Abstract
The ultrafine grinding rate using balls as the grinding media is analyzed as the product of the following items: the number of contact points between balls, the hitting frequency, the volume of nipped particles, the stress applied by hitting balls, and the grinding probability. The representative ball diameter defining the probability, which is equal to the optimum diameter, is empirically correlated with particle size and strength as well as ball density, regardless of grinding mechanisms. Currently published experimental data covering ball milling, vibration milling, planetary milling and stirred milling, mainly wet processes for ultrafine particles, are used for confirmation of the analysis.
Composite ball size is analyzed in terms of the grinding rate, suggesting that a marked improvement can be expected by a specific ball size distribution.
