Granulator Rotors

Cumberland open three bladed granulator rotor design

 

Plastics Granulator Rotor

Rotors hold the rotating knives that drive material into the cutting zone between the rotating and mating stationary knives mounted on the granulator bed. The four main types of rotors are open, closed or solid, staggered and staggered/segmented. Open rotors are good for granulating heat-sensitive resins or feedstocks that are still warm from processing. Closed or solid rotors provide a much stronger knife mounting arrangement to cut through the thickest feedstocks. Staggered rotors are are excellent for cutting most heavy, thick-walled parts.

There are a number of rotors from which to choose. Here are the pros and cons of each:
 

3-Knife Rotor

Cumberland open three bladed granulator rotor design

Good for general purpose applications.

Advantage:
Able to handle a variety of applications including larger parts with overall low risk.

Disadvantage:
May not be the most efficient choice in some applications that benefit from a more specialized rotor design.
 


3-Knife Staggered Rotor

Cumberland 3-knife staggered granulator rotor design

For special applications.

Advantage:
Able to handle thicker cross sections by nibbling at the part and allows horsepower to be applied to smaller section of the rotor for higher efficiency.

Disadvantage:
Can lose bite and create bounce on larger parts and is more expensive for routine maintenance parts.
 

5-Knife Rotor

Cumberland 5-knife granulator rotor design

For special applications.

Advantage:
With more cuts per revolution is able to handle thicker cross sections at higher throughput rates.

Disadvantage:
Can lose bite and create bounce on larger parts and more expensive for routine parts.
 

7-Knife Rotor

Cumberland 7-knife granulator rotor design

For special applications.

Advantage:
Able to handle thicker cross sections and higher throughputs. Good for film, fiber and other applications that do not require ingestion.

Disadvantage:
Can lose bite and create bounce on larger parts and more is expensive for routine maintenance parts.


12-Knife Rotor

Cumberland 12-knife granulator rotor design

For special applications.

Advantage:
Able to handle thicker cross sections and higher throughputs. Good for film, fiber and other applications that do not require ingestion.

Disadvantage:
Can lose bite and create bounce on larger parts and is more expensive for routine parts.

15-Knife Hog Rotor

Cumberland 15-knife hog rotor granulator design

For special applications.

Advantage:
Able to handle thicker cross sections by nibbling at the part and allows horsepower to be applied to smaller section of the rotor for higher efficiency. Solid rotor adds inertia to the cutting system.

Disadvantage:
Can lose bite and create bounce on larger parts and is more expensive for routine maintenance parts. Solid rotor has less airflow and not suited to high temperature applications.
 

30-Knife Hog Rotor

Cumberland 30-knife hog rotor granulator rotor design

For special applications.

Advantage:
Ideal for purgings and other tough applications. Able to handle thicker cross sections by nibbling at the part and allows horsepower to be applied to smaller section of the rotor for higher efficiency. Solid rotor adds inertia to the cutting system.

Disadvantage:
Can lose bite and create bounce on larger parts and is more expensive for routine maintenance parts. Solid rotor has less airflow and not suited to high temperature applications.


Typical rotor options include:


Water Cooling – Used in high temperature applications, water cooling protects the rotor bearings from overheating and helps to reduce heat buildup in the cutting chamber.

Dual Flywheel – A second flywheel increases inertia of the cutting system which reduces required horsepower to process materials and conserves energy.

Rotor Knife Carriers – Knife carriers add strength to the knives and, by increasing mass of rotor assembly, increase inertia of the cutting system.

Hardfacing – Applying Stellite wire to the leading edge of the rotor and chamber increases surface hardness to make the cutting system more wear resistant.