Aluminium Extrusion - Extruding Aluminium Profile
The aluminium extrusion process involves pressing a preheated aluminum billet under high pressure (about 50 kg/mm2 on the billet) through a die the opening of which corresponds to the cross-section of the profile-- much like toothpaste being squeezed through a nozzled tube, by an extrusion press. ("Aluminium" and "aluminium alloy" are used interchangably for daily language),The tons of pressure exerted by the press determines how large an extrusion it can produce. The chemical composition, homogenising condition and hence the microstructure of the aluminium extrusion billet determines how fast it passes through the press. The profile emerging from the press is quenched by air, water or both as it is being moved along the run-out conveyor (rollers or slat conveyor) by a puller (or without a puller in older extrusion line installations). The length of the aluminium extrusion handling system can be 35-60 meters long depending on the size (tonnage) of the extrusion press and the profile section extruded.
When the extrusion of the billet ends, the butt is cut off at the die. Then extruded profile is taken onto the cooling table and then mechanically stretched to get rid of the stress and twisting. Then it is cut into the length and sent to aging oven for "precipitation hardening" if the extruded profile temper is to be T5 or T6.
Extrusion presses are classified according to the force they can create for the process. The unit of the force is spoken as either UST (US Tonnes) or MT (metric tonnes). 1000 MT is equivalent to 1100 UST.
A 1880-UST extrusion press is a machine that can have an extrusion force of 1880 US tonne (about 1650 metric tons) to push the hot billet through the die to make extruded profile. This press uses 178 mm and/or 152 mm diameter extrusion billets. You can extrude profiles with cross-sectional dimension Du up to 200-220 mm. (Du is the "The circumscribing circle size" which is defined as the smallest diameter circle that will completely enclose the entire cross-section of the extruded shape.)
A 2100-UST extrusion press is a machine that can have an extrusion force of 2100 US tonne (about 2000 metric tons) to push the hot billet through the die to make extruded profile. This press uses 203mm and/or 178 mm diameter billets. Therefore you can extrude profiles with cross-sectional dimension Du up to 240-260 mm.
Bigger profiles can be extruded with bigger presses. Therefore, 2100-UST press can produce bigger profiles than a1880-UST press.
Bigger press is more costly than the smaller press, because it has more powerful structure and hydraulic equipment.
Most of the window-doors profile can be extruded with a 1600 MT or 1800 MT extrusion press line.
If you would like to extrude bigger profiles for facades you have to have a 2000-metric tons press.
Many smaller profiles such as shower cabinets, spagetti extrusion profiles can be extruded with a press of 800 MT- 1400 MT extrusion press.
Big extrusion companies have several presses in several sizes to produce a large variety size of aluminium extrusions.
The extruded aluminium profile is generally either anodised or powder coated before use, at an anodising plant or powder coating line, respectively.
QUALITY EXTRUSIONS
Aluminium extruders eliminate unwanted black marks reduce scratches and marring of aluminum extrusions. Nokta Metal supplies roller covers, felt pads, hi-temp belts and spacer covers for extruding aluminium profiles. Use aluminium exrusion handling and runout systems with high temperature roller sleeves (Kevlar running surface) for extruded aluminium.
