To detect the load of a tool of a load detecting spindle unit, applied at the time of the cutting, high accurately and efficiently always, without affected by inertia force due to acceleration at the time of forwarding and retreating movement of a gas bearing spindle; and putout only a main spindle displacement quantity signal.
A main spindle displacement quantity signal KB, generated by only inertia at the time of acceleration when a gas bearing is moved forward and rearward, is subtracted from a main spindle displacement signal A detected by an uncontacted displacement sensor 26, which detects a load applied to a tool at the time of cutting a workpiece by the tool with a gas bearing spindle advanced, and is built in the spindle for detecting the thrust displacement quantity of a main spindle supporting a tool; and a spindle unit for detecting a load outputs only a main spindle displacement quantity signal by only the load applied to the tool. The signal KB can be obtained by determining a signal, in proportion to acceleration, from a signal resulting from the differentiation of the speed signal of a driving motor 1, or the torque signal of the motor 1.
UCHIYAMA NAOYUKI
NAKAMURA KOJI
