Direct extrusion
Direct extrusion process is shown in fig. The raw material used is a billet. It consists of
a press operated ram and a cylinder or container into which the heated billet is placed.
A dummy block is used between the ram and the hot metal. With application of ram
pressure, the metal first plastically fills the cylindrical shape. And it is then forced out
through the die opening until a small amount remains in the container.
Indirect extrusion
In this case, material does not move
but die moves.
Low friction forces are generated as
the mass of material does not move.
25–30% less extruding force
required as compared to direct
extrusion. But hollow ram required
limited application.
Low scrap or material waste only 5–
6% of billet weight.
Extrusion Process: Direct vs Indirect
| Extrusion Process |
Advantages |
Disadvantages |
| Direct Extrusion |
- Close tolerance can be achieved with production of long shells
- Can extrude solid circular or non-circular sections, hollow sections such as tubes or cups
|
- High friction between the container and billet
- Requires greater forces and higher extrusion pressure
|
| Indirect Extrusion |
- Less friction between the container and billet
- Requires less forces
- Can produce hollow (tubular) cross sections
|
- Cannot be used for extruding long extrudes
- Support of the ram becomes a problem as work length increases
|
