What is an Impact Crusher?

An frantoio a urto is a type of secondary or tertiary crushing machine that uses impact force to break rocks and minerals. Unlike a jaw crusher or cone crusher, which crush materials by compression, an impact crusher breaks materials by high-speed collision with a rotating rotor and impact plates.

Impact crushers are widely used in:

• Mining
• Quarrying
• Aggregate production
• Cementifici
• Construction waste recycling
• Road building

Common materials processed:

• Calcare
• Granite (medium hardness)
• Concrete
• Asphalt
• River stone
• Dolomite
• Gesso
• Carbone

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Main Parts of an Impact Crusher

1. Rotore

The rotor is the heart of an impact crusher.

Function:

• Rotates at high speed
• Provides kinetic energy
• Throws material against impact plates

The rotor usually contains:

• Rotor shaft
• Rotor discs
• Blow bars

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2. Blow Bars (Hammers)

Blow bars are wear-resistant bars mounted on the rotor.

Quando il rotore gira:

• Blow bars strike incoming material
• The material is accelerated outward
• High-speed impact breaks the rock

Common materials:

• Lega ad alto tenore di cromo
• Manganese steel
• Ceramic composite materials

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3. Impact Plates (Breaker Plates)

Impact plates are fixed inside the crushing chamber.

Their functions:

• Receive material thrown by the rotor
• Create secondary impact crushing
• Protect the crusher housing

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4. Crushing Chamber

The crushing chamber is where the material reduction happens.

It contains:

• Rotor
• Blow bars
• Piastre di impatto
• Side liners

The space between rotor and impact plates determines the final product size.

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5. Feed Opening

Raw material enters from the top.

Esempio:

Large stone
300 mm
   ↓
Impact Crusher
   ↓
20-40 mm product

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6. Discharge Opening

The crushed material leaves through the bottom.

The discharge size can be adjusted by:

• Changing impact plate position
• Adjusting rotor speed
• Controlling feed size

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How Does an Impact Crusher Work?

Step 1: Feeding

Large rocks enter the crusher through the feed opening.

Esempio:

Raw limestone
500 mm

↓

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Step 2: Rotor Acceleration

The electric motor drives the rotor.

Typical rotor speed:

500–1000 rpm

The blow bars rotate at high speed.

↓

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Step 3: First Impact Crushing

The blow bars hit the material with strong impact force.

The rock is:

• Accelerated
• Thrown forward
• Broken into smaller pieces

↓

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Step 4: Secondary Impact

The broken pieces hit the impact plates.

They are crushed again by:

• Rotor impact
• Plate impact
• Rock-to-rock collision

↓

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Step 5: Discharge

When the material reaches the required size:

• It leaves through the discharge opening.
• Oversized pieces remain for additional crushing.

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Impact Crusher Working Diagram

              Feed Material
                   ↓

        ┌──────────────────┐
        │                  │
        │    ↻ Rotor       │
        │   [Blow Bars]    │
        │       ↓          │
        │      ★★★         │
        │                  │
        │  Impact Plates   │
        │      /\/\/\      │
        └────────┬─────────┘
                 ↓

          Crushed Product

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Types of Impact Crushers

1. Horizontal Shaft Impact Crusher (HSI)

The most common type.

Structure:

• Horizontal rotor shaft
• Blow bars mounted on rotor
• Impact plates around chamber

Applicazioni:

• Frantumazione del calcare
• Aggregate production
• Recycling

Vantaggi:

• High reduction ratio
• Good cubic-shaped products
• High capacity

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2. Vertical Shaft Impact Crusher (VSI)

Material enters the center of a high-speed rotor and is thrown outward.

Crushing methods:

• Rock-on-rock
• Rock-on-metal

Applicazioni:

• Manufactured sand production
• Fine aggregate shaping

Vantaggi:

• Excellent particle shape
• Produces high-quality sand

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Impact Crusher Advantages

1. High Reduction Ratio

Typical crushing ratio:

10:1 to 30:1

A single impact crusher can significantly reduce material size.

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2. Excellent Product Shape

Compared with compression crushers:

• Altre particelle cubiche
• Less needle-shaped stones
• Better for concrete and asphalt aggregates

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3. High Crushing Efficiency

Impact crushing uses:

• Direct collision energy
• Less compressive force

This gives high productivity for suitable materials.

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4. Adjustable Product Size

Output size can be controlled by:

• Rotor speed
• Impact plate clearance
• Dimensione del mangime

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Impact Crusher Disadvantages

1. High Wear Cost

Main wear parts:

• Blow bars
• Piastre di impatto
• Side liners

They need regular replacement.

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2. Non adatto a rocce molto dure

Best for:

• Mohs hardness < 6–7

Less suitable for:

• Quartz
• Very hard granite
• Abrasive ores

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3. Higher Power Consumption

Because crushing depends on high-speed impact, it generally requires more energy than compression crushers.

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Impact Crusher vs Hammer Crusher

Caratteristica	Impact Crusher	Frantoio a martelli
Metodo di frantumazione	Impatto	Impatto
Main crushing part	Blow bars	Teste di martello
Rotor speed	Medium-high	High
Product shape	Better cubic shape	More fine powder
Capacità	Più alto	Medium
Wear rate	High	Very high
Best materials	Limestone, aggregate, concrete	Coal, gypsum, soft materials

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Impact Crusher in a Crushing Plant

A typical aggregate production line:

Large Rock
    ↓
Jaw Crusher
    ↓
Impact Crusher
    ↓
Vibrating Screen
    ↓
Finished Aggregate

A typical mining line:

Ore
 ↓
Primary Crusher
 ↓
Impact Crusher
 ↓
Ball Mill
 ↓
Mineral Separation