Abstract: A control device which controls a tapping device provided with a feed motor for feeding a spindle in an axial direction thereof and a spindle motor for rotating the spindle about its axis. The spindle installs a composite tool having a boring section for forming a bore in a workpiece and a subsequent tapping section for forming a female thread at the bore. An asynchronous control is initially performed for independently controlling rotation of the feed motor and the spindle motor for boring. If the tapping section reaches the workpiece, a control is switched to a synchronous control for controlling the motors in synchronism with each other.

Abstract: A machine tool includes a spindle having a cutting tool for cutting a workpiece. For fault detection, a control unit of the machine tool detects a value representing a torque applied on the spindle while the spindle is stopped in a state the cutting tool is engaged with the workpiece. The control unit further compares the detected value (representing a torque) with a predetermined threshold thereby to determine that a fault has occurs. Since the detection of the value representing a torque is performed while the spindle is stopped, the detection is free from the effects of acceleration or deceleration of the spindle.

Abstract: Axial loads encountered during thread cutting are reduced by controlling interactions between rotation speed, axial feeding speed, feeding (threading) pitch, and feeding position. A counterload is generated by changing a feeding pitch to a corrected feeding pitch, which changes the rotation speed, while keeping the feeding speed constant; by changing the feeding speed, while compensating the rotation speed (which is derived from the feeding speed) to remain constant; by changing the rotation speed, while compensating the rotation speed deviation feedback (to allow the deviation correction to follow the rotation speed change), while keeping the feeding speed constant; by generating a function according to empirical results that controls the feeding pitch, and therefore the rotation speed, while keeping the feeding speed constant; and by combinations of these methods.

Abstract: A threading apparatus is capable of eliminating a rise delay in the feed velocity due to friction resistance and can perform high-precision threading even in high-speed tapping. A feed servo amplifier is controlled to operate using one of a plurality of gains. A gain setter sets the plurality of gains, which include a high gain, which is high enough to overcome static friction resistance, and a normal gain. A gain changer selects one of the plurality of gains for the feed servo amplifier. In particular, the gain changer selects the high gain during a start period of tapping operation and then selects the normal gain after the start period. Therefore, a rise delay in the feed velocity due to friction resistance during the start period of the tapping operation can be compensated for. After the start period, the normal gain is selected. Thus, high-precision threading can be performed over the course of the tapping operation with no errors.

Abstract: A numerical control device can perform machining processes in a short time while maintaining high precision, regardless of the order at which programs are commanded. Consecutive blocks of a numerical control program are retrieved on a block-by-block basis, and a pre-execution in-position value and a post-execution in-position value for each of the blocks of the numerical control program are set and stored in a ROM. The block of the numerical control program is executed in accordance with at least one of the corresponding pre-execution in-position value and the post-execution in-position value.