What are different types of Metal Extrusion Process?

Metal Extrusion is a metal forming process that is used to manufacture longer parts with a fixed cross-section by pushing metal billet through a die with required cross section. Steel, Aluminum, Copper, Magnesium and Lead materials are widely used in metal extrusion.

Various types of Metal Extrusion Process?

Following types of metal extrusion processes are available according to the direction of extrusion flow, how extrusion force is applied and the working temperature.

  1. According to Extrusion Temperature
    • Hot Extrusion
    • Cold Extrusion
  2. According to the Extrusion Direction
    • Direct Extrusion
    • Indirect Extrusion
    • Lateral Extrusion
    • Hydrostatic Extrusion
    • Impact Extrusion

1. Types of Metal Extrusion Process according to extrusion Temperature

1.1) Hot Extrusion

Hot metal extrusion is a hot working metal extrusion operation that is done above recrystallization temperature.

It is used to manufacture long fixed cross section metal profiles for automotive, electrical and construction applications such as window frames, railings, electrical wires, bars and tubes etc. Hot metal extrusion process has the following advantages:

  • Low extrusion forces are required.
  • Low manufacturing cost when manufactured in large quantities.

Along with so many advantages hot extrusion process has following limitations.

  • High lubrication is required.
  • Cost of hot extrusion machines is very high.
  • High working temperature has an impact on extrusion die and other component life.
1.2) Cold Extrusion

Cold extrusion process is a metal extrusion process that occurs at room or slightly higher than room temperature. Mostly Copper, Lead, Tin, Aluminum Alloys, titanium, Molybdenum, Vanadium, Steel, Zirconium, Niobium etc. materials are used in cold extrusion process.

Collapsible tubes, aluminum cans, cylinders, gear blanks are manufactured using a cold extrusion process. This process has the following advantages:

  • Material properties are improved because the manufacturing process occurs at below recrystallization temperature.
  • High strength.
  • Good surface finish can be achieved.
  • Closer Tolerances.
  • High production rate.
  • Fast extrusion speed.

Apart from the above advantages, the cold extrusion process has the following disadvantages.

  • High lubrication cost
  • Highly complex shape can not be manufactured

2. Types of Metal Extrusion according to extrusion Direction

2.1) Direct Extrusion

In the direct or forward extrusion operation a ram or screw is used to push a heated ingot through the die. The cross section cut in die is similar to the required cross section of the extruded material. 

This image shows the process of direct extrusion.

Direct extrusion process has the following advantages:

  • Continuous extrusion process.
  • Large production runs

Along with so many advantages direct extrusion process has following limitations:

  • High force is required to push the ingot because of the frictional force between ingot and container length.
  • Rear end of the ingot is not used.
  • Only uniform cross sectional areas can be manufactured.
2.2) Indirect Extrusion

In indirect or backward extrusion, the die remains at constant position whereas billet along with the container moves to shape extruded material in desired cross section. 

This image shows the process of indirect extrusion.

Indirect extrusion has the following advantage compared to direct extrusion:

  • Reduction in frictional forces required to move the material because the billet moves along with the container.
  • Reduced tool and die wear.

Indirect extrusion process has following disadvantages:

  • Cross sectional area of the manufactured part is limited by the size of the stem.
  • Defects on ingot surface affect the quality of the extruded part.
  • Only uniform cross section parts can be manufactured.
2.3) Impact Extrusion

In the impact extrusion process a material is extruded by placing thin ingot inside a mold. Afterwards a punch is pressed against the ingot with very high force or pressure. This results in the flow of material against the sides of the mold. Stripper plate is used to remove the finished part from the punch. 

Impact extrusion process has following advantages:

  • High Production rate.
  • Extruded parts are non-porous and dense.

Along with the above advantages, the impact extrusion process has the following disadvantages as well.

  • High dissipation of heat.
  • Size of the finished product is limited by the size of die and punch.
2.4) Hydrostatic Extrusion

In the hydrostatic extrusion process a preheated ingot is placed inside a pressure chamber along with a die. Afterwards the chamber is filled with the liquid. A piston is used to apply the pressure in the liquid. That pressure in liquid forces the ingot material out of the die in the shape of the cross- section area of the die.

this image shows the process of Hydrostatic Extrusion

Hydrostatic extrusion process has following advantages:

  • Due to liquid present in chamber frictional forces are very less.
  • Low force or power is required to press the ingot.
  • Large ingots can be extruded.
  • Smooth material flow.

Hydrostatic extrusion has following disadvantages:

  • Ingots require preprocessing to remove surface defects.
  • Leakage of liquid can be a problem.

We will keep adding more updates on various types of metal extrusion processes. Please add your comments or questions or suggestions on various types of metal extrusion processes in the comment box.

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