The cage crusher is a medium-sized horizontal cage-bar crusher composed of a frame, a housing, a large cage, a small cage, and two electric motors. Its core working components consist of two sets of cage-bar assemblies——inner and outer—that rotate at high speeds in opposite directions; these are commonly referred to as “squirrel cages”or “rotating cages.”

This equipment is widely used across industries such as mining, construction materials, chemicals, animal feed, food processing, pharmaceuticals, and plastics, and is primarily suited for crushing materials of low to medium hardness. In the fertilizer production sector, the cage crusher excels at processing relatively hard raw materials——such as monoammonium phosphate (MAP), diammonium phosphate (DAP), and urea——earning it the industry reputation as the “nemesis”of such hard, granular materials.

Working Principle of the Cage Crusher

The cage crusher operates based on the principle of impact crushing. During operation, two electric motors drive the large and small cages to rotate at high speeds in opposite directions. After entering the central area of ​​the inner cage (the smaller cage assembly) through the feed inlet, the material undergoes the following crushing stages:

First, impact by steel rods. The material first falls onto the innermost ring of steel rods; due to the high-speed rotation of the cage, the material is shattered by the violent impact of the rods.

Second, inter-material collision. Driven by centrifugal force, the material is thrown toward the next ring of steel rods (i.e., the innermost ring of the other cage), where it is struck again from the opposite direction. After being accelerated, the material collides with other material moving at high speed in the opposite direction, resulting in further fragmentation.

Third, impact against the inner casing wall. Some material is thrown against the inner wall of the casing, undergoing final breakage upon impact.

The material moves sequentially from the inner rings of steel rods to the outer ones; after completing this multi-stage crushing process, it is discharged from the bottom of the casing. This "inside-out, progressive crushing" design concept enables the cage crusher to perform the entire process——from coarse crushing to fine grinding——in a single pass.

What are the structural components of a cage crusher?

The main structural components of a cage crusher include:

Base and frame: The supporting foundation that ensures the overall structural stability.

Inner and outer cage assemblies (squirrel-cage units): The core working components; each cage consists of steel discs fixed to a hub and multiple rings of steel rods mounted on the discs, with the rods arranged in concentric circles perpendicular to the discs.

Drive system: Two electric motors drive the inner and outer cages to rotate in opposite directions via belt drives.

Feed hopper and housing: A metal housing encloses the cage assemblies, with a feed inlet located at the top.

Bearing support frames and main shafts: Two separate shafts aligned along the same axis.

The steel rods are the primary working components of the cage mill and are also the parts most prone to wear. The rods typically have a diameter of approximately 3 cm and must be replaced immediately when wear exceeds three-quarters of their thickness. To facilitate maintenance and replacement, the equipment is usually equipped with mechanisms that allow for easy installation and removal of the cage assemblies.

What are the application areas for cage crushers?

Fertilizer and Agricultural Processing

Cage crushers serve as the core crushing equipment in organic and compound fertilizer production lines. They are particularly well-suited for crushing compost, manure, and fermented materials, as well as raw materials for granulation such as urea, NPK, ammonium chloride, and ammonium phosphate. They offer distinct advantages when crushing harder chemical fertilizer granules, such as monoammonium phosphate (MAP), diammonium phosphate (DAP), and urea.

Mining and Construction Materials

In the mining and construction materials sectors, cage crushers are used to crush materials such as limestone, gypsum, coal gangue, shale, and industrial slag. In the brick-making industry, they are used for the fine crushing and blending of raw materials like clay and slag.

Chemical and Food Industries

In the chemical industry, they are used to process materials such as salts, potassium salts, and gelatin. They also find extensive application in the food, pharmaceutical, and plastics industries.

Thanks to its simple structure, high crushing efficiency, and strong adaptability, the cage crusher maintains an irreplaceable position in numerous industrial crushing applications. Whether it is used for crushing granular urea in fertilizer production or for the fine crushing of materials in the mining and construction sectors, this equipment delivers stable and reliable crushing solutions. Proper model selection, standardized operation, and regular maintenance are key to maximizing the performance of the cage crusher.