Shredder Technology Options

plastics shredder

Shredders are for large or very dense parts. They can rip up large items into smaller pieces about 2” to 4” in size and are effective on a wide range of materials. Shredders reduce the time and effort required to manually cut up large parts. They can be used to efficiently reduce materials before going to the granulator.

Choosing a shredder depends upon the material to be cut as well as its size, shape and thickness. The amount of material that needs to be shredded and how the shredded material will be processed are also key considerations. The feed hopper must be evaluated for operator safety. It should be sized to receive the largest part being shredded without requiring labor-intensive and potentially dangerous precutting. Most safety devices in today's shredders involve electrical interlocks that prevent access to the cutting chamber until the rotor has stopped turning.

 Key components of a shredder include:
 

plastics shredder rotor

Rotors — There are two main types of rotor configurations: single-shaft and multi-shaft. Rotors drive material into the cutting zone either between the rotating and mating stationary knives like a granulator (single-shaft) or between another mating rotor’s cutter disks (multi-shaft). Learn More


 

plastics shredder knives

Cutters — Shredder cutting disks and knives should be designed for quick removal and re-installation to maximize production uptime. Many shredders utilize keys for disassembly and reassembly of cutters and disks for sharpening. Some systems offer optional magnetic bar trays to assist in capturing ferrous particles to prevent damaging the cutters.



plastics shredder hopper Infeed Hoppers — The material hopper can be configured in a number of ways to meet your unique loading and size reduction needs. Open and closed hopper designs are available, and optional sound reducing features can also be integrated into the hopper design. Some shredders also offer built-in cameras mounted inside the shredder infeed section to allow for visual inspection during operation and to monitor performance. Common shredder options include ram-feed assist to help drive material into the cutting zone and classification screens to control the size of the shredded material output.


 
plastics shredder drives


Drive Types — There are two types of drives for shredders, electric and hydraulic. Electric shredders require less space, are easier to operate and maintain, more energy efficient and tend to be less expensive than hydraulic shredders. Hydraulic drives are often better for more heavy duty processing and particularly for materials that experience frequent overloads from batch feeding.  Learn More

   


Shredder Economics —  How do you assess the value of a shredder to your operation? While no calculations are perfect or guaranteed, a well utilized shredder can increase down-stream equipment performance, such as a granulator, from 25% to 75%, depending on the materials and application. Learn More
 

 How Shredders Work

There are multiple ways to shred material:

Shearing — This action involves the actual cutting of material. As in scissors, shearing efficiency depends on the sharpness of the cutting edges working against each other and the tolerance of the space between them. Newer shredding technology can maintain this tolerance and sharpness, insuring a clean cut even after long operation.

Tearing — Tearing involves pulling the material with such force that it comes apart. Some materials like fabric, soft metals, plastics, and tires, are more tearable than others. Purpose-built tearing reducers are good for reducing mixed waste where small, uniform particle size is not important.

Fracturing — Some materials are brittle, such as glass, hard plastics, and certain metals, and tend to be broken or shattered in a shredder when the cutters aren't sharp or are loose. Unlike tearing, when something breaks it releases energy explosively, sometimes propelling the shards upwards into the faces of the fascinated onlookers. Always wear eye protection.

All three actions, shearing, tearing, and fracturing,  are present when a shredder is being used. However, when the cutters are kept sharp and the tolerances tight, the dominant and most efficient reduction action should be shearing.

Each type of material is best reduced by a certain type and configuration of shredder. Different materials have their own physical characteristics which determine how they will react to the reduction process.

Materials types can be broken down into two major categories:

Ductile Materials —  Ductile materials are not easily fractured but tend to tear into long strips. They are best reduced by shearing to ensure small particle size. Examples are cloth, rubber, soft plastics, paper, cardboard, or soft metals.

Friable Materials — These are materials that are easily fractured (the opposite of ductile) or broken into shards. Examples are stone, glass, cast metals, hard plastics, or wood. Shredded friable materials tend to come out as small pieces rather than the long strips.