Ball Screw Critical Speed Screen

WHAT THIS SCREEN ANSWERS

A screw can have enough torque capacity and still be unusable at the required rpm because its unsupported span becomes dynamically sensitive. Critical speed is a layout question. Diameter, unsupported length, end support, straightness, and the way the nut travels all affect it. This screen is intended to reveal sensitivity early, before a long fast screw is treated as an ordinary rotary shaft.

Enter the screw root diameter, the unsupported length between effective supports, the operating rpm, and a conservative end-condition factor. The model applies the expected diameter-squared and length-squared trend. That makes it useful for comparing layout changes, especially because length has a strong influence. It is deliberately not presented as a final critical-speed value or a catalog substitute.

The practical decision is often architectural. A larger diameter, shorter unsupported length, different support arrangement, lower screw rpm through a different lead, or a stationary screw with a moving nut can each change the risk. A simplistic calculation cannot see bearing preload, actual end stiffness, shaft straightness, nut position, resonances, installation error, or the manufacturer-specific criteria behind a rated value.

Use the result to decide whether a concept needs supplier confirmation immediately. Do not assume a passing-looking comparison validates the screw. Confirm the exact part, root diameter, support arrangement, mounting, travel position, speed, acceleration, lubrication, and application duty with current manufacturer engineering data before release.