16 Types of extrusion you need to know

Types of Extrusion

Extrusion processes are classified based on temperature, direction of material flow, working principle, and application. Each type is chosen depending on material, shape complexity, surface finish, and production requirements.

1. Types of Extrusion Based on Temperature

1.1 Hot Extrusion

Performed above the recrystallization temperature of the material.
Material flows easily due to reduced flow stress.

Characteristics

Large deformation possible
High extrusion speed
Lower extrusion force

Advantages

No strain hardening
Suitable for brittle materials
Complex shapes possible

Disadvantages

Oxidation
Poor surface finish
Die wear

Materials

Aluminum, copper, magnesium, steel

Applications

Structural profiles
Pipes
Automotive and aerospace parts

1.2 Cold Extrusion

Performed at room temperature or slightly above.
Material undergoes strain hardening.

Characteristics

High dimensional accuracy
Excellent surface finish

Advantages

No oxidation
High strength products
Less machining required

Disadvantages

High force required
Limited deformation
Tool wear

Materials

Aluminum, lead, tin, copper

Applications

Collapsible tubes
Fasteners
Small precision components

1.3 Warm Extrusion

Carried out at temperatures between hot and cold extrusion.
Reduces force while maintaining surface finish.

Applications

Steel components
Automotive parts

2. Types of Extrusion Based on Direction of Metal Flow

2.1 Direct (Forward) Extrusion

Material flows in the same direction as ram movement.
High friction between billet and container.

Advantages

Simple die design
Widely used

Disadvantages

High extrusion force
Container wear

Applications

Rods
Channels
Tubes

2.2 Indirect (Backward) Extrusion

Die moves into stationary billet.
Material flows opposite to ram direction.

Advantages

Lower friction
Lower force

Disadvantages

Limited product length
Complex equipment

Applications

Hollow sections
Precision components

2.3 Hydrostatic Extrusion

Billet surrounded by pressurized fluid.
No billet-container contact.

Advantages

Very low friction
Suitable for brittle materials

Disadvantages

High equipment cost
Fluid sealing problems

Applications

Tungsten
Titanium
Ceramics

2.4 Impact Extrusion

High-speed extrusion using mechanical press.
Usually cold extrusion.

Advantages

High production rate
Thin-walled products

Applications

Toothpaste tubes
Aluminum cans
Battery cases

3. Types of Extrusion Based on Working Principle

3.1 Conventional Extrusion

Ram forces billet through fixed die.
Most common type.

3.2 Continuous Extrusion

Material is continuously fed into machine.
Uses rotating wheel and abutment.

Example

Conform extrusion process

Applications

Copper wires
Aluminum strips

3.3 Co-extrusion

Two or more materials extruded together.
Produces multi-layer products.

Applications

Multi-layer pipes
Insulated cables
Packaging films

4. Types of Extrusion Based on Product Shape

4.1 Solid Extrusion

Produces solid sections.

Examples

Rods
Bars
Angles

4.2 Hollow Extrusion

Produces hollow sections using mandrels.

Examples

Pipes
Tubes

5. Types of Extrusion Based on Pressure Medium

5.1 Ram Extrusion

Uses a piston (ram) to apply pressure.
Used in metal extrusion.

5.2 Screw Extrusion

Uses a rotating screw.
Used in polymer extrusion.

6. Special Extrusion Processes

6.1 Micro-extrusion

Produces very small cross-section components.
Used in medical devices.

6.2 Reactive Extrusion

Chemical reaction occurs during extrusion.
Used in polymer processing.

7. Summary Table

Classification	Type
Temperature	Hot, Warm, Cold
Direction	Direct, Indirect, Hydrostatic, Impact
Principle	Conventional, Continuous, Co-extrusion
Shape	Solid, Hollow
Pressure	Ram, Screw

8. Conclusion

Extrusion is a highly versatile manufacturing process with various types tailored to material behavior, product complexity, and production volume. Proper selection ensures high-quality products, cost efficiency, and minimum defects.