How to adjust crushing ratio to increase the cubic shape of crushed material?

April 17, 2024

According to the research conducted by the Nordberg company, the content of crushed material of cubic shape has a negative correlation with the crushing ratio(see below chart). That is to say: A high crushing ratio results in a low content of cubic shape and a high content of needle or flaky shapes. Low crushing ratio results in high content of cubic shape and low content of needle or flaky shapes.  

Crushing ratio
(crushing ratio=average feeding size/average discharging size)

Needle and Flaky shape(%)


Based on this research, we can know that we have to control the crushing ratio to get a high content of cubic shape, and low needle, and a flaky shape. Then, how can we adjust the crushing ratio to increase the cubic shape of crushed material? Generally, we have two solutions: 1) change the discharge port size. 2) add more crushing stages.


1. Adjust the discharge port size

Adjustment of the discharge port size is often needed when the crusher in a closed circuit performs too high a crushing ratio that results in too many needles and flaky shapes. When this happens, we can adjust the discharge port to a little larger than before in the premise of under the crusher’s capacity. As a result, we can lower the crushing ratio of this crusher and successfully increase the content of cubic shape. 

2. Add more crushing stage

This solution is required when the existing crushing stages are not able to leverage the output capacity and discharge shape. We have to add more crushing stages to reduce the crushing load of the existing crushers. For example, a crushing line consists of two crushing stages including a primary jaw crusher and a secondary cone crusher. If it couldn’t meet the expected capacity and expected content of cubic shape, we have to consider adding one more cone crusher at the tertiary crushing stage to reduce the crushing load of the previous jaw crusher and cone crusher. In this way, we can lower the crushing ratio of each crusher and finally get the expected capacity and product shape as well.


Ok, the above is all about how the crushing ratio affects the crushed material shapes and how we can get better product shapes by controlling the crushing ratio. In conclusion, a single crusher always has a certain range of crushing ratio, for example, a jaw crusher’s crushing ratio ranges from 3 to 20 depending on its type. In this way, if we want to get a better product shape by adjusting the crushing ratio, we always have to consider the overall situation of the whole crushing line. Of course, you can consult with professional experts in crushing industries. In the following articles, we will continue to share knowledge about crushing lines and crusher machines.

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