Limited by the current mixing equipment, there have been several mixing problems in the mixing techniques:

1. Hard mixture between the light powder and heavy powder: the light powder usually suspends in the top of the barrel and hard to mix into the main powder as the barrel rolls.

2. The powder of low mobility barely mixes into the other powders. The mobility of dry powder can be detected by the powder piling angle. The smaller the powder piling angle means the smoother the powder, which means better mobility. When the powder piling angle is larger than

40°, the powder is hard to mix well.

3. It is hard to the reach ideal mixture goal --- full mutual mixture of the powder in microcosmic. As the three-dimensional can not conduct enforcement stirring in the powder, the ideal goal is hard to reach.

4. The mixing efficiency is low. As the super-hard material has high requirement on the mixture techniques, it usually takes 2- 10 hours or longer to reach the mixture goal. It is really the only option to raise the efficiency by time.