Call us on: 01379 384 072 or email us at: sales@aadl.co.uk
Call us on: 01379 384 072
Email us at: sales@aadl.co.uk
Frequently Asked Questions...
Aluminium has a unique and unbeatable combination of properties that make it into a versatile, highly usable and attractive construction material.
Weight
Aluminium is light with a density one third that of steel, 2.700 kg/m3.
Strength
Aluminium is strong with a tensile strength of 70 to 700 MPa depending on the alloy and manufacturing process. Extrusions of the right alloy and design are as strong as structural steel.
Elasticity
The Young’s modulus for aluminium is a third that of steel (E = 70,000 MPa). This means that the moment of inertia has to be three times as great for an aluminium extrusion to achieve the same deflection as a steel profile.
Formability
Aluminium has a good formability, a characteristic that is used to the full in extruding. Aluminium can also be cast, drawn and milled.
Machining
Aluminium is very easy to machine. Ordinary machining equipment can be used such as saws and drills. Aluminium is also suitable for forming in both the hot and the cold condition.
Joining
A thin layer of oxide is formed in contact with air, which provides very good protection against corrosion even in corrosive environments. This layer can be further strengthened by surface treatments such as anodising or powder coating.
Conductivity
The thermal and electrical conductivities are very good even when compared with copper. Furthermore, an aluminium conductor has only half the weight of an equivalent copper conductor.
Linear Expansion
Aluminium has a relatively high coefficient of linear expansion compared to other metals. This should be taken into account at the design stage to compensate for differences in expansion.
Non-toxic
Aluminium is not poisonous and is therefore highly suitable for the preparation and storage of food.
Reflectivity
Aluminium is a good reflector of both light and heat.
Aluminium Design
RULES & Tips
Uniform Wall Thickness
Uniform wall thickness within a section reduces the loading on the die and therefore minimises the risk of it being damaged. Big differences in wall thicknesses within a section should also be avoided in order to minimise differences in surface appearance after anodising. Uniform wall thickness is obtained by changing the shape of the extrusion and putting the material where it is most needed.
Rounded Shapes
As a rule all corners should be rounded. Normal radii are 0.4 to 1.0 mm. If the design requires sharper edges and corners, a radius of 0.2 mm is the smallest that can be produced.
Symmetry
With symmetrical extrusion designs, a balanced flow of material through the die is achieved at the same time as the load on the die is evenly distributed. The extrusion shape is more accurate at the same time as the risk for broken dies is significantly.
Diameter of the Circumscribing Circle
Always try to reduce the circle circumscribed around the extrusion. Apart from making it easier to press the extrusion, it also helps keep die and production costs down.
Fewer cavities cut costs
A move towards a hollow extrusion gives better dimensional control
Increased size can cut the weight and increase the rigidity
Heat Sinks; The design of the flanges increases the surface of the extrusion and thermal conductivity.
The design of the flanges increases the surface of the extrusion and thermal conductivity. Decorative lines in an extrusion can conceal irregularities as well as protect against damage during handling and fabrication.
The recommended ratio between the gap depth (h) and the gap width (b) in solid extrusions.
Maximum ratio between the gap height (h) and the gap width (b) in solid extrusions
Gap Width
b
-1
1-2
2-3
3-4
4-5
5-15
15-30
30-50
50-80
80-120
120-
Ratio
h:b
1.0
2.0
2.5
3.0
3.5
4.0
3.5
3.0
2.5
2.0
1.5
Aluminium Design
RULES & Tips
Uniform Wall Thickness
Uniform wall thickness within a section reduces the loading on the die and therefore minimises the risk of it being damaged. Big differences in wall thicknesses within a section should also be avoided in order to minimise differences in surface appearance after anodising. Uniform wall thickness is obtained by changing the shape of the extrusion and putting the material where it is most needed.
Rounded Shapes
As a rule all corners should be rounded. Normal radii are 0.4 to 1.0 mm. If the design requires sharper edges and corners, a radius of 0.2 mm is the smallest that can be produced.
Symmetry
With symmetrical extrusion designs, a balanced flow of material through the die is achieved at the same time as the load on the die is evenly distributed. The extrusion shape is more accurate at the same time as the risk for broken dies is significantly.
Diameter of the Circumscribing Circle
Always try to reduce the circle circumscribed around the extrusion. Apart from making it easier to press the extrusion, it also helps keep die and production costs down.
Fewer cavities cut costs
A move towards a hollow extrusion gives better dimensional control
Increased size can cut the weight and increase the rigidity
Increased size can cut the weight and increase the rigidity
Heat Sinks; The design of the flanges increases the surface of the extrusion and thermal conductivity.
The design of the flanges increases the surface of the extrusion and thermal conductivity. Decorative lines in an extrusion can conceal irregularities as well as protect against damage during handling and fabrication.
The recommended ratio between the gap depth (h) and the gap width (b) in solid extrusions.
Maximum ratio between the gap height (h) and the gap width (b) in solid extrusions
Gap Width
b
-1
1-2
2-3
3-4
4-5
5-15
15-30
30-50
50-80
80-120
120-
Ratio
h:b
1.0
2.0
2.5
3.0
3.5
4.0
3.5
3.0
2.5
2.0
1.5
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Screwport/Captivated Nut Slot/Weather Strip Retaining Groove/ Side Fix Screw Table of Sizes
The extrusion process consists initially of heating an Aluminium billet weighing up to 48kg to a temperature of approximately 500°C. Whilst still in a hot malleable state the billet is placed in a steel container and pushed through a steel die by means of an hydraulic ram capable of exerting over 1600 tonnes of pressure. The billet is forced through the die, emerging as an aluminium extrusion. The profile emerges at a speed of 5–50 metres per minute and reaches a length of 25–45 metres.
The emerging extruded section is cooled afterwards, either by air or by water as it is guided along a moving runout table. To ensure that the profiles are straight and to release internal stresses, the profiles are stretched after cooling. They are also checked to ensure that all key functional dimensions are correct and that the surface quality is satisfactory.
Finally the section is cut to the length specified by the customer and may then go through a further heat treatment operation, depending upon the properties required.