using an electrolytic process that provides a hard, sealed surface.
Natural anodising is most common and various dierent colours
can be introduced.
Extrusion of plastic
The materials PC and PMMA are the most frequently used plastics
in the lighting industry and are mainly used in a transparent form
for shades and covers. The process allows the cost-eective produc-
tion of parts in long designs and with a high degree of precision.
It is also possible to combine materials to produce clear and opal
surfaces, or to combine the strength of polycarbonate with the good
UV resistance of acrylic.
The parts expand as they become warmer, so this must be taken
into consideration when developing new products. Cross-cutting
tolerances on shades should allow for tolerances of other parts they
are to be used with. This, as standard, can result in gaps being vis-
ible at the ends of luminaires.
Properties of materials
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