The extrusion press is an extremely sophisticated machine. Today there is a vast range of extrusion press sizes available. To give an idea of the vast range, extrusion presses from 400 tonnes to 1600 tonnes are quite popular. From the common large extruded profiles to thin-wall extruded profiles, extrusion presses are geared to meet virtually any demand of the extrusion industry. Modern extrusion presses incorporates latest and innovative features like infinitely variable extrusion speeds, PLC control, reducing an operator's need etc. The importance of the extrusion press can be comprehended from the fact that it is the press size that determines the size of an extrusion. In this section Extrusion presses covering the needs of the aluminium extrusion process is discussed.

Selecting an Extrusion Press
For selecting an extrusion press following factors play a decisive role:

• Required tolerance
• Wall thickness
• Circle size for each shape
• Billet diameter
• Ordered quantity

Aluminium Extrusion Press

To get a thorough knowledge of the working of an aluminium extrusion press requires a proper identification of the press parts and and understanding their use. The principle of the extrusion press is described through the image below.

An extrusion press is comprised of a front platen and back platen which is held together by four tie rods. The parts of the extrusion press are as follows:

Parts	Function
Main Cylinder	hydraulic fluid is pumped here for generating ram pressure and movement.
Hydraulic Pressure	Pressure applied to move the ram forward.
Ram	Steel rod that is attached to main cylinder with dummy block on the end.
Dummy Block	Tight fitting steel block connected to the ram, seals the billet.
Container	Chamber in an extrusion press needed for holding the billet.
Tool stack	Solid:
	Hollow:
Press leadout table	Table which supports extrusion
Platen Pressure Ring	Hardened tool steel ring that is inserted into platen for supporting die stack
Run Out Table	Table at immediate exit of press leadout device
Tie rods	Connects the front and back press platen
Canister	Used in guiding the aluminum extrusions from the die
Cradle	Bears the billet while it gets pushed into extrusion press with the pressure from the ram.
Die oven	Here dies are heated up to 750° - 900° F for min of 4-6 hours before it is used.
Die lock	Used for locking die into the die holder.
Die holder	Container for tool stack.

Low Dead Cycle Time Improves Productivity of Extrusion Press Dead cycle time on an extrusion press can be defined as the period of time which remains non-productive during the automatic mode of the extrusion press. Therefore a challenge to the extrusion process lies in minimising dead cycle time. Though speed is fundamental, but this must be got without inducing shocks. Shocks can result in an excessive strain to the machine, causing all sorts of problems and an excessive down time. There is need for a compromise as moving the press quickly is required along with having a full control. The challenge here is to balance the conflicting requirements. Only a detailed and broad understanding of all aspects of the machine can result in the perfect solution.