1. What is Ball Screw Critical Speed?

The critical speed of a ball screw is the rotational speed at which the screw shaft begins to vibrate violently due to resonance. Operating above this speed can cause excessive vibration and potential failure.

2. How Does the Calculator Work?

The calculator uses the critical speed formula:

Where:

• \( E \) — Modulus of elasticity (Pa)
• \( I \) — Moment of inertia (m⁴)
• \( m \) — Mass per unit length (kg/m)
• \( L \) — Length between supports (m)
• \( \text{constant} \) — Factor depending on support conditions (typically 9.87 for simply supported ends)

Explanation: The formula accounts for the stiffness and mass distribution of the screw shaft to determine its natural frequency.

3. Importance of Critical Speed Calculation

Details: Calculating critical speed is essential for proper ball screw selection and operation to avoid resonance and ensure smooth, vibration-free performance.

4. Using the Calculator

Tips: Enter all values in the specified units. The default constant of 9.87 assumes simply supported ends. For different support conditions, adjust the constant accordingly.

5. Frequently Asked Questions (FAQ)

Q1: What happens if I operate above critical speed?
A: Operating above critical speed can cause excessive vibration, noise, and potential failure of the ball screw assembly.

Q2: How can I increase critical speed?
A: Critical speed can be increased by reducing unsupported length, using a larger diameter screw, or changing support conditions.

Q3: What are typical support condition constants?
A: Common constants are 9.87 (simply supported), 15.4 (fixed-free), 22.4 (fixed-supported), and 39.5 (fixed-fixed).

Q4: Does preload affect critical speed?
A: Preload has minimal effect on critical speed as it doesn't significantly change the shaft's stiffness or mass distribution.

Q5: Should I include a safety factor?
A: Yes, it's recommended to operate at least 20-30% below the calculated critical speed for safety.