Question

Ball mill works on the following principle

• A. Compression
• B. Cutting
• C. Attrition and impact
• D. Combustion

Hint:

In mechanical operations, when grinding or breaking material, look for principles such as attrition, impact, or compression to identify the correct mechanism.

Answer 1

The Correct Option is C

The ball mill's mechanism can be identified directly from how it's built and operated.

1. Compression: Not applicable - that's roller mills.
2. Cutting: Not applicable - that's cutter/knife mills.
3. Attrition and impact: Correct - rotating balls striking the material (impact) and rubbing against it (attrition) is exactly how a ball mill grinds.
4. Combustion: Not applicable - this is a chemical process, unrelated to mechanical grinding.

So the correct answer is Attrition and impact.

Answer 2

Instead of comparing the ball mill to other mill types, we can arrive at the answer just by walking through what physically happens inside the mill as it runs.

1. Compression: As the cylinder rotates and the balls tumble, there is no sustained squeezing force applied to the material between two fixed plates, so compression is not the acting force here.
2. Cutting: There are no sharp edges or blades inside a ball mill, only spherical balls, so a shearing/cutting action cannot occur.
3. Attrition and impact: As the mill rotates, the balls are carried up along the inner wall by friction and then cascade or fall back down under gravity, striking the material and other balls (impact), while the continuous tumbling and rolling of the balls against one another and the material also grinds it through rubbing action (attrition).
4. Combustion: No heat or chemical reaction is involved in this purely mechanical tumbling process.

Tracing the actual motion inside the mill leads to the same mechanism.

Hence, the correct answer is Attrition and impact.