Spindle Vibration and Critical Speed
topic
Every spindle has a critical speed (resonance frequency) at which it vibrates excessively, typically 10,000–14,000 RPM for standard spindles. Above the critical speed, the spindle runs in a supercritical regime with acceptable vibration. Passing through the critical speed during acceleration generates high momentary vibration that stresses yarn and bearings. Balancing (dynamic balancing of spindle + bobbin assembly) raises the critical speed and reduces vibration amplitude. Vibration is measured as µm peak amplitude at the spindle tip.
Role
Spindle vibration is the mechanical limit on maximum spindle speed and the cause of high-frequency yarn tension variation that produces yarn faults undetectable by standard testing but visible as fabric mottle. Understanding critical speed theory is essential for evaluating ring frame upgrade proposals and for diagnosing abnormal yarn faults that persist despite correct process settings.