What is the eccentric throw?
The eccentric throw is one of the most important parameters in defining the job that your cone crusher does. The mantle in a cone crusher spins in conical pendulum motion. That means it doesn’t stay in the center of the chamber – it sweeps around moving closer and further away from the concave. This is what creates the crushing action. At a given point on the concave, material is crushed when the mantle is closest, and it falls down the chamber when the mantle is furthest away.
How it works
The eccentric throw is the extent to which the mantle veers from its axis, so it defines the rate at which the material falls through the chamber. If your set-up has a high eccentric throw, then material will fall further with every rotation of the mantle – the mantle moves further away from the concave so there is more room for particles to drop.
You can think about this in terms of crushing zones. The height of a crushing zone is the distance a particle will fall during one revolution, so a chamber with a high eccentric throw will have fewer crushing zones – particles will fall further in one revolution. Thus, having a higher eccentric throw will deliver a coarser product, since it will have been crushed fewer times in it’s descent through the chamber.
The eccentric throw also defines a second parameter – the capacity of your crusher. A higher eccentric throw means fewer crushing zones, so the journey through the crusher is quicker. The quicker the journey through the crusher, the greater its capacity. Therefore, altering the eccentric throw settings significantly changes the way your crusher works – without making any adjustments to the concave. If you increase the eccentric throw, you can increase capacity. If you decrease the eccentric throw, your output will be less coarse.
Coarse output often has to be re-circulated, costing you time and money. Getting the right eccentric throw is about balancing these two factors – capacity and output gradation – to reach the most efficient overall outcome.
Find the balance
Sandvik CH cone crushers help you find the balance between tonnage and exactness, by allowing you to change the eccentric throw quickly and easily. They are constructed with an adjustable eccentric bushing. By turning the keys on the bushing you can easily change the eccentric throw to the one that best suits your goals, allowing you flexibility and versatility.