Extrusion Process : Working, Types, Application, Advantages and Disadvantages

Extrusion Process:

     Extrusion is the process of creating objects having very complex cross-sections. It is a relatively old process and was invented by Joseph Bramah in 1797. The beauty of this process is in its ability to work with brittle metals. The end product is also attributed with the exceptionally good finish.

        The most common materials that are used in this process are polymers, metals, ceramic, concrete, clay and plastic. This process can work on these materials efficiently because the material is only subjected to compressive and shear stresses.

It can either be continuous i.e.producing an item of infinite length, or it can be discontinuous i.e. producing several pieces of a particular item. It can be done with hot and cold materials alike.

In its simplest terms extrusion can be summarized as a set of steps and components:

1. Production of Billet or Ingot: This is nothing but production of a standard sized metal.
2. Billet is then either heated or left at room temperature, depending upon the nature of this process.
3. The billet is then forced inside the die where it takes the desired shape.

Types of Extrusion Process:

Hot Extrusion:

As the name suggests is done with hot materials i.e. the materials are heated to a temperature where they do not recrystallize while going through the die. Most of these are done on hydraulic presses.

In this process, a significant amount of pressure is also involved hence a proper and adequate amount of lubricant is also used.The choice of lubricant used depends upon the operational temperature of the materials used. For low temperature, graphite is used and for higher temperature glass is used.

Cold Extrusion :

It is done either at room temperature or near room temperature.The biggest advantage of this process is that there is absolutely no oxidation. Lead, Tin, Aluminium, zirconium, titanium, and steel are some of the metals that are extruded using cold extrusion process.

It finds its application in production of fire extinguisher cases, collapsible tubes, and shock absorber cylinders.

Warm Extrusion:

This type is done above room temperature and just below the recrystallization temperature of the material used, this process preserves the inherent qualities of the material that is used for extrusion. The end product retains its properties like malleability and ductility almost perfectly.

Friction Extrusion:

It is one of the most complex extrusion processes that there is to date, In this method, the charge is pushed forcefully against the die in a relative rotary motion hence due to the friction heat is generated and no separate method for heating the material to recrystallization temperature is required.

Micro Extrusion:
This process is done at the submillimeter range. the material is pushed through a die and the end product is small enough to fit in a square of 1mm. It has many new systems developed since its inception and still has lots of scope for innovation and improvement.

Advantages :

1. Objects with extremely complex cross sections can be mass produced
2. Brittle and ductile  metals can also be used for crafting objects
3. High mechanical properties and the original properties of the materials used can be retained using or by applying the correct technique.

Disadvantages :

The initial cost of setup is high: Setting up an extruder generally requires a lot in terms of investments. It requires a proper setup in order to operate efficiently.

Power Hungry:
The plant and machinery used for extrusion operate at a very high compressive force and hence are very demanding in terms of power consumption and require the seamless power supply in order to be productive and operationally viable.