How Enamel Manufacturers Determine the Size and Quantity of Grinding Media for Ball Mills

For novice enamel manufacturers, questions about how to use ball mills, how to determine the optimal loading amount of the ball mill, and how to improve grinding efficiency are of great concern. For installed dry ball mills, there are two very important variables: the material loading amount and the size of the grinding media. During the ball milling process, the material loading amount is often overlooked or not checked at all. For determining the optimal loading amount for ball mills, you can refer to the article "How to Determine the Optimal Loading Amount for Ball Mills." This article will introduce the size and quantity of grinding media.

The size of the grinding media is one of the most contradictory independent variables in ball milling. Setting up a ball mill is often considered an "art," but this is merely due to a lack of understanding of the dual nature of this variable. The contradiction lies in the fact that even a slight change in media diameter can lead to significant changes in the mass of individual media and a substantial change in the total quantity of media.

Consideration 1: Media Size vs. Initial Particle Size
The particle size must not exceed 15% of the media size, allowing particles to settle between the media rather than "floating" on top. In hammer mills or roller crushers, larger particle sizes can quickly drop effectively. While adding large particles to the ball mill is possible, it either requires much larger media or the use of a non-optimized mix of media sizes. The typical grinding range is between 6mm (1/4") and 25mm (1"), with a maximum size of 38mm (1.5").

Consideration 2: Use the Minimum Media That Effectively Provides the Desired Final Particle Size and Distribution.
This is usually determined through laboratory tests or production ball milling experiments. Larger media means greater energy per collision, but fewer media and fewer collisions per unit of time (assuming a constant media fill of 50%). The ball mill has a fixed power (kW), so it's essential to optimize energy use rather than simply increasing or decreasing total energy.

Consideration 3: Make Minor Changes to Media Size.
Changing the diameter of the balls from 20mm to 25mm nearly doubles the mass of each ball from 17g to 33g, but the number of balls decreases from 125,000 to 64,000. Both mass and quantity undergo significant changes, which is the foundation of the media paradox—slightly increasing the media size increases the mass and energy of each impact, but the number of impacts is much lower.

The following table shows that for every reduction in media size by one level, the number of balls per unit volume doubles, while the mass of each individual ball is roughly halved.