Thermoelastic Instability Monitoring for Preventing Spindle Bearing Seizure

Abstract

Premature failure of machine tool spindle bearings is a major problem in production that results in enormous loss. One of the most common and costly premature failure modes is bearing seizure caused by excessive thermoelastic distortions. In this paper, a Stability Margin (SM) Chart is proposed to indicate bearing thermoelastic stability based on the expansions of the inner ring and rolling elements vs. the accommodations of the outer ring and housing. This SM Chart is prepared numerically based on a thermoelastic bearing model. The expansion vs. accommodation curve is obtained by a model-based monitor to estimate the temperatures and corresponding expansions of different bearing parts using online measurements of the spindle speed and the bearing outer ring/housing temperature. The experiments conducted on an instrumented spindle bearing with grease-lubricated bearings showed that the proposed SM Chart can indicate the margin of bearing thermoelastic stability more consistently than bearing outer ring/housing temperature or the spindle speed alone.

Presented at the 49th Annual Meeting in Pittsburgh, Pennsylvania May 1–5, 1994

KEY WORDS:

• Thermoelastic Stability
• Machine Tool
• Spindle Bearings
• Bearing Seizure

Notes

Presented at the 49th Annual Meeting in Pittsburgh, Pennsylvania May 1–5, 1994