Thermally induced bearing loads may cause serious problems for metal cutting spindles when used at high speeds. While proper spindle bearing setup can help minimize this problem, ultimately the plethora of factors that cause the loads to vary cannot be accounted for by the setup. Previous work has shown that bearing load control is possible, but that improved performance may be realized if the temperature environment of each bearing of a back-to-back pair is considered separately. The purpose of this paper is to provide the results of an experimental evaluation of a bearing load control strategy using two thermal actuators. A box spindle was modified and two electric heating tapes were placed around the front pair of back-to-back angular contact ball bearings, one around each bearing. Significant control over the bearing loads can be achieved for the conditions tested including some level of independent control. Unfortunately, there is cross-talk between the heat actuators and the bearing loads, and this interferes with the level of independent load control that can be achieved over the individual bearings. The significance of this issue is discussed and future research outlined. The authors conclude that it is possible to significantly reduce the transient load variation in both bearings with two rather than one actuator; additionally, the second control loop usually improves the steady-state behavior over that achievable with single heater placed over the rear bearing.

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