Granulator vs Shredder: What is the Difference?
Within the plastic processing and recycling industry, granulators and shredders are the key to streamlining size reduction tasks.
And whilst they both achieve the same operation, these two machines are very different and thrive under different applications. So, if you’re looking for a size reduction machine, it is vital to understand the differences between granulators and shredders, as well as their similarities.
Size reduction tasks can significantly contribute to the cost and time efficiency of operations and reduce the amount of waste produced by processes, by reclaiming and reusing plastic waste. This means it’s important that you decide upon the right solution for your industrial processes…
A granulator is defined as size reduction machinery which operates at high speed and low torque to cut and slice materials. Rotating and dead blades, which are located in the cutting chamber, granulate material to fine, uniform particles.
But is this machine right for your processes?
Working Principle of Granulators
Granulators achieve a final product that closely resembles the original virgin material, making it suitable for recycling applications as well as for re-entering material into processes. Because of this, applications for granulators include manufacturing plants carrying out plastic processing.
However, in order to produce this result, granulators need to be carefully fed by hand or conveyor during their operation, and the maintenance requirements of this may not be suitable for every production floor.
Granulators can be used for a variety of plastics, including smaller, individual pieces of scrap, as well as some non-plastic materials such as rubber, e-waste and copper.
Types of Granulators
Summit Plastic Automation holds a range of granulators to fulfil a variety of needs. Our granulator types include:
Beside the Press Granulators
Beside the press granulators are used for inline applications, pulling small volumes of scrap from the line, granulating it, and recycling it back into processes.
Beside the press granulators are convenient for integration into injection and blow moulding processes, where granulated recycled plastic can immediately re-enter the processing line.
Central granulators offer the flexibility and capacity to efficiently process a large volume of parts, being stand-alone machines that operate offline. Central granulators include heavy duty and low speed granulators and can be further modified, such as with special hoppers, to aid the granulation of sizeable waste.
Thermoforming granulators are suitable for the granulation of thermoformed and perforated plastic, including:
These specialised machines are fitted with a water-cooling system within their grinding chamber, enabling them to work inline alongside a thermoformer. Thermoforming granulators are able to handle warm sheets for a streamlined, time efficient size reduction process.
In contrast to granulators, a shredder is defined as a size reduction machine which tears apart plastic materials at low speed and high torque and transforms them into manageable pieces, albeit larger pieces than a granulator produces.
Working Principle of Shredders
An advantage of shredders is that they are designed to handle large volumes of scrap and can chew through a range of materials more efficiently than granulators can; materials include metal, plastic, rubber and more. However, they don’t produce a consistently sized pellet which can be immediately reintroduced into processes like granulators do.
Instead, shredders are ideal for reducing the size of bulky scraps. Shredders also aren’t suitable for smaller, individual items which may escape the knife bed.
Single Shaft Shredders
Pipe and Profile Shredders
Pipe and profile shredders are specialised shredders for pipes and profiles up to 2500mm in diameter and up to 6m in length. This avoids the need for pre-cutting, however may require the shredded material passing through a granulator in order to further reduce the size of the output.
Large Part Shredders
Summit Plastic Automation’s range of ZERMA ZIS series have approximately 35% more internal cutting chamber volume and increased hydraulic ram power and speed, suitable for shredding large parts such as IBCs, wheelie bins, pallets and more.
ZERMA ZHS Horizontal Shredders utilise a single shaft and angled hydraulic ram to handle different material shapes and sizes with a minimised risk of jamming or blockages. This shredder is suitable for pieces such as purges, pipe segments and heavy bales.
Key Differences Between Granulators and Shredders
The main differences to consider when choosing between a granulator or shredder include:
Particle Size and Shape
Granulators, with their consistently uniform granules, offer a more precise and refined particle size and shape compared to the rougher output of shredders. This is because granulators are designed to pass materials through specific screen holes, resulting in particles that meet a desired diameter.
With their open-rotor design, granulators employ a cutting mechanism that shears materials, resulting in a more precise and refined particle size and shape. This cutting action is similar to scissors.
On the other hand, shredders tear materials apart using a different mechanism. They use high torque and low speed to forcefully rip the material into smaller pieces. This tearing action is more suitable for coarse size reduction tasks.
Speed and Capacity
Granulators are designed to operate at high speeds with low torque, allowing them to efficiently process smaller materials. On the other hand, shredders work at lower speeds but with high torque, making them capable of handling larger and heavier scraps.
This means that if you have materials that are big and bulky, a shredder is the ideal choice. However, if you are dealing with smaller components that need to be consistently sized, a granulator would be more appropriate.
Granulators require careful feeding to avoid the machine jamming whilst shredders do not require this – shredders work more efficiently with large volumes of scrap.
Both granulators and shredders can handle plastic and non-plastic material. However, shredders are often preferred over granulators for the processing of non-plastic material, such as rubber, copper, and aluminium.
Selecting the Right Machine for Your Needs
With the differences – and similarities – between granulators and shredders explained, what are the deciding factors when choosing between each machine?
Considerations for Material Characteristics
What materials will the machine be handling? Consider the type of material and the output size required. You may also want to consider the most appropriate feeding method for your processes.
Your machine should be capable of handling your scrap throughput in order to minimise unexpected downtime and premature wear. The closed rotor design of shredders mean they work better with higher load volumes (which make it easier for the ram to push through), however do not handle low load volumes as well as granulators.
Maintenance and Operational Costs
Granulators and shredders alike require maintenance, such as replacing rotors and blades. On this note, dual shaft shredders will require higher maintenance levels because there are more blades within the system.
To minimise operational costs, calculating the requirements of the machine, for example, its throughput, is crucial. Operational costs across the whole of your operations can be reduced with the use of granulators or shredders by decreased waste and more efficient methods of size reduction.
Integration with Existing Processes
A final consideration is how your machine will integrate with existing processes. Both shredders and granulators are available with inline and offline types, so considering which is better for your current lines is key to choosing the right machine.
Using our extensive guide, you may find your complete solution in the right granulator or shredder. However, some processes work best with the integration of both a granulator and a shredder, meaning you can achieve size reduction of bulky and high-volume loads and still produce outputs comparable to virgin pellets.
Summit Plastic Automations can advise you on the right size reduction machinery for your processes.