1. What is Ball Mill Critical Speed?

Definition: The critical speed of a ball mill is the rotational speed at which the grinding media will centrifuge against the mill wall instead of cascading.

Purpose: Operating above critical speed causes inefficient grinding and potential damage to the mill.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( N_c \) — Critical speed (revolutions per minute)
• \( D \) — Internal diameter of the mill (meters)

Explanation: The formula calculates the speed at which centrifugal force equals gravitational force on grinding media.

3. Importance of Critical Speed Calculation

Details: Proper operation at 65-80% of critical speed ensures optimal grinding efficiency and media movement.

4. Using the Calculator

Tips: Enter the internal diameter of the ball mill in meters. The value must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why is 42.3 used in the formula?
A: It's a constant derived from gravitational acceleration (9.81 m/s²) and unit conversions.

Q2: What happens above critical speed?
A: Grinding media centrifuges against the mill wall instead of cascading, reducing grinding efficiency.

Q3: How does mill length affect critical speed?
A: Critical speed depends only on diameter, but length affects throughput and residence time.

Q4: What's typical operating speed?
A: Most mills operate at 65-80% of critical speed for optimal grinding.

Q5: Does media size affect critical speed?
A: No, but it affects grinding efficiency and power draw at a given speed.