In these five crushing methods, the impact crushing effect is the best, and the grinding and stripping crushing effect is the worst because the force is acting on the surface of the ore. Only for fine-grained ore, its specific surface area is large. In the other three crushing methods, pressure crushing because of ore and crushing face contact area is large, so the pressure required is also large, the energy consumption is more. The crushing is due to the concentrated force of the ore, and the breaking has the effect of bending moment in addition to the concentrated force. Therefore, the required external force is small and consumes less energy. Experiments show that the force required for crushing and breaking is only 10 % ~ 20 % of the crushing force. The crushing equipment currently used often has the combined effect of the above forces.
It is worth noting that the general ore is composed of a variety of minerals, their physical properties are not the same, and sometimes there is a big difference. When crushing such ores, the situation in which each mineral is crushed is different. Some are crushed into coarse particles, and some are finer. This phenomenon is called selective crushing. The root cause of selective crushing is that the mechanical properties of the minerals in the ore are very different, but the performance of the powder crushing machinery is also affected. Such as impact crusher and grinding machine is easy to produce selective crushing. Attention to this phenomenon is very important in beneficiation process. For example, for the ore whose useful minerals are easier to mud than gangue, the dissociated particles containing more minerals should be separated first, and it is not necessary to wait to grind all the minerals to the same particle size, which is conducive to reducing over-grinding.