Extrusion Presses

The Extrusion Process:
The Extrusion process is used for manufacturing long and straight metal parts. The shape of the cross-sections can be solid round, rectangular, to T shapes, L shapes and Tubes & Pipes etc. Extrusion is done by squeezing the metal in a die by using a mechanical or hydraulic press.

This Extrusion Process is capable of producing compressive and shear forces in the material being formed.  Since tensile is not produced, very high deformity is possible without actually tearing the metal. Wear resistant material usually lines the cavity in which the raw material is contained which helps to resist the high radial loads generated as the material is pushed into the die.

Hot extrusion, a hot working process, is applied above the material's recrystallization temperature to keep the material from work hardening and to make it easier to push the material through the die.

Most hot extrusions are performed on horizontal hydraulic presses that have an applied force range of from 230 to 11,000 metric tons (250 to 12,130 short tons). Pressures range from 30 to 700 MPa (4,400 to 101,500 psi), therefore lubrication is required, which can be oil or graphite for lower temperature extrusions, or glass powder for higher temperature extrusions.

The Presses we sell generally utilize the Hot Extrusion Process. This process is carried out at fairly high temperatures, approximately at 50 to 75 % of the melting point of the metal.

Aluminium & copper with their alloys are commonly used to successfully manufacture products using the hot extrusion process. Electrical wires, bars, various shapes and tubes are some of the items produced with these non-ferrous metals.

Steel Alloys, Nickel-Based Superalloys, Titanium and other exotic materials are utilized to produce various products including Tubing and Pipe which can be used in severe and extreme conditions in applications such as Oil & Gas Production and mining operations.

Direct Extrusion:
Direct extrusion, also known as forward extrusion, is the most common extrusion process. It works by placing the billet in a heavy container. The billet is pushed through the die by a ram. There is a dummy block between the ram and the billet to keep them separated. The major disadvantage of this process is that the force required to extrude the billet is greater than needed in the indirect extrusion process because of the frictional forces introduced by the need for the billet to travel the entire length of the container. Because of this, the greatest force required is at the beginning of the process and slowly decreases as the billet is used up. At the end of the billet the force greatly increases because the billet is thin and the material must flow radially to exit the die. The end of the billet (called the butt end) is not used for this reason and is usually trimmed off by shear or saw.

Indirect Extrusion:
In indirect extrusion, also known as backwards extrusion, the billet and container move together while the die is stationary. The die is held in place by a "stem" which has to be longer than the container length. The maximum length of the extrusion is ultimately dictated by the column strength of the stem. Because the billet moves with the container the frictional forces are eliminated.

This leads to the following advantages:
·  25 to 30% reduced friction, allows extruding of larger billets, increased speed and ability to extrude smaller cross-sections
·  There is less of a tendency for extrusions to crack because there is no heat formed from friction
·  The container liner will last longer due to less wear
·  The billet is used more uniformly so extrusion defects and coarse grained peripherals zones are less likely.
The disadvantages are:
·  Impurities and defects on the surface of the billet affect the surface of the extrusion. These defects ruin the piece if it needs to be anodized or if aesthetics are important. To get around this the billets may be wire brushed, machined or chemically cleaned before being used.
·  This process isn't as versatile as direct extrusions because the cross-sectional area is limited by the max size of the stem.

Utilizing a Mandrel for Hollow products:
There are several methods for forming internal cavities in extrusions. One way is to use a hollow billet and then use a fixed or floating mandrel. A fixed mandrel, means it is integrated into the dummy block and stem. A floating mandrel, floats in slots in the dummy block and aligns itself in the die when extruding. If a solid billet is used as the feed material then it must first be pierced by the mandrel before extruding through the die.

TrueForge is actively engaged in the buying and selling of used, refurbished or rebuilt Extrusion Presses.

If you would like to request a quote for any of our extrusion presses, please send an email to sales@trueforge.com or give us a call at 516-825-7040. If you have idle machinery which is no longer required by your current operations, please send the details to us. We are always interested in purchasing machines that are considered surplus and no longer required by manufacturing operations.