Extrusion press is the most important – and expensive – of all the equipment for the production of aluminum profiles.
7 stages in the selection of the extrusion press
The new extrusion press for aluminum will last 50 years or more. Therefore his choice - it is a very important decision. In his article in the materials Aluminium Extrusion Seminar 2008 a well-known American expert Al Kennedy painted in detail the process of making such a decision and divide it into seven consecutive steps.
Select the type of media – step №1
This is the first step in choosing the press. take a decision on it on the basis of the market situation and the intentions to take on a specific niche market. Most of the new presses have a compression molding without flash and without mandrel.
Press with return compression
In the reverse extrusion die located at the front end of the hollow ram, which moves relative to the container, but relative movement between the workpiece and the container offline. Since in this case there is no friction between the workpiece surface and the container, the pressing force on the 20-30 % below. This reduced effort makes it possible to extrude smaller profiles, and lower preform temperature and, Consequently, increase the pressing speed. The temperature profile more uniform throughout the molding cycle. Contamination from the surface of the workpiece does not go inside the profile, however, necessary to "scalp" blank - mechanically treating the surface thereof, preform surface defects do not cause surface defects Profile. An essential disadvantage is the restriction inverse presses size profile dimensions ram cavity.
Press the firmware and the mandrel
Making truly seamless pipes requires or piercing mandrel for the openings in a solid workpiece, or hollow shell and the mandrel. In both embodiments, seamless hollow profile will have a better microstructure more uniform structure and mechanical properties, than a similar profile, are obtained in a conventional press. Investment in a press are very high, but its performance is less, than conventional presses. Higher quality products can be assessed and, what is important, pay for it, Only a very limited number of customers, producing very responsible products.
Press Direct pressing
Therefore, for the majority of manufacturers of extruded aluminum clear choice is a conventional press with direct passage of metal.
container diameter and the press force – №2 step
Choosing the diameter of the container
The first and most difficult question. What is the maximum circumscribed circle and linear mass profiles, которые будут прессоваться на этом прессе? Можно бы учесть историю заказов профилей, but we must understand, that the market can go very differently in the future. At all, press, that place in recent years, tend to increase the diameter of the container.
The diameter of the preform is typically selected, at least, on 25 mm longer, than the diameter of the largest profile or profile group. Of course, there is always the possibility of extruding profiles even larger than the diameter of the workpiece using a die with a speculum. However, this technology is more complex, It requires more expensive dies and there are limitations to its application.
Selecting media efforts
After that, defined as the diameter preform, it is necessary to select a specific pressure in the range of 60 to 80 kg / mm2. Specific pressure is calculated by dividing the press force by the area of the container cavity (usually more than the diameter of the workpiece by 3 %). A lot of press in the United States operate at specific pressures on 50 to 60 kg / mm2, mostly with simpler sections profiles. However, in this case there is the risk of loss in performance due to slower precipitation preform and the metal matrix initial filling.
Selecting a maximum preform length
The maximum length of the billet diameter 152 mm for a press with a force of 1200 to 1600 t is from 750 to 850 mm, preform diameter and 178 mm for presses with effort from 1600 to 2000 tons - from 850 to 1000 mm.
Dimensions die assembly – №3 step
The length (thickness) of the matrix set determines the deflection of the matrix under load and, Consequently, ability to control the dimensions of the profile and deviations from them. Deflections of the matrix is reduced in proportion to the third power of the matrix set length. On the other hand, the larger the die assembly, the more it is worth. It is necessary to firmly discuss the matter with experts on pressing tools and presses Suppliers, to determine a set of pressing tools, which would combine sufficient rigidity to acceptable price.
According to the experts for a press force 1600 tons typical thickness of the matrix is set 400 mm, and for the press 2000 tons - 450 mm.
Source: Al Kennedy – Seven Steps for Selecting An Extrusion Press, AND 2008