Shredder, grinder and granulator are different machines although they are often used interchangeably. One need to study his application, expected production rates before choosing the right machine for himself, so as to save thousands dollars on equipment he is going to buy.
One need to consider two issues in choosing the right equipment: 1) the material needed to be reduced and 2) size of end product required. These two issues will determine whether one’s money is best invested in a shredder, a grinder, or a granulator – or perhaps even a combination of two or more machines. The only way to make this determination is to analyze the material one need to reduce.
There are two primary questions you will need to answer to determine what kind of machine you will need. First, identify the material, is it plastic, paper, rubber, PVC, MSW, C&D, medical waste, or something else? Next, determine what you want to do with it, and how small you need it reduced to. Then, follow the following guide lines:
Shredder
Shredding is normally carried out in a machine that is “low speed and high torque”. A shredder is designed to take large components and shred them down to random, smaller components – normally in the range of 20 mm – 50 mm and larger. Most often, a shredder is selected if you want to do any of the following:
- Reduce a product down for compacting of space in haul off applications to a landfill.
- Reduction of items such as tires to larger chips for fuel, drain fill, etc…
- The reduction of paper or confidential documents to pieces unrecognizable in regard to their former condition.
- Reduction of plastics for washing
- Destruction of product of liability issues
- Or the preparation of the product for another application.
The above comprise the most common applications for shredding, though it is not all inclusive>. You can find shredder videos in this website to see them in action on various materials.
Grinder
A grinder process the end product to small pieces off of a larger piece, until the original part is in thousands of smaller consistent chips, usually less than 5 mm to 10 mm. The applications of grinding process include:
- Grinding large rejected parts back to smaller chips that can then be recycled into making more parts.
- Reducing larger raw materials to chips that can be mixed with other compounds to make new components.
- Reducing organic materials for bio-fuels production.
- Grinding carpet and other textiles for fiber reclamation.
Essentially, grinding is an application used to take any larger raw or rejected material and process it in the grinder to obtain a small enough particle, chip or fiber suitable for the manufacturing of other components parts. The best example being to grind a raw or rejected piece of rubber or plastic so it can be used to make things like bottles, tires, or those neat storage bins we all have in the garage.
Granulating
Granulators are perhaps the most commonly confused machines with grinders, as they essentially do the same thing; they take larger components and make them smaller. Perhaps the best way to know if you need a granulator is to determine how small you want your discharged component to be. Granulators have the ability to reduce certain materials to a much smaller particle size than a grinder. The reason for this is that a granulator differs in design significantly from a grinder in the following ways:
- Most all granulators have an “open rotor” design. This means that there is a great deal of air space around the rotor for product agitation and cooling. The open rotor allows for better processing of lighter materials that would not be well suited for a closed rotor design.
- Many Grinders on the other hand, especially the type of grinders offered by Harden, have closed rotor designs. Meaning the rotor is closed, high speed and very tight tolerances. These type rotors leave little room for the product being process to go anywhere other than across the cutting edges.
There are advantages to both designs mentioned above, but simply put; each design is more applicable to specific products.
- A granulator, with an open rotor type design, is normally more applicable in taking small components in the ½” to 6” or 8” sizes and reducing them to much smaller chips than a grinder would be used to do. Often in the range of producing 5/16” flake to even powders.
- Granulators are often used as an after process for materials that have been size reduced previously.
- Granulators are well suited for lighter materials such as plastic bottles which do not grind well in a closed rotor design unit.
Final Comments
All of this is a large amount of information to consider when selecting the proper machine for your size reduction needs. And often, so many products can cross over from one machine to the next. In considering your needs, the best way to determine your needs is to answer the following questions:
- What material am I trying to reduce?
- What is the size of the material that will be fed into the size reduction unit?
- How much per hour will I need to do?
- How small do I want the final product to be?
So, grinder vs shredder vs granulator? Once you have answered these questions, application engineers who are experienced in size reduction of materials, such as those at Harden, can help you determine the correct answer.
