4 Things to Consider When Looking For a Granulator

4 Things to Consider When Looking For a Granulator

Granulation, once not essential in the plastic size reduction process, now offers a significant opportunity to provide customers with regrind and recycled materials in products. However, selecting the right plastic granulator can be challenging and potentially risky if the wrong one is chosen for specific environments or situations.

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Cumberland has been a trusted provider of granulators and shredders to the plastic recycling industry since 1939, offering durable and reliable products.

Intended Use

The granulator that best suits your needs will largely depend on its intended use. Incorrect sizing or components can lead to inefficient processing, higher energy use, additional dust and noise, and increased wear on the knives. To ensure you select an appropriate plastic granulator, consider the following factors:

• Application: The type of process (e.g., blow molding, injection molding, extrusion, or recycling) places different demands on the granulator.
• Material: The plastic type affects how it reacts within the granulator.
• Feeding Method: Choices include manual, conveyor, roll feeding, robot, among others.
• Product: Configuration needs may vary for bottles versus sheets.
• Dimensions: The size and thickness of the product being processed matter.
• Capacity: The volume of material processed per hour.
• Screen Size: Determines the final size of the processed material.

Maintenance

Regular and thorough maintenance of plastic granulators is crucial to ensure high-quality output and minimize dust in the material and air. However, maintenance can be challenging for several reasons:

• The equipment may not be designed with maintenance in mind.
• Poorly written or inadequate instruction manuals.
• Maintenance is time-consuming, leading to increased downtime.
• Finding proper maintenance services can be difficult.

Maintaining the knives is especially important. Worn or improperly spaced knives result in excess dust and fines. Sharp knives improve energy efficiency, cutting effectiveness, reducing dust, material tearing, and noise.

A robust plastic granulator should include multiple safety switches, power-assisted tilt-back hoppers, rotor locking devices, and easily accessible screen cradles and screens. Operators should also have a clear visual path to inspect the equipment, especially when cleaning between processing runs.

Knife Design

When considering knife design in a plastic granulator, factors such as the number of knives, their arrangement, tip angle, speed, and sharpness are essential. Knife design significantly impacts the quality of the granulate and equipment efficiency.

Knives can be mounted on either a stationary bed or a rotating rotor. The space between these sets of knives varies based on the size and type of plastic being processed. A smaller space is more efficient and produces cleaner cuts for softer, more ductile materials.

• The angle of the knives also depends on the material type.
• A scissor cutting action angle improves throughput while using less horsepower, generates less noise, and reduces dust and fines.
• Low-angle, blunt-tip knives are typically used for brittle materials.
• High-angle, sharp-edge knives suit softer materials.

If uniform granulate size is essential, a slower knife speed can enhance material uniformity, reduce noise, and lower wear on the knives and cutting chamber. However, a high-speed rotor may cause fraying or inefficient material processing.

Rotors

The type of rotor used in a granulator depends on the material being processed. The primary rotor types include:

• Open: Ideal for heat-sensitive resins or feedstock, providing maximum airflow through the cutting chamber.
• Closed or Solid: With no spaces between the knives and shaft, this type improves knife mounting strength, making it suitable for thick feedstocks.
• Staggered: Suitable for cutting heavy materials and available in both closed or semi-closed configurations.
• Staggered/Segmented: Increases cuts per revolution, making it efficient for heavy materials.

Cumberland’s plastic granulators and shredders are known for their robustness and reliability. We offer a variety of granulators, including beside-the-press, central, heavy-duty, and thermoforming models, suitable for various processing needs.

Our granulators are configurable to handle both small and high-capacity runs and are easy to maintain, ensuring long service life. Cumberland also offers granulator refurbishment and replacement parts to help maximize your return on investment.

Contact Cumberland for all your granulator and shredder needs. Explore more about different plastic machine options available.