The spindle temperature provides the temperature of the spindle at different locations. Exact measurement, particularly on the inner ring of the spindle bearing, presents a difficult technical challenge due to the high rotational speeds of the spindle. In most cases the temperature sensors measure in the interior or exterior of the spindle housing, and from this the temperatures of the shaft and the inner ring of the bearings are estimated. The limit temperatures for the roller bearings depend on the measurement point, the type of lubrication and the cage used. The maximum motor temperature must not be too high in order to prevent the galvanic isolating layer between the copper windings being destroyed. As a guide value, the temperature should not be higher than 110°C.
The manufacturing quality of a machine tool is significantly impaired through thermoelastic deformation of the machine components as a result of the various heat sources. The heat sources can be separated into machine internal influences and thermal environmental influences. The process-dependent internal influences, e.g. the power losses of the motors, transmission and main spindle bearing and the process heat in the tool and in the chippings, as well as external influences such as fluctuating hall temperatures, are changeable and create an unstable temperature environment across the machine structure. [WECK06]