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## How to calculate the number of revolutions of the eccentric shaft of the jaw crusher

For jaw crushers, the number of swings of the movable jaw is determined by the rotation speed of the eccentric shaft. In a certain range, the eccentric shaft rotation speed increases, and the crusher’s production capacity increases accordingly. However, when the movable jaw swings beyond a certain limit, and the rotation speed is increased, the production capacity increases very slowly, and sometimes even decreases. However, its power consumption has risen rapidly. Due to the excessively high eccentric shaft speed, the crushed materials cannot be discharged from the discharge port, which affects the improvement of production capacity. In order to ensure the working capacity of the crusher, it is necessary to reasonably determine the number of rotations of the eccentric shaft of the jaw crusher.

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In order to obtain the rotational speed of the eccentric shaft, the following two hypotheses can be made: Since the jaw body is longer and the swing amplitude is not large, it is assumed that the movable jaw moves in translation and the clamp angle a remains unchanged; when the movable jaw leaves the fixed jaw, the broken The prismatic body with trapezoidal cross-section of the material falls freely by its own weight. In order not to hinder the discharge of materials, the conditions that must be met when the material prism falls are: the height of the crushed material that must fall during the time t of the movable jaw plate should be h; when the eccentric shaft rotates one circle, the movable jaw swings twice .

When the theoretical production capacity of the upper jaw crusher is the highest, the number of swings n of the movable jaw is:

A is the clamp angle, g is the acceleration of gravity (m/s2), and s is the stroke of the lower end of the movable jaw (m). Since the above formula does not consider the influence of factors such as the nature of the material and the type of the crusher, it can only be used to roughly determine the speed of the crusher. Generally, when crushing hard materials, the speed should be lower; when crushing brittle materials, the speed should be higher; for larger size crushers, the speed should be appropriately reduced to reduce vibration and save power consumption.

In fact, since the material is still in a compressed state at the beginning of the idling stroke of the movable jaw and cannot fall down immediately, the speed of the eccentric shaft should be about 30% lower than the value calculated by the above formula. The speed of the eccentric shaft can also be calculated according to the following empirical formula:

For the feed port width B≤1.2m, there are: n=310-145B; for the feed port width B 1.2m, there are: n=160-42B.

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