Aluminum extrusion press selection – 1

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Extrusion press is the most important – and expensive – of all the equipment for the production of aluminum profiles.

7 steps when choosing an 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 the well-known American specialist Al Kennedy described in detail the process of making such a decision and divided it into seven consecutive steps [1].

Here are the steps:

Press type:
– with direct pressing,
– with back pressing,
– with firmware and mandrel.
container diameter and the press force
Matrix kit thickness
Press layout:
– ordinary
– short stroke
– front loading
Press manufacturer
Design, hydraulics, electrician, matrix kit
Spare parts and technical documentation

Select the type of media

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 there is no relative movement between the workpiece and the container (Fig. 1). 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.

Fig. 1 – Schematic of an indirect extrusion press. 1, counter platen; 2, die slide; 3, shear;
4, billet container; 5, moving crosshead; 6, the star 7, sealing element; 8, cylinder crosshead;
and 9, oil tank with drive and controls (Source: Schloemann-Siemag) [3]

Press the firmware and the mandrel

Making truly seamless pipes requires or piercing mandrel for the openings in a solid workpiece, or hollow workpiece and mandrel (Fig. 2). 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.

Fig. 2 – Schematic of a direct extrusion press for seamless hollow and tube.
1, counter platen; 2, die slide or rotary die head; 3, shear; 4, billet container;
5, moving crosshead; 6, stem; 7, mandrel; 8, piercing 9, cylinder crosshead;
and 10, oil tank with drive and controls (Schloemann-Siemag) [3]

Press Direct pressing

For the vast majority of extruded aluminum producers, the clear choice is a conventional direct flow press..

Fig. 3 – Schematic of a direct extrusion press.
1, counter platen; 2, die slide or rotary die head; 3, shear; 4, billet container; 5, moving crosshead;
6, stem; 7, cylinder crosshead; and 8, oil tank with drive and controls (Schloemann-Siemag) [3]

Specifications of a direct extrusion press

Fig. 4 – Specifications of a direct extrusion press [2]

Table 1 Specifications of an extrusion press [2]

Table 2 – Standard press capacity and specific pressure chart [2]

container diameter and the press force

Choosing the diameter of the container

The first and most difficult question. What is the maximum circumscribed circle and linear mass profiles, who will be pressed on this press? You could take into account the order history of profiles, 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 %).

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.

Die stack size

The size (thickness) of the matrix set determines the deflection of the matrix under load and, Consequently, the ability to control profile dimensions and deviations from them (Fig.. 4).
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.
The size of the press tool set must be determined in cooperation with press tool specialists and press suppliers., 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.